Class 1 L. 4>~- Q Book._i_. Gopyii^ht N?___ COPYRIGHT DEPOSIT } / BUILDING AND FLYING AN AEROPLANE PART II INSTRUCTION PAPER PREPARED BY CHARLES B. HAYWARD Member, Society of Automobile Engineers Member, The Aeronautical Society Formerly Secretary, Society of Automobile Engineers Formerly Engineering Editor, The Automobile e o AMERICAN SCHOOL OF CORRESPONDENCE CHICAGO U.S.A. IEUNOIS Copyright 1912 bi American School op Correspondence Entered at Stationers’ Hall, London All Rights Reserved » « /VO' 2 ? / 'Vi~ BUILDING AND FLYING AN AEROPLANE PART II BUILDING A BLERIOT MONOPLANE As mentioned in connection with the description of its con¬ struction, the Curtiss biplane was selected as a standard of this type of aeroplane after which the student could safely pattern for a number of reasons. It is not only remarkably simple in construction, easily built by anyone with moderate facilities and at a slight outlay, but it is likewise the easiest machine to learn to drive. The monoplane is far more difficult and expensive to build. The Bleriot may be regarded as the most typical example in this field, in view of its great success and the very large numbers which have been turned out. In fact, the Bleriot monoplane is the product of a factory which would compare favorably with some of the large automobile plants. Its construction requires skillful workmanship both in wood and metal, and a great many special castings, forgings, and stampings are necessary. Although some concerns in this country advertise that they carry these fittings as stock parts, they are not always correct in design and, in any case, are expensive. Wherever it is possible to avoid the use of such parts by any expedient, both forms of construction are described, so that the builder may take his choice. Bleriot monoplanes are made in a number of different models, the principal ones being the 30-horse-power “runabout,” Figs. 23 and 24, the 50- and 70-horse-power passenger-carrying machines, and the 50-, 70-, and 100-horse-power racing machines. Of these the first has been chosen as best adapted to the purpose. Its construction is typical of the higher-power monoplanes of the same make, and it is more suitable for the beginner to fly as well as to build. It is employed exclusively by the Bleriot schools. Motor. The motor regularly employed is the 30-horse-power, three-cylinder Anzani, a two-cylinder type of which is shown in Copyright , 1912, by American School of Correspondence. Fig. 23. Details of Bleriot Monoplane 60 BUILDING AND FLYING AN AEROPLANE ‘‘Aeronautical Motors,” Fig. 40. From the amateur’s standpoint, a disadvantage of the Bleriot is the very short space allowed for the installation of the motor. For this reason, the power plant must be fan shaped, like the Anzani; star form, like the Gnome; or of the two-cylinder opposed type. It must likewise be air-cooled, as there is no space available for a radiator. Fuselage. Like most monoplanes, the Bleriot has a long central body, usually termed “fuselage,” to which the wings, running gear, and controls are all attached. A drawing of the fuselage with all dimensions is reproduced in Fig. 25, and as the machine is, to a large extent, built up around this essential, its construction is taken up first. It consists of four long beams united by 35 crosspieces. The beams are of ash, 1inches square for the first third of their length Fig. 26. Details of U-bolt Which Is a Feature of Bleriot Construction and tapering to J inch square at the rear ends. Owing to the diffi¬ culty of securing good pieces of wood the full length, and also to facilitate packing for shipment, the beams are made in halves, the abutting ends being joined by sleeves of lf-inch, 20-gauge steel tubing, each held on by two J-inch bolts. Although the length of the fuselage is 21 feet 11J inches, the beams must be made of two 11-foot halves to allow for the curve at the rear ends. The struts are also of ash, the majority of them being J by 1| inches, and oval in section except for an inch and a half at each end. But the first, second, and third struts (counting from the forward end) on each side, the first and second on the top, and the first strut BUILDING AND FLYING AN AEROPLANE 61 on the bottom are 1^ inches square, of the same stock as the main beams. Practically all of the struts are joined to the main beams by u-bolts, as shown by the detail drawing, Fig. 26, this being one of Louis Bleriot’s inventions. The small struts are held by f-inch bolts and the larger ones by tV-inch bolts. The ends of the struts must be slotted for these bolts, this being done by drilling three holes in a row with a or ^-inch drill, according to whether the slot is for the smaller or larger size bolt. The wood between the holes is cut out with a sharp knife and the slot finished with a coarse, flat file. All of the u-bolts measure 2 inches between the ends. The vertical struts are set 1 inch forward of the corresponding horizontal struts, so that the four holes through the beam at each joint are spaced 1 inch apart, alternately horizontal and vertical. To the projecting angles of the u-bolts are attached the diagonal truss wires, which cross all the rectangles of the fuselage, except that in which the driver sits. This trussing should be of 20-gauge piano wire (music- wire gauge) or ro-inch cable, except in the rectangles bounded by the large struts, where it should be 25-gauge piano wire or A-inch cable. Each wire, of course, should have a turnbuckle. About 100 of these will be required, either of the spoke type or the regular type, with two screw eyes—the latter preferred. Transverse squares, formed by the two horizontal and two vertical struts at each point, are also trussed with diagonal wires. Although turnbuckles are sometimes omitted on these wires, it takes considerable skill to get accurate adjustments without them. The extreme rear strut to which the rudder is attached, is not fastened in the usual way. It should be cut with tongues at top and bottom, fitting into notches in the ends of the beams, and the whole bound with straps of 20-gauge sheet steel, bolted through the beams with f-inch bolts. Continuing forward, the struts have no peculiarity until the upper horizontal one is reached, just behind the driver’s seat. As it is impossible to truss the quadrangle forward of this strut, owing to the position of the driver’s body, the strut is braced with a u-shaped half-round strip of J by 1 inch of ash or hickory bolted to the beams at the sides and to the strut at the rear, with two f-inch bolts at each point. The front side of the strut should be left square where this brace is in contact with it. The brace should be steam bent with the 62 BUILDING AND FLYING AN AEROPLANE curves on a 9-inch radius, and the half-round side on the inside of the curve. The vertical struts just forward of the driver’s seat carry the inner ends of the rear wing beams. Each beam is attached with a single bolt, giving the necessary freedom to rock up and down in warping the wings. The upper 6 inches of each of these struts fits into a socket designed to reinforce it. In the genuine Bleriot, this socket is an aluminum casting. However, a socket which many would regard as even better can be made from a 7-inch length of 20-gauge 11-inch square tubing. One end of the tube is sawed one inch through the corners; two opposite sides are then bent down at right angles to form flanges, and the other two sides sawed off. A 1- by 3-inch strip of 20-gauge sheet steel, brazed across the top and flanges completes the socket. With a little care, a very creditable socket can be made in this way. Finally, with the strut in place, a f-inch hole is drilled through 4 inches from the top of the socket for the bolt securing the wing beam. The upper horizontal strut at this point should be arched about six inches to give plenty of elbow room over the steering wheel. The bending should be done in a steam press. The strut should be 1^ inches square, cut sufficiently long to allow for the curve, and fitted at the ends with sockets as described above, but set at an angle by sawing the square tube down further on one side than on the other. On the two lower beams, is laid a floor of half-inch boards, extending one foot forward and one foot back of the center line of the horizontal strut. This floor may be of spruce, if it is desired to save a little weight, or of ordinary tongue-and-grooved floor boards, fastened to the beams with wood screws or bolts. The horizontal strut under this floor may be omitted, but its presence adds but little weight and completes the trussing. Across the top of the fuselage above the first upper horizontal strut, lies a steel tube which forms the sockets for the inner end of the front wing beams. This tube is 1} inches diameter, 18 gauge, and 26} inches long. It is held fast by two steel straps, 16 gauge and 1 inch wide, clamped down by the nuts of the vertical strut u-bolts. The center of the tube is, therefore, in line with the center of the vertical struts, not the horizontal ones. The u-bolts which make this attachment are, of course, the A~inch size, and one inch longer on each end than usual. To make a neat BUILDING AND FLYING AN AEROPLANE 63 job, the tube may be seated in wood blocks, suitably shaped, but these must not raise it more than a small fraction of an inch above the top of the fuselage, as this would increase the angle of incidence of the wings. The first vertical struts on each side are extras, without cor¬ responding horizontal ones; they serve only to support the engine. When the Gnome motor is used, its central shaft is carried at the centers of two x-shaped, pressed-steel frames, one on the front side, flush with the end of the fuselage and one on the rear. Truss Frame Built on Fuselage. In connection with the fuselage may be considered the overhead truss frame and the warping frame. The former consists of two inverted v’s of 20-gauge, 1- by f-inch oval tubing, joined at their apexes by a 20-gauge, f-inch tube. Each V is formed of a single piece of the oval tubing about 5 feet long. The flattened ends of the horizontal tube are fastened by a bolt in the angles of the v’s. The center of the horizontal tube should be 2 feet above the top of the fuselage. The flattened lower ends of the rear V should be riveted and brazed to strips of 18-gauge steel, which will fit over the bolts attaching the vertical fuselage struts at this point. The legs of the front V should be slightly shorter, as they rest on top of the wing socket tube. Each should be held down by a single A-inch bolt, passing through the upper wall of the tube and its retaining strap; these bolts also serve the purpose of preventing the tube from sliding out from under the strap. Each side of the frame is now braced by diagonal wires (No. 20 piano wire, or A-inch cable) with turnbuckles. At the upper corners of this frame are attached the wires which truss the upper sides of the wings. The front wires are simply fastened under the head and nut of the bolt which holds the frame, together at this corner. The attachment of the rear wires, however, is more complex, as these wires must run over pulleys to allow for the rocking of the rear wing beams when the wings are warped. To provide a suitable place for the pulleys, the angle of the rear V is enclosed by two plates of 20-gauge sheet steel, one on the front and one on the rear, forming a triangular box 1 inch thick fore and aft, and about 2 inches on each side, only the bottom side being open. These plates are clamped together by a A-inch steel bolt, on which are mounted the pulleys. There should be sufficient clearance for 64 BUILDING AND FLYING AN AEROPLANE pulleys 1 inch in diameter. The wires running over these pulleys must then pass through holes drilled in the tube. The holes should not be drilled until the wings are on, when the proper angle for them can be seen. The cutting and bending of the steel plates is a matter of some difficulty, and should not be done until the frame is otherwise assembled, so that paper patterns can be cut for them. They should have flanges bent around the tube, secured by the bolts which hold the frame together, to keep them from slipping off. The oval tubing is used in the vertical parts of this frame, principally to reduce the wind resistance, being placed with the narrow side to the front. However, if this tubing be difficult to obtain, or if price is a consideration, no harm will be done by using f-inch round tubing. Beneath the floor of the driver’s cockpit in the fuselage is the warping frame, the support for the wires which truss the rear wing beams and also control the warping. This frame is built up of four f-inch, 20-gauge steel tubes, each about 3 feet long, forming an inverted, 4-sided pyramid. The front and back pairs of tubes are fastened to the lower fuselage beams with i^-inch bolts at points 15 inches front and back of the horizontal strut. At their lower ends the tubes are joined by a fixture which carries the pulleys for the warping wires and the lever by which the pulleys are turned. In the genuine Bleriot, this fixture is a special casting. However, a very neat connection can be made with a piece of rg-inch steel stock, If by 6 inches, bent into a u-shape with the legs 1 inch apart inside. The flattened ends of the tubes are riveted and brazed to the outside upper corners of the u , and a bolt to carry the pulleys passes through the lower part, high enough to give clear¬ ance for 2-inch pulleys. This frame needs no diagonal wires. Running Gear. Passing now to the running gear, the builder will encounter the most difficult part of the entire machine, and it is impossible to avoid the use of a few special castings. The general plan of the running gear is shown in the drawing of the complete machine, Figs. 23 and 24, while some of the details are illustrated in Fig. 27, and the remainder are given in the detail sheet, Fig. 28. It will be seen that each of the two wheels is carried in a double fork, the lower fork acting simply as a radius rod, while the upper fork is attached to a slide which is free to move up and down on a 2-inch steel tube. This slide is held down by two tension springs, consisting BUILDING AND FLYING AN AEROPLANE 65 of either rubber tubes or steel coil springs, which absorb the shocks of landing. The whole construction is such that the wheels are free to pivot sideways around the tubes, so that when landing in a quarter¬ ing wind the wheels automatically adjust themselves to the direction of the machine. Framework. The main framework of the running gear consists of two horizontal beams, two vertical struts, and two vertical tubes. The beams are of ash, 4f inches wide in the middle half, tapering to 3J inches at the ends, and 5 feet 2f inches long overall. The upper beam is If inch thick and the lower 1 inch. The edges of the beams are rounded off except at the points where they are drilled for bolt holes for the attachment of other parts. The two upper beams of the fuselage rest on these beams and are secured to them by two A-inch bolts each. The vertical struts are also of ash, lA inch by 3 inches and 4 feet 2 inches long overall. They have tenons at each end which fit into corresponding square holes in the horizontal beams. The two lower fuselage beams are fastened to these struts by two A-inch through bolts and steel angle plates formed from A-inch sheet steel. The channel section member across the front sides of these struts is for the attachment of the motor, and will be taken up later. The general arrangement at this point depends largely on what motor is to be used, and the struts should not be rounded or drilled for bolt holes until this has been decided. From the lower ends of these struts CC, Fig. 27, diagonal struts DD run back to the fuselage. These are of ash, lA by 2f inches and 2 feet 6 inches long. The rear ends of the struts I)D are fastened to the fuselage beams by the projecting ends of the U-bolts of the horizontal fuselage struts, and also by angle plates of sheet steel. At the lower front ends the struts DD are fastened to the struts CC and the beam E by steel angle plates, and the beam is reinforced by other plates on its under side. Trussing. In the genuine Bleriot, the framework is trussed by a single length of steel tape, If by A inch and about 11 feet long, fastened to U-bolts in the beam A, Fig. 27. This tape runs down one side, under the beam E, and up the other side, passing through the beam in two places, where suitable slots must be cut. The tape is not made in this country, but must be imported at considerable Details of Bleriot Running Gear Fig. 28. Details of Various Fittings for Bleriot Monoplane 68 BUILDING AND FLYING AN AEROPLANE expense. Ordinary sheet steel will not do. If the tape can not be obtained, a good substitute is J-inch cable, which then would be made in two pieces and fastened to eye bolts at each end. The two steel tubes are 2 inches in diameter, 18-gauge, and about 4 feet 10 inches long. At their lower ends they are flattened, but cut away so that a 2-inch ring will pass over them. To these flat¬ tened ends are attached springs and wires which run from each tube across to the hub of the opposite wheel. The purpose of these is simply to keep the wheels normally in position behind the tubes. The tubes, it will be noticed, pass through the lower beam, but are sunk only J inch into the upper beam. They are held in place by sheet-steel sockets on the lower side of the upper beam and the upper side of the lower beam. The other sides of the beams are provided with flat plates of sheet steel. The genuine Bleriot has these sockets stamped out of sheet steel, but as the amateur builder will not have the facilities for doing this, an alternative construction is given here. In this method, the plates are cut out to pattern, the material being sheet steel A inch thick, and a J-inch hole drilled through the center, a 2-inch circle then being drawn around this. Then, with a cold chisel a half dozen radial cuts are made between the hole and the circle. Finally this part of the plate is heated with a blow-torch and a 2-inch piece of pipe driven through, bending up the triangular corners. These bent up corners are then brazed to the tubes, and a strip of light sheet steel is brazed on to cover up the sharp edges. Of course, the brazing should not be done until the slides GG, Figs. 27 and 28, have been put on. When these are once in place, they have to stay on and a breakage of one of them, means the replace¬ ment of the tube as