BMW 802

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The BMW 802 was a large air-cooled radial aircraft engine, built using two-rows of 9-cylinders to produce what was essentially an 18-cylinder version of the 14-cylinder BMW 801. Although promising at first, development dragged on and the project was eventually cancelled to concentrate of jet engines instead.

Design and development

Soon after the 801 entered testing, BMW engineers turned to building much larger versions. One idea was to "simply" bolt two 801's back to back. Although seemingly simple, the resulting BMW 803 was in fact fantastically complicated, and generally proved that piston engines of this size were unworkable. Another idea was to simply add more cylinders to the 801 design, and since radials need to have an odd number of cylinders per row, the next "size up" was a two-row 9-cylinder design, the 802.

One problem with the 801 was its poor altitude performance, due almost entirely to the simple one-stage two-speed supercharger it used. Since the 802 was not a necessity given the success of the 801, the engineers decided to take the time needed to address this problem by including an improved three-speed supercharger. The lowest-speed setting would not "rob" as much power at low altitudes, allowing the engine to produce 2,600 PS (1,912 kW) for takeoff, and still produce 1,600 PS (1,176 kW) at 39,000 ft (12,000 m). This was a dramatic improvement on the 801A's 1,600 PS (1,176 kW) for takeoff and 1,380 PS (1,015 kW) maximum at 15,100 ft (4,600 m), especially notable considering the engine was less than 30% larger in displacement.

Development was still underway in late 1943 when BMW decided the project simply wasn't worthwhile. With their BMW 003 axial-flow turbojet engine finally maturing and considerably larger models of turbojet and turboprop engines entering the prototype phase, it appeared that large piston engines simply weren't worth building.

A further improvement led to P.8011, which replaced the supercharger with two smaller turbochargers, driving contra-rotating propellers. This raised the takeoff power to about 2,800 PS (2,059 kW), some report 2,900 PS (2,133 kW) and dramatically improved altitude performance. As with most German turbocharger projects, the lack of quality high-temperature alloys meant the project was never able to enter production.

Specifications (BMW 802)

General characteristics
  • Type: 18-cylinder supercharged two-row radial engine
  • Bore: 156 mm (6.142 in)
  • Stroke: 156 mm (6.142 in)
  • Displacement: 53.671 L (3,275.2 in³)

  • Valvetrain: One intake and one sodium-cooled exhaust valve per cylinder
  • Supercharger: Gear-driven single-stage three-speed
  • Fuel system: Fuel injection
  • Cooling system: Air-cooled

  • Power output:
    • 1,912 kW (2,563 hp) for takeoff
    • 1,176 kW (1,575 hp) at 12,000 m (39,000 ft)
  • Specific power: 35.6 kW/L (0.78 hp/in³)
  • Compression ratio: 6.5:1

See also

  • Pratt & Whitney R-2800
  • Wright R-3350
  • Bristol Centaurus