Mooney cruise settings

[Mooney E]

I recently purchased a 1966 "E" model Mooney. I have read extensive articles on the Mooney aircraft and it seems like the settings for cruise for RPM and MP are all over the board. Some say 2500 and leave the MP at max, others dispute that. Is it a matter of opinion or can someone clear this up for me? I flew it home from Florida via Wisconsin for a two week vacation and then continued on home to California. I tried various settings and nothing seemed to stand out one over the other. Any help would be appreciated.

[Jason]

Take a peek into the POH to see where the numbers stand or complete your own speed and fuel burn test. I have heard full throttle, 2500 RPM, and 50 degrees rich of peak EGT as a good cruise setting in the E model, but most of my mooney experience is in the K model (231).

[iJustLanded]

I have a Mooney 252 so anything I have for you is pretty much worthless but here's a good resource for you:

http://mooneyspace.org

Enjoy your Mooney!

John

[Tim]

For a normally aspirated Mooney above 6000 feet, the advice I've gotten and followed has been to operate WOT, 2500 RPM, and lean of peak (for well balanced fuel injected engines). A graphic engine monitor really helps with that, as does a fuel flow meter.

[Lance F]

Tim is (IMHO) pretty darn close. However, LOP works just as well at 1000' as 6,000'+. I assume your 1966 E is not fuel injected. As such it may not be as smooth LOP as you (or your passengers) may like it. You will get most power at about 80 dF ROP. What is easiest on the engine ROP is a little more complicated, but 50 dF is about the worst place to be.

If you're serious about knowing how to best operate your new investment, there is plenty of interesting reading on this subject. Educate yourself. There are a lot of old wive's tales out there, and unfortunately your mechanic may or may not subscribe to those.

[Pilawt]

Originally Posted by Lance F

I assume your 1966 E is not fuel injected.

All M20Es back to 1964 are injected - IO-360-A1A

[UP'er]

I've always been curious about why Mooney cruise RPM settings tend to be higher than many other planes?

[Tim]

Originally Posted by alaskaflyer

I've always been curious about why Mooney cruise RPM settings tend to be higher than many other planes?

Well maximum thrust is max MP at max RPM. In lots of cases we pull back the rpm on controllable-pitch propellers to reduce noise/vibration, or to comply with a limitation (usually related to resonances/vibration).

Mooneys are pretty quiet at 2500 RPM. Not sure whether it's related to the airframe, the exhaust system, or the engine/prop combination.

I got the WOT/2500 advice from a MAPA log article by Jerry somebody who is widely acknowledged in the mooney commooneyty as a guru. And in the J - WOT/2500 at 8000 generally gave 158 KTAS on 9.8 GPH.

[Lance F]

Originally Posted by TMetzinger

I got the WOT/2500 advice from a MAPA log article by Jerry somebody who is widely acknowledged in the mooney commooneyty as a guru. And in the J - WOT/2500 at 8000 generally gave 158 KTAS on 9.8 GPH.

Unfortunately Jerry Manthay (something like that) never bothered to learn about LOP operations and espouses OWTs on that subject like too many others.
At 8,000' 9.8gph is going to be rich of peak and probably right at 50dF ROP which is the worst place to be (hardest on the engine). But you do get pretty good TAS at that setting

[Tim]

Originally Posted by Lance F

Unfortunately Jerry Manthay (something like that) never bothered to learn about LOP operations and espouses OWTs on that subject like too many others.
At 8,000' 9.8gph is going to be rich of peak and probably right at 50dF ROP which is the worst place to be (hardest on the engine). But you do get pretty good TAS at that setting

IIRC, in the 1998 J, it was 125 or 150 ROP. We didn't have GAMIs and the airplane didn't run smoothly LOP.

Anyway, we were always at least 100 ROP.

[brywd]

Use your POH to verify/fine tune this but there is a rule of thumb to quickly set power when ROP. This isn't being offered as much to suggest you use it all the time, although you could, but rather to help understand the relationship between MP and RPM for setting power. It's very simple. Take the MP and add it to the rpm/1000. For example if the mp is 23" and the rpm is 2,300 you would add 23+23 for a sum of 46. For 0-360's the numbers come out very close to the following.

MP+rpm=42 the power is very close to 55%
MP+rpm=45 the power is very close to 65%
MP+rpm=48 the power is very close to 75%

Any combination of MP and rpm that add up to the 42,45,48 sums are usable to achieve that power.

For an 0-320 the sums come closer to 43,46,49 to equal 55,65, and 75%.

Of couse temps, and mixtures, etc. will affect power. Again, play around with your POH and see how close this comes. Usually it is close enough to never bother looking anythng up again. I used this method all the time when setting power in my RV. In fact I read about this in the Van's newsletter many years ago.