well. This is a fault of the Bleriot design that can not well be avoided. It should be noticed that the socket at the upper end, as well as its corresponding plate on the other side of the beam, has extensions which reinforce the beam where the eye bolts or U-bolts for the attachment of the steel tape pass through. Forks. Next in order are the forks which carry the wheels. The short forks JJ , Figs. 27 and 28, which act simply as radius rods, are made of 1- by f-inch oval tubing, a stock size which was specified for the overhead truss frame. It will be noticed that these are in two parts, fastened together with a bolt at the front end. The regular Bleriot construction calls for forged steel eyes to go in BUILDING AND FLYING AN AEROPLANE 69 the ends of tubes, but these will be hard to obtain. The construction shown in the drawings is much simpler. The ends of the tubes are heated and flattened until the walls are about A inch apart inside. Then a strip of A-inch sheet steel is cut the right width to fit in the flattened end of the tube, and brazed in place. The bolt holes then pass through the combined thickness of the tube and the steel strip, giving a better bearing surface, which may be further increased by brazing on a washer. The long forks FF, which transmit the landing shocks to the springs, are naturally made of heavier material. The proper size tubing for them is If by f inches, this being the nearest equivalent to the 14 by 28 mm French tubing. However, this is not a stock size in this country and can only be procured by order, or it can be made by rolling out tf-inch round tubing. If the oval tubing can not be secured, the round can be employed instead, other parts being modified to correspond. The ends are reinforced in the same way as described for the small forks. These forks are strengthened by aluminum clamps II, Figs. 27 and 28, which keep the tubes from spreading apart. Here, of course, is another call for special castings, but a handy workman may be able to improvise a satisfactory substitute from sheet steel. On each tube there are four fittings: At the bottom, the collar M to which the fork J is attached, and above, the slide G and the clamps K and L, which limit its movement. The collar and slide should be forged, but as this may be impossible, the drawings have been pro¬ portioned for castings. The work is simple and may be done by the amateur with little experience. The projecting studs are pieces of f-inch, 14-gauge steel tubing screwed in tight and pinned, though if these parts be forged, the studs should be integral. The clamps which limit the movement of the slides are to be whittled out of ash or some other hard wood. The upper clamp is held in place by four bolts, which are screwed up tight; but when the machine makes a hard landing the clamp will yield a little and slip up the tube, thus deadening the shock. After such a landing, the clamps should be inspected and again moved down a bit, if necessary. The lower clamps, which, of course, only keep the wheels from hanging down too far, have bolts passing clear through the tubes. To the projecting lugs on the slides GG are attached the rubber 70 BUILDING AND FLYING AN AEROPLANE tube springs, the lower ends connecting with eye bolts through the beam E. These rubber tubes, of which four will be needed, are being made by several companies in this country and are sold by supply houses. They should be about 14 inches long, unstretched, and If inches in diameter, with steel tips at the ends for attachment. Hub Attachments. The hubs of the two wheels are connected with the link P, with universal joints NN at each end. In case the machine lands while drifting sidewise, the wheel which touches the ground first will swing around to head in the direction in which the machine is actually moving, and the link will cause the other wheel to assume a parallel position; thus the machine can run diagonally on the ground without any tendency to upset. This link is made of the same 1- by f-inch oval tubing used elsewhere in the machine. In the original Bleriot, the joints are carefully made up with steel forgings. But joints which will serve the purpose can be improvised from a 1-inch cube of hard wood and three steel straps, as shown in the sketch, Fig. 27. From each of these joints a wire runs diagonally to the bottom of the tube on the other side, with a spring which holds the wheel in its normal position. This spring should be either a rubber tube, like those described above, but smaller, or a steel coil spring. In the latter case, it should be of twenty f-inch coils of No. 25 piano wire. Wheels. The wheels are regularly 28 by 2 inches, corresponding to the 700 by 50 mm French size, with 3G spokes of 12-gauge wire. The hub should be 5| inches wide, with a f-inch bolt. Of course, these sizes need not be followed exactly, but any variations will involve corresponding changes in the dimensions of the forks. The long fork goes on the hub inside of the short fork, so that the inside measurement of the end of the big fork should correspond to the width of the hub, and the inside measurement of the small fork should equal the outside measurement of the large fork. Rear Skid. Several methods are employed for supporting the rear end of the fuselage when the machine is on the ground. The first Ble¬ riot carried a small wheel in a fork provided with rubber springs, the same as the front wheels. The later models, however, have a double U-shaped skid, as shown in Figs. 23 and 24. This skid is made of two 8-foot strips of ash or hickory \ by f inches, steamed and bent to the u-shape as shown in the drawing of the comolete machine. -„r/ —-f -—.,€/ \ J $ Fig. 29. Details of Framework of Bleriot Main Supporting Planes 72 BUILDING AND FLYING AN AEROPLANE Wings. Having completed the fuselage and running gear, the wings are next in order. These are constructed in a manner which may seem unnecessarily complicated, but which gives great strength for comparatively little weight. Each wing contains two stout ash beams which carry their share of the weight of the machine, and 12 ribs which give the proper curvature to the surfaces and at the same time reinforce the beams. These ribs in turn are tied together and reinforced by light strips running parallel to the main beams. In the drawing of the complete wing, Fig. 29, the beams are designated by the letters B and E. A is a sheet aluminum member intended to hold the cloth covering in shape on the front edge. C, D, and F are pairs of strips (one strip on top, the other underneath) which tie the ribs together. G is a strip along the rear edge, and H Fig. 30. Complete Rib of Bleriot Wing and Pattern from Which Web Is Cut is a bent strip which gives the rounded shape to the end of the wing. The ribs are designated by the numbers 1 to 12 inclusive. Ribs. The first and most difficult operation is to make the ribs. These are built up of a spruce board ^ inch thick, cut to shape on a jig saw, with by f-inch spruce strip stacked and glued to the upper and lower edges. Each rib thus has an I-beam section, such as is used in structural steel work and automobile front axles. Each of the boards, or webs as they are usually called, is divided into three parts by the main beams which pass through it. Builders sometimes make the mistake of cutting out each web in three pieces, but this makes it very difficult to put the rib together accurately. Each web should be cut out of a single piece, as shown in the detail drawing, Fig. 30, and the holes for the beams should be cut in after the top and bottom strips have been glued on. BUILDING AND FLYING AN AEROPLANE 73 The detail drawing, Fig. 30, gives the dimensions of a typical rib. This should be drawn out full size on a strip of tough paper, and then a margin of ^ inch should be taken off all round except at the front end where the sheet aluminum member A goes on. This allows for the thickness of the top and bottom strips. In preparing the pattern for the jig saw, the notches for strips C, D, and F should be disregarded; neither should it be expected that the jig-saw operator will cut out the oval holes along the center of the web, which are simply to lighten it. The notches for the front ends of the top and bottom strips should also be smoothed over in the pattern. When the pattern is ready, a saw or planing mill provided with a saw suitable for the work, should cut out the 40 ribs (allowing a sufficient number for defective pieces and breakage) for about $2. The builder then cuts the notches and makes the oval openings with an auger and keyhole saw. Of course, these holes need not be absolutely accurate, but at least f inch of wood should be left all around them. Nine of the twelve ribs in each wing are exactly alike. No. 1, which forms the inner end of the wing, does not have any holes cut in the web, and instead of the slot for the main beam R, has a lf-inch round hole, as the stub end of the beam is rounded to fit the socket tube. (See Fig. 23.) Rib No. 11 is 5 feet 10§ inches long, and No. 12 is 3 feet long. These can be whittled out by hand, and the shape for them will be obvious as soon as the main part of the wing is put together. The next step is to glue on the top and bottom strips. The front ends should be put on first and held, during the drying, in a screw clamp, the ends setting close up into the notches provided for them. Thin J-inch brads should be driven in along the top and bottom at 1- to 2-inch intervals. The rear ends of the strips should be cut off to the proper length and whittled off a little on the inside, so that there will be room between them for the strip G, \ inch thick. Finally, cut the slots for the main beams, using a bit and brace and the keyhole saw, and the ribs will be ready to assemble. Beams and Strips. The main beams are of ash, the front beam in each wing being 3J by f inches and the rear beam 2J by f inches. They are not exactly rectangular but must be planed down slightly on the top and bottom edges, so that they will fit into the irregularly- 74 BUILDING AND FLYING AN AEROPLANE shaped slots left for them in the ribs. The front beams, as mentioned above, have round stubs which fit into the socket tube on the fusel¬ age. These stubs may be made by bolting short pieces of ash board on each side of the end of the beam and rounding down the whole. To give the wings their slight inclination, or dihedral angle, which will be apparent in the front view of the machine, the stubs must lie at an angle of 2\ degrees with the beam itself. This angle should be laid out very carefully, as a slight inaccuracy at this point will result in a much larger error at the tips. The rear beams project about 2 inches from the inner ribs. The ends should be reinforced with bands of sheet steel to prevent splitting, and each drilled with a f-inch hole for the bolt which attaches to the fuselage strut. A strip of heavy sheet steel should be bent to make an angle washer to fill up the triangular space between the beam and the strut; the bolt hole should be drilled perpendicularly to the beam, and not to the strut. The outer ends of the beams, beyond rib No. 10, taper down to 1 inch deep at the ends. The aluminum member A, Fig. 29, which holds the front edge of the wing in shape, is made of a 4-inch strip of fairly heavy sheet aluminum, rolled into shape round a piece of half-round wood, 2J inches in diameter. As sheet aluminum usually comes in 6-foot lengths, each of these members will have to be made in two sections, joined either by soldering (if the builder has mastered this difficult % process) or by a number of small copper rivets. No especial difficulties are presented by the strips, C, I ), and F, which are of spruce by | inch, or by the rear edge strip G, of spruce | by 1J inches. Each piece II should be 1 by J inch half-round spruce, bent into shape, fitted into the aluminum piece at the front, and at the rear flattened down to \ inch and reinforced by a small strip glued to the back, finally running into the strip G. The exact curve of this piece does not matter, provided it is the same on both wings. Assembling the Wings. Assembling the wings is an operation which demands considerable care. The main beams should first be laid across two horses, set level so that there will be no strain on the framework as it is put together. Then the 12 ribs should be slipped over the beams and evenly spaced 13 inches apart to centers, care being taken to see that each rib stands square with the beams, Fig. 31. BUILDING AND FLYING AN AEROPLANE 75 The ribs are not glued to the beams, as this would make repairs difficult, but are fastened with small nails. Strips C, D, and F, Fig. 29, are next put in place, simply being strung through the rows of holes provided for them in the ribs, and fastened with brads. Then spacers of ^-inch spruce, 2 or 3 inches long, are placed between each pair of strips halfway between each rib, and fastened with glue and brads. This can be seen in the broken-off view of the wing in the front view drawing, Fig. 23. The rear edge strip fits between the ends of the top and bottom Fig. 31. Assembling the Main Planes of a Bleriot Monoplane strips of the ribs, as mentioned above, fastened with brads oi with strips of sheet-aluminum tacked on. Each wing is trussed by eight wires, half above and half below; half attached to the front and half to the rear beam. In the genuine Bleriot steel tape is used for the lower trussing of the main beams, similar to the tape employed in the running gear, but American builders prefer to use J-inch cable. The lower rear trussing should be A- or -inch steel, 12 by 2 inches, is laid flat on J and bolted in place; it is then trussed by wires running from each end to the rear ends of KK. From the lever other wires also run forward to the foot lever which controls the rudder. The wires to the elevator and rudder should be of the flexible cable specially made for this purpose, and should be supported by fairleaders attached to the fuselage struts. Fairleaders of different designs may be procured from supply houses, or may'be improvised. Ordinary screw eyes are often used, or pieces of copper tubing, bound to the struts with friction tape. Covering the Planes. Covering the main planes, tail, elevators, and rudder may well be left until the machine is otherwise ready for its trial trip, as the cloth will not then be soiled by the dust and grime of the shop. The cloth may be any of the standard brands 82 BUILDING AND FLYING AN AEROPLANE t which are on the market, preferably in a rather light weight made specially for double-surfaced machines of this type; or light-weight sail cloth may be used, costing only 25 or 30 cents a yard. About 80 yards will be required, assuming a width of 36 inches. Except on the rudder, the cloth is applied on the bias, the idea being that with this arrangement the threads act like diagonal truss wires, thus strengthening and bracing the framework. When the cloth is to be put on in this way it must first be sewed together in sheets large enough to cover the entire plane. Each wing will require Fig. 34. Method of Mounting Fabric on Main Supporting Frame a sheet about 14 feet square, and two sheets each 6 feet square will be required for the elevators and tail. The strips of cloth run diagonally across the sheets, the longest strips in the wing sheets being 20 feet long. Application of the cloth to the wings, Fig. 34, is best begun by fastening one edge of a sheet to the rear edge of the wing, stretch¬ ing the cloth as tight as can be done conveniently with one hand. The cloth is then spread forward over the upper surface of the wing and is made fast along the inner end rib. Small copper tacks are used, spaced 2 inches apart on the upper side and 1 inch on the BUILDING AND FLYING AN AEROPLANE 83 lower side. After the cloth has been tacked to the upper sides of all the ribs, the wing is turned over and the cloth stretched over the lower side. Finally the raw edges arc trimmed off and covered with light tape glued down, tape also being glued over all the rows of tacks along the ribs, making a neat finish and at the same time preventing the cloth from tearing off over the tack heads. Installation of Motor. As stated previously, the ideal motor for a Bleriot-type machine is short along the crank shaft, as the available space in the fuselage is limited, and air-cooled for the same reason. Genuine Bleriots are always fitted with one of the special types of radial or rotary aeronautic motors, which are always air¬ cooled. Next in popularity to these is the two-cylinder, horizontal- opposed motor, either air- or water-cooled. However, successful machines have been built with standard automobile-type, four- cylinder, water-cooled motors, and with four-cylinder, two-cycle, aeronautic motors. When the motor is water-cooled, there will inevitably be some difficulty in finding room for a radiator of sufficient size. One scheme is to use twin radiators, one on each side of the fuselage, inside of the main frame of the running gear. Another plan is to place the radiator underneath the fuselage, using a supplementary water tank above the cylinders to facilitate circulation. These two seem to be about the only practicable arrangements, as behind the motor the radiator would not get enough air, and above it would obstruct the view of the operator. It is impossible to generalize to much effect about the method of supporting the motor in the fuselage, as this must differ with the motor. Automobile-type motors will be carried on two heavy ash beams, braced by lengths of steel tubing of about 1 inch diameter and 10 gauge. When the seven-cylinder rotary Gnome motor is used, the crank shaft alone is supported; it is carried at the center of two X-shaped frames of pressed steel, one in front of and the other behind the motor. The three-cylinder Anzani motors are carried on four lengths of channel steel bent to fit around the upper and lower por¬ tions of the crank case, which is of the motorcycle type. Considerable care should be taken to prevent the exhaust from blowing back into the operator’s face as this sometimes carries with it drops of burning oil, besides disagreeable smoke and fumes. The 84 BUILDING AND FLYING AN AEROPLANE usual plan is to arrange a sloping dashboard of sheet aluminum so as to deflect the gases down under the fuselage. The three sections of the fuselage back of the engine section are usually covered on the sides and bottom with cloth like that used on the wings. Sometimes sheet aluminum is used to cover the