The Supermarine P.B.31E Nighthawk was a British aircraft of the First World War and the first project of the Pemberton-Billing operation after it became Supermarine Aviation Works Ltd.
It was an anti-Zeppelin night fighter operated by a crew of three to five and had a planned flight endurance of 9-18 hours.
The prototype flew in February 1917 with Clifford Prodger at the controls.
It proved to not meet the promised specification and no more were built.
The Nighthawk had six-bay swept quadraplane wings and a biplane tailplane with twin fins and rudders.
The fuselage filled the gap between the second and third wings; the cockpit, which carried up to the top wing turret, was enclosed and heated.
Along with the intended long endurance, it was suggested it would be able to patrol at low speeds and await the Zeppelin.
For armament, it had a trainable nose-mounted searchlight, a 1½-pounder (37 mm) Davis gun mounted above the top wing with 20 shells, and two .303 in (7.7 mm) Lewis guns.
Power for the searchlight was provided by an independent petrol engine driven generator set made by ABC Motors, possibly the first instance of a recognizable airborne auxiliary power unit.
Although touted as being able to reach 75 miles per hour (121 km/h), the P.B.31E prototype only managed 60 miles per hour (97 km/h) at 6,500 feet (2,000 m) and took an hour to climb to 10,000 feet (3,000 m), which was totally inadequate for intercepting Zeppelins.
German airships, such as P, or R Class military Zeppelins were themselves capable of top speeds of around 60 miles per hour (97 km/h).
Furthermore, given the Anzani engine’s reputation for unreliability and overheating, it is unlikely that the aircraft would have delivered the advertised endurance.
37 ft 0 in (11.28 m)
60 ft 0 in (18.29 m)
17 ft 8.5 in (5.398 m)
962 sq ft (89.4 m2)
3,677 lb (1,668 kg)
6,146 lb (2,788 kg)
2 × Anzani 10 cylinder air cooled radial piston engines,
100 hp (75 kW) each
4 bladed fixed pitch propellers
75 mph (121 km/h, 65 kn)
9 hours normal, 18 hours maximum
Time to altitude
10,000 ft (3,048 m) in 60 minutes
One 1½ pdr Davis gun and one Lewis gun above upper wing