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Aviation History
1919
1919 - 0528.PDF
APRIL 24. 1919 THE PFALZ (D XII) SINGLE-SEATER FIGHTER [Issued by Technical Department (Aircraft Production), Ministry of Munitions] THIS aeroplane, which is allotted G/H.Q./6, was brought down near Dury, on 15/9/18, by Lieut. Cameron (No. 1 Squadron) and Capt. Staton (No. 62 Squadron). Although in construction it is strongly reminiscent of the Nieuport-like type of Pfalz, the design of this machine is entirely new, and is of considerable interest. General Design As will be seen from the general arrangement drawings the D XII Pialz has a car-type radiator in front of the engine, and wings which have two bays a side. The lower planes are faired off into the body in the characteristic Pfalz way, but the fin, which in the earlier model was built of 3-ply as an integral part of the body, is now a separate fitting. Area of upper wings (without ailerons) 104.8 sq. ft. Area of lower wings (both) Area of aileron (one only) Area of balance of aileron Area of elevators (each) Area of balance of elevator (one) Area of rudder .. .. .. Area of balance of rudder Area of tail plane (both sides) Area of fin .'. .. Area, of body (horizontal) Area'of body (vertical) Engine Petrol capacity Guns .. .. 117.6 sq. ft. 8.4 sq. ft. .8 sq. 8.4 sq. .6 sq. 8.8 sq. ft. .4 sq. ft. 16.0 sq. ft. 4.4 sq. 32.8 sq. 53.6 sq. ft. 180 h.p. Mercedes i8| gallons. ft. ft. ft. ft. ft. Two Spandau (fixed). The portion of body 3 -ply which' bears~an inscription re garding weight and permissible load is missing. Wings The flat upper plane is built in. one piece as'before, but the centre se^tipn contains neither gravity tank nor radiator, and tjie tips are no longer heavily raked. The two ailerons of high aspect ratip; are very similar to those of • the D VII Fokker, *as are the placing of the radiator and the form of the interplane struts. The lower planes, which are attached to a" kind of" centre section that may be said to grow out of the body, are of the same chord as the upper plane, and only slightly shorter in span. The lower planes possess a dihedral angle, in this case of 1J0. and the. two pairs of interplane struts on each side slope outwards, f , J Tnlk'attachments of ;£he lower'plane to"the body are un changed. From Fig. i*it will be^seen that the spars are cut down to circular section at their extremities, and a piece of steel tube is bolted over. M* ' - A lug on the fuselage has a-circular-section base round which the open end of the tube on the spar fits, while the lug itself is pinned into tthe forlg on the spar in the usual ^manner. Both front and rear spars are attached in this way. Fig. 2 shows the upper aerofoil section compared with that of the R.A.F. 14, which is shown dotted. It will be noticed that the two sections approximate rnorp closely than^was previously the case. • %.' • -.;. •"" The wing construction of upper and low«r'planes is, similar. Each lower wing contains eleven ribs, sp&ced at equal intervals of approximately, '13$ in. The wood leading edge of the plane is not of the usual " C " section, but is more solid, as will be noticed from Fig. 3. The spars retain the former Pialz design, but the section is of a squarer shape than formerly, and the flanges are not spindled. Dimensioned sketches are given in Fig. 4, and the upper and lower plane spars are exactly similar. At those points where the strut attachments occur, the spars are solidified by the insertion of small blocks of wood, as shown in the lower sketch of Fig. 4. The various components of the spars are very strongly glued together with a casein cement, and fabric is glued round the whole. The tape lattice work that was found in the old-type Pfal2 between the spars, and between the rear spar and trailing edge is no longer present, but a vertical rectangular-section strip of wood lies parallel to the rear spar between that mem ber and the trailing edge, and strips of wood are tacked on to the leading edge, and on to the two spars, and finish just behind this strip. These false ribs are placed midway between the true ribs, and the space between each false and true rib is again bisected by another strip. These pieces simply pass from the leading edge to just behind the front spar, and are built up with a vertical strip so that the whole is of T section. The ribs are of 2 mm. 3-ply, with flanges tacked on in the usual way, and are lightened to the extent shown in Fig. 3, which explains clearly all the features just described. The trailing edge is of wire, and each rib has fabric sewn over it. There are twelve steel compression tubes in the upper plane,: and five in each of the lower planes. The bracing varies from steel tie rods of 5 mm. diameter to 12-gauge piano wire. Ailerons The ailerons, which are fitted only to the upper wings, are very similar to those of the D VII Fokker. . They are balanced, and their high aspect ratio can be judged from the general arrangement -drawings. They are constructed of light welded steel tube, and have the usual welded-up curved aileron lever, which works in a slot cut in the plane. The hinges by which the -ailerons are attached are very simple. A length of &-in. mild steel rod passes through eyebolts fixed alternately to tlje wing and aileron, and is secured at one end by a knob, and at the other end by a split pin. Fig. 5 shows how strongly the false spar, to which the aileron is . hinged, is coupled to th#rear spar. • Struts All the interplane struts of the D XII are of streamline steel tube, and not of wood as before. The centre section struts take the form of two " M's," as is clearly shown by the side view in the scale drawings. A slight adjustment is possible at the three central points, by the means already mentioned in the report on the Fokker biplane, i.e., there is a nut welded to the point of the strut, and a ball-headed bolt is screwed in. The ball, which is drilled, fits into apierced round socket, and a small bolt locks the joint.. The interplane struts are of precisely similar design to those of the D VII Fokker, and are of N-shape when, seen from the starboard side of the machine. They slope out wards from bottom to top, but, since the spars are equal distances apart in top and bottom planes, the front and rear limbs are parallel. They are attached to the spars by similar joints to those of the centre section, but in this case the strut P>ont view of D XII Pfalz. Note radiator and sloping ^'struts 528
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