More leaning questions!

[poadeleted20]

The method I taught (and used) was to descend until the engine told me that I was running too lean by beginning to run rough. Enrich until it smoothed out, continued descent until engine said "Hey, dummy" again, rinse and repeat until I reached approach altitude.

That's the ticket.

 

[cocolos]

The method I taught (and used) was to descend until the engine told me that I was running too lean by beginning to run rough. Enrich until it smoothed out, continued descent until engine said "Hey, dummy" again, rinse and repeat until I reached approach altitude.

Bob Gardner

But would that give you max power? that is if you needed it to go around at a high altitude airport? given that you were clearly cruising higher than that altitude

 

[EdFred]

But would that give you max power? that is if you needed it to go around at a high altitude airport? given that you were clearly cruising higher than that altitude

It's hard to be exactly where max power is on the mixture until you are level, and start leaning/richening it up to see where you need to be. But you should be close enough.

 

[Headspace]

Question 1: Do you have a harder time leaning when you have noise canceling headphones on? if so do you turn off the noise canceling?

Are you running a constant speed prop? Because if not, the RPM gauge can offer some valuable clues.

Nothing like a fouled plug to scare a new pilot. During the summer, when density altitude rises, you tend to run into these sorts of issues if you were running too rich too much of the time.

 

[david0tey]

For those of us who have yet to fly to airports at high elevations, can someone clear up the procedure for take-off and landing? I have always been taught to keep the mixture full rich during take-off and landing. It makes sense that that would be different at higher elevation airports, but I have never been taught.

 

[EdFred]

For those of us who have yet to fly to airports at high elevations, can someone clear up the procedure for take-off and landing? I have always been taught to keep the mixture full rich during take-off and landing. It makes sense that that would be different at higher elevation airports, but I have never been taught.

You do not go full rich*. Lean for somewhere around best power. Maybe a bit richer to keep the CHTs a bit more friendly.



*I'm sure, somewhere, there's some POH that says go full rich even at high elevations.

 

[MAKG1]

If you've ever done a 300 FPM climb out of an airport, you'll lean for best power (highest RPM, fixed pitch). Not "somewhere around" best power.

It's also helpful to approximate a soft field takeoff to build speed in ground effect.

 

[EdFred]

If you've ever done a 300 FPM climb out of an airport, you'll lean for best power (highest RPM, fixed pitch). Not "somewhere around" best power.

It's also helpful to approximate a soft field takeoff to build speed in ground effect.

Been there. DA was 11400, I wasn't going to cook the cylinders. As it was they were upwards of 400F. But you're the expert at everything. So the rest of us should just let you and Ron answer everyones questions.

Attention everyone: No need for any of us to contribute anymore. MAKG1 knows everything about, well everything, our input is no longer needed.

 

[midlifeflyer]

For those of us who have yet to fly to airports at high elevations, can someone clear up the procedure for take-off and landing? I have always been taught to keep the mixture full rich during take-off and landing. It makes sense that that would be different at higher elevation airports, but I have never been taught.

Leaning techniques for landing has been beaten to death already in this thread.

For takeoff, the goal is to product best power and maybe, as EdFred said, a little more rich for cooling.

There are essentially two methods. In some cases, an airplane may have a fuel flow gauge and the POH a chart of targets for takeoff fuel flow at various (density) altitudes. In that case, you want that target. In other cases, the technique would be roughly equivalent to what you do at altitude.

In both, for just about every normally-aspirated single I've flown, the technique taught at high elevation flight schools is to do an approximation at run-up power.

• Lean and watch the RPM climb and then drop.
• Enrichen back to the highest RPM.
• Enrichen a little more. 2-3 twists of a vernier mixture control is generally about right.

The "little more" is for two purposes. One is for engine cooling; the other is because you leaned at run-up power and the demands at full power will be greater.

This is still an approximation and subject to verification and any tweaking on the takeoff roll. Some folks will add a static full power runup as a cross-check. I think that's a good idea when you are unfamiliar with either the airplane or the conditions; the technique I described is based on experience flying and teaching in those areas and different aircraft will react differently (for example, a Cutlas generally requires more enrichening than most others). But the overall goal is to get close to any fiddling around during takeoff is minimal or non-existent.

 

[bobmrg]

Ok. Yes I am having trouble deciphering all the different methods of doing this, so let me recap:

1. taking off from high altitude airport full power and lean to max RPM (fixed-pitch)

2. landing at a high altitude at cruise power enrich it a couple of twist.

3. don't lean at low rpm.


that sound about right? anything I miss?

Nothing to do with descending, but be wary of #3...you want to lean for taxi, which will be low RPM compared to cruise or descent.

Bob Gardner

 

[bobmrg]

Been there. DA was 11400, I wasn't going to cook the cylinders. As it was they were upwards of 400F. But you're the expert at everything. So the rest of us should just let you and Ron answer everyones questions.

Attention everyone: No need for any of us to contribute anymore. MAKG1 knows everything about, well everything, our input is no longer needed.

I will continue to value his contributions, as well as yours, those from Cap'n Ron, aeroncachamp, and others. Closing off avenues of discussion is seldom helpful.

Bob Gardner

 

[cocolos]

Lastly I assume most start learning at a certain density altitude, do most people lean on the climb out every 1,000ft after that altitude you choose? (my POH states 5,000ft)

 

[gismo]

Above 7,500 you can't lean too much in a non trubo engine.

That's not entirely true if you have a C/S prop. The engine manufacturers and most of the "experts" agree that below 65% max rated power (Lyc says 60%) any mixture won't be harmful to the engine. At full rated RPM a NA engine can make 65% at about 10,000 DA and at 7500 they can put out 75%. On the plus side, a fixed pitch prop will generally limit RPM in a climb to something like 85% of max rated so at 7500 DA you'd only be making 65%. It's also true that insufficiently lean is less detrimental at full RPM than it would be with the RPM reduced and since the 60-65% power recommendation typically applies to cruise RPM the practical minimum altitude where mixture can't hurt the engine is probably below 10,000 DA as long as the engine is turning at or near max rated RPM

It's also considered by many knowledgeable folks that it's OK to lean to max power for a high (or even a mid) DA takeoff if the extra power might be important for clearing obstacles and you richen up a bit as soon as practical. The idea behind that is based on the thermal mass of the engine absorbing the extra heat for a short time without letting the temps become excessive. But for a takeoff in the 5000-8000 DA range I'd go with a bit more fuel than max power as long as there was plenty of runway.

 

[gismo]

Lastly I assume most start learning at a certain density altitude, do most people lean on the climb out every 1,000ft after that altitude you choose? (my POH states 5,000ft)

I make my first mixture adjustment using EGT (adjust for the same temp I normally see right after takeoff) shortly after speeding up to a cruise climb configuration which is typically in the 1000-1500 AGL region. Beyond that I readjust the mixtures every 1000-2000 ft depending on how busy I am.