Flight, January 1, 1915.
THE 50 H.P. PARTRIDGE TRACTOR BIPLANE,
THIS machine is one of the several successful tractor biplanes manufactured by Messrs. Partridge and Keller, of the Cicero Flying Ground, at Chicago, Ill. In actual practice all have proved to be very steady flyers, several well-known American pilots, including Miss Katherine Stinson, having put up creditable performances on them. The machine shown in the sketch plan and elevation was built during the latter part of last year, bearing several modifications of the earlier models as the results of experience. The main planes are built up on two main spars of I-section ash measuring 2 1/4 ins. by 1 7/8 ins. front, and 2 1/4 ins. by 1 7/8 ins. rear respectively. The ribs consist of spruce battens and perforated webs. Between the front and rear spars, where the interplane struts are connected, are tapering compression members which relieve the ribs of any compression strains. Internal cross bracing is by 3/32-in. stranded cable. The wing section is a modified monoplane type, having a camber - on the under surface - of 3 ins. at a point 38 per cent, from the leading edge, and with a slight wash out at the tips. The normal angle of incidence is about 2°. The top plane consists of three sections, a small central panel the width of the fuselage, and two outer sections which are attached to the inner section, whilst the lower plane is in two sections, one mounted on either side of the fuselage. Each outer cellule has two pairs of silver spruce struts situated close together near the wing tips, and the central section is supported on the fuselage by two pairs of tubular steel struts. External bracing is by heavy stranded cable, and the strut attachments are of the quick-detachable type enabling the planes to be easily detached. The planes are covered with linen treated with Emaillite. H inged to the outer extremities of the rear spars of both top and bottom planes are ailerons measuring 7 ft. by 1 ft. 6 ins. Each top aileron is connected to that immediately below it by a spruce strut, and right and left hand pairs are interconnected, their operation being by means of Curtiss-type shoulder yoke. The tail consists of a triangular-shaped stabilising surface set at a slight negative angle mounted on the upper longerons of the fuselage. Hinged to the trailing edge of the stabilizing surface are two elevator flaps with a partially balanced vertical rudder in between, which is hinged to the last strut of the fuselage. The latter is of rectangular section built up of four ash longerons, with struts of silver spruce, except those in the engine section which are of ash.
The engine, a 50 h.p. 6-cyl. water-cooled Kirkham, is mounted in the nose of the fuselage, this portion being covered in with sheet aluminium. Behind the engine are the passenger's and pilot's seats, the former being in front, the fuselage being fabric covered as far as the rear or pilot's seat. Two radiators for cooling the engine are mounted one on either side of the fuselage between the engine and passenger. Sheet metal fittings are used in the engine section of the fuselage, and for the rest the usual U-bolts are employed, whilst the whole is strongly braced with cable. The landing chassis consists of two long ash skids connected to the lower longerons of the fuselage by three ash struts each, and a tubular steel axle carrying a pair of 20-inch wheels, which is attached to the skids by means of rubber shock absorbers. The skids extend forward of the 7 ft. 2 in. tractor screw, and are braced transversely by cable, no cross struts being employed.
The principal dimensions of this machine are: Span (top and bottom), 30 ft.; chord, 5 ft.; gap, 5 ft. 8 ins.; supporting area, 290 sq. ft.; area of stabilising plane, 14 sq. ft.; overall length, 24 ft. 1 in.; weight, empty, 730 lbs.; speed, 52 m.p.h.