Interesting innit that people complain about the cost of hiring but never give a second thought about what they cost the aircraft owner by running around full rich in a wet hire aircraft.
Late last year I flew a mates
1956 C180 in the UK for the first time since that aircraft was a P2 registered C180 that I had last flown in 1987 in PNG.
He had sold a share to a retired BA captain who had spent a career in jets.
They operated it full rich all the time based on 'advice' received that leaning was of no value in the 0470
..I suggested that was a load of ****e and proceeded to explain in detail why.
I flew it three sectors from the farm strip, where they keep it, to IOW, West Waltham and back to the Farm totalling around one hour. I leaned it on the ground as soon as it was running smoothly, used full rich for takeoff and climb, leaned in cruise/descent/landing, taxied leaned. We never got above 2000'.
We used 15 liters/hr -
GBP20.00 less fuel per hour than they usually plan on. They previously worked on GBP120/hr DOCs...I suggested that GBP2000.00++/annum was probably a worthwhile saving even ignoring that the engine would give less trouble because it was being operated properly..."Point well made!" was the comment from the retired BA captain as we drove away from the farm.
In general:
ALL 'modern' piston aircraft should be leaned brutally on the ground. You will never hurt the engine doing that and for those engines that foul plugs it will make a big difference.
FULL RICH for every takeoff
except takeoffs above about 5000' DA when they should be leaned for best power...as in the point being made by tinpis about PNG.
Lean appropriately in cruise no matter the cruise altitude.
Appropriately means 80-100 ROP at power settings above 65% power and anywhere you like at 65% or less in aircraft not fitted with balanced injectors and an all cylinder monitor. In aircraft so fitted
appropriately can mean anywhere between 50F LOP and 80F ROP depending on altitude and how fast you want to go..as long as CHTs remain below 380F.
In climb lean
above 5000'...if you
read the POHs they generally say 'don't lean
in climb below 5000'
not 'don't lean below 5000'. 5000' in normally aspirated engines equates to roughly 65% power at full throttle and leaning a little will help climb performance enormously. Just pull the mixture back 'a bit'...you want to be 100F+ ROP
in climb above 5000'. The power curve is very flat in this area of the mixture spectrum so precision is not required...if you have an all cylinder monitor lean until hottest cylinder says 380F...and keep leaning 'a bit' each 1000' on climb
above 5000' until cruise alt is reached.
On descent I don't touch the mixture at all in my Bonanza. I don't touch it usually until I pull it to cut off after I have parked. This because I am almost always cruising LOP. When I reduce MP around 4000' to keep speed in the green arc I am effectively enrichening the mixture because I have reduced the air while leaving the mixture
control unchanged. When I bring the throttle back from wide open to around 18 in you can actually see the EGTs
increase, peak and then fall a little onto the rich side of peak...this is the hottest place to run your engine and on highspeed descent the best place...even at top of the green IAS and 18in MP my cylinders rate of cooling slows and
almost stops.
You do need to remember to select full rich if doing a go around. It is
very good airmanship to check mixture, prop and throttle
in that order whenever you are about to apply maximum power in a piston engine..whether taxi-> takeoff, cruise-> climb or approach-> go around.
Any 'Instructor' that tells you different should not be let anywhere near a student.