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Engine management / leaning / peak / lean of peak (merged)

Both at Peak EGT and LOP all of the fuel gets burned and produces combustion energy so Peak EGT is not more efficient than LOP.

Yes, I was inaccurate. ROP, airflow (throttle) controls combustion as there is an excess of fuel. At Peak, fuel and air are correctly matched, and LOP, fuel flow controls power as there is an excess of air.

EGTK Oxford

400F in cruise at 65% power? How the hell did the PA46 ever get certified?

Even if one goes strictly by the book (most people think 500F is way way too high, and 400F is a reasonable limit to work to) 500F is above Lyco's max official CHT, so that engine installation should have never been certified because it breaches the engine specs. Unless they certified it for LOP-only operation in cruise.

The PA-46 (Lycoming-powered) is supposed to be run ROP to peak. It has to run to FL250 where cooling is poor. I think from memory they say in the POH that 500F should be a red line on CHT which everyone knows is too high.

EGTK Oxford

JasonC,

Are you sure (with regard to PA-46 recommended operating methodology)? I don't fly one, but had thought it was one of the first to specify 50 LOP to peak and not 50 rich and that it was people running 'safe' at 50 ROP that caused the disastrous engine reliability issues early on.

EGTF

I have about 100 hours in a SR22TN (IO550) that expects cruise to be LOP operation only. As I recall, when the Piper Malibu came out, the POH required LOP operation on the TCM engine. Pilot culture and previous training resulting in pilots ignoring this and running ROP resulting in burning up the engines.

Peter, SFC curve is fairly flat around peak EGT and leaner, but even so, the curve peaks LOP and therefore leaner at this point is more efficient. I rarely use EGT for the purposes of leaning, I primarily use the engine analyzer for troubleshooting. I set fuel flow and I am done with it. Fuel flow equals power when LOP. On my Bonanza with an IO520BA, 65% power is always 12.5 GPH. Level off, accelerate to cruise, pull mixture to 12.5 GPH. At about 10,000 feet, I need to keep RPM at 2500 to remain LOP.

Since the digital FF (Shadin in my case) indication lags the actual instantaneous fuel flow, I use the analog FF indicator to rough set the fuel flow. The analog gage is a fuel pressure gage with fuel flow markings. Although it is not as accurate as the digital fuel flow gage, it is instantaneous and highly repeatable. In my airplane, the 12 GPH analog gage corresponds to 12.5 GPH on the digital once it settles down. I use full throttle and 2500 RPM as my normal air control settings and establish power by reducing the mixture using the big pull to set 12.5 GPH as my normal routine for any altitude at or below 10,000 MSL.

KUZA

Are you sure (with regard to PA-46 recommended operating methodology)? I don't fly one, but had thought it was one of the first to specify 50 LOP to peak and not 50 rich and that it was people running 'safe' at 50 ROP that caused the disastrous engine reliability issues early on.

Yes, this was the Malibu (Continental powered). With the Mirage (Lycoming) they went back to ROP.

EGTK Oxford

I'm a bit surprised to read some of you about cruising at peak. Have you read/heard about the 'red fin'? Do you really think that 'operate always out of red fin' is an old wives' tale? Or do you always cruise at <60% power?

LECU - Madrid, Spain

If operating a normally-aspirated engine at or above FL100, then yes.

Frankfurt (EDFZ, EDFE), Germany

I'm a bit surprised to read some of you about cruising at peak.

If operating a normally-aspirated engine at or above FL100, then yes.

Not sure I follow the above...

Administrator
Shoreham EGKA, United Kingdom

I'm a bit surprised to read some of you about cruising at peak.

If operating a normally-aspirated engine at or above FL100, then yes.

Sounds perfekt, at this level the power output is below 65% and I can adjust the tas over the mixture. The POH of the Engine says LOP and Peak at this power is OK. The CHT is not more then 200-250 at this point and the CHT is at a non turbo the only intressting point.

EDAZ

You can achieve 65% or less power below FL100.

Use the throttle lever

Administrator
Shoreham EGKA, United Kingdom
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