section between the wing beams. However, those who are just learning to operate machines and are a little doubtful about their landings often leave off the covering in order to be able to see the ground immediately beneath their front wheels. New Features. Morane Landing Gear. Although the regular Bleriot landing gear already described, has many advantages and has been in use with only detail changes for several years, some aviators prefer the landing gear of the new Morane monoplane, which in other respects closely resembles the Bleriot. This gear, Fig. 35, is an adaptation of that long in use on the Henri Farrnan and Sommer biplanes, combining skids and wheels with rubber-band springs. In case a wheel or spring breaks, whether due to a defect or to a rough landing, the skids often save an upset. Besides, the BUILDING AND FLYING AN AEROPLANE 85 tension of the springs is usually such that on a rough landing the wheels jump up and allow the skids to take the shock; this also prevents the excessive rebound of the Bleriot springs under similar conditions. Another advantage which may have some weight with the amateur builder, is that the Morane running gear is much cheaper and easier to construct. Instead of the two heavy tubes, the four forks of oval tubing, and the many slides, collars, and blocks most of them special forgings or castings—the Morane gear simply requires two short laminated skids, four ash struts, and some sheet steel. The laminated skids are built up of three boards each of §- by 2-inch ash, 3| feet long. These must be glued under heavy pressure in forms giving the proper curve at the front end. When they are taken from the press, three or four J-inch holes should be bored at equal distances along the center line and wood pins driven in; these help in retaining the curve. The finished size of the skids should be If by If inches. Four ash struts li by 2\ inches support the fuselage. They are rounded off to an oval shape except at the ends, where they are attached to the skids and the fuselage beams with clamps of R-inch sheet steel. The ends of the struts must be beveled off carefully to make a good fit; they spread out 15 degrees from the vertical, and the rear pair have a backward slant of oO degrees from vertical. Additional fuselage struts must be provided at the front end of the fuselage to take the place of the struts and beams of the Bleriot running gear. The two vertical struts at the extreme fiont end ma\ be of the same li- by 2|-inch ash used in the running gear, planed down to 1R inches thick to match the thickness of the fuselage beams. The horizontal struts should be 1R by 1^ inches. The wheels run on the ends of an axle tube, and usually have plain bearings. The standard size bore of the hub is R inch, and the axle tube should be R inch diameter by 11 gauge. The tube also has loosely mounted on it two spools to carry the rubber band springs. These are made of 2i~inch lengths of lf-inch tubing, with walls of sufficient thickness to make an easy sliding fit on the axle tube. To the ends of each length of tube are brazed 2j-inch washers of R-ineli steel, completing the spool. 86 BUILDING AND FLYING AN AEROPLANE The ends of the rubber bands are carried on rollers of f-inch, % 16-gauge tubing, fastened to the skids by fittings bent up from i^-inch sheet steel. Each fitting is bolted to the skid with two |-ineh bolts. Some arrangement must now be made to keep the axle centered under the machine, as the rubber bands will not take any sidewise strain. A clamp of heavy sheet steel should be made to fit over the axle at its center, and from this heavy wires or cables run to the bottom ends of the forward struts. These wires may be provided with stiff coil springs, if it is desired to allow a little sidewise move¬ ment. New Bleriot Inverse Curve Tail. Some of the latest Bleriot machines have a new tail which seems to add considerable to their speed. It consists of a fixed tail, Fig. 36, nearly as large as the old-style tail and elevators combined, with two elevator flaps hinged to its rear edge. The peculiarity of these elevators, from which the tail gets its name, is that the curve is concave above and convex below—at first glance seeming to have been attached upside down. In this construction, the 1-inch, 20-gauge tube, which formerly passed through the center of the tail, now runs along the rear edge, being held on by strips of J- by r^-inch steel bent into u-shape and fastened with screws or bolts to the ribs. Similar strips attach the elevators to the tube, but these strips are bolted to the tube. BUILDING AND FLYING AN AEROPLANE 87 The construction is otherwise like that previously described. It is said that fitting this tail to a Bleriot in place of the old-style tail • adds 5 miles an hour to the speed, without any other changes being made. Another slight change which distinguishes the newer Bleriots is in the overhead frame, which now consists of a single inverted V instead of two V’s connected by a horizontal tube. The single V is set slightly back of the main wing beam, and is higher and, of course, of heavier tubing than in the previous construction. Its top should stand 2 feet G inches above the fuselage, and the tubing should be 1 inch 18 gauge. It also requires four truss wires, two running to the front end of the fuselage and two to the struts to which the rear wing beams are attached. All of the wires on the upper side of the wings converge to one point at the top of this V, the wires from the wing beams, of course, passing over pulleys. These variations from the form already described may be of interest to those who wish to have their machines up-to-date in every detail, but they are by no means essential. Hundreds of the old-style Bleriots are flying every day and giving perfect satisfaction. ART OF FLYING Knowledge of the science of aeronautics and ability to fly are two totally different things. Long-continued study of the problem from its scientific side enabled the Wright Brothers to learn how to build a machine that would fly, but it did not teach them how to fly with it. That came as the result of persistent attempts at flying itself. A study of the theoretic laws of balancing does not form a good foundation for learning how to ride a bicycle—practice with the actual machine is the only road to success. The best evi¬ dence of this is to be found in the fact that several of the most suc¬ cessful aviators today have but a slight knowledge of the science of aeronautics. They are not particularly well versed in what makes flight possible, but they know how to fly because they have learned it in actual practice. Reference to the early work of the Wright Brothers shows that during a period of several years they spent a large part of their time in actual experiments in the air, and it was not until these had proved 88 BUILDING AND FLYING AN AEROPLANE entirely satisfactory that they attempted to build a power-driven machine. Methods Used in Aviation Schools. Aviation schools are spring¬ ing up all over this country and there are a number of well-established Fig. 37. Monoplane Dummy Used for Practice in Aviation Schools institutions of this kind abroad. 'In the course of instruction, the student must first learn the use of the various controls on a dummy machine. In the case of an English school, this dummy, Fig. 37, is a motorless aeroplane mounted on a universally-jointed support so F : g. 38. Aerocycle with Treadle Power for Practice Work as to swing about a pivot as desired. This is employed for the pur¬ pose of familiarizing the beginner with the means of maintaining equilibrium in the air. BUILDING AND FLYING AN AEROPLANE 89 A French school, on the other hand, employs a wingless machine, which is otherwise complete, as it consists of a regulation chassis with motor and propeller, all steering and elevating controls. On this, the student may practice what has come to be familiarly known as “grass-cutting,” to his heart’s content, without any danger of the machine taking to the air unexpectedly, as has frequently been the case where first attempts have been made on a full-fledged machine. Usually, most of such attempts result disastrously, often destroying in a moment the result of months of work in building the machine. Fig. 39. Voisin Biplane with Double Control for Teaching Beginners A French aerocycle, Fig. 38, a comparatively inexpensive machine, is also useful for practice in balancing and in short, low flights, the French apparatus in question may accordingly be considered an advance, not only over the English machine, even of the type shown in Fig. 39, which has a double control, and is especially designed for the teaching of beginners, but very much over the practice of attempt¬ ing to actually fly for the first time in a strange machine, as it pro¬ vides the necessary practice in the handling of the motor and the lateral steering. The machine can miake high speed over the ground, 90 BUILDING AND FLYING AN AEROPLANE but is perfectly safe for the beginner, as it is incapable of rising. Hav¬ ing gone through the stages represented by either of these con¬ trivances, the best course for the learner to follow is to try gliding, taking short glides to attain the ability to quickly meet varying con¬ ditions of the atmosphere. The fact that these glides are of extremely short duration at first need not be discouraging when it is recalled that, after several years of work, the Wright Brothers considered that great progress had been made when, in 1902, they were able to make glides of 26 seconds. During six days of the practice season of that year, they made 375 gliding flights of various distances, most of them comparatively short, but each one of value in familiarizing the glider with the con¬ ditions to be met. It is not material whether gliding or manipulation of the control levers is taken up first, as both should be mastered as far as possible before attempting to fly a regular machine. Use of the Elevating Plane. So many things are necessary to the control of an aeroplane that thinking becomes entirely too slow a process—the aviator must be endowed with something approaching the instinct of the bird; he must be so familiar with his machine and its peculiarities that a large part of the work of controlling it is the result of subconscious movement. The control levers of many machines are so arranged that this subconscious movement on the part of the aviator directly operates the balancing mechanism. There is no time to think. When a machine rises from the ground, facing the wind as it should, its path of flight should be a gradual upward inclination, this being something difficult to accomplish at first, owing to the sensitiveness of the elevating rudder, the tendency almost invariably being to give the latter too great an angle of incidence. At this stage, the maximum velocity of flight has not yet been attained and care must be taken to keep the angle of ascent small. Otherwise, the power of the engine, which may not have reached its maximum, would not be sufficient to cause the machine to ascend an inclined path at the starting speed. If the speed of flight be reduced by the increased resistance at this point, the whole machine will slide back in the air, and if a sudden gust of wind happens to coincide with the attempt to rise at too great an angle, there is danger of it being blown over backward. Where the machine is just leaving the ground and the elevator BUILDING AND FLYING AN AEROPLANE 91 has been set at an excessive angle, the rear end of the skids or the tail may slap the ground hard and break off, or they will impose so much resistance upon its movement by scraping over the turf that the machine can not attain its soaring speed. It must be borne in mind, of course, that remarks such as the present can be only of the most general nature, every type of machine having its own peculiar¬ ities—in some instances, the extreme opposite of those characterizing similar machines. For example, in the Voisin 1910 type, the very large and powerful light tail tends to lift before the main planes, and if this be not counteracted, the whole machine may turn up on its end. In order to offset this tendency, the elevator must be raised so as to keep sufficient pressure beneath it; the moment of this pres¬ sure about the center of gravity must be at least equal to the pressure under the tail planes about the center of gravity of the machine, or the tail will rise unduly in the air. At least that is the theory of it naturally, only practice with that particular machine would suffice to enable an aviator to familiarize himself with that particular peculiarity. Again, some machines are “tail heavy.” But there is great difficulty in even approximating the degree of relative motion, for which reason it has been suggested, under Accidents and Iheii Lessons,” that a gradometer, or small spirit level, in plain sight of the aviator, should form part of the equipment of every machine. The Wrights long ago adopted the expedient of attaching a strip of ribbon to the elevator to provide an indication of motion relative to the wind. Aeroplane in Flight. The sensation of motion after the machine leaves the ground is almost imperceptible, and it is likewise extremely difficult to tell at just what moment the aeroplane ceases running on the solid ground and takes to the air. 4 here is a feeling of exhilara¬ tion but very little of motion. Whereas 40 miles an hour over the ground, particularly in an automobile, brings with it a lively appre¬ ciation of the speed of travel, the same speed in an aeroplane is a very gentle motion when high above the ground. If there be no objects close at hand, with which to compare the speed, the sense of motion is almost entirely lost. Center of Gravity. The static balance of a machine should be carefully tried before commencing to fly, and particularly that of a biplane of the Wright type, in which the aviator sits beside the engine. 92 BUILDING AND FLYING AN AEROPLANE When provision is made for carrying a passenger, his seat is placed in the center line of the machine, so that his presence or absence does not materially affect the question of lateral balance. As men are not all of the same weight, in cases in which the aviator only partly balances the engine about the center line, his weight being insufficient for the purpose, extra weights should be placed on the wing tip at the lightest end until the true balance is secured, other¬ wise a permanent warping, or gauchissement as the French term it, is required at this side in order to keep the machine on an even keel. In other words, the machine will carry what sailors term a port helm where the left side of the machine is lighter than the right, and vice versa, and it will be necessary to keep the rudder over to that side slightly during the entire flight to counteract this tendency. In aeroplanes fitted with tails, the center of gravity is usually in the vicinity of the trailing edge of the main planes and, of course, should be on the center line of the machine. The center of gravity of the aviator on a monoplane should approximately coincide with that of the machine. If this be not the case, the stabilizers or the elevator must be permanently set to produce longitudinal balance. Much downward set, or the increase of the angle of incidence of the tail, will create undue resistance to flight and should be avoided when possible by bringing the weight farther forward. The center of pres¬ sure should coincide with the center of gravity, and balance will result. Before even ground work is attempted, the position of the center of gravity should be determined in the manner shown in Fig. 40, the approximate location for four types of machines being shown. At what point the machine must be suspended, so that it can tip only frontward and backward and be evenly balanced, is a question that must be answered in order to ascertain the probability of the machine’s pitching forward whenever mud, grass, or rough ground is encoun¬ tered in alighting. If the center of gravity should lie in front of the axles of the ground wheels in a machine of the Farman type, trouble is sure to follow. Always consider the relation of the center of gravity to the wheels, in order that you may gain some idea of the distribu¬ tion of the weight on the running gear when the machine is tipped forward 10 degrees. If the wheels are not forward far enough there will be trouble in running on the ground. The elevators must correct BUILDING AND FLYING AN AEROPLANE 93 whatever variance there may be from the correct center of gravity and position of the wheels, and the manipulation of the elevators for that purpose requires skill. If the tail be very heavy, the elevator may not be able to counteract that defect. The position of the center of gravity of a machine in regard to lateral stability in flight is a matter of far greater importance than untried aviators realize. Having it too low is quite as bad as too high, as in either case there is a tendency to upset. Although the dihedral angle is considered wasteful of power, it seems to do more to secure inherent stability than any other device. Devices for maintaining stability automatically are to be frowned upon in the present state of the art. The sensitive perception and quick response which come with intimate knowledge of a machine’s peculiarities, are at present worth more than gyroscopes and pendulums. To acquire this intimate knowledge, the aviator must familiarize himself thoroughly with the machine; he must become so accustomed to controls that he and the machine are literally one. A practiced bicycle rider does not have to think about balance, neither does the practiced aviator, yet he must always be prepared to meet motor stoppages, unusual air disturbances, and breakages. A leap from the ground directly into the air, without preliminary practice, means certain accident, to put it mildly. 