spinoff from "do runups work"

[classicrock]

the "do runups work" thread had mentioned some things that as a PPL in process, I never knew in detail.... until recently

I am more or less about 42 hours into my private pilot and naturally the runup is part of what I like every other student pilot and regular pilot learns. the instructor coaches me to look for the 100rpm dropoff after switching from Both to left, back to both, and then from Both to Right. but until recently, no instructor ever told me what do when/if the RPM dropoff EXCEEDS 100. I have now flown with 6 instructors in a 12 month period and only 2 weeks ago did the most recent instructor take some initiative, and show me what to do. its what was revealed in thie "do runups work" thread. (take the throttle wayup to 2000 rpm and slowly lean the mixture and do this for about 2 min). then do the mag check again

my question is: how many of you were actually taught to do this when you took PPL lessons previousl or if you are taking lessons now, have been taught this already?

comments?

 

[James331]

I learned to burn off the plugs before my PPL.

One thing I've always got a kick over is the left, both, right, both. Just go left, right, back to both, it's easier to compare and does the exact same thing without adding the extra both.

 

[FastEddieB]

I do believe both Continental and Lycoming recommend against trying to "burn off" carbon with a lean ground run-up.

From Continental:

11.Never but never attempt to “burn out” a magneto drop this “time honored” procedure succeeds only at the expense of the engine’s mechanical health. (Italics theirs)

Source: http://www.legend.aero/pdf/Tips_On_Engine_Care.pdf

But in practice, it often works.

The "book" recommendation would be to ground the plane until a mechanic found the root cause of the mag drop.

As an aside, an engine analyzer will often point to the plug in question, if that's all it is.

 

[Henning]

the "do runups work" thread had mentioned some things that as a PPL in process, I never knew in detail.... until recently

I am more or less about 42 hours into my private pilot and naturally the runup is part of what I like every other student pilot and regular pilot learns. the instructor coaches me to look for the 100rpm dropoff after switching from Both to left, back to both, and then from Both to Right. but until recently, no instructor ever told me what do when/if the RPM dropoff EXCEEDS 100. I have now flown with 6 instructors in a 12 month period and only 2 weeks ago did the most recent instructor take some initiative, and show me what to do. its what was revealed in thie "do runups work" thread. (take the throttle wayup to 2000 rpm and slowly lean the mixture and do this for about 2 min). then do the mag check again

my question is: how many of you were actually taught to do this when you took PPL lessons previousl or if you are taking lessons now, have been taught this already?

comments?

Lesson 2 when we had a fouled plug to clear on the run up.

 

[Zeldman]

I learned how to clean up the plugs early, and also learned how to not foul the plugs to start with.

And yes, left, right and back to both.

 

[Cpt_Kirk]

I didn't learn this until later on in my training. Of course, I went to a "pilot mill" for both my PPL & IR. After that, I knew it was time to go get some real training.

I have never seen anything recommend against burning off plugs. Interesting. I can tell you that grounding a revenue flight over something as small as that isn't going to get you very far.

 

[jordane93]

I was taught what to do if my mags dropped more than the specified tolerance. It's also one of the first things I teach my students so there are no surprises if it happens when they solo.

 

[Capt. Geoffrey Thorpe]

my question is: how many of you were actually taught to do this when you took PPL lessons previousl or if you are taking lessons now, have been taught this already?

Not me.

Red 80/87 was still available back then so you didn't have the problems you get with 100 Lotsa Lead fuel.

 

[Hank S]

Yes, my CFI taught me to burn off lead.

Yes, a bad runup once made me cancel because the burnoff attempt made it rougher. Ended up rebuilding the Left mag, no issues since.

 

[oregonboy109]

I learned how to burn off lead during my second lesson. The three 152s I trained in were always getting fouled plugs. Also blew a tire on my second lesson too.

 

[RotorDude]

I do believe both Continental and Lycoming recommend against trying to "burn off" carbon with a lean ground run-up.

From Continental:

11.Never but never attempt to “burn out” a magneto drop this “time honored” procedure succeeds only at the expense of the engine’s mechanical health. (Italics theirs)

Source: http://www.legend.aero/pdf/Tips_On_Engine_Care.pdf

But in practice, it often works.

The "book" recommendation would be to ground the plane until a mechanic found the root cause of the mag drop.

As an aside, an engine analyzer will often point to the plug in question, if that's all it is.

