1800 RPM for 30 sec before shut down

jkgoblue

jkgoblue

Pre-takeoff checklist
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John K.
I've heard that prior to shut down, it's good to run up your engin to 1800 RPM for 30 seconds, then back to idle. True? Why?

Do you do it? Should I?
 
Ask the local A&P.
Contact the engine manufacturer.
Ask a CFI only if you trust that they understand engines and aren't repeating what their CFi told them.

One of the A&Ps here will respond with good advice, as will the experienced CFIs who know from which they speak.
 
From Lycoming Service Letter L192B
Prrior to Engine Shut Down (when on parking stand) the engine speed should be maintained between 1000 and 1200 RPM until the operating temperatures have stabilised. At this time the engine speed should be increased to approximately 1800 RPM for 15 to 20 seconds then reduced to 1000 to 1200 RPM and then shut down immediately using the mixture.

In addition our supervising engineer and other publications urge pilots to run at the prescribed 1800 RPM with the mixture leaned off somewhat. This will avoid difficult starts with leaded-up plugs.
 
I've only ever seen one person do this. Now his plane is available for rent and I doubt anyone other than the owner ever shuts down this way. Some people say it's a carry-over tradition from older, dirtier engines or rotaries with cylinders on the bottom. Still others say that the practice of leaning out while on the ground pretty much negates the need to clean the plugs before shutting down. I think I read an anecdote in favor of the practice, though, claiming the plugs were much cleaner during scheduled maintenance.
 
Basically that is the procedure I was taught,to keep plugs from fouling.
 
Same same... I aggressively lean on ground to prevent fouling. A quick run up when leaned in theory should heat up and burn off the lead fouling if its present.

Sometimes I do it, sometimes not. Depends on if anyone is in my hangar row for the most part. Never had a fouling issue.
 
IMHO, this technique has little to do with plug fouling and more to do with allowing the cylinders to cool from working hard. In the pattern for landing we pull the power back and using low power settings for taxi. This can accomplish the same thing.

Piston helos must do this as landing is working the engine hard and temps are at their max. I've been taught 2 minutes minimum cool down prior to engine shut down.
 
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I've had some fouling problems in the past. I haven't since consistently doing 2 things; leaning on the ground and not idling below 1000 rpm.

The instructor at Lycoming engine school shared an experience where they had a chance to visually observe lead formation in a running engine (?? I have no idea ??). He said it was surprising how temperature sensitive the process was. As soon as certain threshold combustion chamber/spark plug minimum temp was reached, lead deposits began forming instantly and quickly.

That suggests to me that leaning and maintaining rpms could prevent lead deposits. It also suggests that over-leaning could contribute to lead fouling if it drops combustion chamber temps, particularly in leaner cylinders.

In my own flying I found that I tended to chop power upon landing and often would find my idle speed had dropped below 1000 at the end of the rollout. I now lean during the roll and bump the throttle up as long as the runway allows.

My plugs look better now than they ever have.
 
many airplanes are carrying excess weight in the form of paint on the tail surfaces. Doing this shutdown routine will help to shed those pounds.
 
JHW said:
many airplanes are carrying excess weight in the form of paint on the tail surfaces. Doing this shutdown routine will help to shed those pounds.
Click to expand...

Helps clear FOD off the taxilane too.
 
Folks in nearby hangars/shadeports/tie downs will enjoy a run up like that.....or not.
 
It's part of our standard shutdown procedure on our Archer.... 1800 rpm for 20 to 30 seconds - ours always seem to run a little rich and we aggressively lean it during taxi operations as it fouls very easy.
 
My plane once started sputtering at 400' on takeoff...fouled lower plugs that were not detected on runup. Serious pucker factor! My mechanic cleaned all the plugs then advised to runup to 1500 RPM before shut down to prevent buildup again...so now I do!
 
Switch to tempest plugs instead of the crappy champions with bad resistors, lean during taxi until it will barley run (yes you will have to richen it to apply power to go up grade)....

The 1800rpm deal sounds stupid. Like sand blasting the prop stupid or blowing debris back into the hanger.
 
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Paul Hamilton said:
From Lycoming Service Letter L192B
Prrior to Engine Shut Down (when on parking stand) the engine speed should be maintained between 1000 and 1200 RPM until the operating temperatures have stabilised. At this time the engine speed should be increased to approximately 1800 RPM for 15 to 20 seconds then reduced to 1000 to 1200 RPM and then shut down immediately using the mixture.

