The engines of combat planes in the First World War
“How miniscule the automatization of the operation of plane engines was, is illustrated by the description of one of the first military flight students, who started in the year 1909 with their training:” The regulation of the gas feed was alone in the hand and last but not least the ear of the pilot. That meant that the right hand, with an outstretched arm, had to be continuously at the needle valve of the engine that was in oblique and in front of the plane. If you took the hand away for just one second you could be sure that the engine would resent that and that it would stop breathing under multiple chokes.” Flight students had been especially unable to cope with the powerful rotary engines. The 80 hp Genôme rotary engine, a licensed product in Germany, was, according to Anthony Fokker, “tricky, unreliable, difficult to operate”. A bottleneck that affected the operation was that the rotary engines had only a very limited rotational speed range, where they ran smoothly. At least the ones produced before 1918 had to be regulated with hand operated lever and gas- and air control valves, to meet these requirements. Throttling – essential for the increasing demand of formation flight – could only be accomplished with about 25% full speed. The regulation wouldn’t remain stable; it had to be adjusted continuously, and this within an especially slow reacting system. “Experienced pilots would ‘feel’ back the fuel lever at frequent intervals, to make sure that the mixture had not got to rich […] if the engine was badly over-rich, it took up to seven seconds to recover, due to the large crankcase volume and the possible presence in it of raw petrol.” Fokker described the problems of the rotary engine in a comparable way and pointed out the fire hazard: […]“
“Only the third way, the possibility to shoot through the propeller, was a truly successful reinterpretation and technological reconstruction of the plane into an integrated weapon. The technical conditions for the possible combination of flying and aiming had to be realized and this could only be achieved by the limitation of the multiple tasks. The means for it was the camshaft controlled, synchronized gear, that combined a heavy machine gun with the crankshaft and that assured that not a single projectile hit the propeller.”
Source: Kurt Möser, Fahren und Fliegen in Frieden und Krieg, Verlag Regionalkultur, Mannheim 2009, p. 195.