The Savvy Aviator #59: EGT, CHT and Leaning - AVweb

Of the many tasks that we have to perform as pilots, leaning the engine is one of the simplest. Leaning is vastly easier than shooting a circling approach in low IMC, picking the smoothest route through a cold front or deciding when to overhaul the engine. Yet no subject I know seems to trigger more discussion and debate among pilots, nor to provide more misinformation and bad advice. Although I usually devote this column to maintenance-related topics, aircraft owners seem to ask me more questions about leaning procedures than just about any other subject. It's obvious to me that, despite the simplicity of this subject, it remains poorly understood by a lot of aviators. So I thought it might be worthwhile to revisit my approach to leaning, and then address some of the questions that pilots seem to have about it. The best source I know for in-depth information about optimal powerplant management is the 2-1/2-day Advanced Pilot Seminars(APS) course developed by my good friends George Braly, Walter Atkinson and John Deakin. This outstanding seminar is offered both as a "live" course several times a year in Ada, Okla., and occasionally elsewhere, and is also available in a home-study, on-line version. Tuition is about $1000 for the live course and about $400 for the on-line course. I've taken both the live and on-line versions, and both are excellent. The objective of the APS course is to offer pilots an in-depth understanding of powerplant management, both theory and practice. It offers a huge amount of information on the subject, and most APS graduates liken the experience to drinking from a firehose. But many pilots are reluctant to invest the time, money and neurons into gaining that level understanding of powerplant management. Many are just looking for a simple, cookbook-like approach to leaning that doesn't require a rocket scientist to master.


This is a companion discussion topic for the original entry at https://www.avweb.com/ownership/the-savvy-aviator-59-egt-cht-and-leaning

Mike -
I appreciate this opportunity to ask you an educated question…
I also have taken the APS course in Ada, Ok and have owned my Pa24-260 Comanche GTO since 2001, presently equipped with JPI830, GAMI injectors, and EIS ignition.

So, here is the dilemma I have. I recently determined by collected data that my “best” speed altitude at 75% Power is 9600 Density Altitude, at very close to Peak EGT (to slightly less, about 10 deg LOP) is 174 KTAS… all with CHT’s at or below 380.

This seems to go against the RED-BOX grain Mantra, operating at 75% Power (13 gph in 260 HP IO540).

  1. Even though my safe-target-CHT-380 is always met, is this potentially unsafe/unhealthy for the engine to operate at Peak EGT with 75% power?

  2. Naturally, operating at 50 deg LOP is CHT-cooler (and slower), but for best speed, and avoiding ROP, what is your opinion regarding operating at Peak EGT at 75% Power, yet with cool CHT’s?

Thanks in advance for your wisdom.

Tom Wolf
N8684P - Comanche 260 LoPresti GTO

I fly a Musketeer with an IO-360 engine.
It has a CHT gauge (which is dubious).
How do I lean this engine on mixture and RPM alone?