New Owner Questions - ROP/LOP & MP/RPM Settings

[helojunkie]

Hello Everyone -

 

I am new to the board here as well as a first time Mooney Bravo owner (SN 27-0047). I had zero Mooney time before purchasing the Bravo, but did a lot of reading and choose it for my "typical" mission as other modes of transportation that I own were killing me on fuel for such a short flight (KCRQ - KDVT Less than 300 NM).

I looked around, found one that I liked that was priced where I wanted it and then purchased it. During the pre-buy inspection I started reading everything I could on the operation of the plane. I had already arranged for a checkout from the local Mooney folks where I was buying the plane, but I wanted a more in-depth view of cross-country operation.

I picked up the plane a few weekends ago and flew it from Ft. Lauderdale, FL to Carlsbad, CA. I read a LOT about ROP & LOP operations as well as about power settings. My engine was a factory new replacement (not overhauled, or factory reman, but factory new) and it has about 750 hours on it since being replaced. I wanted to know how I should operate the machine to keep the engine as happy as I can make it. This included what altitudes to operate at, when and why.

I read several articles from Bob Kromer which basically seemed to state that anyone operating their M20M LOP or at a curise power setting greater than 30"/2400 was asking for trouble and he advocated never operating above the 30"/2400 in cruise and to run 50ROP.

So in planning my flight from KFXE to KCRQ, I planned my first fuel stop at AEX. I loved the fact the Bravo had the long range tanks. I plugged my flight plan into fltplan.com and came up with my first surprise. It appeared there was no real benefit to climbing high in the Bravo (aside from weather which was not an issue). For 8,500' I show 4:08 Flight with a fuel burn of 72.4 gallons and at 16,500' I showed a 4:01 Flight with a 71.7 fuel burn. Coming from flying my CJ and Meridian, I had expected much greater differences in those numbers. In keeping with Bob Kromer's (Mooney Test Pilot) suggestions and to be conservative on the operation of my new (to me) engine, I flew the entire trip 30"/2400 and 50 ROP. I averaged 180 - 185 TAS with 16GPH fuel burn. 

 

So I guess here comes the questions - First, why climb high in the bravo if there is not a large performance increase, or am I simply miscalculating the numbers (I used fltplan.com's built in performance for the Mooney M20M - see attached images)? I understand the weather issue and getting above it when necessary, but in the Meridian and the CJ, the higher I go, the faster I go and the less fuel I burn, by a HUGE amount, but when I do a time-to-climb calculation, put on my O2 and get a 7 minute savings, I don't see any good reason to be up there except in the event of weather.

Second - I see guys like Bob who seem to be experts in the Mooney field make statements like "I would never operate a Bravo above 30"/2400"), etc. Same with LOP operations - he is dead set against them. My engine has GAMI injectors installed and so I presume that LOP operations could be done, but I guess I am curious about how much fuel I am going to save and what it will do to my TBO and associated top overhauls that may be required due to higher temps, etc. I know from reading the posts here that there are LOP pilots and ROP pilots. I don't want to save a few dollars in AvGas just to spend ten's of thousands on a new engine, but I have never owned a piston machine capapble of these types of operations so I am coming from a place of ignorance and before I made a decision, I would really appreciate input from those of you that have been there!

My last question would be the actual leaning procedure. I have the EDM-930 and I was told to allow the aircraft to accelerate, get the power set (in my case 30"/2400), cycle the 930 over to the TIT number (as opposed to using Lean Find) and lean it until peak TIT (or 1750 whichever comes first) and then enrichen the mixture 50 degrees. THis is below FL220. Is this the correct method or is there a better method? I thought the entire LEan Find procedure on the 930 was to help with this process, but the instructor that I flew with siad to use the TIT number as opposed to using EGT numebrs that the Lean Find uses.

Thanks In Advance for any input - I am looking forward to getting the best utilization out my my Bravo!

 

[Skywarrior]

Hi, Richard -

I'm not an expert on all things Bravo, but I can try to answer a couple of your questions.

1. LOP: forget about it - not worth messing with it in a 540.

2. Lean Find determines the actual cylinder that peaks first (EGT). Manually leaning w reference to TIT leans against an aggregate temperature. If you had one cylinder running way leaner than the other five, leaning by TIT could conceivably leave you running richer than you think, and putting you in the Red Zone  (right at Peak).

That said, BOTH EGT and TIT are important measures. You don't want EGT to soften your cylinders, and you likewise don't want to burn through your exhaust pipes. Just speaking for myself, I try to keep both of them low, by running ROP, and increasing the richness as I increase the power. IOW, I will run around 50 ROP when at 24", and around 150 ROP at 30". YMMV.

