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First time I encountered this was several years ago when flying with Tracy. I normally do no descend faster than 1000-1500 FPM but when Tracy decides a open patch is the route for descent - he goes down! So following him with my VSI pegged at 2000 fpm down I became alarmed as my engine started to run rough and seem to be missing.

Tracy then explained the reason - which reassured me - a bit, but I still did not care for it.

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC

----- Original Message -----

From: Russell Duffy

To: Rotary motors in aircraft

Sent: Wednesday, August 11, 2004 8:58 PM

Subject: [FlyRotary] Re: Pressure switch

In fact, I just realized why I run so rough on desent. The MAP is probably getting pulled down below 10" and the pressure probably drops even more making it very lean... hmmm :-)

I mentioned this to Tracy one day, and he said (best I understood it) that the engine basically isn't running under these conditions. For one thing, the injector duty cycle is so low that they effectively aren't opening. I've noticed times in the pattern when I was descending at idle, and the engine noise seemed to almost go away. Opening the throttle some made it start, then going to idle stop. I got the distinct feeling that the engine was not running at idle, just like a car cuts the fuel on deceleration. Interesting.

Rusty (Maaaaaaaayby running Rev-3 by Sunday)