technical question " coupe" button

[fitzee]

Perhaps someone on the forum with more technical knowledge than myself can clear up a question for me. On the control stick of rotary engine aircraft there was a "coupe" button that momentarily" kills" the engine. Was this used as an air brake, and how did it work? Did it it just disengage the prop from spinning?

cheers

Fitzee

[Tom Morgan]

Others will certainly know more than me, but I think it was an ignition switch, and the only engine control there was! The engine ignition was either on (with the engine running at full speed) or off. That was it. There was no accelerator. Of course, the engine would continue to rotate for some time with the ignition off, so it would re-start when the ignition was swiched back on. You couldn't disengage the propeller, which was bolted to the engine, and they both spun together.

Landing was a fine art involving switching the engine on and off as required to bring the plane slowly down till it was doing the right speed in the right place, until finally switching off and letting it land.

Tom

[Terry_Reeves]

This article mentions the coupe switch and its function:

http://en.wikipedia.org/wiki/Rotary_engine

Terry Reeves

[MikeW]

Others will certainly know more than me, but I think it was an ignition switch, and the only engine control there was !

Aaaarrrgggghhhh.

No. Just about every rotary had a carburettor of some sort with control of "petrol" and "air". The pilot had to adjust both for correct running. The "petrol" lever worked a needle valve and the "Air" lever worked a butterfly flap.

The "blip" switch cut out the feed from the magneto, it could cut everything to temporarily kill the engine (which would continue spinning due to the slipstream over the prop) or more sophisticated version would cut every other cylinder or every two cylinders or whatever to reduce the power. Releasing the switch would hopefully return full power. The switch was used as a "convenience", it was of no use when compensating for the change of load just after take off or adjusting the machine's speed when flying in formation.

[Adrian Roberts]

There's an article in this months (nominally, December) issue of Aeroplane Monthly about flying a preserved Sopwith Pup that describes the throttle controls of a rotary engine very well.

Essentially, as Mike says, they did have throttles, but these were far more sensitive to operate than on other engines; you had to adjust the mixture (with the air control) every time you adjusted the power (with the petrol control). You couldn't just shove the throttle right open, or closed. The blip control made things easier by obviating the need to do this in some circumstances, such as the landing approach and taxying.

Adrian

[LowNslow]

There's a pretty extreme example of the use of the "blip switch" on this video... http://www.youtube.com/watch?v=qtprTL66-FY