Leaning technique for a high elevation airport Cirrus

Tantalum

Tantalum

Final Approach
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San_Diego_Pilot
I've been into Big Bear and other relatively high DA airports. In carburetor planes my technique is usually that if I'm over 3,000 ft I'll lean on runup to "best RPM" (truthfully I usually go a little richer than that to help with cooling, but still well lean of a typical near sea level take off)

The Cirrus I occasionally fly has an altitude compensating fuel pump... and with the fancy prop "leaning to best RPM" is not really practical. I could try leaning to "best power" using the power read out, but that is not in the POH. In fact, from what I see in the POH they all say to do the takeoff and climb at full rich since the fuel pump is altitude compensating

Do any of the Cirrus drivers here have some more real world evidence and technique they can share?
 
I wonder what your EGTs look like on take off at a high DA airport compared to what the are on take off at sea level. That would seem to me to be a fair test of how well your Cirrus's altitude compensating fuel pump is doing its job.
 
Other than ballparking for taxi to prevent plug fouling, AFAIK there should not be any need to lean for takeoff with an altitude-compensating fuel pump. That's why the POH says full rich. That's kind of the idea. It's an inspection item for the annual.
 
Tantalum said:
I've been into Big Bear and other relatively high DA airports. In carburetor planes my technique is usually that if I'm over 3,000 ft I'll lean on runup to "best RPM" (truthfully I usually go a little richer than that to help with cooling, but still well lean of a typical near sea level take off)

The Cirrus I occasionally fly has an altitude compensating fuel pump... and with the fancy prop "leaning to best RPM" is not really practical. I could try leaning to "best power" using the power read out, but that is not in the POH. In fact, from what I see in the POH they all say to do the takeoff and climb at full rich since the fuel pump is altitude compensating

Do any of the Cirrus drivers here have some more real world evidence and technique they can share?
Click to expand...
Is that a +1 Cirrus? Ask the owner, they'll know. I haven't flown one for awhile but my recollection is that you can set a particular fuel flow and that will take care of it.
 
wilkersk said:
I wonder what your EGTs look like on take off at a high DA airport compared to what the are on take off at sea level. That would seem to me to be a fair test of how well your Cirrus's altitude compensating fuel pump is doing its job.
Click to expand...
that's a great point, I'll check that out. I'm suspect of the "altitude compensating giving best rich mixture" because when I go through the lean assist there's a very substantial rise in temps.. so I believe it still gives a very wide margin of "rich" - to the point where I wondered if it robs power in a high DA setting at takeoff

midlifeflyer said:
Other than ballparking for taxi to prevent plug fouling, AFAIK there should not be any need to lean for takeoff with an altitude-compensating fuel pump. That's why the POH says full rich. That's kind of the idea. It's an inspection item for the annual.
Click to expand...
True, still a weird feeling leaving at full rich when the DA is something like 8,500

jkaduk said:
Is that a +1 Cirrus? Ask the owner, they'll know. I haven't flown one for awhile but my recollection is that you can set a particular fuel flow and that will take care of it
Click to expand...
It's the one over at Coast. I like +1 fleet a lot but the Cirrus at Coast has much lower barriers to entry, at least I thought so. If I'm going somewhere long-ish (over 1 hr) with my wife we take the Cirrus as it's a more comfortable plane to cruise in... but that's just personal opinion. My choices are a one door old Archer with one axis autopilot or a Skyhawk with no autopilot where I have to step on the rudder the whole time (and that's a Skyhawk thing, not a +1 dig, I love +1). The Cirrus is a much better XC machine I find
 
Tantalum said:
that's a great point, I'll check that out. I'm suspect of the "altitude compensating giving best rich mixture" because when I go through the lean assist there's a very substantial rise in temps.. so I believe it still gives a very wide margin of "rich" - to the point where I wondered if it robs power in a high DA setting at takeoff


True, still a weird feeling leaving at full rich when the DA is something like 8,500
Click to expand...
no "weirder" than doing it with a turbo, although in this case, it's metering the fuel flow to accomplish leaning rather than simulating sea level air density.
 
I haven't flown at less that 7,000 da this summer and the mixture is always full rich. Then lean to 1250egt at cruise. Let the equipment do it's job as it was designed. You just follow the checklist :)
 
Do you have a maximum power fuel flow chart in section 4 of your AFM?
 
I presume you've got a SR-20 - a non-turbo? I hate asking stupid questions but in aviation you learn that there are no stupid questions.
 
comanchepilot said:
I presume you've got a SR-20 - a non-turbo? I hate asking stupid questions but in aviation you learn that there are no stupid questions.
Click to expand...
The only thing to presume is, the aircraft is equipped with an altitude compensating fuel pump. That is typically a non-Turbo feature since a turbo compensates for high density altitude in a different way. Cirrus is not the only company which uses one. I know there are A36 Bonanza models which use it.
 
midlifeflyer said:
The only thing to presume is, the aircraft is equipped with an altitude compensating fuel pump. That is typically a non-Turbo feature since a turbo compensates for high density altitude in a different way. Cirrus is not the only company which uses one. I know there are A36 Bonanza models which use it.
Click to expand...

Correct. The Cirrus mixture management systems in the SR2X range are actually pretty varied - the SR20 has an altitude compensating fuel pump, the SR22 NA requires leaning for altitude and the SR22 TN and T models operate more like the SR20 but due to their ability to hold sea level (or higher in the T's case) MP through turbocharging.

And the SF50 doesn't have a mixture lever at all!
 
There are full power fuel flow charts in Section 4 of the AFM for both the SR22 and SR20. Maybe they are published so the pilot can use them.
 
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