Armstrong Whitworth (Aerial Dept.) Low Volume Production

Single seat, single-bay unstaggered tractor biplane fighter (though originally concieved as a monoplane), of mixed wood and steel construction, with a fabric covered square section box girder fuselage. The fuselage terminated in a horizontal knife edge, with divided elevators but no fixed horizontal tailplane, but a small fixed tailplane was fitted after testing. Likewise, the original constant chord ailerons were replaced with inverse tapered ones of larger area. One 50 h.p. Gnôme powerplant.

F.K.1 Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
26 ft 11 in	24 ft 3 in	10 ft 2 in					75 mph/ 65 kn
8.2 m	7.39 m	3.1 m					121 km/h

Three seat single bay escort fighter triplane, the centre wing was nearly twice the span of the equal span upper and lower wings and was located at mid level to the slender fuselage immediately behind the engine, the wide gap to upper and lower wings requiring them to be attached to the fuselage by a series of struts. The two gunners nacelles were mounted above the centre wing. The undercarrige consisted of a single centrally placed shock absorbing strut terminating in two closely spsced wheels, with a small wheel under each wingtip for stability. The tail was supported by long struts attached to the fuelage just aft of the wing. One 250 h.p. Rolls-Royce Eagle powerplant with a four bladed propeller.

Three seat two bay escort fighter triplane derived from the earlier F.K.5. Overall dimensions were larger, but the overhang of the centre was now less pronounced. The centre wing was now attached directly to the fuelage upper longerons, the fuelage itself now much deeper, allowing the lower wing to be attached to the lower longerons. The gunners nacelles were moved to be below the centre wing. A more conventional undercarriage was fitted, consisting or two pairs of mainwheels attached to the intersection of the fuselage with the lower mainplane leading edge, which resulted in a very narrow track, with a supporting tailskid attached to the rudder post. One 250 h.p. Rolls-Royce Eagle powerplant with a four bladed propeller.

F.K.6 Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
62 ft	37 ft	17 ft
18.9 m	11.28 m	5.18 m

Single seat, two-bay biplane fighter with a square section fuselage to meet Air Board Specification A.2(a). The fuselage, a simple wire braced box girder with ply side panels, filled the gap between the wings. The position and shape of the cockpit broke the continuity of the upper longerons, consequently the forward fuselage embodied duralumin girders of channel section; these also bore the fuel and oil tanks, along with the pilot's seat. The equal span wings were of unequal chord, with slight stagger to the leading edge, dihedral on the lower wing only, and featured ailerons on both upper and lower wings. The twin Vickers machine guns werre completely enclosed in a fairing above the deep engine cowling, leaving poor forward and downward visibility for the pilot. One 230 h.p. Bentley BR2 powerplant.

F.M.4 Armadillo Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Endurance	Service Ceiling
27 ft 9 in	18 ft 10 in	8 ft 7 in	232 sq ft	1250 lb	1860 lb		125 mph/ 109 kn	2-3/4 hr	24000 ft
8.46 m	5.74 m	2.62 m	21.55 m2	567 kg	844 kg		201 km/h		7315 m

Single seat, two-bay biplane fighter to meet RAF Specification Type 1. The slab sided fuselage was flat at the bottom, but featured a curved upper coaming above the upper longerons forward of the tailplane. The unequal chord wings featured stagger on both leading and trailing edges, both sets of mainplanes having slight dihedral. Very small ailerons were provided to both upper and lower mainplanes. Unlike the Armadillo, the upper mainplane was raised above the fuselage to the level of the pilots eyes. On the first aircraft the lower wing was attached directly to the lower longerons, but the second machine had increased wing gap, with the fuselage mounted between the wings. One 320 h.p. ABC Dragonfly powerplant.

Ara Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
41 ft 9 in	27 ft 8 in	11 ft 7 in	433 sq ft	1803 lb	2707 lb		108 mph/ 94 kn		18000 ft
12.73 m	8.43 m	3.53 m	40.23 m2	818 kg	1228 kg		174 km/h		5486 m