Avro Type D and Duigan Biplane

Two seat tractor biplane, with a triangular section ash fuselage, divided in two-halves bolted together behind the cockpit for ease of transportation. The fuselage was constructed of wire-braced ash, metal covered forward of the cockpits. Initially the rear section was uncovered, but was fully fabric covered on later aircraft. The fabric covered, wooden wings were of rectangular planform, unstaggered and initially of equal span and chord, but later variants introduced a sesquiplane wing of 33 ft upper, 23 ft lower span. The wings were braced in an irregular three-bay layout, the interval between the pairs of interplane struts increasing from the centre section outwards. Lateral control was by wing warping. The lower wing was mounted directly to the lower longeron of the fuselage, at the front of which was the engine, with the radiator mounted flat behind it in the direction of travel under the upper wing, between the fuselage and upper wing. Behind this a small coaming protected the passenger, with the pilot sitting behind. The empennage featured a D-shaped rudder, equally disposed above and below the rear fuselage, and a large triangular tailplane bearing D-shaped elevators. Early aircraft had a small rectangular fixed fin, but this was later dispensed with. The undercarriage had two forward-projecting skids, each mounted with a pair of wheels on a short axle. Various single 35 h.p. to 60 h.p. powerplants as indicated.

Type D Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
31 ft	28 ft	9 ft 2 in	310 sq ft		500 lb		50 mph/ 43 kn	100 mi
9.45 m	8.53 m	2.79 m	28.8 m2		227 kg		80 km/h	161 km

Two seat tractor biplane for Australian John Robertson Duigan, a major refinement of the Type D, having a square rather than triangular cross section fuselage, simplifying construction and allowing the crew seats to be lower down, giving more protection. The fuselage was constructed of wire-braced ash, metal covered forward of the cockpits and fabric covered aft. The observer sat in front with the pilot sitting behind the cut away trailing edge, and there was a small "Cellon" window in the floor to improve downward vision. The fabric covered, wooden wings were of two-bay layout, with English ash spars and poplar ribs, with rounded wingtips formed of rattan cane. Lateral control was by wing warping. The tailplane was steel framed, with a rectangular fixed stabiliser and elevator and rudder. The undercarriage was simpler than the Type D, a V-strut below the wing leading edge bearing a leaf-spring axle whose wheels had the refinement of covered spokes, and under this a single long skid supported by a second V-strut below the trailing edge and a single strut from the extreme nose of the aircraft. A sprung tailskid was mounted below the rudder and small hoops were fitted below the outer interplane struts to protect the wingtips. One 40 h.p. Alvaston (later 35 h.p. ENV Type D) powerplant.

Duigan Biplane Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
34 ft	29 ft 6 in		300 sq ft				40 mph/ 35 kn
10.36 m	8.99 m		27.87 m2				64 km/h