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Subject: Re: [FlyRotary] Re: First lift off with single rotor
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From: Tracy <rwstracy@gmail.com>
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Date: Mon, 9 Jul 2012 12:30:30 -0600
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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My guess is that it is not excess pressure that is the problem.   (we all wi=
sh we had more MP available  : ).  =20
One possibility is  turbulence around the mouth of the carb,  had that happe=
n on hod rods in my younger days.   I turned the air scoop on carb around ba=
ckwards  and problem went away.  You running an air cleaner or other intake p=
lumbing that helps smooth the airflow at the entry of carb?  =20
Better yet, go EFI which isn't sensitive this problem!

Tracy

Sent from my iPad

On Jul 9, 2012, at 10:36 AM, "Richard Sohn" <res12@fairpoint.net> wrote:

>=20
>=20
> -----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
>=20
> 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.
>>=20
>> 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.
>>=20
>> The conclusion is, I have to open the cowling exits a lot.
>=20
> I don't get it.  The pressure under the cowl sounds like it would be a goo=
d thing, because it sounds like it is enough
> to cause the engine to lean out.  If the cooling isn't a problem, why woul=
dn't you just enrichen the mixture to
> accommodate the extra air and accept the increase in power?
>=20
> Ernest,
>=20
> I am not using electronic fuel injection. My fuel system operates pretty m=
uch like a carb with mixture control. In addition, I would not want to have t=
o adjust the mixture when changing the air speed.
> Your comment certainly reflects one advantage of EFI.
>=20
>=20
> Richard Sohn
> N2071U
>=20
> http://www.fairpoint.net/~res12/home.html
>=20
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tml=20
>=20
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