Simanaitis Says

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NOEL PEMBERTON BILLING had a fertile imagination, exemplified by his four-winged P.B. 31E Zeppelin buster. We continue the tale of this quadruplane in Part 2 today and view one in the air, albeit the virtual air of Microsoft Flight Simulator via GMax.

1917 Supermarine P.B. 31E. This and the following images of my GMax model for Microsoft Flight Simulator.

Lighting the Mission. The 1917 Supermarine P.B. 31E Nighthawk’s mission was to climb to 10,000 ft. and wait for a dreaded Zeppelin to loom into view. To aid this, the Nighthawk’s nose had a trainable searchlight, one so powerful that it required its own dedicated powerplant to drive a dynamo providing the necessary electricity.

The British firm ABC Motors provided a flat-twin-cylinder 5-hp engine, which resided in one of the primary engines’ nacelles. ABC 1.5-hp versions had already been employed as auxiliary power units on Coastal class blimps of the Royal Naval Air Service in 1916. Modern jets are also equipped with APUs, as they’re known today.

The P.B. 31E cabin. The red tanks are armor-plated fuel and oil supplies. The silver cannisters are ammo. The Davis recoilless rifle up top displays its Janus-like design.

P.B. 31E Accommodations. The Nighthawk’s extended missions called for pilot and backup pilot, plus two gunners, fore and up top. A single “hot-bunking” opportunity was provided, and the entire glass-enclosed cabin was heated. The pilot, by the way, had added side glass for low-angle viewing.

The P.B. 31E’s airy view for the pilot. I might be a little nervous about all that gasoline residing near the ammo.

Designers also came up with the idea of lining the wooden fuselage with heavy fabric to mitigate the danger of inevitable splinters when the Nighthawk was fired upon.


These technical drawings for the Nighthawk bear the initials of R.J. Mitchell. A junior draftsman at Supermarine at the time, he was to lead design of the renowned Spitfire two decades later. Image from Plane Encyclopedia.

For its 18-hour missions, the P.B. 31E required around 950 gallons of aviation fuel, weighing some 2000 lb. and carried in nine separate tanks arranged throughout the cabin, the tanks and fuel lines armor-plated.

Armament supplies included 20 shells for the Davis recoilless rifle and six double cartridges for the Lewis machine guns, together with incendiary flares for use in the event of the Nighthawk finding itself above a Zeppelin.

The P.B. 31E had an empty weight of 3677 lb. Fully loaded for battle, its gross weight was 6146 lb.

Less Than Adequate Power. Though Zeppelins weren’t particularly maneuverable, chances of a Nighthawk outmaneuvering one were modest indeed. The P.B. 31E’s huge four-bladed wooden propellers were swung by two engines, each producing 100 hp. By comparison, the Sopwith Camel’s 112 hp had less than quarter as much mass to propel.

What’s more, these Anzani ten-cylinder air-cooled radials had a reputation for overheating and unreliability.

My modeling of the Anzani ten-cylinder air-cooled radial. Microsoft and GMax coding allows its rocker arms to display animation.

The Nighthawk had an intended maximum speed of 75 mph. In actuality, it was hard pressed to match the Zeppelin’s 60 mph (and Zeppelins got more powerful and faster as WWI evolved). What was particularly disheartening was the P.B. 31E’s lethargic rate of climb: It took 60 minutes to reach Zeppelin territory of 10,000 ft.

The first prototype crashed. A second Nighthawk confirmed that if it somehow climbed quickly enough to encounter a Zeppelin, the enemy could evade it with greater speed. Also confirming the non-deal, introduction of incendiary bullets fired from more agile fighters proved more effective in Zeppelin defense.

Rich Duisberg wrote in Motor Punk that the P.B. 31E flew a “fine line between genius and insanity…. We love the Nighthawk, though; mad designs like this should be celebrated, don’t you think?”

I agree, especially as a GMax/Microsoft Flight Simulator project. ds

© Dennis Simanaitis,, 2020

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