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Date: Tue, 01 Oct 2013 07:30:27 -0400
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Subject: Re: [LML] Engine surging
From: Charles Brown <browncc1@verizon.net>
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References: <list-6495845@logan.com>

Just a thought ... if there wasn't any rpm change, and you heard or felt =
surging, it could be a torque increase that causes a pitch increase, and =
increased thrust.  And if MP was constant, then the only thing *that* =
leaves is mixture.  If you're running lean of peak, power depends =
significantly on mixture.

The thing is, this sounds backwards.  If it's worse when you turn the =
boost pump ON, then it sorta seems that you were running so far rich of =
peak that additional fuel pressure degraded power?  I'm not aware that =
the engine can even produce a mixture that overrich, except at very low =
power settings.
Charley

On Sep 30, 2013, at 7:58 AM, Art Jensen wrote:

Looking for thoughts from the collective minds of the LML.  Last flight =
in my IO-550 normally aspirated legacy, I noticed surging in the engine =
with the low boost pump on. I did not notice any surging when I turned =
the boost pump off. Also did not notice any fluctuation in RPM. Nor did =
I see any fluctuation in RPM when I downloaded the engine data. The =
obvious question would be what are the possible causes and does it make =
the airplane unsafe for flight as there is no surge when the boost pump =
is off. I don't understand how I could feel and hear surging in the =
engine yet see no fluctuation in RPM, so I'm stumped. Any ideas would be =
appreciated, thank you.=20
Art

Sent from my iPhone; Art Jensen
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