Run up for plug clearing

I can't remember where I "learned" it but I always thought 1800 RPM was the
limit for ground running leaned to clear plugs. I had a really bad one
yesterday with 250 RPM drop. I taxied back to the shop and they said to try
full throttle before pulling the plugs.

It worked but running the engine full power (near sea level) while leaned
for best power and peak EGT with minimum airflow for the minute it took
seems pretty abusive to me. Maybe you can get away with it because the
CHT's have not yet risen to max.

Any thoughts? What were you taught?

--

Roger Long

I've only had 2 incidents of plug fouling. The first, ironically, right
after I had asked my stage 3 check instructor if I should lean during taxi.
He said no. A few minutes later, I learned to clear my first plug. I
remember using runup power and just leaning aggressively. No CHT or EGTs
available. That was in a C150.

I had a real bad mag drop a couple of weeks ago in my Tripacer. My brakes
were a little on the weak side and, being that it's a hand brake, I couldn't
go higher than 1800 without starting to roll. I ran it up (1800) and leaned
until It was barely running smoothly (probably lean of peak). I did this
twice for about 30 seconds each. There were planes waiting behind me and the
second time didn't get it, so I pulled off the taxiway and repeated the
procedure for a full minute nad that got it. Had that not worked, I wasn't
going flying that day.

I don't think there's a real limit. If I had toe brakes, I might have tried
a higher power setting. Even now, in my TP, my brakes are back to full
strength, I would have tried as much power as the brakes would hold.


Just my $.02-and worth every bit of it. :-)

mike regish

"Roger Long" wrote in message
...
I can't remember where I "learned" it but I always thought 1800 RPM was the
limit for ground running leaned to clear plugs. I had a really bad one
yesterday with 250 RPM drop. I taxied back to the shop and they said to
try full throttle before pulling the plugs.

It worked but running the engine full power (near sea level) while leaned
for best power and peak EGT with minimum airflow for the minute it took
seems pretty abusive to me. Maybe you can get away with it because the
CHT's have not yet risen to max.

Any thoughts? What were you taught?

--

Roger Long

On Sat, 09 Oct 2004 10:54:44 GMT, "Roger Long"
wrote in ::

It worked but running the engine full power (near sea level) while leaned
for best power and peak EGT with minimum airflow for the minute it took
seems pretty abusive to me.

That's what I was taught. Often it only takes 10 - 15 seconds to
clear/burn the carbon deposit without the necessity of leaning. I
don't see anything abusive or abnormal about this procedure, as the
engine sees full throttle on each takeoff.

In article ,
Larry Dighera wrote:


That's what I was taught. Often it only takes 10 - 15 seconds to
clear/burn the carbon deposit without the necessity of leaning. I
don't see anything abusive or abnormal about this procedure, as the
engine sees full throttle on each takeoff.

A difference between a runup and the takeoff roll is the cooling air
flowing thru the cowling when moving. There is very little airflow when
stationary, even with high power settings. I'm not saying you shouldn't
do a high power runup, but you should be cautious and aware of the
possibity of heat problems.

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

On Sat, 09 Oct 2004 07:30:28 -0800, Dale wrote in
::

In article ,
Larry Dighera wrote:


That's what I was taught. Often it only takes 10 - 15 seconds to
clear/burn the carbon deposit without the necessity of leaning. I
don't see anything abusive or abnormal about this procedure, as the
engine sees full throttle on each takeoff.

A difference between a runup and the takeoff roll is the cooling air
flowing thru the cowling when moving.

True.

There is very little airflow when stationary, even with high power settings.

Are you able to cite a credible source that supports that assertion?
I'm not saying it isn't true, but I'd like to hear the input of an
A&P.

I'm not saying you shouldn't do a high power runup, but you should be
cautious and aware of the possibity of heat problems.

A pilot should always be aware of that possibility.

As the plugs tend to foul more easily when the engine is cold, the
admonition for caution in this instance is mitigated by the fact that
the engine temperature usually hasn't reached a point where it is a
factor at run up time. At least here in California that is what I've
found. In colder climates plug fouling may occur more frequently, but
I would expect the ambient temperature to also mitigate the cautionary
advice.

In article ,
Larry Dighera wrote:


Are you able to cite a credible source that supports that assertion?
I'm not saying it isn't true, but I'd like to hear the input of an
A&P.

No, I say this from my experience and common sense. The prop next to
the hub doesn't move much air. I've rarely had a hot engine while
inflight, but often have temps come up while on the ground.

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

In article ,
Larry Dighera wrote:


Are you able to cite a credible source that supports that assertion?
I'm not saying it isn't true, but I'd like to hear the input of an
A&P.

No, I say this from my experience and common sense. The prop next to
the hub doesn't move much air. I've rarely had a hot engine while
inflight, but often have temps come up while on the ground.

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

On Sat, 09 Oct 2004 07:30:28 -0800, Dale wrote in
::

In article ,
Larry Dighera wrote:


That's what I was taught. Often it only takes 10 - 15 seconds to
clear/burn the carbon deposit without the necessity of leaning. I
don't see anything abusive or abnormal about this procedure, as the
engine sees full throttle on each takeoff.

A difference between a runup and the takeoff roll is the cooling air
flowing thru the cowling when moving.

True.

There is very little airflow when stationary, even with high power settings.

Are you able to cite a credible source that supports that assertion?
I'm not saying it isn't true, but I'd like to hear the input of an
A&P.

I'm not saying you shouldn't do a high power runup, but you should be
cautious and aware of the possibity of heat problems.

A pilot should always be aware of that possibility.

As the plugs tend to foul more easily when the engine is cold, the
admonition for caution in this instance is mitigated by the fact that
the engine temperature usually hasn't reached a point where it is a
factor at run up time. At least here in California that is what I've
found. In colder climates plug fouling may occur more frequently, but
I would expect the ambient temperature to also mitigate the cautionary
advice.

--

Roger Long



"Larry Dighera" wrote in message
...
On Sat, 09 Oct 2004 10:54:44 GMT, "Roger Long"
wrote in ::

It worked but running the engine full power (near sea level) while leaned
for best power and peak EGT with minimum airflow for the minute it took
seems pretty abusive to me.

That's what I was taught. Often it only takes 10 - 15 seconds to
clear/burn the carbon deposit without the necessity of leaning. I
don't see anything abusive or abnormal about this procedure, as the
engine sees full throttle on each takeoff.

#&*(^%$#!)+=- Microsoft.

With the budgets that world domination provides, you would think someone
would have figured out that putting the Send button under the Reply button
would lead to inadvertent blank replies.

With Windows 98, you could move the buttons around so that didn't happen
when you accidentally double clicked. Eliminating that option seems to have
been one of those "Innovations that users demand."

--

Roger Long



"Roger Long" wrote in message
. ..


--

Roger Long



"Larry Dighera" wrote in message
...
On Sat, 09 Oct 2004 10:54:44 GMT, "Roger Long"
wrote in ::

It worked but running the engine full power (near sea level) while leaned
for best power and peak EGT with minimum airflow for the minute it took
seems pretty abusive to me.

That's what I was taught. Often it only takes 10 - 15 seconds to
clear/burn the carbon deposit without the necessity of leaning. I
don't see anything abusive or abnormal about this procedure, as the
engine sees full throttle on each takeoff.