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LOP again


Danb

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Documents say 29.5 2500 17 gph equals ROP but 29.5 2500 at 14 equals LOP. OTHER stuff say differing stuff. I like flying say 26- 2400 around 14-15 gph but I know wonder if that ROP LOP or around Peak, the lean find seems stupid as does the pilot. If som Acclaim pilots can chime in on there trip cruise numbers it’d be greatly appreciated. D

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29.5 and 17gph is definitely not ROP. It is a tad higher than im accustomed to but tit is all that matters. 
I used the lean page a few times but you don’t need to use it every time, once you know your ff. 
at those power settings, ROP would be 19-21ish gph

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The POH power setting tables are crap IMHO.  I suspect they are an artifact of certification standards rather than an indication that Mooney doesn’t understand power settings. The ROP settings are way leaner than what you’ll get, and LOP settings adjusted for OAT are stupid. The Best Economy settings cannot be duplicated in my plane (published FF is near or at peak TIT.). No matter…

Mid teens…

if I fly 30.5x2500, 100ROP is something like 22.5 GPH. I don’t fly cruise settings ROP.

LOP, power is a function of fuel flow. Period.  13.7* FF  is approximately the power produced.

This table is a dog’s breakfast of various power settings. 18.7 != 17.6 != 16.4 in terms of power. And if you’re flying LOP and fixated on a MP/RPM combination, you’re doing it wrong.


I fly 30.5 ish x 2400 @ 16.5 GPH.  16.5*13.7= 226HP, or 73%. Same FF at different RPM/MP combinations are very similar in IAS. I vary MP to achieve desired FF at desired TIT-EGT’s.

so… 16-17,000, where I cruise most of the time, that is 203-205 KTAS on the G1000, which is 2ish knots below true-true. 
 

My plane has TKS, which probably costs 5-10 knots in cruise.

It really is an amazing machine.

-dan

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So yesterday most of my trip was 29 2450 at 15.3 stayed at 10000 due to icing and freezing rain, used my TKS down to 2.5/ gal so I had no clue if I was peak or whatever the. Lean find is stupid, when do you use ?

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34 minutes ago, Danb said:

So yesterday most of my trip was 29 2450 at 15.3 stayed at 10000 due to icing and freezing rain, used my TKS down to 2.5/ gal so I had no clue if I was peak or whatever the. Lean find is stupid, when do you use ?

Considering that there is a TIT probe on the right side only, using TIT to set power doesn’t seem really precise to me. I lean my 2 richest cylinders (3&5) 50* LOP.

  • set power
  • big mixture pull
  • enrichen to 18.5
  • find peak in 3 & 5
  • take a picture of the engine page with my phone
  • lean to 50 LOP in those 2 cylinders, which is usually about 65* LOP on the TIT gauge.
  • add back an inch or so of MAP if fuel flow is below what I want (16.5 GPH)

Mine is a Platinum Edition engine, which supposedly has balanced injectors.  It runs quite happily down to 100* LOP or more on the TIT gauge.

-dan

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On 4/21/2024 at 9:14 PM, M20TN_Driver said:

I’m usually flying 12.5k and above.  I normally cruise at 27/2400 and 50ish LOP and get 14.7gph.  

Similar.  I usually run 28/2400 at about 15.2.  Puts my TIT at about 1580, which is what matters to me. 

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Some notes from my kneeboard yesterday, and looking now at the G1000 logs....

Yesterday I was at 15K with OAT at one point -22C, saw: 

29"/2500     72LOP TIT 1618 FF 16.7 TAS 194
29"/2500     90LOP TIT 1600 FF 16 TAS 183
29"/2500        FF 16.9    TIT 1638  (so would be about 52LOP)  TAS 190 (not sure that makes sense, that was captured a bit later)

25"/2500    83LOP  TIT 1584    FF14.3    TAS prob around 173 avg (decelerating, and other things changing then)

I was looking over the posts, and some guidance from @Schllc and others about staying below TIT 1600 (before I'd registered an intuition for these #s).  Doh. I'd been shown how to use the lean find during transition, according to the POH, and that leaves me significantly north of 1600 at times. 1650 was mentioned by another experience pilot as a caution #. 

