...flying very slowly, with their turn signal on.
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Leaning While Climbing
- Thread starter mfleming
- Start date
...flying very slowly, with their turn signal on.
This. Is. GOLD!!!!
Aren't you leaning for best power before takeoff if you're significantly above sea level? You should know exactly where you're setting the mixture.
All you're doing is tweaking the fuel supply lower to match the lower air density as you climb. If you hold EGT more or less constant during the climb, mixture should be more or less constant too, and if it was correct at the beginning of the climb it'll still be correct at the end of it.
- mark
PilotjohnS
Well Known Member
I have a Lycoming factory clone Bendix fuel injection system, RSA type. It actually does a pretty good job of automatically leaning out as I go up; I don't need to lean very much, if at all, until I start leaning for cruise.
Well, here's the thing:
If you start your takeoff at best power, and progressively lean as you climb, you're still pretty close to best power at 8000', which isn't that far ROP, so "lean for cruise" is only a turn or two of the red knob in either direction, depending on whether you want to be ROP or LOP.
If you're not leaning as you climb, then when you get to the top you have to start thinking about "leaning for cruise."
I'm running a Silverhawk fuel injection system, which is also a Bendix clone, and if I don't lean during the climb I see EGT trending downwards. If EGT is trending downwards during a climb that starts at best power, that means the mixture is getting richer during the climb and I'm not at best power any more by the time I get to the top. Progressively leaning to maintain best power mixture means I get a better climb rate and/or a higher service ceiling.
But RV climb rates are good enough that maybe it doesn't matter. We're still out-climbing sea level Cessnas when we're full rich at 8500'
The converse is true too, btw: The mixture will get leaner as you descend into denser air. If you're starting the descent ROP, you might end up in a zone where adding too much power causes detonation unless you wind in the mixture knob to add fuel first.
- mark
Until yesterday, I have flown 100% of my hours over 15 years above 5500 feet MSL. I moved my plane to Illinois yesterday due to a new job (and much cheaper hangars!!!!). What a difference. I actually needed to adjust BOTH the throttle and prop controller. Such a new environment.
Illustration, AFP FM-200, IO-390, WOT and full rich from 200 to 15000 feet. Bendix-type metering is based on velocity and density, so it tracks the density loss due to altitude rather well for a purely mechanical device. However, it's not perfect, and does moderately drift rich as density is reduced.
Progressively leaning in the climb to maintain the EGT noted immediately after takeoff simply makes the blue fuel flow line track the red density line.
Concerned about leaning at WOT? Note the EGT seen immediately after liftoff from sea level is based on a fuel/air ratio necessary to maintain detonation margin, based on certification tests, which are run at worst case temperature. Leaning to keep the blue line matched to the red line merely maintains the same ratio, and thus provides no basis for a detonation concern based on mixture. If CHT's get too hot, it's because cooling system performance is inadequate.
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There ya go Dan. Trying to baffle us with facts and real science again
PilotjohnS
Well Known Member
Good data, so I should be leaning a little bit during climb. I like real data! Thanks
Think I will lean to maintain peak manifold pressure during climb. Best I can do.
Reviewing my 140 hours of Garmin flight logs, the fuel flow drops drastically up above 10k when lean of peak. I was surprised how much more efficieny I could gain lean of peak up high. Catto told me as much when he suggested a three blader for high altitude cruising. Seems Catto optimized my prop for just this scenario.; couldnt be happier.
During my full throttle TO, the mixture was full rich. I observed the EGT temp shortly after TO and leaned to this number as I climbed. There's been a lot posted since I did this flight and I'm now reading John Deakin's writings...trying to get educated ;- )
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Can you explain this method and what you're seeing with the lean assist on before TO?
What O2 sensor do you use and any long term life results (assuming you use 100LL)?
I installed a Bosch and NTK to see if one was better, but haven’t got many hours yet.
I go LOP shortly after takeoff (staying outside the ”red box”) as I’m step climbing down low under v complicated airspace and with v expensive 100LL. (IO550N in plastic plane). I love the AFR displays.
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Ballenger AFR500v2 gauge with NTK calibration-grade sensor. I run 100LL by necessity (I wish I had an alternative available) and have about 160 hours on the sensor.