In addition our supervising engineer and other publications urge pilots to run at the prescribed 1800 RPM with the mixture leaned off somewhat. This will avoid difficult starts with leaded-up plugs.
Click to expand...

Those procedures are preceded by this specific comment (emphasis mine):

For operators experiencing lead fouling, the following operating recommendations are made:
Click to expand...

If you're not experiencing lead fouling, the nine operating details/items listed in L192B don't apply.

For the O-540 and IO-540, here's the recommended shut down procedure direct from Lycoming operators manual:

attachment.php


Point is, "it varies". :)

Regarding "decided decrease" in the shut down list above... discuss. 25 degrees? 50 degrees? Old analog gauge moves a few needle widths?
 

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For most aircraft in most instances where you do not have a major fouling issue, you can just lean the engine when you are doing your after landing cleanup, i.e. raise flaps, carb heat in (if applicable), lean. Then just try to keep your RPM over 1000 while taxiing unless it gets you taxiing too fast. Besides any fouling that does occur during taxi and shutdown is easily burned off by leaning during the run-up for the next flight.
 
I use my power turn for parking to clean the plugs. It works out to about the time recommended by the service bulletin.
 
At idle or taxi power it is impossible to lean too much. That is, you can and should lean to barely keep it running for ground ops. For me that happens once I exit the active. I have no need to do more in the tiedown and since there are airplanes tied in my propwash that supports what I do now.
 
Geico266 said:
TIMHO, this technique has little to do with plug fouling and more to do with allowing the cylinders to cool from working hard. In the pattern for landing we pull the power back and using low power settings for taxi. This can accomplish the same thing.
Click to expand...

Typically speaking, I see engine temperatures INCREASING once you stop the airplane before shutting down. Even those that tell me they need to let things "cool down" end up pretty surprised when I tell them to watch the temps on the engine monitor during this "cool down" phase.

I can't say this is always the case, but simply an observation I've made in many aircraft with good engine monitors. As a result, I don't personally teach people to do anymore idling after they've taxied to their shutdown location.

In turbocharged aircraft you'll often have people sit for several minutes so the turbo will "cool down". Again, if you watch the TiT temperature during this time period, it's going up if anything...not down...

The only time I've personally seen an engine that might be better off idling for a bit before shutting down is if you just had a long taxi up hill, or if you're flying with someone that likes to taxi at 1300 RPM while riding the brakes the whole time.

Taxied properly, the power setting won't be much different at all from your idle once stopped. As a result, since you're now stopped, less airflow through cowling, temps go up..

YMMV. Not an A&P. Just one of those dumb CFI's you should ignore :)
 
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jesse said:
Typically speaking, I see engine temperatures INCREASING once you stop the airplane before shutting down. Even those that tell me they need to let things "cool down" end up pretty surprised when I tell them to watch the temps on the engine monitor during this "cool down" phase.



I can't say this is always the case, but simply an observation I've made in many aircraft with good engine monitors. As a result, I don't personally teach people to do anymore idling after they've taxied to their shutdown location.



In turbocharged aircraft you'll often have people sit for several minutes so the turbo will "cool down". Again, if you watch the TiT temperature during this time period, it's going up if anything...not down...
Click to expand...


Exactly. The 'let the turbo-charged engine run at lie RPM before shutdown' is an OWT. Flying or Aviation Safety did a study a few years back where they measured temps during flight up to shutdown and found as Jesse notes that temps actually went up during the taxi to the ramp and before shutdown. There are reasons up run some engines 30 seconds or more at low RPM before shutdown, but cooling is not one of them.
 
Yep, that's to clear the plugs after taxi, you can eliminate the need by go going as lean as she runs as you get off the runway.
 
IMHO, this procedure is exactly what caused two engines at my last Aero Club to each eat a piston before half of their normal TBO.

Let's get the engine super hot, with inadequate cooling, and then shut it down right away and let the oil collect & coke up against the rings in smoking hot cylinders. And since it is a rental bird, let's do it 4x per day?

Until the rings seize and blow-by begins, then everything goes down hill quickly...

Not with my $64k sticker-price engine (O-360-D2J).

BTW, Lycoming won't give you a core credit on said engines either! (ask me how I know)

It wasn't 2 engines out of 20, it was 2 out of 3!
 
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I'm not a fan of the procedure either and never use it unless the owner asks me to. I go as lean as I can as I get off the runway, pick it up to 1200 rpm as I park, then pull ICO from there. On my planes I will also do a 'mags cold' check before picking up the RPM. I prefer to control loading up the engine by not loading up the engine rather than clearing it.
 
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