This video explores leaning technique in several aircraft types.
Watch in HD!

After nearly 20 years of being a “weekend warrior” private pilot, I have to admit that I am still not as on top of leaning as I should be.
I am a rental pilot, and most of my flying is local so leaning is not always top of mind… but as I am starting to fly more types, and do more cross country flying, I am trying to get better about leaning – and doing so properly.

The big 3 reasons to Lean:

1) Save money by reducing wasted fuel.
(and save on maintenance; see #3)

2) Save the environment by having cleaner emissions.

3) Save your engine!
(plug fouling is the easiest way to see what is also happening to other components such as valve stems, etc.)

I want to thank everyone at Island Air in Toronto, as well as the folks at Spectrum Airways in Burlington for tolerating all my shooting around their planes.
And a big thanks to Dennis for helping out directly with the videos.

Email excerpt from Dennis:

Hey Steve,

Some leaning facts/fiction and follies for you.

First of all, the ideal or stoichiometric ratio…fancy word, simple
formula: 14.7 pounds of air to one pound of fuel. Every carbon atom gets to mate with the right number of oxygen atoms to make the most amount of power with the least amount of waste.
While efficient, this also results in the most amount of heat which can damage an engine under load and cause detonation and can even melt metals such as aluminum. Therefore, it is not advisable to lean on takeoff as it can overheat and damage an engine since the “wasted” fuel is actually used to carry off the excess heat (in fact, most carbs have a “rich circuit” that kicks in at full throttle to help this process), BUT…you may need to lean at high density altitude situations in order to get full power but this must still be done conservatively.

Now as to the debate about rich of peak, or lean of peak…
Peak means peak EGT or exhaust gas temperature, also where peak power is typically found. What to do when an EGT gauge is not present? The “bush pilot” method was to establish cruise flight, slowly lean ’til rpm peaks (not easy to do in bumpy air, or with a jiggly tachometer or if you are tone deaf) and if you didn’t notice the RPM peaking, wait for the engine to cough and then turn the mixture back in until the engine ran smooth again. Maybe not perfect ‘stoich’ but close enough and better than nothing. And maybe this is where the ‘no leaning below 3000’ came from…pilots were worried about snuffing the engine and not having the altitude to restart.
If a reliable EGT is available, now you can lean to peak, LOP or ROP but how and why? The engine/airframe POH is the bible but generally LOP is max fuel efficiency (maybe), ROP is for running a bit cooler in high load, high temp situations and PEAK is max power (speed in cruise).
It’s generally believed that you can’t hurt an engine running LOP in cruise, but debate rages on as to whether it’s worth it, after all, you lose a bit of power and therefore speed, so what are you gaining?
The whole process is tougher in the modified Warrior since you have a constant speed prop and therefore can’t see the RPM rise or fall, there is no EGT anymore so no temperature peaks to see, and the lever type control which is hard to adjust accurately.

But you can detect the loss of power if you are attentive and
even a bit of leaning is better than none.
On the ground, lean as much as possible until the engine starts to stumble or doesn’t respond to power applications. That’s the best way to save gas, keep plugs from fouling and help the environment.
Hope this helps.

Chief Flight Instructor
Spectrum Airways


DISCLAIMER: I am a “weekend warrior” private pilot, I fly for fun with no intentions of going commercial.I have had my PPL for over 15 years, but still consider each flight a learning experience – I generally take detailed notes after each flight to remind myself what went well or what I could do to improve…. Having the GoPro cameras to record flights like this is invaluable. I find these self analysis videos very helpful in my constant quest to improve, and am happy to share.Feed back is invited; however, please keep it positive

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