Lean during climb??

[VH-BIG]

Hi all,

I fly a piston singles and when distance permits, I like to high ( up to A095 ). I've often wondered if it's ok to lean slightly in the climb and if so what procedure to use. :O

[Hornet_26]

Read the pilot operating handbook / flight manual, fly the aircraft accordingly and you should be right.

[NAMPS]

The best place to look would be in the flight manual of the particular a/c you are flying.

However, common sense would say that there is no problem with leaning progressively as you gain altitude. This is because the engine(s) are designed to operate at a certain (constant) fuel/air ratio.

Obviously there is less air the higher you go.

Consequently, in order to maintain the optimum fuel/air ratio it is necessary to reduce the amount of fuel being introduced to the engine.

I used to stooge around in a C152 and found that if I left the mixture at full rich until top of climb, there would be a reduction in RPM as I gained altitude. I then began to progressively reduce the fuel on climb and this maintained the RPM.

[Not_Another_Pot]

Once at FTH I'm leaning back to the %HP being produced but with regard to CHT's.

Generally I climb at 2400rpm and by 6.5k the MP is down to 24" and therefore %HP is 75% or less so why not lean to nearly that point?

Mid Teens is my solo cruising altitude providinf I have a tail wind!

NAP

[Chimbu chuckles]

All the engine cares about is fuel/air ration and temperatures.

There is no gadget that tells the engine it's climbing/cruising/descending.

You will never read the words "Do NOT lean in climb" in the POH of a normally aspirated engined aircraft. What you may read is 'do not lean above 75% power and do not lean for best power above 65%'....which is lawyerspeak to avoid litigation.

The same POH will tell you to lean for best power on TAKEOFF above certain altitudes, why not in climb above similar altitudes?

If you want to truly understand the issues go to avweb.com, click on 'columns' and find John Deakins articles on engine management....everything you'll read in POHs and most everything you have learned to date about leaning is BS....it's just plain wrong!!!

Read JD's stuff and you'll understand, hopefully, how I run my IO550b lean of peak at 75% power, including on climb sometimes, and have lovely cool CHT temps and how I never have probs with plug fouling/compressions.

Chuck.

[Bevan666]

Yup - I lean during climb. Technique I use (courtesy of JD) is to note the EGT on initial climb, and every 1000ft lean to that EGT. Keeps it on the rich side of peak (away from the red box) and I do notice more power (greater ROC) the higher I climb. Cuts 5-8 minutes off the time to climb to 9k in the Bonanza.

I do notice that the fuel flow using this technique closely follows the altitude marks on the FF guage.

If the CHT's are a bit too high (as has been the case recently down here with temps 20+ at 9k) I enrichen slightly and lower the nose to keep the temps down. Preferably below 195C.

Bevan..

[QSK?]

This topic was extensively covered under "Non-Airline Forums: Private Flying: page5" a couple of weeks ago.

For what its worth, here's my two bobs worth from that forum:

The following link to John Deakin's fabulous article answers all your questions on leaning during the climb.

http://www.avweb.com/news/columns/182176-1.html

JD's technique of noting the EGT on take-off (assuming the engine has been properly leaned, before the takeoff roll if at altitude); and then maintaining a constant EGT reading by gradually leaning every 1000 or 2000ft until the FTH limit (about 8/9000ft) works extremely well (talking non-turbocharged engines here). It also means that by the time you have reached cruising level the aircraft is essentially correctly leaned and, if the climb has been protracted, you have also made some significant fuel savings whilst climbing with full available climb power.

The same site also has other articles covering recommended leaning techniques during ground running, cruise and descent.

Definitely mandatory reading for any serious pilot so they are worth printing off, studying carefully and filing in a safe place so one can regularly refer to them for refresher training.