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Aviation History
1918
1918 - 0858.PDF
the pc at of intersection of the two formers supports a short transverse cylindrical piece of wood, around which is wrapped the shock absorbers for the tail skid. The details of both these joints are shown in the sketches of Fig. 6. The small tail pi me root is covered, on the actual machine, with ply- wood, but this has been omitted in the sketch in order to better show the constructional details. The tail plane itself is in one piece, and fits into the slot provided for it in the body. The manner in which it is secured after being placed in its slot will be clear from an inspection of Fig. 7. The front spar rests in the slot in the body, and is secured against lateral tilting by a steel band <m each side, overlapping the butt joint between the front part of the rib and the tail plane root, as shown in Fig. 7. The rear spar of the tail plane is locked in place by two long ;t>olts and a stud. The two bolts are placed one on each side <M the stern, as indicated in the sketch in Fig. 7, while the 1 &tud passes through a lug welded on to the extreme rear of the steel shoe surrounding the heel of the fuselage into another Jlug near the foot of the stern post. The whole tail plane with jits elevator can therefore be removed by undoing five nuts, ind, of course, the connections in the elevator control cables. As regards the tail plane and elevator themselves, these are constructed along more or less standard lines and do not OLLArtSPINNED &\ BRAZED TO RUDDERPOST Fig. 8.—The rudder of the Pfalz is built up of steel throughout. The sketches show the main features of the detail construction. ; - > i present any especially remarkable features. It has already been pointed out that the tail plane appears at first sight to have been put on " upside down," having a flat top surface and a convex bottom surface. The reason for this is not -—ap**aventr\£>ut i;. is possible that the disposition of the various i weights and surfaces is such that there is either a lift-weight couple~or a thrust •segistance couple or both; and that this section tail plane has bfjen employed to equalise such couples, However, in a later machine captured and now at the Enemy Aircraft View Rooms the shape of the tail plane hag been altered to a svmmetrical section, so that it would appear that the " inverted " section has either been found unsatisfactory in practice o~ the reasons for its employment removed in a later design. Structurally the tail plane is built up of spruce spars with rios having ash flanges and poplar webs. The inner ribs an covered with three-ply to give extra rigidity for attachme-.t to the body. The front spar is of I section • -**irile the rea; spar is channel section, with recesses top and bottom for forming a flat surface with the rib flanges. There is no internal wire bracing, the necessary rigidity being obtained fa/ means oi diagonal ribs and by plates of three-ply placed overthe joints between-ribs and spars. The leading edge, which AUGUST I, 1918. is also bent back to form the tips of the tail plane, is laminated as shown in Fig. 7, and is lightened by spindling between the ribs. The laminations are probably steamed so as to be easily bent to form the rounded corners of the tail plane. The elevator, owing to the fact that the rudder has no downward projection, is in one piece, and is built up in a manner similar to that of the tail plane. Its leading edge is formed by a box spar, and the ribs are similar to those of the tail plane. The attachment of the ribs to the trailing edge is somewhat unusual. Instead of the flanges of the ribs passing over the trailing edge they are thinned down and pass into a slot in the trailing edge as shown inset in Fig. 7. They are then secured in place by a small metal clip. The glots in the trailing edge appear to have been made with a circular cutter of about 3 in. diameter, the ends of the rib flanges being placed where the slot is deepest. The elevator hinges are formed by forked bolts passing through the rear spar of the tail plane, and corresponding with eye bolts through the leading edge of the elevator. The elevator crank levers are of a type frequently found on German machines. The crank itself is of streamline section, and is welded to a channel section base plate surrounding three sides of the leading edge. Another base plate of similar shape, but made of lighter gauge, is slipped over the leading edge from the front, and forms a washer for the hinge bolt, which passes through the leading edge at a point coincident with the crank lever. The attachment of the elevator and rudder cables to their respective cranks is in the form of a ball and socket, joint, or, more correctly speaking, the ball portion of it is not a complete ball but a slice of a sphere, formed integrally with the bolt passing out of the socket into the barrel of the wire~strainer. The socket, and also the ball have a flat formed on one side so as to prevent the ball from turning in the socket. Behind the ball a small split-pin passes transversely through the socket, thus prevent- ing the ball from dropping out of the socket when the control cables are removed. The socket is kept filled with grease. The rudder, which, as already pointed out, is placed wholly •above the elevator, is built entirely of steel tubing. The ribs are joined, not directly to the rudder post, but to a collar of very light gauge, which is in turn pinned and braced to the rudder post. The object of this construction probably is to avoid weakening the rudder post by welding, since all the rudder ribs can then be welded to their collars on a jig, the rudder post being inserted afterwards and the collars pinned in place. The rear end of the ribs is joined direct to the trailing edge by welding. The method of tapering the rib tubes down towards the trailing edge is different from any- thing we have yet seen on a German machine. A vertical slice is taken out of one of the tubes, and the edges thus formed are pushed over the other tube of the rib as indicated in Fig. 8, the two tubes being held together by short welds at intervals. The foot of the rudder post rests in a.cup or shoe on the trailing edge of the vertical tin, while additional hinges are provided at intervals. The form these hinges take is shown in Fig. 8. To prevent the rudder post from sliding up and down a collar is placed above and one below each hinge. To these collars are welded two U-shaped rods around which is wrapped fabric in order to form an air tight joint at the points where the hinge pierces the rudder covering. This is also shown in Fig. 8. The fabric wrapping has been omitted for the sake of clearness. The tail skid is of somewhat unusual shape, as shown in the right-hand sketch of Fig. 7. Owing to the fact that there is no vertical fin below the bod ' of the Pfalz, and no down- ward projection of the rudder, it has been possible to reduce head resistance of skid by making it horizontal for the greater part of its length, with just a downward curve at the rear to give greater clearance for the tail plane. The skid is pivoted on a bolt passing through a lug on the heel of the fuselage. Its free end is sprung by rubber cord from the short cylindrical piece of wood already referred to, and shown in Fig. 6. This attachment looks remarkably weak— a piece of wood, slotted at its ends to fit overthe cross formed by the two sloping body formers. Yet in all the captured specimens of Pfalz machines that we have had an opportunity to examine, this particular member has never been broken, so that one can only infer that it is sttpnger than it appears. As to the skid itself, it is built up of ten laminations of wood, each about 5 mm. thick. At the rear the skid is provided with a sheet metal shoe to protect it against wear. (To be continued.) The King and the A.A. Defences. Commanding-in-Chief, Great Britain), Major-General E. B. IT was announced in the Court Circular that the King, Ashmore (Commander-in-Chief of the London Air Defence accompanied by the Queen and the Prince Albert, and Area), and Capt. B. Godfrey-Faussett, R.N., visited some ^ended by General Sir William Robertson (General Officer of the London Air Defences oh the morning of July 26th 856
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