Learning to fly, or thinking of learning? Post your questions, comments and experiences here

Moderator: AndyR

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By kingbing
#1637088
Leaning is usually above 3000ft, IIRC, and I don't think I ever got any higher than that in my PPL apart from the odd bit of stall training...
By TopCat
#1637109
kingbing wrote:Leaning is usually above 3000ft, IIRC, and I don't think I ever got any higher than that in my PPL apart from the odd bit of stall training...

This is quite correct. 3000 feet is in fact a magic altitude, above which engines work differently.

And as everyone knows, it is impossible to recover from a stall in less than 3000 feet.
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By Irv Lee
#1637125
I have to emphasise to anyone going to S Africa, even coastal fields, they have to chat to the CFI and confess the parochial aspect of UK training and ask for engine management briefings before going near an aircraft. If you don't lean prior to taxi there, even at sea level, that is possiblly the end of flight as they don't know what else you havent been taught and suspect you printed your own ppl. I have also heard of the opposite here, an experienced UK cri threatening to terminate a session before taxi because the pilot leaned to keep the plugs cleaner during taxi. I hear he threatened to jump out if the mixture was touched again before shutdown. Not sure how that would work well in the air, perhaps he hadn't heard of it being used in the air too.
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By TopCat
#1637131
Irv Lee wrote:...an experienced UK cri threatening to terminate a session before taxi because the pilot leaned to keep the plugs cleaner during taxi. I hear he threatened to jump out if the mixture was touched again before shutdown. Not sure how that would work well in the air, perhaps he hadn't heard of it being used in the air too.

Dear god... :roll:

Just out of interest, what kind of continuous professional development, if any, is in place for instructors, that would give even a fighting chance of weeding out this sort of gross ignorance?

It's not like if you lean properly for taxying, you're not going to notice if you forget to push it rich again, and then open the throttle for take off.

Well... one would hope not... but if you have even one brain cell, you're really not going to do that too many times.
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By Irv Lee
#1637199
Usually a forgotten leaned mixture on taxi shows on power checks by a rise in rpm on application of carb heat. (Obviously guilty, or i probably wouldn't know that, but i would have picked it up on vital actions before line up unless i was completely incompetent that day)
By Cessna57
#1637232
When was the last time a school had an engine failure?

I’m used to working on old pushrod engines in cars and understand what a lean mixture can do.

It strikes me that by never leaning, schools protect their engines from incorrect leaning and melted piston crowns.
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By Flyin'Dutch'
#1637267
Cessna57 wrote:When was the last time a school had an engine failure?

I’m used to working on old pushrod engines in cars and understand what a lean mixture can do.

It strikes me that by never leaning, schools protect their engines from incorrect leaning and melted piston crowns.


There's nothing magic about leaning - however there is a lot of hubris surrounding it.

Using the money stick, aka mixture lever, saves money and promotes engine health.

Lycoming even states that below 65% it is not possible to damage the engine by leaning (even if you over lean it) - that is where the 3000ft comes from. Above that altitude normally aspirate engines give < 65% even when you're flying around with the throttle wide open.
By TopCat
#1637467
Flyin'Dutch' wrote:Lycoming even states that below 65% it is not possible to damage the engine by leaning (even if you over lean it) - that is where the 3000ft comes from. Above that altitude normally aspirate engines give < 65% even when you're flying around with the throttle wide open.

Do you have a reference for this, FD? I can't comment on the first bit, but I think the second bit (my bold) is wrong...

Unless I'm misinterpreting the table, looking at the Cruise Performance pages in my POH, the %BHP column goes up well over 65% with increasing throttle, at altitudes well above 3000 feet.

For instance...

Image

Am I missing something?

At 2400 rpm it's less than 65% at all altitudes from 3000' up, but not at full throttle.
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By Flyin'Dutch'
#1637487
The 65% or less is referred to here:

https://www.lycoming.com/content/leanin ... ng-engines

I will try to find the 3000ft reference - was it in one of the Pelican Perch articles? Will report back once found.
By TopCat
#1637498
Flyin'Dutch' wrote:The 65% or less is referred to here:
https://www.lycoming.com/content/leanin ... ng-engines

There's nothing in that article that I can see that supports the assertion that:

Lycoming even states that below 65% it is not possible to damage the engine by leaning (even if you over lean it)


The closest thing I can see is the bit at the end referring specifically to supercharged engines:

Lycoming wrote:Recommended standard cruise power for the supercharged engine is 65%. At 65% power or less, this type of engine may be leaned as desired as long as the engine operates smoothly, and temperatures and pressures are within manufacturer’s prescribed limits.

... which isn't the same thing at all.

Is this the article you meant?
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By Flyin'Dutch'
#1637510
Nope - that is 1094D which has replaced Service Letter112 which IIRC had the statement re the 65% in it.

Maybe their lawyers advised them that a65% recommendation was more likely to avoid claims than the earlier statement.

The 3000ft must have a different origin as you correctly state that 65% can easily be exceeded with WOT at that altitude, also by other jalopies than the mighty Cheetah.

Only ever flown the straight AA5, never the A or B.