94 BUILDING AND FLYING AN AEROPLANE Center of Pressure. But although the center of gravity remains approximately constant, the center of pressure is continually vary¬ ing and is never constant for many seconds. The center of pressure on an aerocurve constructed to Phillips’ design, Fig. 41, is about one-third of the chord from the leading edge of the plane under normal conditions, i. e., when the angle of incidence is about 8 degrees between the direction of motion of the plane and that of the air. At the moment this angle is increased the center of pressure moves toward the rear, and vice versa. The center of gravity must be moved to coincide with this new position, or the center of pressure must be artificially restored by the use of supplementary planes or elevators, moving in a contrary direction. A forward movement of the center of pressure tends to lower the tail of the machine, when the intensity of the pressure is unchanged, and to counterbalance this the rear elevator must have its angle of incidence increased in order to increase the lift at the rear of the machine, or it will slide down backward. The alternative to be adopted in case of temporary lack of engine power is to decrease the angle of the elevator and allow the aeroplane to sweep downward, thus gaining momentum. The increase of speed will then be sufficient probably to enable the machine to con¬ tinue in a horizontal flight, when the center of pressure is again restored to its normal position. Ground Practice. First of all, the aviator should familiarize himself with his seat for it is from that place that he must judge wind effects, vibration, motor trouble, and the thousand and one little creaks and hums that will ultimately mean so much to him. Not until he has thoroughly accustomed himself to his seat, should he try to run along the ground. This done, hours should be spent running up and down and around the field to learn the use of the rudder, particularly on rough ground. The runs should be straight so that when the time comes to leap into the air, the aviator may be sure that he is on an even keel, and flying straightaway. In order to prevent the possibility of leaving the ground unexpectedly in practice, trials should be made only in calm weather and with the motor well throttled down so that the machine will be reduced to a Fig. 41. Aerocurve of Phillip’s Design BUILDING AND FLYING AN AEROPLANE 95 speed of not more than 15 miles per hour. After a time this may be increased to 20, but the latter is the maximum for ground practice, as the machine will rise at speeds slightly exceeding this. In these practice runs on the ground, the student should learn to gauge the rush of air against his face, as when aloft his best gauge will be the wind pressure on his cheeks, as that will tell him whether he is mov¬ ing with sufficient speed to keep up or not. It will also tell him ulti¬ mately whether he is moving along the ground fast enough to leap up. In this stage of experimenting on the ground, the elevator is kept neutral as far as possible. With increasing skill its use may be ventured, but only sparingly, for it takes very little to lift the machine from the ground with a speed in excess of 20 miles per hour. It will soon be discovered that the elevator can be used as a brake to pre¬ vent pitching forward. The tail elevators on the Farman or Bleriot running gear are very effective owing to the blast of the propeller, even when the main planes are not moving forward at lifting speed. With the Curtiss type of running gear and a front elevator only, it is often possible at 18 to 20 miles per hour to raise the front wheel off the ground for a second or two—facts which indicate that at 25 to 28 miles per hour, the elevator is far more effective. First Flight. The first actual flight should be confined to a short trip parallel to the ground and not more than one or two feet above it. At first, the student should see how close he can fly to the ground without actually touching it,- which he can do by gradually increas¬ ing his forward speed. This must be done in an absolute calm as an appreciable amount of wind will bring in too many other factors for the student to master at so early a stage. This practice should be continued in calm air until short, straight flights can be made a foot or two from the ground with the motor wide open. If it be found that the machine barely flies straightaway with the full power of the motor, the latter is either badly out of adjustment, or a more power¬ ful engine is required. In an under-powered machine turning would be suicidal. Moreover, the resistance encountered in the air is greater than on the ground and may be such that the speed is not sufficient for sustentation. Fig. 42, (a) and (b), show why it is possible to run along the ground faster than it is possible to travel in the air, under certain conditions, and why the ground can be left at low speed. If it were possible to drive a machine with such enormous 96 BUILDING AND FLYING AN AEROPLANE projected areas as BB, shown in Fig. 42 (b), a man could fly slowly for an indefinite period/ But the projected area is greater than the air displaced by the propeller, and it is impossible to fly except with a moderate angle of incidence, giving projected areas A A, Fig. 42 (a). The student, as he increases in skill, may venture to a height of 10 feet, which should be maintained as accurately as before, and after making a run of 100 yards, the machine should be pointed down, but ever so.slightly. The wind pressure on the face immediately becomes greater. Within a foot or two of the ground the motor should be cut oft* or throttled. This should be tried ten or fifteen times, and the height increased to 30 or 40 feet, in order that the student may familiarize himself with the sensation of coasting. At the end of each glide the machine will seem to become more responsive, as indeed it does, for gliding down greatly increases the efficiency of the elevator and other controls, because of the increased speed. Gliding down steep angles is often the aviator’s salvation in a tight place, particularly when the motor fails, a side gust threatens, or an air pocket is encountered. Warping the Wings. When sufficient confidence has been attained at a height of 30 to 40 feet, the ailerons or warping devices may be tried judiciously. Here the intention should be to correct any tendency to side tipping, and not purposely to incline the machine as far as possible without actually causing a wreck. The use of the lateral control may cause the machine to swerve a little, but that may be ignored. Before landing, a straight course should be taken so that the machine will always come down on an. even keel. With increasing practice, the student may fly higher, but always with the understanding that there is a limit to the angle of incidence. An automobile is retarded when it strikes a short, steep hill; so is an aeroplane. No aeroplane has yet been built that can take a steep angle and climb right up that grade continuously. Altitude is BUILDING AND FLYING AN AEROPLANE 97 reached by a series of small steps and at comparatively low angles, as unless the course is straightened out at regular intervals, a machine will lose its speed and tend to plunge tail first, just as is the case when an attempt is made to rise from the ground at too sharp an angle. In warping the wings an increase of lift imparted to one wing of the machine is produced by increasing the angle of incidence of the whole or part of the wing, or by an increase of pressure under that wing, and will tend to cause that side of the machine to rise and the other side to lower, the result being that the machine will be liable to slide through the air diagonally. In the majority of aeroplanes there are no fins or keels to counteract this movement, and lateral stability must be restored by artificially increasing the lift of the depressed wing. This can be done by warping, or lowering the trailing edge of the depressed wing and increasing its lift, and simultaneously raising the trailing edge of the other wing, thus decreasing the angle of incidence of the latter and reducing its lifting effect. This applies to flight on a straight course, whatever the cause may be that tends to upset lateral stability. It will be seen, there¬ fore, that the center of gravity remains constant and the center of pressure must be manipulated to restore stability. This manipula¬ tion is much more rapid and positive than the alteration of the center of gravity by the movement of the aviator’s body resorted to in the early gliding flights of pioneer experimenters. Making a Turn. The first turn should be made over a large field and the diameter of the turn should be at least half a mile. The height should be not less than 50 feet. After that le\el has been maintained, the rudder should be moved very gingerly. The machine will lean in almost immediately, because the outer end travels at a higher speed than the inner and therefore has a greater lift. Warping or working the ailerons should be resorted to as a means of counter¬ acting this tendency, and the rudder swung to the opposite direc¬ tion, if necessary. It is obvious that if the rudder will cause the machine to bank when swung in one direction, it will right the machine again when swung in the opposite direction. It is even possible to turn the machine on an even keel by anticipating the banking, simply by correctly using the rudder, which was necessary in the old Yoisin machine flown by Farman in 1908, because it had no mechanical lateral control. The student should learn the correct angle of bank- 98 BUILDING AND FLYING AN AEROPLANE ing, i. e., the angle at which the machine will neither skid nor slide down and which is most economical of power because it requires less use of the lateral controls. The necessity of “feeling the air” is greater in turning than in any other phase of flying. By “feeling the air” is meant the ability to meet any contingency intuitively and not until this is acquired can the student become an expert aviator. When it has been acquired, safe flying is assured and is dependent only upon the integrity of the planes, motor, and controls. By using the rudder discreetly and by banking simply far enough to partially offset the centrifugal force of turning, the use of the lateral control will not be necessary in still air. Even too short a turn can be corrected by a quick use of the rudder. The peculiarities existing between different types of mono¬ planes become even more marked than between the biplane and the monoplane. For example, in piloting a Bleriot monoplane, Fig. 43, it is necessary to take into account the effect of the engine torque. As the engine rotates in a right-hand direction, from the point of view of the pilot, the left wing tends to rise in the air, owing to the depression of the right side of the machine. The machine also tends to turn to the right, and this must be counteracted by putting the rudder over to the left. An aeroplane answers its controls with com¬ parative slowness, with the exception, perhaps, of the Wright machine, which is noted for its sensitive and quick response to every move¬ ment of the levers. All control movements must, therefore, be very gentle, as the behavior of an aeroplane is more like that of a boat than that of an automobile. The action of the elevator has already been described, and it is, perhaps, the most difficult of all the con¬ trols to manipulate, in that it requires the exercise of a new sense. The direction rudder is naturally a more familiar type of control, and in action is similar to the rudder of a boat. The torque of the motor renders it advisable for a novice to turn his machine to the right, if a right-hand propeller be used, and vice versa. If two propellers, turning in opposite directions, are employed, as in the Wright biplane, there is no inequality from the torque of the motor. Since torque is not noticeable in straight fly¬ ing, straightening out again will always serve the student when he finds himself in trouble on a turn. When the use of the rudders and ailerons has reduced the speed, a downward glide will increase BUILDING AND FLYING AN AEROPLANE 99 Fig. 43. Making a Start with Bleriot Monoplane 100 BUILDING AND FLYING AN AEROPLANE it again, and if the motor should stop on a turn, such a downward glide is immediately imperative. When the machine is thus gliding, a change in the fore-and-aft balance becomes at once apparent, because the blast of the propeller no longer acts on the tail, and the elevator must then be used with greater amplitude to obtain the same effect. Only by constant practice in calm air can the student familiarize himself with exactly the amount of warping and rudder control to employ to properly offset the lowering of the inner wing in rounding a turn. If this be not corrected, the whole machine tends to bank excessively and will be apt to slide downward in a diagonal direc¬ tion, Fig. 44. This is a perilous position for the aviator and must be guarded against by the manipulation of the warping control so as to increase the lift of the inner wing of a biplane, at the same time, employing the rudder to counteract this tendency. The use of the rudder is of even greater importance on the monoplane, as, in this case, warping the inner wing tends to direct the whole machine downward instead of raising the inner wing itself. Several bad accidents have resulted from monoplanes refusing to respond to the warping of the inner wing when making a turn. In such machines, the rudder must be practically always employed in connection with the warping of the wings in order to keep the machine on an even keel, although the controls may not actually be interconnected, this being one of the grounds on which foreign manufacturers are trying to make use of the Wright principle, without infringing the Wright patents, as while they employ warping in connection with the simultaneous use of the rudder, the controls are not attached to the same lever as in the Wright machine. Lateral resistance must also be taken into consideration in turning, otherwise the machine, if kept on an even keel, will tend to skid through the air and turn about its center of gravity as a pivot. In the case of an automobile, the resistance to lateral displacement is great, though on a greasy surface it may be small, as when the machine skids sideways, a suitable banking of the road being neces¬ sary to prevent this on turns. Many hold that the banking of the aeroplane'on turns is only the direct effect of the turning itself, but the fallacy of this will be apparent upon a consideration of the law of centrifugal force. It is obvious that to make a turn, some force BUILDING AND FLYING AN AEROPLANE 101 Fig. 44. An Aeroplane “Banking” as it Rounds a Pylon 102 BUILDING AND FLYING AN AEROPLANE must be imparted to the machine to counteract the effect of the cen¬ trifugal force upon the machine as a whole. And as the sidewise projection of the machine is small, a compensating force must be introduced. This can be done only by previously banking up the machine on the outer wing, so that the pressure of the air under the main plane can counteract the tendency to lateral displacement. The force then acting under the planes is in a diagonal direction, and the angle at which it is inclined vertically depends upon the banking of the planes, it being normal to their greater dimension. This force can be resolved into two forces, one perpendicular and one horizontal, the magnitude of each being dependent upon the degree of banking. When the speed of the machine is higher, the amount of banking must be greater in order to increase the value of the hori¬ zontal component in proportion to the increase of the value of the centrifugal force at the higher speed, in spite of the fact that the forces acting under the planes are also greater due to the higher speed. As the curve commences, the rudder being put over, the difference of the pressures on the two wings, owing to their different flying speeds comes into account, as already explained, and care must be taken that the banking does not increase abnormally. When the turn is completed, the rudder is straightened and the machine is again brought to an even keel with the aid of the wing-warping control, or the ailerons. The effect of a reverse warping to prevent excessive banking, lowering the inside wing tip incidentally, puts a slight drag on that wing and assists in the action of turning, as does also the provision of small vertical planes between the elevator planes of the original Wright machine. Since the adoption of the headless type, these surfaces are placed between the forward ends of the skids and the braces leading down to them. In making a turn, say, to the left, the outside or right-hand wing is first raised by lowering the wing tip on that side and the rudder is then put over to the left. When the correct amount of banking is acquired, the wing tip is restored to its normal position, and probably the left wing tip may have to be lowered slightly to increase the lift on that side owing to its reduced speed. When the turn is completed, the rudder is straightened out and the left wing tip lowered to restore the machine to an even keel. Both Glenn BUILDING AND FLYING AN AEROPLANE 103 Curtiss in this country and R. E. Pelterie in France have shown that it is possible to maneuver without using the rudder at all, the ailerons or wing tips alone being relied upon for this purpose. Before flights in other than calm air are attempted, much practice is required. The machine must be inspected over and over again, and the wind variations studied with a watchful e\ e. ^^ot until this familiarity with machine and atmosphere be acquired should flying in a wind be attempted. To the man on the ground, wind is simply air moving horizontally, but to the man in the air it is quite different. Not only must he consider horizontal movement, but vertical draughts and vortices as well. A rising current of air lifts a machine, a downward current depresses it, and he must learn to take advantage of the former as the birds do. Hori¬ zontal currents affect forward speed over the ground; swirls and vortices create inequalities in wind pressure on the planes and disturb lateral balance. Familiarity with all these atmospheric conditions can be acquired only after long practice. Against every tree, house, hill, fence, and hedge beats an invisible surf of air; upward currents on one side and downward on the other. 