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WORLD WAR 1
X-PLANE


Supermarine (Pemberton-Billing) P.B.31E


Quadruplane Airship Interceptor Prototype Aircraft


One flyable and one incomplete aircraft was all that was had of the optimistic P.B.31E airship hunter for Britain during World War 1.
Authored By: Staff Writer | Edited: 5/5/2019

Specifications


Year: 1917
Status: Cancelled
Manufacturer(s): Supermarine Aircraft / Pemberton-Billing - UK
Production: 2
Roles: Interception; X-Plane;
Crew: 3
Length: 37.01 ft (11.28 m)
Width: 60.04 ft (18.3 m)
Height: 17.72 ft (5.4 m)
Weight (Empty): 3,682 lb (1,670 kg)
Weight (MTOW): 6,173 lb (2,800 kg)
Power: 2 x Anzani 9-cylinder air-cooled radial piston engines developing 100 horsepower and driving multi-bladed propeller units in puller fashion.
Speed: 75 mph (120 kph; 65 kts)
Ceiling: 16,076 feet (4,900 m; 3.04 miles)
Range: 447 miles (720 km; 389 nm)
Rate-of-Climb: 165 ft/min (50 m/min)
Operators: United Kingdom (cancelled)
Prior to becoming the storied "Supermarine" concern of World War 2 fame, the company existed under the Pemberton-Billing brand label. One of the company's earliest original projects became the P.B.23E pusher biplane fighter of 1915. In December of 1916, the company officially changed its name to the better-remembered Supermarine brand and its first project under this title was the "P.B.31E". The P.B.31E was based in the earlier, ultimately abandoned, P.B.29E "Nighthawk", a twin-engined quadruplane interceptor, but had little impact (if any) in the war effort for Britain.

The original P.B.29E was conceived of as a Zeppelin/airship hunter and developed around the concept of long-range / long-endurance for operations principally in low-light hours. A complete set of four wing mainplanes was featured to provide the needed lift, drag, and maneuverability of the gunnery platform. Three crewmembers were carried aloft with the third set to manage a single 7.7mm machine gun at the center-section of the fuselage. The massive aircraft was quite the spectacle for its time, its stacked mainplanes rising high into the sky.

This aircraft was completed and flown during late-1915 into early-1916 but was eventually lost to accident during testing. Nevertheless, the concept was interesting enough to British authorities that another version of this aircraft was furthered - this to become the P.B.31E.

The P.B.31E was readied as soon as February 1917 and flown for the first time that same month. It essentially retained the form and function that made the P.B.29E noticeable to interested observers. The three-bay, quadruplane wing configuration played its part in the design and was situated well-ahead of midships. The wings held a noticeable rearward-crank along their outer sections - essentially showcasing an early-form of sweptback wing. The fuselage was slab-sided and deep while offering enclosed working spaces for the crew (some being heated). The tail unit was a complex structure relying on a twin-finned, double-planed approach common to some World War 1 bomber designs.




From the outset the P.B.31E needed the range and loitering times envisioned for the P.B.29E for the aircraft would have to be present prior to the arrival of German airships in British airspace. From there, the aircraft would need the firepower and performance to bring these fragile airships down before they could reconnoiter or drop their modest war loads on the British populace or targets-of-opportunity. Engineers estimated their new design to have an endurance window of some eighteen hours of flight time which was a very optimistic proposal.

For power the design team selected a pair of Anzani 9-cylinder air-cooled radial piston engines, each outputting 100 horsepower and driving multi-bladed propeller units in typical puller fashion.

Proposed armament was centered on 1 x 37mm Davis Gun cannon (detailed in the Small Arms section of this site) at the nose (also included here was a generator-fueled searchlight) fed by a stock of twenty projectiles. Supporting this was a trainable 7.7mm machine gun aft of the Davis Gun's position as well as a second 7.7mm machine gun also located aft of the top wing. All told, this provided the crew with formidable firepower at range.

Flight testing of the first of two P.B.31E prototypes was undertaken in the early-middle part of 1917 but its failings quickly shown through. The aircraft only managed a speed of 60 miles per hour (far short of the advertised 75mph limit) and its rate-of-climb proved poor as it took sixty minutes to reach 10,000 feet. On top of this was the propensity for the already unreliable Anzani series engines to overheat when pushed. All this worked against the P.B.31E seeing maturity in its prototype stage.

With such a showing, work was stopped on the second, still-incomplete prototype and the first prototype was scrapped as soon as July 23rd, 1917 - ending this first Supermarine venture in full.








Graphical image of an aircraft medium machine gun
Graphical image of an aircrat automatic cannon

Armament



PROPOSED:
1 x 37mm Davis Gun cannon.
1 x 7.7mm trainable machine gun aft of Davis Gun mounting.
1 x 7.7mm trainable machine gun aft of uppermost wing member.

Variants / Models



• P.B.31E - Base Series Designation; one flyable prototype completed; second incomplete prototype scrapped.
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