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Mixture setting when taking off from higher altitude airfields ?

Daube

Daube

SOH-CM-2025
Hi all,

It's just a quick question regarding the actual recommendations for setting the mixture when taking off.
As far as I understood, usually it's recommended to set the mixture to full-rich when taking off, or when climbing or whenever we ask a lot of power from the engine.
But what when you're taking off from an airfield that is, say, above five or six thousand feet altitude ? Do you still set to full rich, or do you set to "best power for that altitude" ?

The reason I asked is because I have recently tried a takeoff from the Johnson Creek airfield (from OrbX) in Idaho. That was just a few days ago with real weather. I was using the A2A Comanche which had 50% fuel load, and I had set 100% rich mixture for the takeoff... and well, the takeoff has been very difficult due to limited engine power. I passed way too close to the trees tops. So I was wondering, should I have leaned the mixture a bit before taking off ? What is the actual correct way to proceed, here ?
 
I would say anytime your takeoff is at at altitude of 2,000 feet or more, it's best to lean that mixture before starting the engine. I'm surprised that the engine started at full rich mixture
to begin with. Bet it ran pretty rough.
 
Indeed it was quite unhappy. Then I leaned it on the ground, at least for warm-up and taxi. But when it came to taking off, then I wondered... and I set the mixture to 100% and made quite a dangerous takeoff, out of pure luck I think. If there had been any serious turbulences, I would probably have ended in a stall...
 
Thanks for the video, Bushpounder !
So it confirms that the "100% rich for takeoff" was just a misunderstanding from my side, and the actual correct way is "set mixture to best power before takeoff".
It makes sense, actually...
 
MSFS has the same fundamentally broken mixture model that previous MS sims had, since it's way too sensitive to altitude changes, and unless developers specifically enable a fixed version, it also doesn't react properly for turbocharged engines.

I typically use the "set best mixture" keybind on the ground and then fine-tune in the air, since the MSFS mixture model is way too finicky.
 
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