1 he upward draught is not usually dangerous, for it simply lifts the machine; but the down draught will cause it to drop. A swift downward glide under the full power of the motor must then be made, to increase the forward speed and consequently the lift, dhis explains why it is dangerous to fly near the ground in a wind; likewise why the beginner should never attempt flying at first in anything but a dead calm. Turning in a Wind. When turning in a wind, two velocities must be borne in mind, that of the machine relative to the air and that relative to the earth. The former is limited at its lower value to that of the flying speed of the machine, and the latter must be considered on account of the momentum of the machine as a whole. Change of momentum is a matter of horse-power and weight and is the governing factor in flying in a wind on a circular couise. Sup¬ pose the flying speed of a machine is a minimum of 30 miles an hour relative to the air, and a wind of 20 miles an hour is blowing. The actual speed of the machine relative to the earth in flying against the wind will be 10 miles an hour. If it be desired to turn down th^ wind, the speed of the machine relative to the earth must be increased 104 BUILDING AND FLYING AN AEROPLANE from 10 miles to 50 miles an hour during the turn and a correspond¬ ing change of momentum must be overcome. There are two ways of accomplishing this, either by speeding up the motor to give the maximum power, or by rising just previous to making the turn and then sweeping down as the turn is made, thus utilizing the accelera¬ tion due to gravity to assist the motor. The wind’s velocity will assist the machine also and during the turn it will make considerable leeway, a small amount of which is deducted to counteract the centrifugal force of the machine. Turning in a contrary direction, i. e., up into the wind when running with it, requires considerable skill, as when flying 50 miles an hour, *the tendency on rounding a corner into a 20-mile-an-hour wind would be for the machine to rise rapidly in the air. The centrif¬ ugal force at such a speed is also considerable, causing the machine to make much leeway with the wind during the turn. Turning under such circumstances should be commenced early, particularly if there are any obstructions in the vicinity, and considerable skill should be acquired before an attempt is made to fly in such a wind. Starting and Landing. A machine should always be started and landed in the teeth of the wind, and no one but the most experi¬ enced aviators can afford to disregard this advice, certainly not the novice. The precaution is necessary because in landing the machine should always travel straight ahead without the possibility of lurch¬ ing and consequently breaking a wing, as frequently happens. Contact with the ground is necessarily made at a time when the machine is traveling over it at a speed of 30 to 40 miles per hour and skidding sideways at 10 to 15 miles per hour, all circumstances which tend to wreck an aferoplane. Planning a Flight. It is easy to lose one’s way in the air. For that reason it is best to follow the Wright idea of starting out with a definite plan, and of landing in some predetermined spot, as aimless wandering about may prove disastrous to the inexperienced aviator, lie may forget which way the wind was blowing, or how much fuel he had, or the character of the ground beneath him. Should the motor stop, he may make an all too hasty decision in landing. It is an easy matter to lose one’s bearings in the air, not only because Uie vehicle is completely immersed in the medium in which it is traveling, but also because the earth assumes a new aspect from the BUILDING AND FLYING AN AEROPLANE 105 seat of an aeroplane. Cecil Grace was one of those who lost his bearings and, as a consequence, his life. Ordinary winds blowing over a level country can be negotiated with comparative safety. Not so the puffy wind. To cope with that, constant vigilance is required, particularly in turning. In a circular flight in a steady wind, the only apparent effect is that the earth is swept over faster in one direction than in the other. Before a cross-country flight is attempted, the starting field should be circled over at a great height, as not until then may the long distance flight be started in safety. Cross-country flying is, of course, fascinating, and it is a sore temptation, at an altitude of a few hundred feet, to throw off all caution and flv off over that strange country below, which is, indeed, a new land as viewed from aloft. To quote a professional aviator: ‘TIere the greatest self-restraint must be exercised. Not until the necessary practice has been acquired, not until the right kind of confidence has been gained, may one of these trips be attempted, and then only after it has been properly planned.” Training the Professional Aviator. Look back over the achieve¬ ments in the air during the comparatively short time that man has actually been flying, and it will be noted that the beginners, burning up with the enthusiasm of the novice, have performed the most spectacular feats and flown with the greatest fearlessness. Curtiss was comparatively new at aviation when he won the Gordon-Bennett at Rheims in 1909. John B. Moisant, the sixth time he ever went up in an aeroplane, flew from Paris to London with a 187-pound passenger and'302 pounds of fuel, oil, and spare parts. Hamilton made his successful flight from New \ ork to Philadelphia and return when he was hardly more than a novice, while Atwood’s great flights from St. Louis to New York and Boston to Washington were made before his name had become known, and Beachey had been flying only a few months when he broke the world’s altitude record at Chicago, while more recent achievements, notably Dixon’s flight across the Rockies, have emphasized the work of the beginner. All of this substantiates the belief held at every aviation headquarters in the country—namely, that the older men already in aviation may improve the art by executive ability and scientific experiments, but most of them will degenerate as flyers. Beyond a certain point, frequency of flight does not necessarily create a feeling of confidence 106 BUILDING AND FLYING AN AEROPLANE and safety; rather it brings a fuller appreciation of the dangers, and the men who best know how to fly are most content to stay upon the ground. Professional aviators are drawn from every walk of life, but trick bicycle performers, acrobats, parachute jumpers, and racing automobile drivers make the most promising applicants. By a kind of sixth sense, both the Wrights and Curtiss weed out the promising ones after a brief examination. They select men who have an almost intuitive sense of balance. Most of these, provided they have nerve, have in them the stuff of which aviators are made, even though they may have had no experience in any line akin to aviation. Neither Curtiss nor the Wrights will accept women under any condition. The Moisant school does not share this discrimination and trained three women for pilot’s licenses during 1911. Curtiss and the Wrights are keen in their realization that recklessness is pulling a wing feather from aviation every time a man is killed, and they are doing their utmost to promote conservatism. Curtiss said in an interview: I do not encourage and never have encouraged fancy flying. I regard the spectacular gyrations of several aviators I know as foolhardy and unneces¬ sary. I do not believe that fancy or trick flying demonstrates anything except an unlimited amount of a certain kind of nerve and perhaps the possibilities of what is valueless—aerial acrobatics. Some aviators develop the sense of balance very rapidly, while others acquire it only after long practice. It may be developed to a large extent by going up as a passenger with an experienced man. Therefore, in teaching a beginner, I make it a point to have him make as many trips as possible with someone else operating the machine. In this way the pupil gains confidence, becomes accustomed to the sensation of flying, and is soon ready for a flight on his own hook. This is the method used in train¬ ing army and navy officers to fly. I have never seen novices more cautious and yet more eager to fly than these young officers. They have always learned every detail of their machines before going aloft, and largely because of this they have developed into great flyers. Perhaps it is due to the military bent of their minds; at any rate, they have made good almost without exception. ACCIDENTS AND THEIR LESSONS Press Reports. Whenever an industry, profession, or what not, is prominently before the public, every event connected with it is regarded as “good copy” by the daily press. Happenings of so insignificant a nature that in any commonplace calling would not be considered worthy of mention at all, are “played up.” This is BUILDING AND FLYING AN AEROPLANE 107 particularly the case with fatalities, and the eagerness to cater to the morbid streak in human nature’ has been responsible for the unusual amount of attention devoted to any or all accidents to flying machines, and more especially where they have a fatal ending. In fact, this has led to the chronicling of many deaths in the field of aviation that have not happened—some of them where there was not even an accident of any kind. For instance, in many of the casualty lists published abroad from time to time, such flyers as Hamilton, Brook¬ ins, and others have figured among those who have been killed, ever since the date of mishaps that they had months ago. It will be recalled that five years ago, when the automobile began to assume a very prominent position, every fatality for which it was responsible was heralded broadcast where deaths caused by other vehicles would not be accorded more than local notice. To a large extent, this is still true and will probably continue to be the case until the automobile assumes a role in our daily existence as commonplace as the horse-drawn wagon and trolley car. There is undoubtedly ample justification for this and particularly for the editorial comment always accompanying it, where the number of lives sacrificed to what can be regarded only as criminal recklessness is concerned. Still, the fact that in a city like New \ork the tiuek and the trolley car are responsible for an annual death roll more than twice as large as that caused by the automobile, does not call for any particular mention. Horses and wagons, we have always had with us, and the trolley car long since became too commonplace an institution around which to build a sensation. As the most novel and recent of man’s accomplishments, the conquest of the air and everything pertaining to it is a subject on which the public is exceedingly keen for news and nothing appears to be of too trivial import to merit space. Where an aviator of any prominence is injured, or succumbs to an accident, the event is accorded an amount of attention little short of that given the death of some one prominent in official life. During the four years that aviation has been to the fore, about 104 men and one woman have been killed, not including the deaths of three or four spectators resulting from accidents to aeroplanes, during this period i. e., from the beginning of 1908 to the end of 1911. In view of the lack of corroboration in some cases, the figures are made thus indefinite. 108 BUILDING AND FLYING AN AEROPLANE Naturally most of these deaths have occurred in 1910 and 1911— in fact, 50 per cent took place from 1908 to the end of 1910, and the remainder during 1911, since these years were responsible for a far greater development, and particularly for a greater increase in the number engaged, than ever before. More was accomplished in these two years than in the entire period intervening between that^ day in December, 1903, when the Wright Brothers first succeeded in leaving the ground in a power-driven machine, and the beginning of 1910. Fatal Accidents. Conceding that the maximum number men¬ tioned, 105, were killed during the four years in question, throughout the world, it will doubtless come as a surprise to many to learn that this is probably not quite twice the number who have suc¬ cumbed to football accidents during the same time in the United States alone. Authentic statistics place the number thus killed at 13 during 1908, 23 in 1909, 14 during 1910, and 17 in 1911, or a total of 67. But we have been playing football for a couple of centuries or more and this is regarded as a matter of course. The death of a football player occurring in some small, out-of-the-way place would not receive more than local attention, unless there were other reasons for giving it prominence, so that, in all probability, the statistics in question fall far short of the truth, rather than otherwise. The object of mentioning this phase of the matter is to place the question of accidents in its true light. That the development of any new art is bound to be attended by numerous mishaps, many of them fatal, goes without saying and it is something that can not be ignored. Nothing could be worse than attempting to gloss over or belittle the loss of life for which aviation has been responsible and doubtless will continue to be. Progress invariably takes its toll and it is more often founded upon failure than unvarying success, for every accident is a failure, in a sense, and every accident carries with it its own lesson. Where the cause is apparent, it gives an indication of the remedy which will bring about the prevention of its recurrence. In other words, it serves to point out weaknesses and shows what is necessary to overcome them. For that reason alone is the question of accidents taken up here, as a study of those that have occurred points the way to improvement. Table III gives a resume of the more impor- Fatal Aeroplane Accidents ?-< o S3 a> bfi TP 0 44 02 0 02 02 S3 02 • pH f-i 02 33 X 02 S3 • -H 43 bfi 0 O 4h O 0 • pH > c3 02 -t-3 ~ a 33 02 43 S3 O S3 o • H +- 1 3 o o co 0) a o co 0 co 02 J-i 02 43 Sh o O S-H S3 O o to co O 0^0) £43 si +■’ 33 1 <*h 02 bC° 33 33 ^ 3 T5 to co 44 oj (3 fe u <3 34 p s3 S?43 *= « O f-. 43 -4> <3 — O Jh 0) 2 O 43 ^ . H 02 4 J S ^ ffl O '<12 -42 o <3 -+J . cP 0 f-> £ 0 33 O 02 co co O Jh ^ 0 0 &i -■. t—i 5} JT 0 'S-£3‘ ■+j o3‘> 33 h ^ O aj -g* 3 cP > ••-H +J --H (jl) S3"C 042 o 3 • -H co S3 02 > • pH bfi 02 H 0 >> 02 43 c3 •<-• '0 02 | a co « a'TP 02 S3 S O TP co a; cP 02 co >> 3 33 0 0 02 .2 b +-> cP Sh a S3 8.8 S3 a 0 0 ^ bfi^ 02 02 *-i 02 £ 02 H 02 (O 43 op all f -4- 5 p^3 T5 ^ >3 ^ ° co 33 0 ^ 0 oj 02 on 33 ^ 3S „ *“ H 33 5-2 F-2* CO'-fJ 02 co CO 32 Cp 02 ,Q “ o co +-> 33 02 CO 02 5-i 5-H 33 ^43 • .-I cp T 1 02 > 33 s-. 02 02 33 O 02 33:33 02 c3 fH 3 ! "co co $ & > o 02 cp 02 bfi.2 “ 33 -(J 0/4 ; ’~~1 H (7^ 02 T3 8 - s - 02 32 ^ X=3 -T3 m 02 O •?"! o 02 Cj 3Q U Q no BUILDING AND FLYING AN AEROPLANE tant fatalities that have resulted from the use of a heavier-than-air machine during the past four years: Fatalities greatly increased in number during 1911, but not out of proportion to the greatly augmented number of aviators. With comparatively few exceptions, however, the accidents were more or less similar in their nature to those already tabulated, so that it would be of no particular value to extend the comparison in this manner to cover them. Many of the fatalities during that year were not of the aviators themselves, but of the spectators, a fact which calls attention to a danger that has not been fully appreciated before. At the start of the Paris-Madrid race, the French minister of war and another official were killed by a monoplane plunging into the crowd, and on the same day, May 21, 1911, five people were killed at Odessa, Russia, in the same manner. An unusual type of mishap, not mentioned in the tabulation and in which three or four aviators lost their lives during 1911, was the burning of the aeroplane in midair, or the explosion of the gasoline, setting fire to the wings and either burning the aviator at his post or killing him by the fall. One such accident occurred in France in September, another in Spain two days later, and a third in Germany, in which two men were killed. Accidents of an even more unusual nature were the collision of two biplanes in midair at St. Petersburg, the collision of a motorcycle with a biplane as it swooped down on a race track, and the partial wrecking of Fowler’s biplane by a bull upon landing near Fort Worth, Texas, but these, of course, had no bearing on the design of the machines. Apart from those specially referred to, the great majority of accidents during 1911 may be ascribed to two or three of the causes detailed in connection with the comparative table. Of these? lack of experience and foolhardiness stand out prominently, the latter un¬ doubtedly causing the double fatality at Chicago when two aero¬ planes plunged into Lake Michigan, drowning one of the aviators, while a third machine collapsed in mid-air, hurling the aviator to his death on the field. Careful reading of the reports of a large number of these accidents usually brings to light the statement “in attempting to make a quick turn,” or similar phrase, showing that the moving cause of the accident was due to subjecting the parts of the machine to excessive stresses, as outlined in the following pages. BUILDING AND FLYING AN AEROPLANE 111 Causes. Lack of Experience. It will be at once noticeable bv Table III that out of a total of 28, no less than 16, or considerably more than half of the accidents, were due in one way or another to lack of experience. In other words, the aviators had not fully com¬ plied with the cardinal principle for success in flying upon which the Wright Brothers have always laid so much stress, i. e., you must first learn to fly before you can attempt to go aloft safely. Nothing short of a thorough mastery of the machine can suffice to give the aviator the ability to do the right thing at the right moment, in the great majority of cases. There will always be occasions when even the most skilled aviator will make errors of judgment and frequently they cost him his life. But this is equally true of every dangerous calling, whether it be running an automobile, driving a locomotive, or doing any of the thousand and one things where the responsibility for his own and other lives is placed in one man’s hands and depends to a large extent on his discretion and judgment in cases of emergency, so that there will be fatalities from this cause as long as man con¬ tinues to flv. This involves the personal equation that must always be reckoned with. Just how many of the accidents that have resulted in the fatalities set forth, have been due to the fallibility of the operator and for how much the design of the current types of machines is responsible, would be hard to say. Fig. 45, for example, which shows H. V. Roe in the act of striking the ground in his triplane, illustrates an accident due to bad design. Methods of control will be improved and simplified and made as nearly “fool-proof” as human ingenuity can accomplish, but experience in other fields has demonstrated