Is that really from Continental?
If so, it would be in direct conflict with their official FAA approved "Operator's Manual" for (for example) the O-470 series engines, where they state (p. 3-6):

...
b. Minor spark plug fouling can usually be cleared as follows:
(1) Magnetos - Both On.
(2) Throttle - 2200 RPM.
(3) Mixture - Move toward idle cutoff until RPM peaks and hold for ten seconds. Return mixture to full rich.
(4) Magnetos - Recheck (per paragraph 5a).
...

 

[James331]

Is that really from Continental?
If so, it would be in direct conflict with their official FAA approved "Operator's Manual" for (for example) the O-470 series engines, where they state (p. 3-6):

Yup

 

[Dan Thomas]

I learned how to burn off lead during my second lesson. The three 152s I trained in were always getting fouled plugs.

The 152 has the Lyc O-235, an engine famous for fouling plugs. It runs too cool no matter what. Savvy mechanics will replace the REM38E or REM40E plugs with REM37BY plugs and instantly and forever cure the problem. I put those plugs in every engine approved for them if a customer needs new plugs.

The left plug is an REM37BY. Its electrodes stick out far enough that the well can't fill up with lead deposits and short them. They also seem to fire better, being out in fresh air/fuel mixture instead of in a socket that might be harboring burnt gases. The right plug is example of the tip seen on the usual REM38E or 40E, whose well can easily fill up and short the electrodes.

 

[FastEddieB]

Is that really from Continental?

Pretty sure it was. It came with the documentation with my Cirrus.

If so, it would be in direct conflict with their official FAA approved "Operator's Manual" for (for example) the O-470 series engines, where they state (p. 3-6):

Seems that way. A change in procedures over time, perhaps?

 

[RotorDude]

Pretty sure it was. It came with the documentation with my Cirrus.



Seems that way. A change in procedures over time, perhaps?

Not sure about Cirrus, but certainly in the case of Cessna, you don't get the engine manufacturer's Operator's Manual with the plane you buy from Cessna. You'd only get the engine OM when you buy a replacement engine directly from the engine manufacturer (or perhaps an overhaul shop).
So in your case that blurb is very likely NOT from Continental, but I stand to be corrected.
(Regarding procedures changing "over time", I got the OM I quoted from with my latest recent engine purchase from Continental, so it's very much valid.)

 

[Bill Watson]

I learned from experience and shop talk to clean up the plugs with some higher RPMS if I get a mag drop.

Later I learned out to avoid the problem by aggressive leaning and keeping the RPMs up in ground ops. Or just shutting down if in an extended wait.

Then I learned to use the engine instruments to watch a rise in EGTs during the mag check. It helps in determining where a problem might exist.

Then when I couldn't pass a mag check after an extended conga line at Oshkosh, and when doing leaned higher power burn offs wouldn't fix it, I was able to go directly to the correct plug, replace it, and fly off. Later I was able to clean off the plug deposits with a blaster and a pick (I don't have a vibrator).

My experience suggests to me that proper leaning and throttle operation will generally avoid plug fouling except in extreme situations.

 

[455 Bravo Uniform]

I am not a full fledged PPL yet, but I built engines and drag raced for 25 years. That plug on the left is also a "hotter" plug, meaning it is more resistant to fouling (it has half the threads, and thus dissipates heat slower than the plug on the right, and does not allow as much carbon build up).

Question - does the left plug stay somewhat recessed from the combustion chamber vs. the plug on the right? If so, the it's acting like an "anti-fouler" in a way.

Again, I don't know my way around aircraft engines, maybe they are different but - I have heard of carbon fouling, never heard of lead fouling...and race gas is heavily leaded. Running rich is the cause of carbon fouling in auto engines, but another common cause is oil blow-by from a tired engine.

 

[Tom-D]

And yes, left, right and back to both.

I'll bet that isn't what your POH says.

 

[FastEddieB]

Is that really from Continental?

Not sure about Cirrus, but certainly in the case of Cessna, you don't get the engine manufacturer's Operator's Manual with the plane you buy from Cessna...
So in your case that blurb is very likely NOT from Continental, but I stand to be corrected.

Now I'm sure it is - Copyright 2010 by "Teledyne Continental Motors, Inc".

On page 41.

