In the mid 'twenties, the British Air Ministry found attractive the possibility of the 37mm COW (Coventry Ordnance Works) gun for use against bombers. Accordingly, Specification F.29/27 was issued calling for a single-seat dedicated bomber-interceptor armed with this large and heavy weapon. The specification called for the gun to be mounted in a fixed position to fire forward and upward at an oblique angle of at least 45°. Provision was to be made for oversize and automatically-fed ammunition clips totalling 50 shells, the entire COW gun mechanism had to be easily accessible to the pilot and steadiness as a gun platform was a prime requisite.
Vickers submission to this Specification, the Type 161, was extraordinary in that it reverted to the long-abandoned pusher biplane formula with tail surfaces carried by booms. Despite its configuration the Type 161 embodied some advanced features and became the subject of a single-aircraft Air Ministry contract. An unequal-span two-bay biplane with comparatively high aspect ratio wings with duralumin plate and tube structure, it had a metal mono-coque nacelle, accommodating the pilot to port and the COW gun to starboard, which was faired into the upper wing and raised above the lower wing by splayed N-type struts. The 530hp Bristol Jupiter VIIF nine-cylinder radial carried at the rear of the nacelle drove a four-bladed propeller, aft of a long tapered cone which, intended to promote directional stability, was supported by struts from the tubular tail-booms and the tailplane.
The Type 161 was flown for the first time on 21 January 1931, and after provision of a broader-chord rudder, it flew extremely well, arriving at Martlesham Heath in September 1931 for official evaluation. Development was discontinued when official interest in promoting the quick-firing COW gun lapsed.
Engine: Bristol Jupiter VIIF, 530hp
Max take-off weight: 1520 kg / 3351 lb
Empty weight: 1080 kg / 2381 lb
Wingspan: 9.75 m / 32 ft 0 in
Length: 7.16 m / 24 ft 6 in
Height: 3.76 m / 12 ft 4 in
Wing area: 25.08 sq.m / 269.96 sq ft
Max. speed: 298 km/h / 185 mph