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Battle P.24 Monarch

Experimental Aircraft



In October 1938, an experimental P / 24 Monarch propulsion system with counter-rotating coaxial propellers was installed at Fairey-Battle.

In the early 30s, three units were built in two modifications: Fairey V-12 Prince I and Super Prince II. The third "Prince" was of a completely different design, but used the same cylinders. The Fairey H.16 Prince III was actually two twin eight-cylinder boxer engines, each working on its own shaft and on its own propeller - the shafts were coaxial, and the propellers, respectively, were coaxial, of opposite rotation. The cylinders were located vertically, cooling - liquid, gas distribution - poppet valves, two-speed single-stage supercharger. Each half had its own fuel system, oil supply system, etc. So the Fairey motors weren't actually H-shaped.

The Fairey P.24 Monarch was a vertical H engine in which the left and right sides of a 12-cylinder engine could operate independently of each other. The aluminum crankcase consisted of an upper and lower half. Each block of six cylinders was attached to the crankcase. An aluminum cylinder head is attached to the cylinder block. P.24 retained the bore and stroke of the P.12 (and P.16). Each cylinder had two intake valves and one exhaust valve, all driven by a single overhead camshaft driven from the rear of the engine. The 1.8125 "(46 mm) intake valves were actuated by a T-type tappet, while the 2.25" (57 mm) exhaust valves were actuated directly from the camshaft.

Fairey P.24 Integral Passageways

Drawing, from British Patent 463,501. The configuration shown is almost identical to that used on the actual engine. The section on the right shows the numerous sharp turns of the fuel / air mixture on the way to the cylinders.

The development of the engine family began in 1935 under the leadership of the chief designer of the engine building department of A.G. Forsyt, although the first estimates began in the early 30s. The first copy of the "Monarch" in October 1938 was installed at the Fairey Battle (K9370). Due to its design, the power plant had the reliability of a twin-engine aircraft, the failure of one half did not lead to the termination of the operation of the other.

In the period 39-41. The Monarch passed a number of tests, a resource of 50 hours was obtained in 1939, in the 41st the engine worked 15 hours at a maximum power of about 2200 hp. and flew 87 hours in the Battle. Apparently in 1941, it was decided that the UK would not produce Fairey engines, and in December 1941 the plane with another additional "Monarch" was transferred to the United States, flew there another 253 hours on tests and was transferred to the British back through 18 months. The reviews were rather negative about the motor: some design features were considered controversial, others did not meet American standards, and still others hindered the further development of the motor. A surprising feature is indicated by reports from the United States - the lack of counterweights on the crankshaft. The engine worked, but according to the Americans, it took 2-3 years before its final development, the desire to spend time on this and the lack of production capacity put an end to the idea of ​​producing the engine in the United States. But it was supposed to put it on the P-47, Fairey Barracuda, Fairey Firefly, Blackburn B.20 ...

Fairey P.24 Monarch (Prince 4) repeated Prince III, but there were 24 cylinders of 12 in each group. The "Monarch" supercharger was a two-stage four-speed - most likely, we are talking about two separate superchargers (one stage / two speeds), each working on its own block. "Prince" was designed for a power of about 1500 hp, "Monarch" - about 2200 hp (with the prospect of up to 3000 hp).


P.24 flew a lot in the USA, but the Americans were mainly interested in counter-rotating coaxial propellers. Battle retained its serial number on the fuselage, but the British markings were painted over and replaced with American markings. Notice the star under the wing and the stripes on the rudder.

Fairey-P.24-Monarch in US

On trials in the USA, the Fairey P-24 Monarch showed the following characteristics:

Takeoff power 2140 hp. from. at 3000 rpm.

Power: 2030 hp at 2600 rpm at an altitude of 1524 m, 1780 hp from. at 2600 rpm at an altitude of 3657 m.

Maximum power: 2100 hp from. at 3000 rpm at an altitude of 1828 m, 1850 hp from. at 3000 rpm at an altitude of 3962 m. All tests were carried out on 87 octane fuel.

In 1943, the history of the engine ended.


  • Fairey Aircraft since 1915 /by H. A. Taylor (1988)/
  • British Piston Aero-Engines and their Aircraft /by Alec Lumsden (2003)/
  • World Encyclopedia of Aero Engines /by Bill Gunston (2006)/
  • Fairey Firefly /by W. Harrison (1992)/