Proper Leaning Procedures in Mountain Flying

[BYUFlyr]

I did all of my flight training in FL where we only lean during cruise above 3,000 msl. I moved to Utah for school and I'm wondering what the proper procedure is for leaning during T/O and landing, if any. I've heard both sides: "Lean for best performance during T/O," and "Full rich for T/O and landing." Is there a right answer? Thanks.

 

[minitour]

If the D.Alt is too high and you've got full rich for TO and Landing, you're robbing horsepower from yourself at a critical time.

Do a runup and lean for peak, that's your takeoff setting. Don't have time to toss out the exact procedure right now but when I get back I'll put it in if someone hasn't.

-mini

 

[BYUFlyr]

Thanks for the response, but my question wasn't how to lean... if it's the same procedure as in FL at 4,000 msl; I think I figured that one out by now. My question is wether or not to lean; I've heard both "to lean" and "not to lean," both with good arguments. I've heard to keep the mixture rich during T/O to aid with cooling, and I've also heard to lean for max performance.

I personally think leaning for max performance above 3,000 msl DAlt should be applied to all phases, including T/O.

I'm looking for what the experts say....

 

[VFR on Top]

Absolutely lean during your runup and leave it there (actually, lean it out as soon as you start the thing). Absolutely do NOT go full rich for takeoff or landing at those altitudes--you're begging for fouled plugs at best and the engine quitting at an inopportune moment at worst.

p.s., sorry about your choice in schools, man.

 

[BYUFlyr]

Thanks VFR on Top.... I won't hold your choice in school against you... I'm sure it wasn't your choice, there must be a perfectly rational explanation to your misfortune. (J/K)

Thanks for the tip! That's what I was thinking, I was just looking for someone to confirm it.

One last question: What do you enrich to when descending to land?

 

[IP076]

Just remember...if you are leaning on runup, and want to get it right, you must do the runup at full static power. If you only runup to 1800 and then lean it out, and when you take off you use 2300, you will be operating the engine too lean.

The proper procedure if you want to get it right would be to do a full static runup and lean the mixture there to peak RPM, which will give you the "Best Power" setting for take-off.

You could also check the POH and see what it says, it probably states to lean above 3000 or something.

 

[minitour]

Thanks for the response, but my question wasn't how to lean...My question is wether or not to lean...

I thought I answered that one...

If the D.Alt is too high and you've got full rich for TO and Landing, you're robbing horsepower from yourself at a critical time.

Yes, lean for t/o and landing if you're that high up. Even if you aren't that high up if the D.Alt is "high" enough on a hot, humid, summer day you should still lean for T/O. As IP076 said, the POH is really the final authority in this situation...although maybe Lycoming or Continental (or whoever) would be the more appropriate sources of information since we're talking about engine performance and not the airframe itself...dunno about that one.

-mini

 

[Monkeyfist]

Some POH's don't say anything about high density altitude T/O and LD->BE-36

This is a good question for avbug

 

[avbug]

First, I gotta ask what your instructor has been doing all this time that you don't know how or when to lean an engine. This is pre-solo stuff. Really.

For those who are leaning during ground idle operation...what do you think it is that you're doing?

Get a maintenance manual and look into the specifics of the carburetor function for your engine. A fuel injected engine is a little different in practice and function, but leaning a carbureted engine on the ground is a fools errand. The only function your mixture control has in the leaning process at idle is cutoff. There is a very, very small narrow point just prior to cutoff when you can affect the mixture at idle, but a very minute point, and only because you're passing into cutoff.

Idle mixture is a maintenance function, and outside of your ability to adjust or control.

Manufacturers generally recommend against leaning above 75% power. Not because it can't be done safely, but because pilots are idiots, and they know this. Pilots often fail to use good judgement in their actions often failu to learn or use proper technique or airmanship and the recommendations provided by manufacturers take this into account. Manufacturers also recommend against lean of peak operation in some cases. Not because it's unsafe, or dangerous, or damaging...properly done it's better for the engine. Only because piltos aren't usually well enough trained, and don't use proper judgement, to do it properly.

Lean your engine as necessary, whenever necessary. Period. It's not rocket science.

 

[westwind]

Sparky Imeson's "Mountain Flying Bible" is chock full of the info you are looking for, and a lot more. You should also be able to find an excellent mountain flight instructor in Utah. Get a mountain checkout with a thorough ground school if you can as well. It will be both very instructional and a flight you will never forget. Avbug's last paragraph nails it in a nutshell. Hey Avbug, you going to be in my neck of the woods anytime soon?

http://www.sancarlospilots.org/mf1.htm http://www.midlifeflight.com/stories/comntn.htm#start_story

Listed above are a couple of writeups on what a mountain checkout entails, the bottom story was taken with Midlifeflyer, a flightinfo member and Denver CFI.