BTW, the 'usual' temp limit for TIT is 1650. Lycoming raised it to 1750 when they added a special coating to the blades. Personally, I discount the effectiveness of that coating, and I try to never go over 1600.

And this is just a thought - I've never tried it - maybe try pulling your prop back to 2200 at high altitude. That might reduce your fuel burn a bit.

[carqwik]

 A few comments:

1) The Bravo is faster at higher altitudes than lower altitudes.  It shines in the high teens given the tradeoff between survivable atlitudes in event of O2 loss, engine cooling, and no traffic (usually).  At FL200, at my normal cruise settings, I see 198 kts on 18.5 gph.

2) Bob Kromer is the guru - his advice is well founded (at least for me).  I never cruise at more than 30/2400 with 80-100 ROP.  LOP doesn't seem to work in the TIO-540 for most.  You should burn around 18-19 gph regardless of altitude.  Turbo piston engines burn the same fuel for a given power setting regardless of altitude.

3) CRQ-DVT is a perfect flight for a Bravo.  BTDT.  Eastbound go into the low- to mid-teens and get the benefit of the tailwind (usually); coming westbound, with any headwind, I do that trip at 10k or 12k.  You'll make good use of the speedbrakes if IFR into CRQ....some controllers treat the Bravo as if it was a t-prop and figure you can get down and slow down at the same time.

4) Manage the engine by TIT and CHT mostly.  First, never go above 1650 TIT for more than 60 seconds.  Second, keep the CHTs below 400...sometimes you need to leave the cowl flaps open a bit even in cruise in the summer out in the desert southwest. 

5) Utilize cruise climb at 34/2400 at 140 kts IAS...usually around 23.5 to 24.0 gph with flaps in half trail....set fuel flow with TIT at 1550.

Just my opinions but after 11 years of Bravo ownership....

[Parker_Woodruff]

Richard,

Unfortunately there is a lot of mistruth mixed with some realities about the Bravo in your post.

The mistruth:

- "operate at 50 ROP" - This is one of the worst places to run an aircraft engine.  You will be getting some blazin' hot cylinder temps if you run high power settings.  You would be better off running at Peak EGT (seriously!), because the pressure inside the cylinder will be less.

- If your airplane can fly LOP, then do it!  However, the realities of the Bravo are that most will not run LOP.  It's worth a try, though!  You can only improve the longevity of your engine by flying LOP.

- I don't know how much Fltplan's numbers are based on what owners typically claim to fly in the M20M.  The reality is that it is a much faster plane up high.  Case in point: I get about 160 knots out of my turbocharged M20K at 12 GPH LOP down at 6000'.  I get 190 knots out of the same fuel flow at ~18,000 feet.

- Who assigned the FL220 leaning procedure for you?  And why at 50 ROP?  I don't know what those power settings translate to in % power, but you would seriously be better at peak EGT/TIT or 100+ ROP instead of 50 ROP, assuming that peak doesn't exceed max TIT.

[helojunkie]

Thanks for all the great information, but as is often the case, suggestiong bring more questions:

1) So what I am getting from Skywarrior's reply is that I should use the Lean Find on the EDM 930 to do the leaning for me as opposed to "just" using the TIT correct?

2) Skywarrior - You also suggested pulling the prop back to 2200 at higher altitudes. The article I read from Bob Kromer says never to operate the Bravo below 2400 rpm as it results in "making the turbo work harder, increases internal operating temperatures and pressures and is the worse case for detonation". So I was staying far away from anything below 2400. 

This is the article I was pointed to when I purchased the plane: http://www.mooneypilots.com/mapalog/cruisepower.html

This is also the article that pointed me to 50 ROP. Bob is emphatic that 50 ROP is the place to be, right between best power and best economy. (30"/2400/50ROP).

3) Ken - You had said (Utilize cruise climb at 34/2400 at 140 kts IAS...usually around 23.5 to 24.0 gph with flaps in half trail....set fuel flow with TIT at 1550.) My question is that beyond takeoff I have never heard of climbing with flaps, so maybe I am misreading your comment. When you say flaps in half trail, what exactly do you mean? Also, nothing I have read advocated leaning the engine at all in climb with climb power settings - but you are saying that it is OK to lean on the climb (assuming EGT/CHTs stay within limits?).

 

Again thanks so much to everyone for your help and information. I am learning a good deal about the Bravo from these forums!

 

[carqwik]

I meant cowl flaps open about 1/2 way....and yes, lean in climb to 1550 TIT at 34/2400 per Bob Kromer. I go to cruise climb at 1000' AGL after takeoff conditions/terrain permitting.

