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Aviation History
1918
1918 - 0677.PDF
JUNE 20, 1918. THE DE HAVILLAND IV BIPLANE.* 300 H.P. ROLLS-ROYCE ENGINE. THIS large aeroplane, employed for long distance reconnais- sance and for bomb dropping, is chiefly built by the Aircraft Manufacturing Co., Ltd. The different machines show minor differences in construction and outfitting according to the time of construction. Both wings of the two strutter biplane, which have distinctly rounded tips, have a span of 12.93 metres and a chord of 1.67 metres. The stagger is 0.32 metres. There is no sweep-back, but the upper and lower planes are attached respectively to a centre section 0.7 metre wide and direct to the body, at a dihedral angle of 1740. The pilot, whose seat is right under the top plane centre section, has a good view forward. The centre section and wings have their trailing portions cut away in the centre to give a better view backwards. The angle of incidence is 30 at the body and at the top plane centre section. Both main spars, which are of spruce, are of one section, left solid where occur the compression ribs. At these points and where fittings occur the spars are not only left solid but are reinforced by mahogany pieces glued and screwed on. At a point between the inner inter-plane struts and the commencement of the wing flaps the main wing spars are spliced (see Fig. 2) and bound with fabric. The wing ribs are only very slightly cambered on the under surface. Leading and trailing edges are slightly raised. Into grooves in the two flanges, which measure 13 mm. in width and 4.5 mm. in thickness, are glued and tacked with brass tacks the three-ply webs, which are provided with large lightening holes. The ribs at the struts and in the middle of each bay have flanges as wide as 37 mm. and the * Translated from Flugspori. web between them is solid spruce between the spars. Be- tween every two ribs, which are spaced 310 to 400 mm. apart, there is a false rib extending from the leading edge to the front spar. The internal wing bracing, which is of thick- ended wire, is in duplicate up to the middle of the outer bay. The wing covering is of a yellowish-white colour, and is sewn WOOD P 153 - Fig. 2 Wing spar splice. to the ribs in such a way that the stitches surround the whole rib. In front of the trailing edge, which is in the form of a strip of wood, eyelets are incorporated in the under surface, which serve to equalise pressure and to drain out moisture. The crank levers of the wing flaps, which in all the planes are hinged direct to the rear spars, are made of 1.5 mm. sheet aluminium, which is reinforced on either side by facings of wood riveted on. The same construction is employed for the elevator and rudder cranks. At their outer end, where the control cables are attached, the aluminium cranks are doubled over. The very simply arranged wing bracing con- 29,5%. 35,t% -mir 5BCTION : UPPttR AND LOWER.DISTAMCB BETWBSM RIBS, t UPPER: S/O to 3 SO L.0WER1 3/O to 4OO -200- -S20 PLANE STRUTS SECTIONS .• Y670 Centre' Section. Struts.. H 71 OUTER STRUTS. LI SPAR 3BCT/ON& I ~ S Uppzr and Lower. TAIL. PLANE and. ELEVATOR . ir^7T5 •6*0- Ta.tl P7d7?e front Spar t . Rear Spar SO m/m.. Fig. 3.—Wing section and tail plane section of the de Havilland IV biplane. 675
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