Advancing the throttle on shutdown

I undersand the 1000prm at shutdown to be intended to keep the engine from dieseling. By the time the forward momentum is low enough that the engine could kick-back, there is no combustible mixture left.

IN the Conti fuel injection there is some idle FF setting that is re-set by reving the engine to 1700. This is part of the fuel pressure adjustment process and not related to the shutdown.
 
My plane will idle VERY low, super low with one mag off, the plane shuts off right quick by pulling the mixture, even with very low RPMs. Anything else I'd have it in the shop.
 
The POH for the C172SP I rent says to pull throttle to idle before shutdown:

SECURING AIRPLANE
1. Parking Brake - SET
2. Throttle Control - IDLE (pull full out)
3. Electrical Equipment - OFF
4. AVIONICS Switch (BUS 1 and BUS 2) - OFF
5. Mixture Control - IDLE CUTOFF (pull full out)
6. MAGNETOS Switch - OFF
7. MASTER Switch (ALT and BAT) - OFF
8. STBY BATT Switch - OFF
9. Control Lock - INSTALL
10. FUEL SELECTOR Valve - LEFT or RIGHT (to prevent crossfeeding between tanks)
 
MassPilot said:
The POH for the C172SP I rent says to pull throttle to idle before shutdown:

SECURING AIRPLANE
1. Parking Brake - SET
2. Throttle Control - IDLE (pull full out)
3. Electrical Equipment - OFF
4. AVIONICS Switch (BUS 1 and BUS 2) - OFF
5. Mixture Control - IDLE CUTOFF (pull full out)
6. MAGNETOS Switch - OFF
7. MASTER Switch (ALT and BAT) - OFF
8. STBY BATT Switch - OFF
9. Control Lock - INSTALL
10. FUEL SELECTOR Valve - LEFT or RIGHT (to prevent crossfeeding between tanks)
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For a long time I did exactly that in the 172SP G1000. But that made hot starts a little difficult. Now for step #2 I set 1100RPM for hot starts.
 
asicer said:
For a long time I did exactly that in the 172SP G1000. But that made hot starts a little difficult. Now for step #2 I set 1100RPM for hot starts.
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Do you prime when you do the hot start?
 
weilke said:
By the time the forward momentum is low enough that the engine could kick-back, there is no combustible mixture left.
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This makes the most sense why this practice would be done, and goes along with what I've been told in the past that it "clears the exhaust out" - but I'm still not entirely sold, since if your mixture works properly and it is fully pulled out than you really shouldn't have combustible material left in there to begin... 1,000 RPMs means that cylinder is still pumping up and down something like 16 times per second... that seems like plenty of oomph to blow any air out after the combustible material is gone

**Having said that, I don't see there being anything *bad* about doing that other than the next clown potentially starting the engine at full power...
 
When I learned to fly many years ago in the Tiger Moth, the standard shut down procedure was to turn off both mags and open the throttle to prevent detonation that might occur otherwise. Seemed to work OK back then!
 
Tantalum said:
**Having said that, I don't see there being anything *bad* about doing that other than the next clown potentially starting the engine at full power...
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They do that anyway, even if the throttle was left at idle before they got in. :)
 
creweite said:
When I learned to fly many years ago in the Tiger Moth, the standard shut down procedure was to turn off both mags and open the throttle to prevent detonation that might occur otherwise. Seemed to work OK back then!
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Standard procedure for the Auster's Gipsy Major, too. The mixture lever was rich when pulled full aft, and the throttle lever next to it had a dog that pulled it rich when you closed the throttle. The engine also had a habit of forming lots of carbon in the heads that would get hot spots and make the engine diesel on after the mags were shut off, so we'd push the throttle and mixture full forward to stop that. It would get lean enough to quit.
 
labbadabba said:
So, I noticed something weird that a buddy picked up from his CFI.

During shutdown with the throttle at idle, he pulled the mixture. Just as the engine started to sputter he advanced the throttle to the firewall. The engine for just a moment came back to life and then shuttered to a stop.

I asked him why he pushed the throttle in and he said that his CFI told him that it burned out the remaining fuel in the cylinders.

I guess I can kind of see that, but is there any real benefit to this? More importantly, is there harm done here?
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If you do that on a carbureted engine most of them have an accelerator pump that will shoot fuel into the engine, actually doing the opposite of what he is intending to do.

I run up to 1000RPM then pull the mixture out. Some of this is making sure the spark plugs are clean for the next start. That's why some manufacturers have you take the extra step of running to 1800 rpm for a bit.


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N659HB said:
Do it all the time with my A65. By the book, per Continental.
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Your A65 has most likely has a stromberg carb with no accelerator pump and that's why,. Also no mixture


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JimNtexas said:
What do the people who make the engines and the manufactures who publish checklists know? Just follow what some random dude told you, because random dude (CFI or otherwise) clearly knows more!
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True for 90% of it, but there are always some tricks that are found in the wild which help in life, ofcourse it's evidence based for the more intelligent crowd, if I can't see how it makes a positive difference I don't pay much mind to starting/shutdown tricks.
 
I've never done it and don't recall seeing that specifically in any Piper POH. In fact, I thought I recall seeing to REDUCE the throttle to help slow/stop the engine/prop smootherly. I think I recall seeing the word smootherly specifically in the POH. But now I reckon I have to go back and maybe read that thing.
 
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