|Allison V-3420 Engine|
|Type||Liquid-cooled W-24 piston engine|
|National origin||United States|
|Manufacturer||Allison Engine Company|
|Major applications||Fisher P-75 Eagle|
|Number built||150|
|Developed from||Allison V-1710|
Design and development
In 1937, at the behest of the United States Army Air Corps, the Allison Engine Company agreed to design and build a large-displacement high-power aircraft engine. The resulting V-3420 was essentially a pair of 12-cylinder Allison V-1710 engines mated to a common crankcase with a 30° angle between the inner cylinder banks. The crankshafts of the two V-1710 engines were geared together to drive a common propeller shaft. Most V-3420 parts were interchangeable with those for V-1710-E and -F engines.
The V-3420 had a power-to-weight ratio of 1.6 kW/kg or 1 hp/lb, excellent for its time. It was envisioned as a powerful yet compact engine for several advanced USAAF projects of the day, including the Douglas XB-19, the Boeing XB-39 Superfortress, the Lockheed XP-58 Chain Lightning, and the Fisher P-75 Eagle. As none of these designs saw more than limited production, only about 150 V-3420s were built.
- V-3420-A16R (-11)
- V-3420-A16L (-13)
- left-hand rotation of propeller, single-stage supercharger with single-stage turbocharger and intercooler
- V-3420-A18R (-17)
- Supercharger ratio 7.2:1
- V-3420-B (-23)
- Similar to the -A but with mechanically driven supercharger in two variable-speed stages
Engines on display
- A V-3420-23 (B10) is on public display at the Aerospace Museum of California in North Highlands, California.
- A V-3420 is on public display at the Glenn H. Curtiss Museum in Hammondsport, New York.
- A V-3420-23 engine is on public display at the National Museum of the United States Air Force in Dayton, Ohio alongside a Fisher P-75 Eagle
Specifications (V-3420-A18R (-17))
Data from Aircraft Engines of the World 1946
- Type: 24-cylinder turbosupercharged double-"Vee" liquid-cooled piston engine
- Bore: 5.5 in (139.7 mm)
- Stroke: 6 in (152.4 mm)
- Displacement: 3,420 in3 (56 L)
- Length: 97.7 in (2,482 mm)
- Width: 60.0 in (1,421 mm)
- Height: 38.7 in (863 mm)
- Dry weight: 2,655 lb (1,204 kg)
- Valvetrain: Single overhead camshaft per 6-cylinder block, two intake and two exhaust valves per cylinder, sodium-cooled exhaust valves.
- Supercharger: Single-speed one-stage gear-driven supercharger
- Turbocharger: General Electric turbocharger with intercooler
- Fuel system: Bendix-Stromberg PR-58B3 three-barrel injection-type downdraught with automatic mixture control.
- Fuel type: 100/130 Octane
- Oil system: Pressure fed at 60-70 psi (4.2 - 4.9 kg/m2)
- Cooling system: Liquid-cooled with a mixture of 70% water and 30% ethylene glycol, pressurized.
- Power output:
- 2,600 hp (1,940 kW) at 3,000 rpm at 46.0 inHg / +8.0 Lb boost for 15 minutes
- 2,600 hp (1,940 kW) at 3,000 rpm at 25,000 ft (7,625 m) for 15 minutes
- 2,100 hp (1,565 kW) at 2,600 rpm at 25,000 ft (7,625 m) maximum continuous power
- Max. Cruising
- 1,575 hp (1,175 kW) at 2,300 rpm at 25,000 ft (7,625 m)
- Specific power: 0.76 hp/cu in (34.6 kW/l)
- Compression ratio: 6.65:1
- Specific fuel consumption: 0.41 lb/hp/hr (249.4 g/kW/hr)
- Oil consumption: 0.025 lb/hp/hr (15.2 g/kW/hr)
- Power-to-weight ratio: 1.0 hp/lb (1.64 kW/kg)
- Bridgman, Leonard. Jane's All the World's Aircraft 1945-46. Hammersmith, London: HarperCollinsPublishers (1994 reprint). ISBN 0-00470831-8
- Gunston, Bill. World Encyclopedia of Aero Engines: From the Pioneers to the Present Day. 5th edition, Stroud, UK: Sutton, 2006. ISBN 0-7509-4479-X
- White, Graham. Allied Aircraft Piston Engines of World War II: History and Development of Frontline Aircraft Piston Engines Produced by Great Britain and the United States During World War II. Warrendale, Pennsylvania: SAE International, 1995. ISBN 1-56091-655-9
- Wilkinson, Paul H. (1946). Aircraft Engines of the World. London: Sir Isaac Pitman & Sons.