Lorraine Pétrel

Design and development

The Pétrel was an upright V-12 engine with two banks of six cylinders, arranged at 60° to each other, driving a common crankshaft. The cylinder blocks were bolted onto the crankcase, all light alloy parts. The crankcase came in two pieces, with seven crankshaft bearings in the upper section. Roller bearings were used at the crankshaft ends; the remaining five were plain. The upper crankcase section also had integrally cast water channels as part of the cooling system.

Steel cylinder liners were screwed into the heads, with their lower parts projecting into the crankcase. Steel seats for valves and sparking plugs were shrunk into the heads. The pistons were forged from alugir, with three compression and one scraper ring and floating bronze bushes for the gudgeon pins. The twelve pistons were connected to the six crankpins in pairs, each with a master and an auxiliary connecting rod. The master rods had forked big ends with white metal bearings; the auxiliary rod ends ran between the forks on bronze bushes.

The Pétrel had four overhead valves per cylinder, two exhaust and two inlet, in bronze valve guides. Each bank had its own overhead camshaft and each cam operated a pair of valves through T-shaped tappets, the stem of the T moving in a guide to avoid sideways force on the valve stems. There were two spark plugs per cylinder and twin magnetos. A carburetor fed the mixture into the intake of the supercharger, at the rear of the engine. The Pétrel's output could be left or right handed; a Lorraine patent planet gearset, with six satellite gears, provided an 11:17 reduction of propeller shaft speed.

Engine lubrication was by forcing pressurized oil through the crankshaft, with sump scavenging. The supercharger had its own lubrication system.

First run in 1932, the early Pétrels produced only 370 kW (500 hp), but by 1938 the engine had been developed into the 12Hars model which gave 640 kW (860 hp).

Operational history

Many of the aircraft types to use the Pétrel were one-offs, testing the Lorraine against better known engines from Hispano-Suiza and Rolls-Royce. The 12Hars model was used in the Koolhoven F.K.55 prototype fighter to drive a pair of counter-rotating twin-bladed propellers.

The Potez 542 (a version of the Potez 540) was built in numbers, with 74 of these twin-engined, multi-role (bomber, reconnaissance and transport) aircraft supplied to the French and Spanish air forces.

Variants

;12H Pétrel :Initial power 370 kW. ;12Ha :370 kW ;12Hars :477 kW. ;12Hdr :370 kW at 2300 rpm ;12Hdrs :536 kW at 2300 rpm ;12Hfrs Normale :536 kW. ;12Hfrs Chasse :Designed for fighter aircraft produced higher powers, 567 kW at 2,800 rpm and 4000 m. ;12Hgrs:608 kW at 2800 rpm

Applications

• Breguet Br.19.10
• Fokker D.XVII
• Hawker Fury
• Hawker Hart
• Koolhoven F.K.55
• Nieuport-Delage NiD 82
• Potez 39
• Potez 542
• P.Z.L. P.8/II
• Renard R-31
• Société Aérienne Bordelaise AB-21
• French Motor Torpedo Boat Prototype 40K

Engines on display

• A Pétrel is on display in the aircraft section of the Musée Royal de l'Armée, Brussels.

Specifications (12Hfrs, Normale)

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• Ignition system: 2 plugs per cylinder; 2 magnetos |power/weight=

References

References

1. Gunston, Bill. (1989). "World Encyclopaedia of Aero Engines". Patrick Stephens Ltd.
2. Grey, C.G.. (1972). "Jane's All the World's Aircraft 1938". David & Charles.