I realize that you were seeking Mooney specific advice, but that Lyc has no idea it resides in a Mooney. Play around with this, I think you'll like it. In my Beech I fly WOTLOPSOP and have never looked back.

[iHenning]

Doesn't matter to the engine or plane where you set the MP & RPM so long as the combination keeps the needles in the green arcs. Pick a speed and a fuel flow you're happy with.

[Jaybird180]

Originally Posted by Henning

Doesn't matter to the engine or plane where you set the MP & RPM so long as the combination keeps the needles in the green arcs. Pick a speed and a fuel flow you're happy with.

Agreed, if oversimplistic. There are settings that help the engine last a bit longer and some that although they are green arc, will reduce TBO.

[iHenning]

Originally Posted by Jaybird180

Agreed, if oversimplistic. There are settings that help the engine last a bit longer and some that although they are green arc, will reduce TBO.

LOL, if there were any proof of that there would be a lot less arguments. Reality, in a naturally aspirated engine you are typically so performance limited by MP that you run higher RPM than may be optimum to keep your speed up. With a Turbo, I'll pull the props to the bottom of the green and MP to the top, pull 25 LOP and let her roll, pretty much gets best efficiency and reasonable speed.

[Jaybird180]

Makes perfectly good sense. 'Cept one part: generally speaking RPM doesn't hurt engines, it's internal cylinder pressure AKA Manifold Pressure AKA load.

If it weren't for the dang valves being unstable at transonic speeds, RPM would be unlimited...oh and that little thingy that moves up and down, stops and starts in the cylinder. Other than that...

Besides, technical people would argue anway...LOL

[iHenning]

Originally Posted by Jaybird180

Makes perfectly good sense. 'Cept one part: generally speaking RPM doesn't hurt engines, it's internal cylinder pressure AKA Manifold Pressure AKA load.

If it weren't for the dang valves being unstable at transonic speeds, RPM would be unlimited...oh and that little thingy that moves up and down, stops and starts in the cylinder. Other than that...

Besides, technical people would argue anway...LOL

That's why Wankels are kinda cool, you keep feeding them fuel and they'll keep spinning faster. Not efficient engines, but a ton of fun. I had one in a test cell over 24,000 rpm and it didn't come apart. We were all hiding behind the console though lol....

As for ICP, yeah, but as long as you aren't in detonation you're ok. Low RPM + High MP = maximum use of combustion = higher efficiency= more work for your fuel $$$$ This is as old as Lindberg.

[Pilawt]

Originally Posted by brywd

For 0-360's the numbers come out very close to the following.

MP+rpm=42 the power is very close to 55%
MP+rpm=45 the power is very close to 65%
MP+rpm=48 the power is very close to 75%

Any combination of MP and rpm that add up to the 42,45,48 sums are usable to achieve that power.

Yup, that's exactly what I use in the C-172N-180 (fixed-pitch, MP gauge installed). Close enough for government work.

[Bill Jennings]

Wow, this is old, but what the hey.

If I have a good tailwind or am economy minded, I fly wot, 2400, lop. (whatever lop runs reasonably smooth)

If I have getthereitis, wot, 2500, 100 rop.

80% of the time it is the former.

[iGismo]

Originally Posted by Jaybird180

Makes perfectly good sense. 'Cept one part: generally speaking RPM doesn't hurt engines, it's internal cylinder pressure AKA Manifold Pressure AKA load.

It's the peak intercylinder pressure that causes stress in an engine and that's affected by mixture and ignition timing more than anything else. MP and RPM (less RPM and more MP increases peak ICP) definitely have an effect but for the most part it's the rate of pressure buildup during combustion and the resulting position of the piston in the cylinder when the peak occurs that has the most effect.

[Jesse]

Originally Posted by gismo

but for the most part it's the rate of pressure buildup during combustion and the resulting position of the piston in the cylinder when the peak occurs that has the most effect.

What is the ideal position?

[iGismo]

Originally Posted by jesse

What is the ideal position?

I'd have to look that up. The crank angle where the peak pressure occurs is called ThetaPp and there's a ThetaPp that's optimal for producing torque. IIRC that's around 20° ATDC but I'm not certain. Worst case is anywhere within a few degrees of TDC or even before TDC.

[TheDon]

sorry but just testing out how to upload a youtube video into a post...disreguard to all who will see this

[YOUTUBE] http://www.youtube.com/watch?v=UP4mRz_laVk[/YOUTUBE]

[Mooney E]

I would like to thank everyone for their responses to my question of 12-27-2010 about flying the Mooney by the numbers. I have to admit, the Mooney is a different type of plane to fly than I ever thought. She is slick and loves to continue to fly. I have about 70 hours in it now and love it more each time. The flying by numbers was a tremendous help and again I want to thank you. Maurice

[Jaybird180]

At your current rate, you're doing a little over 4hr/month.

I guess that Mooney get's you there so fast you can't put much time on it Go out a fly.