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Aviation History
1921
1921 - 0294.PDF
APRIL 28, 1921 THE U.S. "G.A.X." GROUND ATTACK TRIPLANE THE U.S. ''GA.X,' GROUND ATTACK TRIPLANE : Side (left) and front (right) views, the lattershowing armoured fuselage and engine nacelles. THE accompanying illustrations, which we reproduce from our American contemporary Aviation, show one of the ten ground attack triplanes forming a contract with the Boeing Airplane Co., of Washington, U.S.A., placed by the U.S. Army Air Service. This machine was built to the designs of the Engineering ' Division of the Air Service, and the general characteristics are as follows. It is a twin-engined triplane of more or less conventional design, the main distinctive features consisting of the armoured front half of the fuselage, armoured engine housings, and the sloping N interplane struts. The latter arrangement is employed in order to give the same overhang on all wing extremities, the planes decreasing in span from top to bottom. The machine carries one pilot and two gunners, operating in all eight machine-guns and one cannon. These three occupants are practically enclosed in armour, which, together . with that protecting the engines, weighs about 2,000 lbs. The pilot, who occupies the front cockpit, operates one 37-mm. cannon, a row of four Lewis machine-guns firing forward and downward, and one machine-gun firing upward and over the wings. [This pilot would do well in a jazz band !—ED.] The gunners' cockpit at the back has two Lewis guns firing downward to the rear through a tunnel in the fuselage, and one shooting up and over the wings. Bomb gear may also be fitted. Aft of the rear gun cockpit the fuselage is of veneer construction. The weights and performance of the U.S. G.A.X. are as follow :— Weight empty (inc. water) .. 7,532 lbs. Useful load: Petrol .. .. 615 ,, ...... Oil • 60 „ • Crew (3) .. .. 540 „ ..• •. Armament .. .. 933 ,, , Equipment, etc. .. 140 ,, •_. V • Total weight fully loadedWeight/h.] Weight/sq Performance. Altitude, Time, ft. min. 000 2.000 3*7 4,000 8-2 6,000 14-1 8,000 22-8 11,500* 36-1 ". ft. In Climb. Engine, r.p.m. 1,665 1,660 1,650 ' 1.6351.625 . •• Climb, ft./min. 600 495 39O 285 185 100 * Service ceiling. .. 9,820 1 11.2 9-6 bs. ,, In Horizontal Flight Speed m.p.h. 105 103-7 102 99-5 95<o89-5 Engine r.p.m. 1,800 1,780 1,760 1.735 1,700 1,665 Landing speed 50 m.p.h. Minimum speed 63-6 m.p.h. (atsea level). The top plane has an overall span of 65 ft. f> ins., that of thelower plane being 58 ft. 6 ins. The chord is 6 ft. 8 ins. for the top, and 5 ft. 8 ins. for the middle and lower planes ;the gap is 5 ft. There is no dihedral angle on the top plane, but the middle and lower planes have i£° and 3° respectively ;the angle of incidence of all planes is 1 J°. There is no stagger and no sweepback. Ailerons are inserted in the upper andmiddle planes only; the area of the upper ailerons is 36.8 sq. ft., and of the middle ones 21.8 sq. ft., 10 per cent, of eachbeing balancing area. The total supporting surface of the planes is 1,016 sq. ft. The tail consists of a divided triangularstabilising surface of 53.3 sq. ft., to the trailing edge of which are hinged balanced elevators of 36.4 sq. ft. The balancedrudder (45.8 sq. ft.) is hinged to a vertical fin. Dep. control is used. The landing chassis consists of a laminated spruce Vlocated under each engine nacelle, braced by a steel tube running from the axle to the centre of the bottom of the THE U.S. "G.A.X." GROUND ATTACK TRIPLANE: Three-quarter rear view. 294
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