Lean of Peak

[Piedmont85]

I know this is a heavily discussed item, lots of different points of view, but do you Skymaster owners run lean of peak? I have an engine monitor, but otherwise just the standard engine/ignition/fuel injection system. Just wondered what everyone does????

[JeffAxel]

I ran my P337 LOP for the three years I owned it, would true out at 180-185KTAS in the high teens on 23-24gph. Ran cool CHTs in cruise, clean spark plugs.

[Piedmont85]

Originally Posted by JeffAxel

I ran my P337 LOP for the three years I owned it, would true out at 180-185KTAS in the high teens on 23-24gph. Ran cool CHTs in cruise, clean spark plugs.

Thanks Jeff: You are turbocharged? Correct? Does it make any difference that I'm normally aspirated?

[JeffAxel]

doesn't make any difference, if you have an engine monitor, you can do a GAMI lean test to see how wide your fuel flow spread is between first to peak and last to peak. If you get a lot of rough running or the spread is greater than 0.3gph, you will likely need GAMInjectors. The plane likely will not run quite a smooth as ROP, but it will use less fuel. Less of a benefit in NA engines than turbocharged.

[patrolpilot]

My NA G has the GAMIs, but I've ended up running ROP as my engines don't seem to like the LOP, particularly my rear engine. They develop a high-frequency vibration at about 15° LOP that progressively worsens.

I've done the Advanced Pilot Seminars training and the Busch book, but it comes down to some airplanes that don't care for LOP ops (addressed in both the training and the book.)

I've tried to get LOP many times, but the last time was on a flight from FL back to TX. I was over the FL panhandle at 10K, LOP, and could feel that light HF vibration; I thought I would give it a bit. My attitude indicator was blurry when I scanned the panel, so I checked the O2 flow to my cannula. It was appropriate. So, I moved the mixtures back through peak to ROP, and the high-frequency vibration of the AI settled, reflecting and confirming what my body was feeling.

So now, I fly on the ROP side of the GAMI placard settings.

[cjordan]

My 73G NA with Gamis will run LOP ~100. I never do this above 65%, or for long, just tests as only a single egt/cht. It seems if 65% or less (usually here 65% or less at cruise altitudes if going somewhere) it’s safe to just run peak egt. Basically follow the Mike Busch method, but more conservative at peak.

[Dr.Dan]

I have an engine monitor but still using stock injectors. My engines will not run LOP with the current injectors; the spread is too great. I would like to put GAMIs in it so that I could cruise LOP with lower CHT.

[hharney]

Originally Posted by Dr.Dan

I have an engine monitor but still using stock injectors. My engines will not run LOP with the current injectors; the spread is too great. I would like to put GAMIs in it so that I could cruise LOP with lower CHT.

C337C NA, Gami's, JPI Engine Monitor, and Fine Wire Plugs. I can set up for lean of peak at cruise using the JPI. Typically 9,000 ft, WOT, 2400 RPM lean about 40 to 60 degrees lean of peak and see about 14-15 GPH total. I will lose 10 kts GS at these settings. I can run same settings at 50 degrees ROP and see 18-19 GPH and back to my normal 155 - 160 kts TAS. I don't see the savings in running LOP. At 9,000 to 11,000 ft when operating at LOP the airplane is lethargic, especially if facing head winds. Watching the GS at 125 - 130 kts at LOP against the head winds just makes no sense to me. Airspeed is not the most important factor here to go across the country but I can't sit and watch those speeds.

The cylinders are cooler, maybe 25 - 30 degrees cooler.

Be careful running at Peak, you should be 60% HP or less. Remember Mike Busch says the most dangerous part of adjusting for fuel flow is when you are in the red box or shark fin

I have flown other planes, A36 w/550, Cirrus, Lancair, Navajo and these planes operate totally different when using LOP ops. Except the Navajo where those are run nomal at Peak not LOP