I found this in Of Wings and Things Volume 1: 1972-1979 - Reprints from The Flyer by Peter M. Bowers:
Steam-powered engines
The only one to make a full-pattern manned flight was the 150-horse, two-cylinder Besler
1st May 1974
Back in the days before the Wright brothers' first flight, would-be inventors of flying machines had no suitable powerplants with which to experiment. The few individuals who had progressed to the point of flying large-scale models or their full-size contraptions used steam engines. The first to achieve any degree of success was Professor Samuel P. Langley’s scale-model Aerodrome, which flew for some 3,000 feet along the Potomac River in May 1896.
While steam engines produced the necessary power, they were far too heavy for flying machines, so it remained for the gasoline engine to make the airplane work. While such things were in wide use for marine, automotive and fixed operations by the turn of the century, there were no available adaptations for aircraft use. The Wright bothers had to build their own before they made the first successful powered flight in December 1903.
However, despite the gas engine’s total monopoly of the airplane industry ever since, inventors have periodically considered the steam engine as the proper powerplant for aircraft. Various experimental installations have been made over the years, but none have been practical.
The most successful, and the only one to make a proper full-pattern flight, was the Besler, a two-cylinder, 150-horsepower design developed by brothers George and William Besler. The engine was installed in a Travel Air 2000 biplane and was successfully flown at the Oakland (California) Airport on April 12, 1933.
The 180-pound engine was quite light for steam, but its accessories — boiler, water, pump, condensers, etc. - increased its weight to more than 500 pounds, which actually wasn’t much more than the World War I-surplus Curtiss OX-5 that had been removed from the plane. An inlet pressure of 1,200 pounds was used, and the propeller was turned at 1,625rpm, a couple of hundred more than the old OX-5 at its best.
The steam-powered plane made only one flight, a short trip around the airport, but it did prove that steam could be used as a means of propulsion for airplanes. There is a big difference between being merely successful, however, and being competitive, and nothing more was done with the steam engine. The Beslers continued their association with the Dobel Steam Car Company of Emeryville, Califomia, and made steam-based smoke generators for the Army during World War II.
When I last saw it, the Besler engine that was removed from the Travel Air was on display in the engine shop of the Boeing School of Aeronautics at the Oakland Airport in 1942.
The Army took the school over during the war, and it was closed afterward. If the engine still exists, it should be placedin a suitable museum.
The photographs
1. The experimental 150-horsepower Besler steam engine replaced the 90-horsepower, water-cooled Curtiss OX-5 in this standard Travel Air 2000.
2. The two-cylinder Besler steam engine that went in the Travel Air had a vertical boiler and firebox immediately behind it.
3. Close-up of the steam-powered Travel Air shows the two radiators that were necessary to condense steam back into water so the supply could be maintained long enough for the plane to make a full-circuit flight.
