Very low density altitude power settings.

[Mountain Doctor]

With very cold OATs at near sea level airports DA less than -2,000' are common.

At these DA's the engine will make more than 100% power.

Do you guys operate your engines differently (ie, less MP) in these conditions, or just firewall it on takeoff and enjoy the increased juice (such as I do with my fixed pitch 180)?

[TomD]

I figure horsepower not used on take off is in the same category as runway behind you and sky above you as useless things in aviation.

[Rezrider]

I heard about a guy who was taking off below sea level and couldn't get enough fuel through to the engine despite the mixture being full rich.
The next time he tried it turned the boost pump on and that helped enrich the mixture enough for a smooth take off.
I'm not sure if that's bogus but it sounds plausible to me.

[Kirk]

I would think if the extra power boost was a problem, the FAA would have put an operating limitation on it when it was certified.

From long ago, I do recall the Lycoming O540 and IO540 stumbling a bit if you rapidly advanced the throttle at extremely cold temps. As I recall, we might encounter that below about -20 F. Never tried anything with the mixture.

Slow throttle movements aren't a bad idea anyway in cold temps, with thickened oil and everything running at much different clearances than they usually do

Kirk

[TomD]

Here is a question for those of you that run in cold temps a lot.

I have an O-540J1A5D and it seems ( or I am imagining) the EGT's are higher at low temps ( very low DA ) when plugging along at ~2000 ft MSL.

My logic is the "heavier" air produces a leaner mixture thus higher EGT's.....or not.

Thoughts?

TD

[Av8rPaul]

Have many hours of part 135 flying in Alaska and have encountered low DAs often. Full power takeoffs and usually didn't reduce power as much in cruise to try and keep the engine (and cabin) warm.

Most of my Arctic flying is behind Continental IO-520s.

[VA Maule]

TomD: I think you may be on to something there ,low density altitude would be the inverse to high density altitude where you have to lean for maximum power so an extremely low temperature at sea leave or below would cause a leaner mixture.
Perhaps Andy Young will chime in on this I seem to recall he mentioned he has worked in Antarctica that's coldest place I can think of.