leaning and power settings

[podair]

yet another thread on LOP. power settings etc...

has anyone got any comments, good or bad, on my power setting procedure on my M20F equipped with and EDM 700 without GAMIs, and a 3 blade hartzell , no mods. I have been operating it like that for a year now (since the edm installation) and everything (checks , oil consumption and analysis) seems fine. Previously I was running 100 rop on stock gauge. I get consistent 145kt tas on 8.5gal which is pretty good

my regular flights involve a climb to 10k ft from sea level (crossing the english channel to France so like to stay high, I have o2), and then 2hrs cruise

- take off: full throttle, full rich, at 500ft reduce RPM just a hair (off the mechanical stop) , but not MAP

- climb : 120mph, full rich until 5000ft, start leaning to 150 rop, ram air open since 3k if in clear air. CHTs in the mid 300s, only get 400 on number 3 with very high OAT (90F plus) in summer, other cyls are around 360 and that I think is also due the bayonet probe on 3 as it seems to read 40 higher on average (stock gauge stays in green). I tried the constant EGT approach but not comfortable with it. In hot weather if I get 400 I lower the nose if practicable.

- level off at 10k: still full throttle, reduce to 2500rpm , at this point I get 21-22in MAP, lean to peak EGT?slighly lop (20F). All cylinders peak within a litre of each other so dont think I need GAMIs.

invariably, I get 145 kt TAS , 32 ltrs per hour (8.5gal) and all temps nice and cool. My CHT are in the low 300s with number 3 being 40 higher (due to bayonet probe), usually no more than 360 in cruise. According to the power charts that 's around 65-68% power. At 9k I get 0.75gal higher. at 12k , 0.75 lower, roughly same tas. If lower , I reduce MAP to be below 70% power.

- descent: reduce MAP a tad, to 20, and 500fpm descent, keeping 20map and enriching slightly to keep peak, keeping an eye on chts to avoid shock cooling.

- slow down for approach, close ram air, continue to reduce map as far as 15 and rpm to 2300.

The plane seems very happy at 2500. 2350-2400 has more vibration. 2200 and low map (21-22) is perfect for loafing at low alt for fun at 120mph and low consumption. Only restriction the the 3blade is between 1950 and 2150 at low map.

I am pretty happy with the above technique. The only thing that I am having doubts about is that effectively I am full throttle from takeoff to top of descent! I ve read all the MAPA articles about continuous rate power etc etc , but maybe I should reduce to 26/2600 rpm at 500ft and then continue climbing on that setting.

[Ned Gravel]

I do much the same, a little lower because I do not have O2.  Started this three years ago when numbers 3 and 3 were replaced and my AME (Cdn for A&P) convinced me to spend the money on the JPI 700.

I have also not yet taken to climb management based on a target EGT.  I might try that this year after the new engine has its 50 hours completed.

 

 

[Nemesis]

Stick with WOT as much as you can. Let that engine breathe. For a normally aspirated engine, intake air will always be the limiting factor. The more the engine can breathe, the more performance we are able to achieve for both ROP and/or LOP operations. The same is true whether you are talking economy performance or high power performance.

[KSMooniac]

Your procedure is almost perfect in my opinion.  I would add the "Target EGT" leaning method for takeoff and climb to your bag of tricks...it is very simple and will give you a slightly faster climb on less fuel.  You have the instrumentation to do it...now you just need to read a little more and convince yourself it is optimal.

8.5 GPH = 63% power when you're LOP.  No charts needed...simply multiply fuel flow by 14.9 to get HP.  8.5 * 14.9 = 126.7 HP, or 63% of 200 HP.

No reason to reduce MP for descent IMO either....just nose it over and re-trim!  Stay out of the yellow arc if it is bumpy, but otherwise you might as well keep the engine operating at maximum efficiency.  No need to enrichen either in the descent since your engine seems to run fine LOP...it will go slightly leaner as you descend if you don't touch anything, and that is a good thing.  Dave's comment above is spot-on...keep WOT as long as you can to maximize efficiency.  I only reduce MP when setting up for an approach or loafing along on a local sight-seeing excursion.

There is no such thing as shock cooling.  Otherwise we would have problems from shock heating every time we applied take off power, or shock cooling when flying through rain.  It is an old wives tale.

Carry on!

[alun]

sounds fairly similar but i am leaning well before 5,000 ft on a climb. usually after passing 1,000ft. 

[N57039]

me too. lean for target EGT all the way up.