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From: "Richard Sohn" <res12@fairpoint.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: First lift off with single rotor
Date: Mon, 9 Jul 2012 11:36:21 -0500
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-----Original Message----- 
From: Ernest Christley
Sent: Monday, July 09, 2012 11:12 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: First lift off with single rotor

Richard Sohn wrote:
> Cleared the ground for a brief period today. As far as the airplane is
> concerned, everything is good. CG seems to be right on the spot. Much
> better as it was 12 years ago at the first flight with the SOOB.
> Here is the reason why it was not a flight. A few days ago when I
> started high speed taxi, as soon as it picked up air speed, the engine
> started to sputter and almost cut out totally. This was at the same RPM
> as at a run up, where it does not do that. With a wiggly tail dragger as
> the Avid is, there was no way reading enough instrument for making a
> preliminary analysis. I recorded the instrument panel with a GoPro at
> 2sec intervals.
> Looking at the first pictures, the answer came up right away, increasing
> pressure under the cowl where the intake for the engine is located. Like
> the EGT shot up over 1600 just before the sputtering started. Since my
> radiator air is going to the outside of the cowling, there was no impact
> on cooling. Btw cooling is really good. At an OAT of 95F, oil and water
> stayed at around 170F no matter what I did.
>
> For todays runs, I taped the inlet around the prop hub shut. Sure
> enough, the sputtering occurred at higher airspeed, and was not as
> total, however, EGT was still going to around 1600.
>
> The conclusion is, I have to open the cowling exits a lot.

I don't get it.  The pressure under the cowl sounds like it would be a good 
thing, because it sounds like it is enough
to cause the engine to lean out.  If the cooling isn't a problem, why 
wouldn't you just enrichen the mixture to
accommodate the extra air and accept the increase in power?

Ernest,

I am not using electronic fuel injection. My fuel system operates pretty 
much like a carb with mixture control. In addition, I would not want to have 
to adjust the mixture when changing the air speed.
Your comment certainly reflects one advantage of EFI.


Richard Sohn
N2071U

http://www.fairpoint.net/~res12/home.html

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