Throttle Idle on Ground?

A150K said:
Another reason you want to be at 1000 instead of idle is cooling.
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No. There's not enough heat made at idle to need any additional cooling. Up north we have to keep the idle high for warmth. I can't get my oil temp in range at idle on even a 50F day.
 
The only argument I've heard that suggests you get better cooling at 1000 is the additional air flowing over the spinner drawing more air into the inlets, but I could be mistaken...Wouldn't be the first time :p
 
A150K said:
The only argument I've heard that suggests you get better cooling at 1000 is the additional air flowing over the spinner drawing more air into the inlets, but I could be mistaken...Wouldn't be the first time :p
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You could take the prop off at idle power and there would be sufficient cooling.
 
It's SOP to leave it the power at 1000RPM and lean accordingly in every recip I have flown, including turbo'ed engines.
 
Pilot121 said:
Hello,

During my flight lesson the other day, I was holding short of the runway, waiting for takeoff clearance and performing the run up. I set the power to idle, but my instructor told me not to do that because it could foul the spark plugs. The mixture was full rich, and it was hot outside - about 26 C. Is this a common practice? I always thought you should have the power back at idle instead of holding the brakes, but is that not the case?

Thanks,
Pilot121
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I can only think of a few reasons to ever be near or at max idle while on the ground. Sometimes it's useful during the runup once the engine is warm to see if the engine will continue to run while at max idle, also there are some people who do dead mag checks at max idle before or after a flight and I could maybe see some taxi ways or runways that are rather steep it might be more advantageous to be idled mostly back as it might be better than riding the brakes too hard/long. That and if you're flying seaplanes when you're trying to dock you might want to be max idle and only one mag to slow yourself down as much as you can without killing the engine.

Depending on how many lights, what avionics and if you have any other equipment installed and operating you might be draining more energy than your alternator is creating at max idle. I would also very, very highly recommend that you always have your feet on the brakes or the parking brake pulled when you mean to be stopped and never, ever rely on your rpm alone.
 
z987k said:
No. There's not enough heat made at idle to need any additional cooling. Up north we have to keep the idle high for warmth. I can't get my oil temp in range at idle on even a 50F day.
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I assume you use an oil cooler plate on the winter?
 
JustinS said:
On the ground while at 800-1,000 RPM if you lean until you get a slight rise in RPM (30-50 RPM) then you've leaned it enough. If it starts to cough and sputter, you went too far, put the mixture back in a little bit. Be careful if you have it too leaned out, and you want to goose the power to make a tight turn on the ramp or run up area, she might quit on you or stumble...
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Or, if you somehow goofed up your "flow" and forgot to shove the mixture home, it might quit if you stand it up to takeoff power.

Wait, that's a good thing. Lean that sucker WAY out. ;)
 
Doesn't the 172R checklist call for running throttle to idle as a "check", then back up to 1000ish RPM?
 
Pilot121 said:
Hello,

During my flight lesson the other day, I was holding short of the runway, waiting for takeoff clearance and performing the run up. I set the power to idle, but my instructor told me not to do that because it could foul the spark plugs. The mixture was full rich, and it was hot outside - about 26 C. Is this a common practice? I always thought you should have the power back at idle instead of holding the brakes, but is that not the case?

Thanks,
Pilot121
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One other reason to increase to 1000rpm. The engine runs a lot smother.

Watch it when the cowl is off, at 700rpm +/- the engine is bouncing all over the mounts I don't care how well the prop is balanced.
 
1000 rpm will also ensure that your alternator is taking most of the electrical load on the ground. In some of the G1000 Cessna's at least, you'll get some low vacuum annunciators (super annoying buzzer bell to go with it) as well as the occasional low volts annunciator if you let it idle too low. If you're not moving, bump it back up to ~1000 rpm and all is solved.
 
1) Pull to idle

2) Lean until RPM rise

3) Taxi

It's pretty easy, and the mechanic's will appreciate it. This is a must if you are flying a C-152 with the O-235-L2C engine.
 
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