unmistakably that they can never be developed to a point where it is impossible to do the wrong thing. With skill at such a premium in callings of responsibility which involve only conditions that have been familiar for years, how much more so must it be in the air about which so little is known? Consequently, the real danger is to be found in the personal equation, just as it is in every other mode of conveyance, despite the fact that it has been perfected to a point which apparently admits of little further development where safe¬ guarding it is concerned. Obstructions. Obstructions are bound to play a prominent part in accidents to any method of conveyance, but less so in aviation than in any other, as it is only in rising and alighting that this danger 112 BUILDING AND FLYING AN AEROPLANE Fig. 45. Roe’s Multiplane as it Struck the Ground. An Accident Due to Poor Design BUILDING AND FLYING AN AEROPLANE 113 Fig. 46. DeLesseps’ Machine after Striking an Obstruction 114 BUILDING AND FLYING AN AEROPLANE is present. Of the two fatal accidents ascribed to this cause, one resulted from colliding with an obstruction while running along the ground preparatory to rising, and the other from striking an obstruc¬ tion in flight, Fig. 46. In view of the numerous cross-country flights that have been made, trips across cities and the like, it is to be mar¬ veled at that up to the present writing no fatalities have been caused by what the aviator most dreads when leaving the safety of the open field, that is, being compelled to make a landing through stoppage of the motor, whether from a defection or lack of fuel. While no fatalities have as yet to be put down to this ever-present danger in extended flights, an accident that might have had a fatal termina¬ tion, occurred to Le Blanc during the competition for the Gordon- Fig. 47. Overturned Monoplane Due to a Start in a Gale Bennett trophy, which was the chief event of the International Meet in October, 1910, at Belmont Park, near New A T ork. Le Blanc and his fellow compatriots who were eligible were all experienced cross¬ country flyers, the former having won the Circuit de U Est, a race around France, and by far the most ambitious of its kind which had been attempted up to that time. They accordingly protested most vigorously against flying over the American course to compete for the cup which Curtiss had captured at Rheims the year before, owing to the fact that it presented numerous dangerous obstructions in the form of trees and telegraph poles. But as it was impossible to provide any other convenient five-kilometer circuit (3.11 miles) c.s called for by the conditions, the protest was of no avail. After BUILDING AND FLYING AN AEROPLANE 115 having covered 19 of the 20 laps necessary to complete the distance of 100 kilometers in time that had never been approached before, Le Blanc was compelled to descend through lack of fuel, and as he had not risen more than 80 to 100 feet at any time during the race, this meant coming down the moment the motor stopped. The result was a collision with a telegraph pole, breaking it off and wrecking the mono¬ plane, the aviator fortunately escaping any serious injury. During the same meet Moisant demolished his Bleriot monoplane by trying to start in the face of a high wind, Figs. 47 and 48. Stopping of Motor. The mere fact that the motor stops does not necessarily mean a disastrous ending to a flight, as is very com- Fig. 48. View of Moisant Monoplane after a Bad Spill monly believed, this having been strikingly illustrated by Brookins’ glide to earth from an altitude of 5,000 feet with the motor dead, and Moisant’s glide from an even greater height in France. But it does mean a wreck unless a suitable landing place can be reached with the limited ability to control the machine that the aviator has when he can no longer command its power. Motors will undoubtedly become more and more reliable as development progresses, but the human equation—the partly-filled fuel tank, the loose adjustment that is overlooked before starting, and a hundred and one things of a similar nature—will always play their role, so that compulsory landing in unsuitable places will always constitute a source of danger as flights become more and more extended. 116 BUILDING AND FLYING AN AEROPLANE Breakage of Parts of Aeroplanes. In studying the foregoing table, it can only be a source of satisfaction to the intelligent student and believer in aerial navigation, to note how large a proportion of the accidents is due to the breakage of parts of the machine. This implies a fault in construction, but not in principle. It reveals the fact that, in the attempt to secure lightness, strength has some¬ times been sacrificed, chiefly through lack of appreciation of the stresses to which the machine is subjected in operation. At a time when weight is regarded almost as the paramount factor by so many builders, it is inevitable that some should err by shaving things too fine. Lightness is an absolute necessity and failure to achieve it in every instance without eliminating the factor of safety has been due more to the crude methods of construction and lack of suitable mate¬ rials, than any other cause—conditions that are bound to obtain in the early days of any art. Construction is improving rapidly, but progress is bound to be attended with accidents of this nature. The fact that their proportion is greatly diminishing despite the rapidly increasing number of aviators is the best evidence of what is being accomplished. When machines are built with such a high factor of safety in every part that breakage is an almost unheard-of thing, failures from this cause will have been reduced to an unsurpassable minimum. Failure of the Control Mechanism. Under the general classifica¬ tion B, are included not alone those accidents directly due to break¬ age of some vital part, but also those instances in which some element of the control, such as the elevator, has become inoperative through jamming. When an accident happens in the air, it takes place so quickly and the machine is so totally wrecked by falling to the ground, that it is usually difficult to determine the exact nature of the cause through a subsequent examination of the parts, so that it can seldom be stated with certainty just what the initial defection consisted of, though it may be regarded as a foregone conclusion that, in the case of experienced aviators who have previously demonstrated their ability to cope with all ordinary emergencies, nothing short of the failure of some vital part could have caused their fall. This was the case with Johnstone’s accident at Denver—an occurrence illustrating another phase of the personal equation that must be taken into consideration when noting the lessons to be BUILDING AND FLYING AN AEROPLANE 117 learned from a study of accidents and their causes. It is simply the old, old story of familiarity breeding contempt — the miner thawing out sticks of dynamite before an open fire. Due to the rarefied air of Denver, which is at an elevation of more than 5,000 feet, Johnstone had underestimated the braking powers of the air on the machine in landing the day previous and had crashed into a fence, breaking one of the right outermost struts between the sup¬ porting planes. Proper regard for safety should naturally have called for its replacement by an entirely new strut, but conditions at flying meets as at present conducted make quick repairs to damaged machines imperative. The damaged upright was accordingly glued and braced by placing iron rings around it, the rings themselves being held in place by ordinary nails passing through holes in the iron large enough to let the nail head slip through. The vibration of the motor and the straining of the strut in warping the wings caused the nails to work out of the holes, permitting the rings to slide out of place, as well. Johnstone was an accomplished aviator, much given to the execution of aerial maneuvers only possible to the skilled flyer of quick and ready judgment. But such performances impose excessive stresses on the supporting planes and their braces, and one of John¬ stone’s quick turns caused the repaired struts to collapse through the strain of sharply warping the wing tips on that side. He imme¬ diately attempted to restore the balance of the machine by bringing the left wing down with the control, then tried to force the twisting on the right side, succeeding momentarily, and a few seconds later losing all control and crashing to the ground. It appeared to demon¬ strate that even when disabled an aeroplane is not entirely without support, but has more or less buoyancy—something which is really more of an optical illusion than anything else due to underestimating the speed at which a body falls from any great height. Johnstone’s accident was the first of its kind, in that he fell from a height of about 800 feet, during the first 500 of which he struggled to regain control of the machine, finally dropping the remaining 300 feet apparently as so much dead weight. It showed in a most striking manner the vital importance of the struts connecting the supporting surfaces of the biplane, any damage to them resulting in the crippling of the balancing devices and the end of all aerial support. 118 BUILDING AND FLYING AN AEROPLANE Biplane vs. Monoplane. It requires only a glance at Table III to show that the greater number of accidents have happened to the biplane, yet the latter is generally regarded as the safer of the two. Prior to Delagrange’s fatal fall in January, 1910, there had been only four fatalities with modern flying machines: Selfridge and Lefebre were killed in Wright machines, the latter of French manufacture, Ferber lost control of his Voisin biplane, and Fer¬ nandez was killed flying a biplane of his own design. In one case at least, that of Lieutenant Selfridge, the accident appears to have been due to the failure of a vital part—the propeller. It has since become customary to cover the tips of propellers for at least a foot or so with fabric tightly fitted and varnished so as to become prac¬ tically an integral part of the wood. This prevents splintering as well as avoiding the danger of the laminations succumbing to cen¬ trifugal force and flying apart. At the extremely high speeds, par¬ ticularly at which direct-driven propellers are run, the stress imposed on the outer portion of the blades by this force is tremendous. In making any attempt to compare the number of accidents to the biplane and the monoplane, it must also be borne in mind that the former has been in the majority. Delagrange’s accident offers two special features of technical interest. It was the first fatality to happen with the monoplane and was likewise the first fatal accident which appeared to be dis¬ tinctly due to a failure of the main structure of the machine. For obvious reasons, it is usually difficult to definitely fix the cause of an accident, but in this case there seemed good reason to suppose that the main framing of one of the wings gave way altogether. Curiously enough, Santos-Dumont had an accident the day following from an exactly similar cause, the machine plunging to the ground. But with the good fortune that has attended this experimenter throughout his long aerial career, he was uninjured. It was definitely established that the cause was the fracture of one of the wires taking the upward thrust of the wing. In the case of the biplane, the top and bottom members are both of wood, with wooden struts, the whole being braced with numerous ties of wire. In the monoplane, however, the main spars are trussed to a strut below by a compara¬ tively small number of wires. The structure of each wing is, in fact, very much like the rigging of a sailboat, the main spars taking the BUILDING AND FLYING AN AEROPLANE 119 place of the mast while the wire stays take that of the shrouds, with this very important difference, that the mast of the -boat is provided with a forestay to take the longitudinal pressure when going head to the wind, while the wing of an aeroplane often has no such pro¬ vision, the longitudinal pressure due to air resistance being taken entirely by the spar. It is quite possible that this had something to do with Dela- grange’s accident, as, in the effort to make a new record, his Bleriot had just been fitted with a very much more powerful motor. In fact, double that for which the machine was originally designed, and this was given by the maker as the probable cause of the mishap. As the new motor was of a very light type, the extra weight, if any, was quite a negligible proportion of the total weight of the machine. The vertical stresses on the wings and their supporting wires would, therefore, not be materially increased. But as the more powerful engine drove the wings through the air a great deal faster, the stresses brought upon them by the increased resistance would be substan¬ tially augmented and, unless provision were made for this, the factor of safety would be much reduced. Whether the failure ot the wing was actually from longitudinal stress or the breaking of a support¬ ing wire, as in Santos-Dumont’s case, will never be known, but it 1 o quite clear that the question of ample strength to resist longitudinal stresses should be carefully considered, especially when inci easing the power of an existing machine. The question of the most suitable materials and fastenings for the supporting wires is, moreover, a matter which requires very careful consideration. In the case of the biplane, the wires are so numerous that the failure of one, or even more, may not endanger the whole structure, but those of the monoplane are so few that the breaking of but one may mean the loss of the wing. In this respect, as in others, the conditions are parallel to the mast of the sailboat. It is only reasonable to expect, therefore, that similar mateiials would be best adapted to the purpose. At present, however, the stays of aeroplane wings are almost invariably solid steel wire, or ribbon, while marine shrouds are always ol stranded wire rope, solid wire not having been found satisfactory. Weight foi weight, tin solid wire will stand a greater strain when tried in a testing machine than will the stranded rope, but practice has always demonstrated 120 BUILDING AND FLYING AN AEROPLANE that it is not so reliable. The stranded rope never breaks without warning, and sometimes several of its wires may go before the whole gives way. As the breakage of the strands can be easily seen, it is possible to replace a damaged stay before it becomes unsafe. In the case of a single wire, there is nothing to show whether it has dete¬ riorated or not. It seems a doubtful policy to use in an aeroplane what experience has shown not to be good enough for a boat, and stranded wire cables particularly designed for aeronautic use are now being placed on the market in this country. Record Breaking. Striving after records has undoubtedly proved one of the most prolific causes of accident. What is wanted to make the aeroplane of the greatest practical use is that it should be safe and reliable. The tendency of record-breaking machines is the exact opposite of this, as the weights of all the most essential parts must be cut down to the finest limits possible in order to provide sufficient power and fuel-carrying capacity for the record flight. It is, in fact, generally the case in engineering that the design and materials which will give the best results for a short time are essentially different from those which are the most reliable, and striving after speed records consists simply in disregarding safety and reliability to the greatest extent to which the pilots are willing to risk their necks, and there is no difficulty in getting men to take practically any risk for the substantial rewards offered. The performance of specially sensational feats in the air is like¬ wise a fertile source of accidents. One noted aviator who has the reputation of being a most conservative and expert operator, while endeavoring to land within a set space, made too sudden a turn, which resulted in the tail of the machine giving way, precipitating him to the ground. In fact, the number of failures resulting from abrupt turns shows conclusively that there is too small a factor of safety in the construction, not because the added weight could not be carried, but because the extreme lightness alone made possible the stunts for which there is always applause or financial reward. It may seem strange to the man whose only interest in aeronautics is that of an observer, that so many should be willing to take such unheard-of chances; that an aeronaut will rise to great heights, knowing in advance that a vital part of his machine has been deranged, or is only temporarily repaired; and that many others will attempt ambi- BUILDING AND FLYING AN AEROPLANE 121 tious flights with engines or other parts that have never been tested previously in operation in the air. Many young and inexperienced aviators are not content to thoroughly test out each new part on the ground, or close to it, but must go aloft at once to do their experi¬ menting, with the usual result of such foolhardiness. If in other sports safe conditions were absolutely disregarded in this manner —take football as an instance—the resulting fatalities would not be charged against the sport itself. But aviation is so extremely novel and likewise so mysterious to the uninitiated that this is never taken into consideration. Excessive Lightness of Machines. If, even at the present early stage of aviation, machines are being made excessively light for purposes of competition, it is time that the contest committees of organizations in charge of meetings formulate rules as to the size of engines, weight of machines, and similar factors, so that accidents will not only be reduced to a minimum, but competition along proper lines will develop types of machines which are useful and not merely 'racing freaks, as has already been done in the automobile field. Hair-raising performances also should be prohibited, at least until such time as improvements in the construction of machines make it reasonably certain that they are able to withstand the terrific strains imposed upon them in this manner. Suddenly attempting to bring the machine to a horizontal plane after a long dip at an appalling angle is an extremely dangerous maneuver, whether it be taken in the upper air or is one of the now familiar long glides to earth, which require pulling up short when within a few feet of the ground and after the dropping machine has acquired considerable inertia. The aviator is simply staking his life against the ability of the struts and stays to withstand the terrific stresses imposed upon them every time this is done.