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Run up for plug clearing



 
 
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  #1  
Old October 9th 04, 11:54 AM
Roger Long
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Default 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




  #2  
Old October 9th 04, 01:11 PM
mike regish
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Default

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






  #3  
Old October 9th 04, 01:11 PM
mike regish
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Posts: n/a
Default

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






  #4  
Old October 9th 04, 02:13 PM
Larry Dighera
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Default

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.
  #5  
Old October 9th 04, 02:13 PM
Larry Dighera
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Default

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.
  #6  
Old October 9th 04, 03:45 PM
Daniel L. Lieberman
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Default

The answer to questions such as this can be found in the POH from the
manufacturer who supposedly knows more than the average flight instructor or
public thought about what is right.

For the Cessna Model 152 Section 4 Normal Procedures under "Takeoff" "Power
Check" says
"It is important to check full-throttle engine operation early in the
takeoff run. Any sign of rough engine operation or sluggish engine
acceleration is good cause for discontinuing the takeoff. IF THIS OCCURS,
YOU ARE JUSTIFIED IN MAKING A THOROUGH FULL-THROTTLE STATIC RUNUP BEFORE
ANOTHER TAKEOFF IS ATTEMPTED. The engine should run smoothly and turn
approximately 2280 to 2380 RPM with carburetor heat off and mixture leaned
to maximum RPM."
(Emphasis added.)

You will not harm the engine therefore if you use 2000 RPM and lean to clean
the plugs.

I suggest if you are serious about this you discuss the matter with a
mechanic.


  #7  
Old October 9th 04, 03:45 PM
Daniel L. Lieberman
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Posts: n/a
Default

The answer to questions such as this can be found in the POH from the
manufacturer who supposedly knows more than the average flight instructor or
public thought about what is right.

For the Cessna Model 152 Section 4 Normal Procedures under "Takeoff" "Power
Check" says
"It is important to check full-throttle engine operation early in the
takeoff run. Any sign of rough engine operation or sluggish engine
acceleration is good cause for discontinuing the takeoff. IF THIS OCCURS,
YOU ARE JUSTIFIED IN MAKING A THOROUGH FULL-THROTTLE STATIC RUNUP BEFORE
ANOTHER TAKEOFF IS ATTEMPTED. The engine should run smoothly and turn
approximately 2280 to 2380 RPM with carburetor heat off and mixture leaned
to maximum RPM."
(Emphasis added.)

You will not harm the engine therefore if you use 2000 RPM and lean to clean
the plugs.

I suggest if you are serious about this you discuss the matter with a
mechanic.


  #8  
Old October 9th 04, 03:59 PM
Larry Dighera
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Default

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

Any thoughts?

http://www.sacskyranch.com/faq_spark_plug/index.html
http://www.sacskyranch.com/faq_spark_plug/FAQ00007.htm
  #9  
Old October 9th 04, 03:59 PM
Larry Dighera
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Posts: n/a
Default

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

Any thoughts?

http://www.sacskyranch.com/faq_spark_plug/index.html
http://www.sacskyranch.com/faq_spark_plug/FAQ00007.htm
  #10  
Old October 9th 04, 04:30 PM
Dale
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Default

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
 




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