Spats and a Big Gun - the Vickers Type 161A Viagra
Vickers (Aviation) Ltd had a problem. In response to Air Ministry Specification F.29/27, chief designer R.K. Pierson CBE had designed a pusher biplane cannon fighter. In competition was the Westland C.O.W. Gun Fighter - a svelte, low-winged monoplane. Pundits derided the Type 161 as a throwback to the Vickers Gunbus from the First World War. Worse, newly-appointed Vickers chief test pilot, Captain Joseph Summers noted yaw stability issues and a disappointing turn of speed on the Type 161's maiden flight. This prompted a crisis-management meeting of all heads of department at Vickers (Aviation) Ltd.
Rex Pierson prepared to correct stability problems with a reshaped rudder and small finlets added at the tailboom mounting points. That would addressed the yaw issues. 'Mutt' Summers' speed concerns might be addressed by replacing the Jupiter VIIF with Bristol's latest air-cooled radial engine - the higher-powered Mercury IIIA. To that was added an undercarriage clean-up as suggested by Vickers' head of Aircraft Structures. (Barnes Wallis also held forth at length about basket-weaving techniques but nobody else could quite glean his point.) So, Vickers' plan of attack was more power, improved stability, and an aerodynamically-efficient undercarriage.
It was quickly realized that Wallis' suggestion of a fully-retractable landing gear had to be shelved (along with his musings on baskets, profound though they may have been). In place of a retracting gear, Pierson proposed a spatted main gear on the prototype with reduced 'struttery'. If desired by the Air Ministry (or RAF), production machines might include a semi-retractable spatted gear. This was agreeable to all (at least after a lengthy dissertation on bird's nest from Barnes Wallis) and a plan to implement the scheme begun.
In the meantime, Vickers Elswick had also reviewed the specified weapon. The C.O.W. gun was a 1½-pounder firing 37mm x 190 rimmed cartridges from a five-round clip. Elswick remained convinced of the superiority of their rival design which had lost out to the C.O.W. gun back in 1917. That Vickers 1 Pr Mk III was much lighter but also much less powerful. [1] As concessions to modernity, Elswick redesigned their concept to take a longer barrel and to fire standard 37mm x 94 rimmed ammunition (from the 1 Pounder 'Pom-Pom' anti-aircraft gun). The result was a weapon which was almost as powerful as the C.O.W. gun but weighed almost half as much. [1] This new Vickers gun was offered as a lighter weight option to the 200 lb C.O.W. gun.
Within a week, the prototype (J9566) had been re-jigged and re-engined at Vickers' experimental assembly shed. 'Mutt' Summers ferried the revised Type 161A to Martlesham Heath for further service testing. As soon as they laid eyes upon the cleaned up Vickers, the competition at Westland Aircraft cried foul. Their Westland C.O.W. Gun Fighter was already powered by a Mercury radial. Given a time-extension, they too could devise a cleaner main gear fitted with spats. But the Air Ministry was having none of it. Testing at Martlesham Heath was already well underway and an A&AEE report imminent.
The outcome of the competition surprised no-one. Between the jaunty angle of its big, 37 mm C.O.W. gun and those highly-intimidating spats, the Type 161A was a shoe-in. Vickers soon received a production contract to supply 24 Type 161As which the RAF had dubbed the Vickers Viagra Mk.I. The debate continues over the origin of this 'popular name'. The commonly-accepted explanation is that Viagra began as an acronym for the official parlance 'Vickers Interceptor Aircraft - Gun, Repeating, Airborne'. Whatever the name origin, flying the heavily-armed Vickers Viagra Mk.I certainly perked up the personnel of No.54 Squadron RAF. [2]
The RAF operated the Viagra Mk.Is until September 1936 when No.54 Sqn traded in its Vickers for more conventionally-armed Gloster Gauntlet fighters. Vickers demonstrated a single Viagra Mk.II as a 'private venture' but the RAF declined to accept its Vickers 1 Pr Mk IV autocannon into service. That cannon was then offered for export as a light anti-aircraft gun with some success - notably sales to Bolivia, Siam, and China. Several attempts were made by Vickers to sell the gun to the French but, for inexplicable Gallic reasons, such pitches always elicited titters. In its export form, the 1 Pr Mk IV was marketed as the Vickers Aviation Cannon, High-Explosive or 'VACHE'.
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[1] The original Vickers 1 Pr Mk III had fired a much smaller 37mm x 69 rimmed round from a belt.
[2] No.54 had been formed in 1930, flying Armstrong-Whitworth Siskin Mk.IIIAs from RAF Station Hornchurch.