* As at present constructed, many of the machines are not suf¬ ficiently strong to withstand the utmost in the way of speed and sudden turns which the skilled operator is likely to put on them. They should be made heavier, or of materials providing greatly increased strength with the same weight. That they can be made heavier without seriously damaging their flying ability has been ♦This is exactly what occurred at the Chicago Meet, August 15, 1911, when Badgers Baldwin biplane collapsed at the end of a long dive, causing the death of the aviator. 122 BUILDING AND FLYING AN AEROPLANE clearly demonstrated by the numerous flights with one and two passengers, and on one occasion in which three passengers besides the driver were taken up on an ordinary machine. This was likewise tempting fate by overloading, but it served to show the possibilities. Landings. Then there is a class of accidents for which neither the aviator nor the machine is responsible, as where spectators have crowded on the field, causing the flyers to make altogether too sudden Fig. 49. Monoplane is Liable to Stand on its Head if Landing is Not Properly Made or impromptu landings at angles which would otherwise not be con¬ sidered for a moment. This, of course, refers solely to exhibition meets, and the comparative immunity of cross-country flights from fatal accidents as compared with the latter, speaks for itself in this respect. In the open, even the novice seems to be able to pick a safe landing, especially if high enough to glide some distance before reaching the ground. This brings out the fact that, as a rule, the machines are BUILDING AND FLYING AN AEROPLANE 123 safer in the air—a large part of the danger lies in making a landing. Starting places are usually smooth, but landing places may be the reverse. When alighting directly against the wind, which is the only safe practice, most of the machines will remain on an even keel until they come to a stop, but the slightest bump or depression, in connec¬ tion with a side gust of wind, may swerve it around and capsize it, as demonstrated by the illustration of a bad landing by De Lesseps, Fig. 49. This was emphasized by some of the minor accidents at the International Meet near New York. There is no precision or accuracy in the movements of a flying machine when rolling slowly over the ground after the engine has been shut off, and the aviator is, to a cer¬ tain extent, helpless. The wheels on most machines are placed too near the center and too close together. When an attempt is made to land with the wind on the quarter or side, although the machine may strike the ground safely, owing to the accuracy with which it may be controlled in the air while at speed, it is apt to turn after rolling a short distance and the wind will then easily capsize it, break¬ ing a wing, smashing a propeller, and sometimes injuring the motor or the aviator. Accidents from this cause have been common. These accidents and collisions with obstructions make plain the fact that brakes are quite as necessary on an aeroplane as on any other vehicle intended to run on the ground. Practically all aero¬ planes are fitted with pneumatic tires and ball-bearing wheels and, as there is very little head resistance, they will run a considerable distance after alighting at a speed of 20 to 30 miles an hour. The employment of a brake on the wheels would have averted one of the fatal accidents abroad, as noted in Table III. They would have enabled Johnstone to stop his machine before colliding with the fence surrounding the aviation grounds at Denver, and they would have prevented several minor accidents at various meets, which, though not endangering the aviator in every instance, have often seriously damaged his machine. Every exhibition field is obstructed by fences, posts, buildings, and the like,-and to avoid com¬ ing in contact with these, as well as with the irrepressible spectator, the aviator should certainly have an effective means of bringing the machine to a standstill when it is running along the ground. How much more so is this necessary for cross-country flying when the choice of a landing place is a difficult matter at best. Ability to come to a 124 BUILDING AND FLYING AN AEROPLANE stop quickly would make it possible to land in restricted places where only a very limited run along the ground could be had. Lack of Sufficient Motor Control. Another class of accidents that take place on the ground suggests the necessity for improving the motor control. In alighting, the motor is usually stopped by cutting off the ignition—ordinarily by grounding or short-circuiting. Throttling to stop appears to be seldom resorted to, but as several instances have occurred in which the aviator found it impossible to cut off the ignition, resulting in a collision with another machine or a building, it is evident that the control should be arranged so that both methods could be employed. With the increasing use of air¬ cooled motors that may continue to run through self-ignition after the spark has been cut off, this is more necessary than ever. While it has been demonstrated that the stoppage of the motor does not necessarily involve a fall, most aviators will naturally prefer to command the assistance of the motor at all times, and in the case of motors using a carbureter this should be jacketed either from the cooling water or the exhaust, and means provided for increasing the air supply to prevent the motor stopping at a great height owing to the cold and the rarefied air. The reasons for this have been gone into more at length under the heading of “Altitude.” With these and similar improvements that will be suggested by experience and further accidents, there appears to be no reason why aviation can not be made as safe as the personal equation will permit it to be. There will always be reckless flyers. Ignorance and incompetence can not be altogether eliminated any more than they can in sailing, hunting, or any other sport. The annual hunting fatalities from these causes in this country alone make a total beside which the aggregate of four years in aviation the world over, is but an insig¬ nificant fraction. Parachute Garment as a Safeguard. To save as many as pos¬ sible of these reckless ones from themselves, so to speak, a parachute garment has been devised to ease the shock of the fall. It will be recalled that Voisin would not fly in his biplane until he had pro¬ vided himself with a heavily-padded helmet, somewhat on the order of the football headpiece. But neither a padded headpiece nor padded clothing would avail much against a fall of any kind from an aero¬ plane; hence, the parachute garment. Its object is not to take the BUILDING AND FLYING AN AEROPLANE 125 shock of a fall, as are the pads, nor is it to prevent a fall, but to reduce the rate of drop by interposing sufficient air resistance to make the fall safe. This new parachute is in the form of a loose flowing gar¬ ment, securely fastened to the body and fitted over a framework carried on the aviator’s back. The lower ends of the garment are secured to the ankles. The arrangement is such that when the aviator throws out his arms, the garment is extended somewhat in umbrella or parachute form, thus creating sufficient resistance to prevent too rapid a descent. Experiments have been made with this parachute dress in which the wearer has jumped from buildings, cliffs, and other heights, and the garment has assumed its role of parachute at once, permitting a safe and easy descent. Study of Stresses in Fancy Flying. To sum up, it will be seen that the most prolific cause of fatalities is the personal equation. Of all the many dangers encountered in aeroplaning, one of the most clearly defined, as well as one of the most seductive, results from fancy flying: from wheeling round sharp, horizontal curves; from conic spiraling; from cascading, swooping, and undulating in vertical plane curves, popularly dubbed “stunts.” These are forms of flying in which aviators constantly vie with one another. They frequently result in imposing stresses upon the machine which are far beyond its capacity to withstand. The danger is particularly alluring to reckless young aviators engaged in public exhibitions. The death of St. Croix Johnstone, at the Chicago Meet in the summer of 1911, affords a typical illustration of what may be expected as the lesult of such performances. Nevertheless, partly because they do not adequately appreciate the risk, and largely, no doubt, because of the liberal applause accorded by an admiring throng which also fails to realize the hazardous nature of the fascinating maneuvers, there will doubtless always be aviators to undertake such feats. Singularly enough, the exact magnitude of such hazards, or more accurately, the extent of the increased stress in the machine, though beyond even the approximate guess of the aviator, is capable of nice computation in terms of the speed and curvature of flight. During an exhibition meet in Washington, D. C., during the summer of 1911, Glenn H. Curtiss found difficulty in restraining one of his young pupils from executing various hair-raising maneuvers. He would plunge from a great elevation to acquire the utmost speed. 126 BUILDING AND FLYING AN AEROPLANE then suddenly rebound and shoot far aloft. He would undulate about the field, and on turns would bank the machine until the wings appeared to stand vertical. Curtiss solemnly warned the young aviator and earnestly restrained him, pointing out the dangers of sweeping sharp curves at high speed, of swooping at such dangerous angles, and the like. Curtiss then turned to A. F. Zahm and expressed the wish that someone would determine exactly the amount of the added stress in curvilinear flight. The following, published by Zahm, in the Scientific American, gives the method of calculating this: When a body pursues a curvilinear path in space, the centripetal force urging it at any instant may be expressed by the equation Fn = (absolute units) mV 2 - -—< (gravitational units) 9 R in which Fn is the centripetal force, m the mass of the body, V its velocity, and R the instantaneous radius of curvature of the path followed by its center of mass. Since the mass may be regarded as constant for any short period, the equation may be expressed by the following simple law: The centripetal force varies directly as the square of the velocity of fliqht and inversely as the instantaneous radius of the curvature of its path. In applying the above equation to compute the stress in an aeroplane of given mass in, we may assume a series of values for V and R, compute the corresponding values for Fn, and tabulate the results for reference. Table IV has been obtained in this manner. It may be noted that on substituting in the equation, V is taken as representing miles per hour, R as feet, and g as 22 miles an hour, in order to simplify the figuring, this being 32.1 feet per second. The table shows at a glance the centripetal force acting on an aero¬ plane to be a fractional part of the gravitational force, or weight of the machine and its load. For example, if the aviator is rounding a curve of 300 feet radius at 60 miles per hour, the centripetal force is 0.55 of the total weight. At the excessively high speed of 100 miles per hour and the extremely short radius of 100 feet, the centripetal force would be 4.55 times the weight of the moving mass. The pilot would then feel heavier on his seat than he would sitting still with a man of his own weight on either shoulder. For speeds below 60 miles per hour and radii of curvature above 500 feet, the centripetal force is less than one third of the weight. The table gives values for speeds of 30 to 100 miles per hour, by increments of 10 miles, and for BUILDING AND FLYING AN AEROPLANE 127 TABLE IV Centripetal Force Acting on Aeroplane at Various Speeds and Curvatures of Flight (V) Velocity or Speed of (R) Radius of Curvature in Feet Aeroplane 100 200 300 400 500 Miles per hour Weight Weight Weight Weight Weight 30 0.41 0.20 0.14 0.10 0.08 40 0.73 0.36 0.24 0.18 0.15 50 1.14 0.57 0.38 0.28 0.23 60 1.64 0.82 0.55 . 0.41 0.33 70 2.23 1.11 0.74 0.56 0.45 80 2.91 1.45 0.97 0.73 0.58 90 3.68 1.84 1.23 0.92 0.74 100 4.55 2.27 1.52 1.14 0.91 radii of curvature of 100 to 500 feet, by increments of 100 feet, so that intermediate speeds and radii may readily be calculated. The entire stress on the aeroplane in horizontal flight, being substantially the resultant of the total weight and the centripetal force, can readily be figured by compounding them. Thus in hori¬ zontal wheeling, the resultant force as shown in the diagram, Fig. 50, is approximately F= V Fn 2J rW 2 In swooping, or undulating in a vertical plane, the resultant force at the bottom of the curve has its maximum value F= (. Fn+ W) and at any other part of the vertical path, it has a more complex though smaller value, which need not be given in detail. It is obvious that the greatest stress on the machine occurs at the bottom of a swoop, if the machine be made to rebound on a sharp curve. The total force (Fn-\- IF) sustained at this point may be found from the table, if V and R be known, simply by — adding 1 to the figures given, then multiplying by the Fig. 50. Force Diagram in Horizontal Wheeling weight of the machine. For example, if the speed be 90 miles per hour and the radius of 128 BUILDING AND FLYING AN AEROPLANE curvature 200 feet, the total force on the sustaining surface would be 2.84 times the total weight of the machine. In this case, the stress on all parts of the framing would be. 2.84 times its value in level flight, when only the weight has to be sustained. The pilot would feel nearly three times his usual weight. From the foregoing, it is apparent that in ordinary banking at moderate speeds on moderate curves, the additional stress due to centripetal force is usually well below that due to the weight of the machine, and that in violent flying, the added stress may consider¬ ably exceed that due to the weight of the machine and may accord¬ ingly be dangerous, unless the aeroplane be constructed with a spe¬ cially high factor of safety. But there is nothing in the results here obtained that seems to make sharp curving and swooping prohibitive. If the framing of the machine be given an extra factor of safety, at the expense perhaps of endurance and speed, it may be made prac¬ tically unbreakable by such maneuvers, and still afford to the pilot and spectators alike all the pleasures of fantastic flying. Methods of Making Tests. In order to obtain actual data for the fluctuations of stress in an aeroplane in varied flying, it is sug¬ gested that the stress or strain of some tension or compression member of the machine be recorded when in action; or simpler still, perhaps, that a record of the aeroplane’s acceleration be taken and particularly its transverse acceleration. A very simple device to reveal the transverse acceleration of an aeroplane in flight would be a massive index elastically supported. A lath or flat bar stretching lengthwise of the machine, one end fixed, the other free to vibrate, and carrying a pencil along a vertical chronograph drum, would serve the purpose. This could be protected from the wind by a housing as shown in the sketch, Fig. 51. An adjustable sliding weight could be set to increase or diminish the amplitude of the tracing, and an aerial or liquid damper could be added to smooth the tracing. The zero line would be midway between the tracings made on the drum by the stationary instrument when resting alternately in its normal position and upside down; the distance between this zero line to the actual tracing of the stationary instru- Fig. 51. Method of Boxing an Acceleration Recorder BUILDING AND FLYING AN AEROPLANE 129 ment would be proportional to the aeroplane stresses in level, rec¬ tilinear flight; while in level flight on a curve, either horizontal or vertical, the deviation of the mean tracing from the zero line would indicate the actual stress during such accelerated flight. Of course, the drum could be omitted and a simple scale put in its place, so • that the pilot could observe the mean excursion of the pencil or pointer from instant to instant; also, the damper of such excursion could be adjusted to any amount in the proposed instrument if the vibrat¬ ing lath fitted its encasing box closely with an adjustable passage for the air as it moved to and fro; or if light damping wings were added to the lath, or flat pencil bar. Another method would be to obtain by instantaneous photog¬ raphy the position of the centroid of the aeroplane at a number of successive instants, from which could be determined its speed and path, or V and R of the first equation, by which data, therefore, the stress could be read from Table IV. Perhaps the simplest plan would be to add an acceleration pen¬ holder, with its spring and damper, to any recording drum the aero¬ plane may carry for recording air pressure, temperature, speed, and so forth. Indeed, all such records could be taken on a single drum. A score of devices, more or less simple, but suitable for reveal¬ ing the varying stress in an aeroplane, will occur to any engineer who may give the subject attention. And it is desirable in the interests both of aeroplane design and of prudent manipulation that someone obtain roughly accurate data for the stresses developed in actual flight. Increment of Speed in Driving. It is commonly supposed by aviators that the increment of speed due to driving is very prodigious. An easy formula will determine the major limit of such speed incre¬ ment. If the initial and natural speed of the aeroplane be v, and the change of level in diving be h, while the speed at the end of the dive be V, the minimum change of level necessary to acquire any increment of speed, V—v, may be found from the equation If, as before, g be taken as 22 miles per hour, the equation reduces 130 BUILDING AND FLYING AN AEROPLANE TABLE V Minimum Change of Level Necessary to Produce Various Speed Increments Natural Speed v of the Aeroplane Increments of Speed V — Miles per hour, 10 Miles per hour, 20 V Miles per hour, 30 Miles per hour Feet Feet Feet 30 23.3 53.3 90.0 40 30.0 66.7 110.0 50 36.7 80.0 130.0 60 43.3 93.3 150.0 70 50.0 106.7 170.0 to the