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Date: Tue, 01 Oct 2013 14:57:21 -0400
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Subject: Re: [LML] Re: Engine surging
References: <list-6497477@logan.com>
From: Art Jensen <flycassutts@yahoo.com>
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Charley,
The surging was first noticed after take-off with low boost ON at about 800 f=
eet AGL leaned for altitude 2500 RPM WOT. Being under the KFTG TCA climbs we=
re in steps to 9500 MSL where I leveled off to try to understand what's goin=
g on and see how changes in operation affected what I was seeing and feeling=
. I reduced power and went LOP same results. Then turned off the low boost a=
nd the surging stopped. The engine ran very smooth. Turned the low boost bac=
k on and the surging came back. Again I turned it off and it went away. I de=
termined I had found the cause (fuel pump) but still don't understand why (w=
hat is beginning to fail) or the connection (how it plays a roll to create t=
he results I experienced).

Still looking for the expert who can put it all together so that I can come u=
p with a plan of action for repair.=20

Called Lancair to price a new Dukes Fuel Pump, $3350, might be a bargain tom=
orrow but at that price I'm not going to R&R as a test. Haven't checked a pr=
ice for overhaul assuming my problem is in fact the pump.=20

Any and all advice appreciated.=20

Art

Sent from my iPhone; Art Jensen

> On Oct 1, 2013, at 1:30 AM, Charles Brown <browncc1@verizon.net> wrote:
>=20
> Just a thought ... if there wasn't any rpm change, and you heard or felt s=
urging, it could be a torque increase that causes a pitch increase, and incr=
eased thrust.  And if MP was constant, then the only thing *that* leaves is m=
ixture.  If you're running lean of peak, power depends significantly on mixt=
ure.
>=20
> The thing is, this sounds backwards.  If it's worse when you turn the boos=
t pump ON, then it sorta seems that you were running so far rich of peak tha=
t additional fuel pressure degraded power?  I'm not aware that the engine ca=
n even produce a mixture that overrich, except at very low power settings.
> Charley
>=20
> On Sep 30, 2013, at 7:58 AM, Art Jensen wrote:
>=20
> 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 t=
he low boost pump on. I did not notice any surging when I turned the boost p=
ump off. Also did not notice any fluctuation in RPM. Nor did I see any fluct=
uation in RPM when I downloaded the engine data. The obvious question would b=
e what are the possible causes and does it make the airplane unsafe for flig=
ht 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
>=20
> Sent from my iPhone; Art Jensen
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