Sender: <marv@lancaironline.net>
To:  lml@lancaironline.net
Date: Wed, 02 Oct 2013 08:36:35 -0400
Message-ID: <redirect-6499142@logan.com>
Received-SPF: pass
 receiver=logan.com; client-ip=209.85.223.170; envelope-from=2thman1@gmail.com
References: <list-6499092@logan.com>
In-Reply-To: <list-6499092@logan.com>
Mime-Version: 1.0 (1.0)
Content-Type: text/plain;
	charset=us-ascii
Content-Transfer-Encoding: quoted-printable
From: John Barrett <2thman1@gmail.com>
Subject: Re: [LML] Re: Engine surging

Someone may have mentioned this already.  Do you have an EFIS or other instr=
ument that monitors and records engine data? If so that would be a good tool=
 for you to review, for the bloggers here to help you with and/or Mike Busch=
 on the Savvy aviator, and/or George Braly and crew at Turbo Alley.

John Barrett

Sent from my iPad


On Oct 2, 2013, at 6:51 AM, Charles Brown <browncc1@verizon.net> wrote:

> OK well if your MP and rpm stayed steady (and I think ordinary instruments=
 are responsive enough to display any significant variations -- this is not a=
n aliasing problem), then I'll stick to my assessment that you have irregula=
r fuel flow causing mixture variations causing power variations that are bei=
ng soaked up by prop pitch adjustments and appear as fluctuating thrust.  It=
 sure sounds like your boost pump is producing irregular flow and maybe some=
 simple diagnostics are in order before removal/overhaul:
>=20
> 1.  Do your fuel flow and fuel pressure (panel instrumentation) fluctuate w=
hen you turn it on, with a period similar to the surging period?
>=20
> 2.  Dumb but very fundamental question:  does fuel press go UP like it sho=
uld or does it go DOWN when you turn on the pump?  (wild thought, but worth v=
erifying).
>=20
> 3.  Ground test -- check the boost pump fuel flow by pumping through the s=
ystem and out of the fuel filter, with the filter outlet disconnected from t=
he engine and streaming into a bucket/catchbasin -- is it steady?
>=20
> 4.  Other quick check -- is the fuel filter clean?  (is there anything tha=
t could get stirred up, like water, even, at higher flows driven by the boos=
t pump?
>=20
> Those are all my ideas.  If you do these diagnostics you may find a smokin=
g gun.  If not, I'd swap the pump out.  And, here's a free opinion, I'd rega=
rd a boost pump that causes surging as an unreliable backup and consider tha=
t you're now flying with a single point of failure (the mechanical pump) tha=
t could force a landing any time.  Strictly speaking your airplane is airwor=
thy, but you've peeled off a big safety layer.
>=20
> On Oct 1, 2013, at 1:57 PM, Art Jensen wrote:
>=20
> Charley,
> The surging was first noticed after take-off with low boost ON at about 80=
0 feet AGL leaned for altitude 2500 RPM WOT. Being under the KFTG TCA climbs=
 were in steps to 9500 MSL where I leveled off to try to understand what's g=
oing on and see how changes in operation affected what I was seeing and feel=
ing. I reduced power and went LOP same results. Then turned off the low boos=
t and the surging stopped. The engine ran very smooth. Turned the low boost b=
ack on and the surging came back. Again I turned it off and it went away. I d=
etermined I had found the cause (fuel pump) but still don't understand why (=
what is beginning to fail) or the connection (how it plays a roll to create t=
he results I experienced).
>=20
> Still looking for the expert who can put it all together so that I can com=
e up with a plan of action for repair.=20
>=20
> Called Lancair to price a new Dukes Fuel Pump, $3350, might be a bargain t=
omorrow but at that price I'm not going to R&R as a test. Haven't checked a p=
rice for overhaul assuming my problem is in fact the pump.=20
>=20
> Any and all advice appreciated.=20
>=20
> Art
>=20
> Sent from my iPhone; Art Jensen
>=20
>> 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 boo=
st pump ON, then it sorta seems that you were running so far rich of peak th=
at additional fuel pressure degraded power?  I'm not aware that the engine c=
an 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 i=
n 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
>> --
>> For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.ht=
ml
>>=20
>>=20
>> --
>> For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.ht=
ml
>=20
> --
> For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.htm=
l
>=20
>=20
> --
> For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.htm=
l