convenient formula 30 in which V and v are taken in miles per hour. Assuming various values for V and v, Table V has been found for the corresponding values of h in feet: For example, if the natural speed of the aero¬ plane in level flight be 50 miles per hour, and the aviator wishes to increase the speed by 20 miles per hour, he must dive at least 80 feet, assuming that the aeroplane falls freely, like a body in vacuo , or that its propeller overcomes the air resistance completely; other¬ wise the fall must be rather more than SO feet. It has been suggested that a contest be arranged to determine which aviator could dive most swiftly and rebound most suddenly, the prize going to the one who should stress his machine most as indicated by the accelerograph above proposed. But to avoid dan¬ ger, the contest would have to be supervised by competent experi¬ mentalists, and would be best conducted over water. It is safe to sav that more than one well-known aeroplane would be denied entry in such a contest because of lack of a sufficient factor of safety in its construction. Dirigible Accidents. Because its wrecks are spectacular and the loss involved tremendous, the dirigible has probably earned an undeserved reputation, though it must be admitted that the big airships have come to grief with surprising regularity. The fact must be noted, however, that when an aeroplane is wrecked, the BUILDING AND FLYING AN AEROPLANE 131 aviator seldom escapes with his life, while the spectators’ lives are endangered to an even greater extent, whereas in the case of the dirigible, the loss is simply financial, both the crew and passengers usually escaping without a scratch. This is largely due to the fact that the majority of accidents to dirigibles have happened on the ground, and have been caused by lack of facilities for properly handling or “docking” the huge gas bag. Of course, lack of flotation or an accident to the motors, or both combined, have brought two of the numerous Zeppelins to earth in a very hazardous manner, though no one was killed, while four French army officers lost their lives in the Republique disaster, the exact cause of which was never definitely ascertained. This was likewise the case with Erbsloeh and his companion who were dropped from the sky, their airship having taken fire. It was thought that ignition was. caused by atmos¬ pheric electricity, in this instance. By far the great majority of later dirigible accidents have been due solely to the crude methods of handling the airships on the ground, and the frequency with which these have occurred should certainly have been responsible for the adoption of improvements in this respect at an earlier day. For instance, the Morning Post, a big Lebaudy type bought for English use, had the envelope ripped open by an iron girder pro¬ jecting from its shed. Repairs took several months, and at the end of the first trial thereafter, the ship was again wrecked in landing. A company of soldiers failed to hold the big craft and it drifted broad¬ side into a clump of trees, hopelessly wrecking it. In attempting to dock the Deutschland I, 200 men were unable to hold it down, a heavy gust of wind catching the big airship and pounding it down on top of a wind break that had been specially erected at the entranee of the shed for protection. A similar accident happened to the big Parseval, a violent gust of wind casting it against the shed and tearing such a hole in the envelope that the gas rushed out and the car dropped 30 feet to the ground. The big British naval dirigible of the rigid type, the Mayfly, was broken in half in attempting to take it out of the shed the first time. A cross wind was blowing and the gas bag of one of the central sections was torn, deflating it and show¬ ing in a striking manner that the solidity of a rigid dirigible results chiefly from the aerostatic pressure of the gas in its various compart- 132 BUILDING AND FLYING AN AEROPLANE ments. Without the gas lift, a rigid frame is so in reality only for certain limited distances, as was shown by the total collapse of the Mayfly’s frame after having been subjected to the opposed leverage of the parts on either side of the original break. This, of course, was an error in design, as the frame of a rigid dirigible should cer¬ tainly not be so weak in itself as to collapse upon the deflation of a single one of the central compartments. The incident on the trip of the Zeppelin III to Berlin, in 1909, when the flying blades of a brokeli propeller pierced the hull without causing an accident, shows how much resistance it mav offer. AMATEUR AVIATORS It will probably come as a surprise to the average reader to learn that at the end of 1910, there were more than a thousand ama¬ teur aviators in this country, though all the flights which form the subject of newspaper reports have been the work of not more than a dozen flyers and doubtless half the population has not as yet seen an aeroplane in flight. The desire to fly, whether it be to satisfy one’s desire to soar above the world in seeming defiance of natural laws, or merely to obtain the financial reward that is won by successful flight, attracts a great many from all stations and walks of' life. This is particularly true among older boys who look on aviation as an advanced form of kite-flying. An example of rather serious work along this line may be cited of two high school boys of Chicago, Harold Turner and Fred Croll, who built a monoplane weighing 125 pounds, Fig. 52. This machine, although too small for a motor, was equipped with rudder and other operating planes and levers, the elevating plane and ailerons being automatically operated by an electrical device. On one of its flights the machine, carrying a 120-pound operator, was started and propelled by attaching it to an automobile; it rose to a height of 15 feet, and remained in the air 43 seconds. • Contrary to all precedent, the average amateur is bent upon achieving what the skilled professional considers as beyond even his talent and resources—that of building his own flying machine. With every other mechanical vehicle, the amateur learns to drive first and the majority are content with that achievement—for example, very few chauffeurs have any great ambition to build their own BUILDING AND FLYING AN AEROPLANE 133 automobiles. With flying machines (one of the most difficult of mechanical contrivances), nearly all amateurs want to construct new types for themselves and all confidently expect to fly with no more knowledge than that gained in constructing them. We all have to be apprentices before becoming masters, so all aviators neces¬ sarily have to be learners and “grass cutters” before being professionals. Charles K. Hamilton was an exception, but he was already an expert •pilot of dirigible balloons, and he did not try to build his own aero¬ plane. Willard, Mars, and Ely, all Curtiss pupils, flew after a very short training, but they did not attempt to construct aeroplanes for Fig. 52. What an Amateur Aviator Can Do in Building an Aeroplane themselves. This is also true of Clifford B. Harmon, the champion amateur. Classes of Amateurs. Inventors. Generally speaking, ama¬ teurs are of two classes. Those of the first class believe they have conceived some entirely new system or invention, or an improve¬ ment on some machine that has previously proved a failure; they think they have discovered the secret which other inventors who preceded them failed to grasp. They expend their meager capital in trying to realize high hopes. A comparatively small number ever get as far as completing the machine and one trial on the field is usually sufficient to put a quietus on those who do, as it is disap¬ pointing, to say the least, to see the result of a number of months’ 134 BUILDING AND FLYING AN AEROPLANE work undone in a twinkling without the machine having shown the least disposition or ability to get off terra firma. Would-Be Performers. The second class finds its chief incen¬ tive in the munificent reward to be gained with what appears to be comparatively little effort or expenditure, and the amateur who is seeking financial returns has no alternative except to build his own machine, or enter either the Wright or Curtiss school of flying and secure a berth with one of these companies. Wright and Curtiss Patents. This is the result of conditions at present obtaining in the field of aviation. The only generally successful type§ of American aeroplanes are the Wright and Curtiss, and the acquirement of a biplane of either type means the expendi¬ ture of at least $5,000 for the machine alone, and they are sold only to individuals on the express condition that the machines are not to be used for exhibition or as a means of profit to the owner. The manufacturers have expert flyers of their own who attend meets and fairs throughout the country. It would make their monopoly impossible to allow outsiders to fly their aeroplanes publicly or to exhibit them. By this restriction the price of the machines is kept up and large returns are gained by exhibitions and flying. To break this monopoly by importing European machines is not possible. All the successful aeroplanes made abroad such as the Farman, Cody, and Sommer biplanes; and the Bleriot, Antoinette, and Grade monoplanes are fitted with devices of control or stability, or both, covered by the Wright patents and can not be flown in this country without legal trouble. The numerous foreign aviators who brought over their machines in the fall of 1910 to compete at the International Meet, did so only on being granted a concession by the Wright Company to the effect that they would not be con¬ sidered as infringers and sued. Similar arrangements were made at subsequent meets and this handicap will always be present where foreign machines are used. Evasion by Invention of New Types. But when he thinks of the unprecedented sums paid professionals for simply exhibiting their machines and making short flights, the amateur is anxious to obtain a share of the profits. No thought is given the fact that were he and all his kind permitted to fly, the achievement would soon be commonplace and the aviator’s golden age would be over. There BUILDING AND FLYING AN AEROPLANE 135 are accordingly hundreds of would-be aviators in this country today who are striving to evade the Wright basic patents by either devis¬ ing entirely new types of aeroplanes, or by inventing new methods of control and stability that will not infringe. Others, reasoning that the old aeroplanes built before the advent of the Wright machine cannot be held as infringements owing to priority, propose to develop Maxim, Langley, and Ader machines, though the dictum in the New York Court of Appeals decision referred to under the head of “Legal Status of Wright Patent,” which states that a prior machine which had never been known to fly woidd not be considered an antici¬ pation of a modern successful machine, may prove a stumbling block in their case as well. Thus, a round of the workshops of these enthu¬ siasts reveals a host of heavier-than-air machines of every conceiv¬ able type and shape, every one of which, according to its builder, is an aeroplane that will fly . Mineola and Garden City, Long Island, harbor a score of these little shops the year round, but the same scenes are being enacted on a smaller scale in almost every state in the Union, and particularly in California, Ohio, Kansas, Massachu¬ setts, and Arizona, in addition to which there are many who are carrying their experiments on in secret. Each believes deep in his heart that he will succeed where a master failed. “Maxim failed with this type of machine,” quotes one. “Plow did he expect to fly when his control was not proportionate to the machine’s lift capacity?” Seemingly, nobody ever thought of that and our friend will make a fortune by going Maxim one better, but he does not. After months of labor and a great deal of expense he finds that some unforeseen difficulty develops which keeps his machine to earth as if it were part and parcel of it. Another has conceived a type of monoplane that is entirely new—different from any existing type—and as the latter are all foreign, he prides him¬ self on having developed a monoplane that will be entirely x\meri- can—the first and only American monoplane. Theoretically, it is a wonder; mechanically it is correct; and it speeds over the turf with surprising velocity; but when the elevating rudder is operated to make the machine rise, it balks and plunges head first into the ground. Again and again, the propeller and other broken parts are replaced at no small expense; again and again the inventor goes over every part of the machinery and computes the dimensions of 136 BUILDING AND FLYING AN AEROPLANE the supporting surface to see if it all corresponds with the formula of his special theory. But time after time, the aeroplane acts like a jumping frog and lands head first. At last, its builder becomes con¬ vinced that there is something radically wrong and begins to depart from his original plans, involving changes that simply mean a waste of effort and money, since the inventor does not himself know what he is trying to correct and no one else knows better than he what the trouble is. Evasion by Acquiring European Types. Others still, realizing from the. foregoing experiences that it is almost impossible to con¬ struct an entirely new type of aeroplane off-hand, acquire European types and propose to fit them with new control and stability devices, such as are not covered by the Wright patents. So far, none has succeeded. Somehow, the Wrights seem to have covered all the conceivable working devices for control and stability, and the numer¬ ous attempts have accordingly resulted in failure. Undoubtedly, some of these aeroplanes built by amateurs may really be capable of flight; but how is the inventor to know it when he lacks the ability to operate it? To know how to fly an aeroplane is a condition prece¬ dent to success in the field of aviation that can not be met by build¬ ing of a machine. The beginner is thus badly handicapped. Even though his machine may embody the elements essential to success¬ ful flight, he may never be able to establish the fact, since his first blundering attempt or two frequently ends by wrecking the machine, and many have neither the means nor the stamina to persevere fur¬ ther after a few bad wrecks, involving weeks and weeks of rebuilding each time. He can not engage an expert to fly his machine for him, as the expert’s time per minute figures out a price that makes him gasp, and even at that the expert professional’s time is pretty much all taken. Furthermore, very few would run the risk of attempting to fly an untried aeroplane—they have more to lose through acci¬ dental injury than the builder has through the failure of his theories. And so it is with most inventors. They may have conceived something really good, but it is not complete, and an aeroplane is hardly worth its weight as junk unless it is. Hundreds of patents are taken out every year on devices to be used on heavier-than-air machines; inventors by scores make daily rounds trying to interest financiers in some seemingly wonderful mechanical scheme, and BUILDING AND FLYING AN AEROPLANE 137 dozens of companies are organized each year to exploit some espe¬ cially promising inventions. Numbers of aeroplanes are constructed and hailed as marvels, but, somehow, when a successful flight is made by an amateur it is always with some standard aeroplane, either of the Curtiss or Farman types, and mostly the former. In fact, the Curtiss has become a favorite with the amateur since the Federal court refused to sustain the granting of a preliminary injunction in favor of the Wright Company against Glenn II. Curtiss. It is accord¬ ingly being taken for granted in general that the outcome of the Wright vs. Curtiss litigation will be to declare the Curtiss machine non-infringing. Should it be the other way about, there will certainly be gloom and despair in the amateur camps throughout the country. However, neither the Wrights nor Curtiss impose any restriction upon the building of machines of their types for experimental pur¬ poses, so that the amateur who wishes to copy them may safely do so, provided no attempt be made to employ the machine for pur¬ poses of public exhibition or financial gain. - ' EXAMINATION PAPER BUILDING AND FLYING AN AEROPLANE PART II Read Carefully: Place your name and full address at the head of the paper. Any cheap, light paper like the sample previously sent you may he used. Do not crowd your work, but arrange it neatly and legibly. Do not copy the answers from the Instruction Paper; use vour own words, so that we may he sure you understand the subject. 1. Contrast the Bleriot with the Curtiss in every essential t/ particular. 2. Give details of the Bleriot running gear. 3. How is the supporting plane of the Bleriot built and reinforced? 4. What sort of fabric is used to cover the plane and how is it fastened on? 5. Describe by sketch the Bleriot control system. 6. How does the location of the motor in the Bleriot com¬ pare with its location in the Curtiss? 7. What is “grass-cutting” and why is it practiced? 8. Describe some of the devices used in aviation schools. 9. How is the elevating plane manipulated to start the aero¬ plane from the ground? 10. How is the static balance of a machine determined? 11. How does w r arping the wings affect the behavior of an aeroplane? How should this be practiced? 12. Give the process of making a turn in an aeroplane. 13. • What is “banking”? What must be done to prevent excessive banking on a turn? 14. How can a turn be made in a wind? 15. Why should the start and the landing always be made in the teeth of the wind? 10. What is the attitude of the masters of aviation toward fancy flying? BUILDING AND FLYING AN AEROPLANE 17. Classify the most common sources of accidents. 18. What must an aviator do in case his motor stops in mid¬ air? Is this considered a dangerous situation? 19. What are the relative merits of biplane and monoplane as regards the avoidance of accidents? 20. What are some of the devices used to protect the aviator in case his machine collapses? 21. Analyze rather carefully the additional stresses put upon an aeroplane when an aviator suddenly swoops and then rights his machine by a quick movement of the control. After completing the work, add and sign the following statement: I hereby certify that the above work is entirely my own. (Signed)