One thing on leaning though...if you use lower power cruise settings (like 25"/2300), then I lean to about 50 ROP.  Don Kaye has a formula that any combination of MAP/RPM that totals to 53 means you're operating at 75% power (so 29" + 2400 =53) so any lower "number" is running less than 75% power and engine temps are lower.

 

Also, in the flight levels, 100-150 ROP at higher power settings is mandatory per the POH IIRC.

[Seth]

Hello Richard and welcome to Mooney Space!  Congratulations on the purchase of your Bravo.

As others have stated, do not run at 50 ROP - that will lead to a premature top overhaul.

-Seth

[helojunkie]

Ken & Seth - Thanks for the information. Just trying to get it all figured out before spending a bunch of time flying at the wrong settings!

[jetdriven]

It depends on CHT.  Remmeber Kromer had a 440 CHT on the M20C aircraft report and said nothing of it.  At peak our CHT are lower, and LOP, lower still (M20J).   At 50 ROP our J would also have a 400+ CHT.  So, run the FF up to 12 GPH to keep it cool, and you cut your range by 30% with 6$ avgas.

Of course your engine is turbocharged, and Bravos have a reputation for not running well LOP.  But if you can do 65% power or less, keep all CHT under 400, TIT under 1650, and it runs smooth, why not?

[Parker_Woodruff]

Quote: helojunkie

This is also the article that pointed me to 50 ROP. Bob is emphatic that 50 ROP is the place to be, right between best power and best economy. (30"/2400/50ROP).

 

[jetdriven]

Parker, no correlation I can find between engine wear and RPM in the normal operating range.  There is a correlation to noise, RPM, and pilot fatigue, however.

[helojunkie]

Thanks Parker - But the question begs to be asked: Who is Advanced Pilot and who says the engineering test pilot (Bob) is wrong and Advanced Pilot is right? How do I sift through the LOP/ROP issues and get the right information? It seems everyone has a different opinion and everyone thinks they are right!

I am just looking for the "right" answer!

[Parker_Woodruff]

Quote: jetdriven

Parker, no correlation I can find between engine wear and RPM in the normal operating range.  There is a correlation to noise, RPM, and pilot fatigue, however.

[Parker_Woodruff]

Quote: helojunkie

Thanks Parker - But the question begs to be asked: Who is Advanced Pilot and who says the engineering test pilot (Bob) is wrong and Advanced Pilot is right? How do I sift through the LOP/ROP issues and get the right information? It seems everyone has a different opinion and everyone thinks they are right!

I am just looking for the "right" answer!

[PTK]

Quote: helojunkie

Thanks Parker - But the question begs to be asked: Who is Advanced Pilot and who says the engineering test pilot (Bob) is wrong and Advanced Pilot is right? How do I sift through the LOP/ROP issues and get the right information? It seems everyone has a different opinion and everyone thinks they are right!

I am just looking for the "right" answer!

[jlunseth]

Quote: helojunkie

Thanks Parker - But the question begs to be asked: Who is Advanced Pilot and who says the engineering test pilot (Bob) is wrong and Advanced Pilot is right? How do I sift through the LOP/ROP issues and get the right information? It seems everyone has a different opinion and everyone thinks they are right!

I am just looking for the "right" answer!

[fantom]

 

[helojunkie]

Understood! I will check out APS and their seminars. My Bravo does have the GAMI injectors installed so it would be interesting to see how it all pans out. Thanks again for all the info.

[KSMooniac]

I'm not a Bravo operator, but will echo Parker and John's comments regarding the APS course.  I took the course in 2007 soon after buying my J, and it REALLY opened my eyes.  Kromer's experience and articles are very, very good regarding Mooney behavior throughout the envelope, but his engine management recommendations are very, very wrong.  50 ROP at power settings above 70% are bad, but none of us will be able to convince you of that in a web forum.  You probably went to a week-long class on the CJ, and I'd encourage you to consider investing a small bit in learning about your expensive and capable Bravo engine.

The GAMI/APS crew have done OUTSTANDING work theorizing, testing, and measuring the combustion event with their very sophisticated test cell in Ada, OK.  As mentioned above, a lot of their work was already discovered and put into practice decades ago, but then lost for a while until the mid- to late-90s when they got active with it.  The single best investment you can make as an aircraft owner is to take their live course.  It is a modest cost relative to other ownership expenses, but it will pay off in spades over the course of your ownership timeframe.  You'll learn WHY to put the mixture at a certain setting (ROP or LOP) and how to interpret what your engine monitor is telling you during normal operations and abnormal situations.  I learned more there in 2.5 days than I did in many semester-long engineering courses....it is that good.  After a weekend there, you'll be able to explicitly state why Kromer's engine management recommendations are not consistent with long engine life and why many here are advising you as such.  Typically they have a course in June, so I'd encourage you to check it out.

