Editing Rotary engine (section)

==="Normal" rotaries===
Most rotaries had normal inlet valves, so that the fuel (and lubricating oil) was taken into the cylinders already mixed with air - as in a normal four-stroke engine. Although a conventional carburetor, with the ability to keep the fuel/air ratio constant over a range of throttle openings, was precluded by the spinning crankcase; it was possible to adjust the air supply through a separate flap valve or "bloctube". The pilot needed to set the throttle to the desired setting (usually full open) and then adjust the fuel/air mixture to suit using a separate "fine adjustment" lever that controlled the air supply valve (in the manner of a manual choke control). Due to the rotary engine's large rotational inertia, it was possible to adjust the appropriate fuel/air mixture by trial and error without stalling it, although this varied between different types of engine, and in any case it required a good deal of practice to acquire the necessary knack. After starting the engine with a known setting that allowed it to idle, the air valve was opened until maximum engine speed was obtained.

Throttling a running engine back to reduce revs was possible by closing off the fuel valve to the required position while re-adjusting the fuel/air mixture to suit. This process was also tricky, so that reducing power, especially when landing, was often accomplished instead by intermittently cutting the ignition using the blip switch.
 
Cutting cylinders using ignition switches had the drawback of letting fuel continue to pass through the engine, oiling up the spark plugs and making smooth restarting problematic. Also, the raw oil-fuel mix could collect in the cowling. As this could cause a serious fire when the switch was released, it became common practice for part or all of the bottom of the basically circular cowling on most rotary engines to be cut away, or fitted with drainage slots.

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.<ref name=nahum44/>

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.