Better link here:

http://www.insightavionics.com/pdf files/Continental.pdf

Remember, I'm not arguing against a practice I've used, often successfully, hundreds of times.

 

[Bill Watson]

Again, I don't know my way around aircraft engines, maybe they are different but - I have heard of carbon fouling, never heard of lead fouling...and race gas is heavily leaded. Running rich is the cause of carbon fouling in auto engines, but another common cause is oil blow-by from a tired engine.

Not an expert here by a long shot....

I've been doing the plug work on my RV10's IO-540. Lead fouling occurs on all plugs, slowly, over time. Plugs are greyish and otherwise operating fine but I clean them up at 100-150 hours. However, they would appear to continue to function okay for another 100 or more if left alone.

I've been told that long extended idles where the plugs are allowed to cool can increase the lead deposit significantly. I went to Lycoming engine school a few years ago and the instructor vividly described how rapidly lead will form if the plug/chamber gets below a critical temperature - in seconds. Letting things get cool and rich after landing being a common but avoidable culprit.

As described previously, I allowed this to happen during extended idling at Oshkosh and one plug was unrecoverably clogged with lead. During a mag check I could easily see that cylinder was 'dead' when running on that plug. When I got home, I could see that the other plugs were on their way.

On the ground, lean aggressively and keep the RPMs up.

...but I'm just a builder/pilot, not a mechanic/engineer.

 

[FastEddieB]

As an aside...

Imagine "burning off" deposits works 99 times out of 100, but in that 1 outlier a brief return to normal functioning is masking an underlying problem - an intermittent mag issue, let's say.

I can see why Continental might be motivated to recommend against a practice that works well in the field most of the time.

Especially if lawyers are involved!

 

[RotorDude]

As an aside...

Imagine "burning off" deposits works 99 times out of 100, but in that 1 outlier a brief return to normal functioning is masking an underlying problem - an intermittent mag issue, let's say.

I can see why Continental might be motivated to recommend against a practice that works well in the field most of the time.

Especially if lawyers are involved!

But why would they tell you to do it in their official FAA approved Operator's Manual (my copy is dated August 2011) if they discourage it in another publication?
This makes no sense to me.

 

[FastEddieB]

Sure is contradictory.

I was surprised to see the recommendation against burning off deposits, since it so often works.

 

[oregonboy109]

The 152 has the Lyc O-235, an engine famous for fouling plugs. It runs too cool no matter what. Savvy mechanics will replace the REM38E or REM40E plugs with REM37BY plugs and instantly and forever cure the problem. I put those plugs in every engine approved for them if a customer needs new plugs.

The left plug is an REM37BY. Its electrodes stick out far enough that the well can't fill up with lead deposits and short them. They also seem to fire better, being out in fresh air/fuel mixture instead of in a socket that might be harboring burnt gases. The right plug is example of the tip seen on the usual REM38E or 40E, whose well can easily fill up and short the electrodes.

Thanks, that's very interesting. Wonder why the flight school didn't fit those. Didn't want to lose the 3-5 minutes of billed time it takes to clear them probably.

 

[NoBShere]

I learned during training because it happened a few times. On a a cold morning the other day, the mag drop was more than 400 rpm. After re-confirming the oil temp was up, I was able to clear the mags. Since, I had never seen that kind of drop before, even in cold weather, I taxied back to confirm that it was ok.

As a low time pilot, I am constantly reminded that there is a lot I don't know. Sometimes it makes me wonder...

 

[Caramon13]

Only time I had to taxi-back was when we had a hot mag during runup. Typical mag-check, left, 100 RPM drop, right, nothing. Tried again, nothing.

Turned keys to off, engine still running. This was in a C162.

I've had some roughness lately on runups, but its easily cleared with no more than 30 seconds or so leaned.

 

[exncsurfer]

to the OP, I don't think I was told this procedure. It is possible that my CFI told me this when I was in fire-hose dousing mode and it went right over my head as I was concentrating on my checklist. I've just assumed if I got more than the allowed drop the flight was over. I'll have to ask next time we fly to get his take.

 

[Caramon13]

Jim, I asked the same thing of my CFI when I first hit roughness on runup. He showed me how to burn off the lead, and I've used that technique countless times since.

Of course, if you do get a massive drop and it's not lead, well then..time to taxi back.

I also used to do a mag check before shut down, to ensure the engine would quit when the key is turned off (check for a hot mag), haven't done that recently though.