If there is no way you can take the live course, the web version is cheaper and more convenient, but you miss out on the very valuable Q&A sessions and of course witnessing the various recommendations and results in the test cell.  Sometimes they have other live courses throughout the year, but I'm not sure how often and when they publish a schedule.

And finally, welcome to Mooneyspace!  I think we have a good, friendly group here and there is a lot of good info to be learned.

[testwest]

Hi Richard

That's quite a list of aircraft you have there in your sig! Going from a Robinson R44 to a CJ and MD500 and Meridian in between is a good range. That says you are used to learning an lot of new things...which is awesome.

For your fltplan.com profile, I notice you are using the hourly fuel flow method. You'll get better predictions by filling out the advanced fuel burn calculation. Plan all your cruise climbs at about 1.3 time your published Vy. Find your 65% power fuel burns from the POH for all altitudes and enter those data and the descent data.

I assume 30"/2400 RPM is 65% power for your engine. Read through everything you can find on the APS site, or the Pelican's Perch articles by John Deakin. Set your EDM-930 to its fastest data rate and perform a GAMI lean test. If your GAMI spread is more than .5 gph, send the EDM data to John-Paul Townsend at GAMI and he may be able to have you swap injectors.

If you are at 65% power, you should be able to pull the mixture through the peak TIT and get to the other side. Your TIT may exceed limits, momentarily. You should be able to get 50 deg LOP and your TIT will be back below limits. What is impressive is the drop in CHT due to the "spread out, slightly later" pressure profile in the cylinders.

I am running an angle valve turbo normalized IO-540 at 2200 RPM and 26" MAP, LOP. It's hard to get a cylinder above 310 deg in this scenario.

If you get your RPM a little too low compared to the MAP demanded, it is possible to stall the compressor. Racers call this the "surge line" take a look here: http://www.rbracing-rsr.com/turbotech.html

You'll get a sudden drop in MAP, but not to ambient. Bring the RPM back up and the compressor will unstall. Don't do it lots but it is not catastrophic.

Winds make a HUGE difference in your cruise, obviously. With the correct data in fltplan.com's advanced fuel burn calculator, you can trade off the various altitudes versus your mission requirement (best speed, least fuel or soon, best CAFE parameter which is (speed^1.3) times (distance/fuel used).

Don't forget the Wind Matrix button at the bottom left of the Navlog page, you can look at additional altitudes for the tradeoff.

For everyone else, our Mooney M20J has an advanced fuel profile that anyone can copy. Donor name is testwest, donor N-number is N201JX.

Happy flight planning!

BTW, I am an engineering test pilot as well. USAF Test Pilot School, class 91B.

[jetdriven]

Look here where detonation peaks, right at ~25-40 ROP. Right where CHT peaks as well.  This is Lycoming's own data, FWIW, from 2002.  This is newer than what the data your POH is based on and the colossal screw up paper by Lycoming called "Experts are Everywhere"

[helojunkie]

Norman - Thank you so much for the information. I used a M20M profile off of fltplan.com but I guess it was not set up correctly! I will try and work out the profile and see if will make any better sense!

 

Scott - Thank you as well for the information - It seems like everyone likes APS and after reading some reviews of their class  I have signed up for their live course on July 12, 13 and 14th. In the mean time, I will figure out the fltplan.com profile and try Norman's leaning to LOP and watch the CHT and EGT results. My plane is in the shop getting new avionics, so this will have to wait until then, but I can play with the fltplan.com stuff.

 

Anyone with a Mooney Bravo have a profile on fltplan.com I could use other than the one that I have?

 

Thanks Again for the great information everyone!

[helojunkie]

Quote: testwest

For your fltplan.com profile, I notice you are using the hourly fuel flow method. You'll get better predictions by filling out the advanced fuel burn calculation. Plan all your cruise climbs at about 1.3 time your published Vy. Find your 65% power fuel burns from the POH for all altitudes and enter those data and the descent data.

[testwest]

Hi Richard

Make sure you turn OFF the hourly method on the fltplan.com "Edit Aircraft Performance" page, assuming you have the detailed advanced fuel burn data entered. This is one of the "endearing" features of fltplan.com, each page is a wealth of data but you have to look closely to find everything.

[helojunkie]

Thanks Norman - I went ahead and did that but it does not change the listed fuel in the chart, just shuts off the "Hourly Fuel Burn" number at the bottom, all other fuel burns stay the same regardless if I am showing the hourly method or not it would appear.