Alvis Leonides
The Alvis Leonides is an air-cooled radial engine with nine cylinders. It was manufactured in its first version by the British manufacturer Alvis from 1937. The company was building French engines from Gnôme et Rhône under license at the time.
history
The engine was developed by George Thomas Smith-Clarke . The first prototype ran in December 1936 and achieved an output of 415 hp. Development was pushed ahead and the engine was tested in a converted Bristol Bulldog . Airspeed provided a test pilot with George Errington . The Air Ministry issued the civil license before the war began. Nevertheless, the development work was initially largely stopped, but resumed after the end of the war.
After further testing in an Airspeed Oxford and an Airspeed Consul , the engine was offered in the versions 500 and 510 for airplanes and 520 for helicopters. Both had a starting power of 500 hp. The Percival Prince was the first aircraft to have Alvis-Leonides engines. The approval took place in August 1958. The RAF chose the engine in the version 503/6 (Mk.126) as drive for the standard training aircraft Percival Provost . From 1959, the engines were built with an increased output of 650 hp and a stroke increased to 121.9 mm as the 530 series, especially for the Scottish Aviation Twin Pioneer . The President and Pembroke versions, derived from the Percival Prince, were also powered by Leonides motors. The Bundeswehr had 34 of the latter in service until 1972, the engines of which were designated Mk.127.
The helicopter variant was first used in the British license production of the Sikorsky S-51 , and later also in the Bristol 171 Sycamore . This required a blower and a modified oil supply that enabled the engine to operate in any position of the crankshaft between horizontal and vertical.
Production stopped in 1967 when the company became part of the British Leyland Motor Corporation .
From 1951 there was also a double star variant with 14 cylinders and 870 hp takeoff power, the Alvis Leonides Major .
Technical design
The cylinders are made of steel, the screwed and shrunk cylinder heads of aluminum. The cylinder sliding surfaces are nitrided. In the cylinder heads there is one inlet and one outlet valve made of austenitic steel for each cylinder, the outlet valve is also sodium-cooled. Both valves are actuated via rocker arms and push rods from a two-track cam drum with four cams each. The bumpers run with rollers on the cam drum. The entire valve train is completely encapsulated. The pistons are made of forged light metal and have two compression and two scraper rings. All connecting rods are made of steel and have a double-T profile. The main connecting rod has a white metal bearing , the secondary connecting rods linked to it have bronze bearings . The crankshaft rotates in the housing in two cage-free ball bearings and has a separable crank pin that is designed as a splined shaft . A ball bearing was also used to absorb the propeller thrust in the axial direction. The crankcase itself consists of two parts and is made of light metal.
The ignition takes place with two magnets from BTH. Each cylinder has two spark plugs . The ignition system is completely shielded.
It is charged by a single-stage radial charger with a ratio of 6.5: 1. The fuel is injected into the intake manifold behind the throttle valve through a Hobson single-point injection system. The throttle body is heated by oil. The engine is supplied with oil through dry sump lubrication . A pressure pump and two suction pumps are available for this purpose. The oil pressure is between 4.2 and 5.6 bar. The motor can be equipped with a constant speed propeller as standard. The cooling air flow rate is regulated via electrically adjustable slats on the rear of the engine casing. The engine is started either with a pyrotechnic starter (starter cartridge) or with a combined hand / electric starter.
Technical specifications
| Type | 502/2 | 502/4 | 502/5 | 503/5 | 503/6 | 503/7 | 503/8 | 521/1 | 523/1 | 524/1 | 531/8 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Bore (mm) | 122 | ||||||||||
| Stroke (mm) | 112 | 121.9 | |||||||||
| Displacement l | 11.78 | 12.84 | |||||||||
| compression | 6.8: 1 | ||||||||||
| Starting power (PS) | 520 | 520 | 520 | 520 | 520 | 520 | 520 | 480 | 520 | 500 | 615 |
| Dry weight kg | 356 | 361 | 363 | 367 | 367 | 367 | 367 | 358 | 358 | 331 | 390 |
| Reduction | 0.625 | 0.5 | 0.8 | 0.8 | without | 0.5 | |||||
| Diameter (mm) | 1054 | 1143 | |||||||||
| Length (mm) | 1382 | 1397 | 1397 | 833 | 1382 | ||||||
swell
- FAA Type certificate (PDF file; 36 kB)
- Jane's all the world's aircraft 1963/64
- British Piston Aero Engines and their Aircraft , Alec Lumsden, ISBN 1-85310-294-6 .
- Aero engine encyclopedia , Bill Gunston, ISBN 3-613-01422-X .
