A Travel Air 2000 biplane made the world's first piloted flight under

steam power over Oakland, California, on April 12 1933.  The strangest feature of the flight was its relative silence; spectators on the ground could hear the pilot when he called to them from mid-air. The aircraft, piloted by William Besler, had been fitted with a two-cylinder, 150 hp reciprocating engine.

William Besler in front of the Airspeed 2000

An important contribution to its design was made by Nathan C. Price, a former Doble Steam Motors engineer.  Price was working on high pressure compact engines for rail and road transport; the purpose of the flight was to obtain publicity for this work.
 

Besler steam plane in flight.

Following its unexpectedly favourable reception Price went to Boeing and worked on various aviation projects, but Boeing dropped the idea of a steam aeroengine in 1936. Price later worked for Lockheed where his experience with developing compact burners for steam boilers helped to design Lockheed's first jet engine.

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The advantages of the "Besler System" that were claimed at the time included the elimination of audible noise and destructive vibration;
greater efficiency at low engine speeds and also at high altitudes where lower air temperatures assisted condensation; reduced likelihood
of engine failure; reduced maintenance costs; reduced fuel costs, since fuel oil was used in place of petrol; reduced fire hazard
since the fuel was less volatile and operating temperatures were lower; and a lack of need for radio shielding.
For capacities in excess of 1000 horse power a turbine captures the energy released by the expansion of steam more efficiently
than a piston. Thus, the steam reciprocating engine turned out to be unsuitable for scaling up to the needs of large aircraft.
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A very rare shot of the steam powered Airspeed 2000.

Approaching under steam!

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Engine layout as published in "Luftwissen"/Germany 1941.

Concept of the Besler steam plane demonstrator.

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Besler steam aero engine.

The Besler brothers proudly posing in front of their design.

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