AIRCRAFT PROPULSION — TAYLOR 



257 





Figure 5. — "Gnome" engine, 1910, sectional drawing. 



I had the pleasure of flying with a "Gnome" engine in 1920. It 

 was exceptionally free of vibration and also relatively quiet. The 

 only disagreeable feature was the castor-oil fumes discharged from 

 the exhaust. Lubrication was achieved by pumping castor oil into 

 the crankshaft at a fixed rate, and oil which was not burned eventually 

 found its way out of the exhaust ports, after which much of it im- 

 pinged and remained on the airplane (and on the pilot !) . One of my 

 first assignments in aviation (1917) was to make tests to show that 

 mineral oil could be used in aero engines. Previous to that time castor 

 oil had been considered as indispensable for aero engines as it was for 

 young children. 



Another interesting feature of the "Gnome" engine was its method 

 of control. No carburetor was used, the fuel and air being introduced 

 through the hollow crankshaft using separate valves controlled by 

 the pilot. Because of the large inertia of the rotating engine, it was 

 possible to adjust to the appropriate mixture by trial, without danger 

 of stalling the engine. After starting the engine with a known set- 

 ting of the valves for idling, the air throttle was opened wide, at which 

 time firing ceased, but rotation continued. The fuel valve was then 



