Sunday Fail : Supermarine PB 31E Night Hawk

Military projects do not always work out as you know but usually the end result is something reasonably close to the original project aims (once you throw enough extra billions at it). But in this weekly series i will present projects that never made it. Military projects that simply never worked, not to say the projects were all bad. They failed for a variety of reasons, for the PB 31E it was probably just a bit ahead of it's time...

In this first week we go back to the First World War and the first aircraft to bear the Supermarine name, the company changed it's name from Pemberton Billing in 1916 (after Mr Pemberton Billing sold his interests to the company's other directors). One of the last aircraft Pemberton Billing had been working on had been the PB 29E, a large quadruplane for anti-airship defence. Unfortunately the sole PB 29E crashed during flight testing but the Admiralty decided to continue pursuing Pemberton Billing's ideas for combating the zeppelin menace so sponsored a further aircraft (Bruce 1969).

Supermarine PB 31E

This was the PB 31E, like the 29E it was a large quadruplane 37ft (11.27m) long and with a wing span of 60ft (18.28m). It was made more sturdy than the 29E with a planned crew of 5 and heavily armed with a 1½-pdr recoiless gun and twin Lewis machine guns. It was intended to be able to stay aloft for up to 18 hours and carried a searchlight that was powered by a separate engine and thus was probably one of the first aircraft to carry an auxiliary power unit (Andrews & Morgan 1981). Because of the long planned duration it was fitted with some basic comforts for the crew including a heated cabin. The aircraft also carried armour in some key areas and the cockpit was bound with fabric to avoid wood splinters in the event of a crash to protect the crew.

The problem with all of these features was weight, the PB 31E weighed over 6100lb (2787kg) when loaded and there simply wasn't the engine technology of the time to properly handle such a plane. Two 100hp Anzani engines powered the PB 31E and was enough to get it airborne but not enough to give it sufficient performance to perform in the anti-zeppelin role. The PB 31E took an hour to climb to 10,000ft which meant that zeppelins could easily escape it by ditching ballast and climbing rapidly. The design speed had been 75mph (120kph) which was considered fast enough to catch zeppelins (though some zeppelins could go faster than that in favourable conditions) but it is reported the PB 31E struggled to pass 60mph (97kph) (Bruce 1969).

Front view showing the search light on the nose

The PB 31E first flew in February 1917 but by then it was apparent there were flaws in the concept, highlighted by the PB 31E's poor performance. Unable to pursue a zeppelin it's only chance of success would have been the sheer luck of being in the right place at the right time and firing on the zeppelin before it got out of range (Bruce 1969). It's main armament, a 1½ pounder Davis non-recoil gun, was also rather unwieldy.

The sole PB 31E was scrapped in the Summer of 1917, the second planned example never being built. The PB 31E, which was given the name Night Hawk, was technically innovative and it's concept could maybe have worked with a better performance. It was an early example of what we would call today a "weapons system" (Andrews & Morgan 1981). In the event the zeppelin was near the end of it's time as a military weapon anyway, Supermarine survived the war. You may have heard of one of their later products.

Further reading :

Supermarine Aircraft Since 1914 (Andrews & Morgan, Putnam, 1981)
Warplanes Of The First World War - Volume 3 (Bruce, Macdonald, 1969)