I read or heard one time that radial engine biplane engines were turned off just before touchdown because if the throttle was used, the torque could cause the wing of the plane to contact the ground and a lot of pilots were killed just landing biplanes. Is that true?
Did Biplane pilots turn off their engines before landing?
Rotary engines had rather primitive throttle arrangements, so a pilot would often use a "coup" button or "blip" switch, mounted on the control stick, to "blip" the ignition on and off and give partial power.
However, an alternative technique was recommended for some rotary engines:
By 1918 a Clerget handbook advised maintaining all necessary control by using the fuel and air controls, and starting and stopping the engine by turning the fuel on and off. The recommended landing procedure involved shutting off the fuel using the fuel lever, while leaving the blip switch on. The windmilling propeller made the engine continue to spin without delivering any power as the aircraft descended. It was important to leave the ignition on to allow the spark plugs to continue to spark and keep them from oiling up, so that the engine could (if all went well) be restarted simply by re-opening the fuel valve. Pilots were advised to not use an ignition cut out switch, as it would eventually damage the engine.
Pilots of surviving or reproduction aircraft fitted with rotary engines still find that the blip switch is useful while landing, as it provides a more reliable, quicker way to initiate power if needed, rather than risk a sudden engine stall, or the failure of a windmilling engine to restart at the worst possible moment.
(Source: https://en.wikipedia.org/wiki/Rotary_engine#Monosoupape_rotaries, quoting Nahum, Andrew (1999). The Rotary Aero Engine. NMSI Trading Ltd. pp. 44–45. ISBN 1-900747-12-X.)
The key here is "rotary", not "radial", and regardless of which technique was used, the concern wasn't to avoid a hazard from engine torque or other related effects per se, but just to control the power output of the engine to allow the aircraft to descend for landing.
Of course, at other times, such as when taking off, the gyroscopic reaction to the whirling mass of the engine was a very significant factor while flying with a rotary engine, and the low ground clearance of the lower wingtips of most biplanes wouldn't have helped matters.
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