Primarily for general aviation discussion, but other aviation topics are also welcome.
User avatar
By Dodo
FLYER Club Member  FLYER Club Member
#1911926
I like to fly between 3 and 5 thousand feet when airspace and cloud allow as there seems to be less traffic around.

Let us discount any fuel savings from leaning at altitude for the purposes of this question.

I presume I use more fuel getting to my cruising altitude, but then I use less in the descent.

Do I burn more, the same, or less fuel than if I had stuck doggedly to 2000ft as most people seem to do?

I suspect it is more, but I don't really know.

Please show your workings. You may be marked (not really).
User avatar
By Rob P
#1911930
A lot depends on if you have ever been taught to lean properly.

And the length of time in the cruise compared to the time climbing.

But for any significant distance, higher will always be better.

Rob P
User avatar
By Milty
FLYER Club Member  FLYER Club Member
#1911940
At the risk of starting another never ending topic with no right answer and 50 subjective replies, how do you ‘lean properly’?
#1911941
Milty wrote:At the risk of starting another never ending topic with no right answer and 50 subjective replies, how do you ‘lean properly’?


Based on what the POH recommends or lean of peak/using GAMI if you have the courage, confidence and wisdom.

In terms of the original post - use your PPL theory:
Use the POHs time, fuel and distance to climb and descent figures, along with TAS/cruise performance to see what your fuel burn would be at 2 v 5kft in still wind.

What will actually make the difference on the day is more likely to be leaning and also headwind/tailwind at various levels (unless you’re going a long distance)
Rob P, Milty liked this
User avatar
By Rob P
#1911942
In lieu of anything else and requiring no sophisticated engine monitors, pull it out until the engine falters and then push it in a bit. But do it for every flight, even at 2,000 ft.

This will give you 90% of the benefit of l.o.p for which better kit will be required.

Rob P
Wishing I'd remembered the wind v altitude factor for my original answer.
Last edited by Rob P on Wed May 18, 2022 10:33 pm, edited 1 time in total.
Milty liked this
User avatar
By AndyR
FLYER Club Member  FLYER Club Member
#1911943
Milty wrote:At the risk of starting another never ending topic with no right answer and 50 subjective replies, how do you ‘lean properly’?


Varies according to aircraft type. Some may have far more comprehensive instrumentation to fine tune it too. And what @marioair wrote (saves me some typing :thumleft: ). And go up with an instructor who understands it. Many have never leaned in my experience.

I have a feeling @Dodo knows how to lean to be fair. His question is an interesting one, but purely from a bar room conversation point of view (imho).
Milty, Dodo, johnm liked this
User avatar
By Rob L
#1911946
Milty wrote:At the risk of starting another never ending topic with no right answer and 50 subjective replies, how do you ‘lean properly’?

Here's one of your fifty: If for example you fly a carburetted Lycoming-powered aircraft, the engines are designed to run rich for added internal cooling.

I learned about leaning with Goana in Australia in 2003 (C172, 180hp normally-aspirated Penn-Yan Lycoming, fixed-pitch prop, no CHT or EGT guages or electronic engine monitoring).
They said once finished climbing, and after cruising a bit to stabilise temperatures, lean it out 'til in runs rough then enrichen a bit. Irrespective of altitude. So we leaned out even cruising at 500' AMSL. We wouldn't have had enough fuel to arrive at our intended destinations without doing that.




Awaiting the other (edit) 45 or so
Last edited by Rob L on Wed May 18, 2022 10:55 pm, edited 1 time in total.
AndyR, Milty liked this
User avatar
By Smaragd
FLYER Club Member  FLYER Club Member
#1911947
Dodo asks for the effect of leaning to be ignored for the purpose of his exercise - but 80% of the replies talk about leaning! In the spirit of his question, quick thoughts about where the energy goes. Potential energy is gained in climbing but dissipated equally in descending, so ignore this. Energy is used in overcoming drag and in losses within the engine. Overall speed is likely to be slower for the higher profile so at first thought drag losses may be lower - but the higher flight profile involves a slightly greater air path, hence drag losses will increase due to this - what's the net effect? Energy loss within the engine will be higher in the extended climb at higher power, but lower in the descent - what's the net effect? Short answer - don't know!
Dodo liked this
User avatar
By Rob P
#1911966
Smaragd wrote:Dodo asks for the effect of leaning to be ignored for the purpose of his exercise - but 80% of the replies talk about leaning!


I suppose it's because removing leaning from a discussion on aircraft fuel consumption doesn't seem to make a lot of sense?

Rob P