LOP Climb To Cruise Transition

[201er]

Ok, given an LOP climb... how do you move the levers to transition to LOP cruise? How do you set power and mixture properly when you were already LOP to begin with.

[aaronk25]

Oh good question. First when your lean of peak use 10gph as 75% 9gph as 65% and 8gph as 55%.

I take off everything forward full cowl flapsopen then when 1000agl watch fuel flow and pull read knob to 10.4-10.6 which is lop 30-60 degrees and move cowl flaps to trail. Prop to 2600 for better efficiency.

The heads actually come down in temp! Lop is cooler than ROP climb.

Ok now to answer your question: the fuel injection does compensate some so as you climb say from 1000agl to 6000 if you leave all the levers the same what once was 10.6gph of flow will turn into about 9.6 gph which is just bit lop maybe 10degrees. So in the climb if you want pull mixture back maybe .5 of a gallon or so on way up, not all at once maybe .1-.2 pr 1000 feet.

Once leveled off set your fuel flow to the power setting you want don't need to touch anything, maybe pull prop back to 2400-2500 for efficiency.

Not sure how the fuel injection system compensates but if your at 9.6gph at 6000 and climb to 12000 the 9.6 turns in to lower 8ish gph must have some sort of pressure compensation deal maybe air impact tubes or whatever there called.

9.2 gph is a really nice cruise speed between 4-5k.

Try this in cruise say at 6k. Watch fuel flow and go from rop to lop and pull back until you note power reduction look at you gas flow and after a min look at airspeed then pull mix back more note fuel flow and airspeed after a couple min and see what you think. Get the calculator out and figure your mpg and pick a setting good for you.

[kmyfm20s]

Great info! You helped answer a few questions I have had after reading John Deakin's series of articles. I plan on starting to run LOP but wanted some general fuel flow to start off with. I was hoping those of you using this method could help me out.

I have a 82 M20J and my airport is 425' ASL. I was planning on taking off full rich target EGT, which puts me around 22gph. At 1000' dial the prop back to 2600 RPM and continue to climb to 2500 feet which get me above all the adjacent airspace. At 2500' I was going to transition to LOP climb which from the above aaronk25 says should be approximately 10.4gph and which Deakin show on his graph should be 30 LOP on the rich side and 60 on the lean side. Continue my climb to 7500' and adjusting .1-.2 GPH ever 1000' in the climb if needed. Transition to cruise simply by dialing back RPM which I think I will pick 2500 to start with and slight mixture adjustments if even required. Start descending by simply pointing the nose down and decreasing RPM as the IAS increases to high.

Does that sound correct?

[201er]

The discussion we had (which surprisingly seems to be missing) is that it's kinda pointless to climb LOP for xcountry because the savings are virtually non-existent vs climbing Vz (~120KIAS). Basically LOP climb is only good for local flying around when you just want to fly slow on the least fuel possible. Also there's no benefit of reducing RPM in climb and possibly even harm.

[kmyfm20s]

Gotcha! Might be missing as a result of the server crash. Thanks for the reply.

[Hank]

Target EGT climb is the best, which will be rich. Level off at altitude, give her a minute to accelerate, then set as desired. There was once recently a very long and spirited discussion, with the end result being less than ½ gallon difference in fuel used in the climb between Target EGT and LOP climb; I think the plane was climbed to 9500 msl Target EGT and flown 100 nm from departure, then returned, refueled and made the same trip climbing LOP. Not worth the hassle to save $3.

[aaronk25]

Ok I didn't get a chance to do the lop vs rop climb yet, but my position has changed some after running the numbers.

I think it doesn't make much of a fuel burn difference for a rop climb. Probably less than I thought. I do however think the more time you stay lop the cleaner the oil.

With that if I'm traveling for work and in a hurry I climb rop target egt. If not in a huge hurry I climb LOP.

I was surprised to learn how much prop efficiency is lost by climbing at lop power settings. It almost eliminates savings from more efficiently managing the engine.(lop).

Learn a little every day I guess.....

[kmyfm20s]

I will have to read more on prop efficiency, I have a 2 blade. I was attracted to the LOP climb because I routinely fly from a below sea level airport KIPL in the summer time at 100 plus temps. I have been doing what I learned and is exactly what I not supposed to do and climb out at 50 to 100 ROP. I have always had a hard time keeping CHT down. This luckily has been in previous planes and yes I went through cylinders but the mechanics at the time said I was doing it right. This is a new plane and the first Mooney I have owned but flown many in the past. I have not tried the target EGT in the summer time yet to see if the CHT will stay below 380, looking forward to it.

[garytex]

The fuel savings can be more than a gallon , I usually see more than that, but the real benefit is keeping CHTs low. I climb LOP in TX in the summer, as ROP overtemps the cyls. when OAT is 100df or better on the dirt, and I,e seen 80df at 7000 feet.  

Works like a charm, about 130 indicated and 500 fpm in the low 9 gph range.  Warmest (#3) will stay below 380df.  It doesn't work so well when I am heavy, but solo works like a champ. 

[201er]

You have to measure gas savings not only over altitude but simultaneously over distance... that's where the Vz profile ends up playing a greater role. You may save a gallon in the climb but then you spend an extra gallon to get to the same point where the cruise climb would have leveled you, thus spending half a gallon more and ending up with only half a gallon saved. Think of LOP climb as going up, then forward. Vz climb is taking the hypotenuse route and moving up/forward at the same time.