The engine has a GAMI spread of 0.6-0.7gph and a few folks think the injectors would help narrow further. I've sent a log to GAMI and got a few calls in to them (I think they're behind due to Sun n Fun). 

I could also just keep leaning it out past the above points, as the engine needs to go quite a bit further to get noticably rough. 

Has anyone written a "procedure guide" for these LOP ops for the Acclaim? I'm particularly confused during the descent, where I want to stay a bit lean until go-around,  but probably not the wildly LOP from up at altitude. I understand that the system is supposed to adjust up to a point with power changes, but when walking back the MP during the descent, it would be nice to have a procedure to follow. 

Well, that was longer than intended, but this is an interesting conversation! 

David


 

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17 hours ago, dkkim73 said:

Some notes from my kneeboard yesterday, and looking now at the G1000 logs....

Yesterday I was at 15K with OAT at one point -22C, saw: 

29"/2500     72LOP TIT 1618 FF 16.7 TAS 194
29"/2500     90LOP TIT 1600 FF 16 TAS 183
29"/2500        FF 16.9    TIT 1638  (so would be about 52LOP)  TAS 190 (not sure that makes sense, that was captured a bit later)

25"/2500    83LOP  TIT 1584    FF14.3    TAS prob around 173 avg (decelerating, and other things changing then)

I was looking over the posts, and some guidance from @Schllc and others about staying below TIT 1600 (before I'd registered an intuition for these #s).  Doh. I'd been shown how to use the lean find during transition, according to the POH, and that leaves me significantly north of 1600 at times. 1650 was mentioned by another experience pilot as a caution #. 

The engine has a GAMI spread of 0.6-0.7gph and a few folks think the injectors would help narrow further. I've sent a log to GAMI and got a few calls in to them (I think they're behind due to Sun n Fun). 

I could also just keep leaning it out past the above points, as the engine needs to go quite a bit further to get noticably rough. 

Has anyone written a "procedure guide" for these LOP ops for the Acclaim? I'm particularly confused during the descent, where I want to stay a bit lean until go-around,  but probably not the wildly LOP from up at altitude. I understand that the system is supposed to adjust up to a point with power changes, but when walking back the MP during the descent, it would be nice to have a procedure to follow. 

Well, that was longer than intended, but this is an interesting conversation! 

David


 

Long term, for the sake of your Turbos, Turbo transitions - which need to be inspected often, Cylinders, exhaust system, and for that matter even not burning up your tit probe and keeping its accuracy longer, you want your TIT 1600 or under.

For the sake of your wallet also. Depending on your settings, if the reason you are running high TIT is to save fuel, a little extra fuel is almost free compared to most of the above items.

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14 hours ago, Fly Boomer said:

Closer to peak?  Wouldn't that increase TIT?

Yes, to clarify I am trying to understand if I should consistently always lean it a lot further out. 

Someone mentioned adjusting  MP to further affect FF. It isn't clear what the relationship would be to TIT LOP; is the higher mass flow cooling in it's effects?  Or is it going to lean it further despite the mechanical mixture.

And then since FF determines energy flow LOP, one could adjust MP and RPM for whatever gives the best mechanical efficiency. Eg use the POH or do test runs to fill in a matrix of TAS. 

(I am) Overcomplicating this for sure. But ty for verifying the concern re < 1600F.

D

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2 hours ago, dkkim73 said:

Yes, to clarify I am trying to understand if I should consistently always lean it a lot further out. 

I was just asking for clarification.  I agree with an earlier post that 1600 TIT sounds like a good maximum, but I was trying to understand how more fuel would help bring the temps down.  If you are already lean of peak by 52, 72, 83, or 90 and your TIT is over 1600, it seems to me that more fuel will raise TIT, not lower it.  I would think that, if ALL EGTs go up when you increase fuel, that would verify that you were indeed lean of peak, and to lower EGTs (and consequently TIT), you would need less fuel, not more.  I'm still learning, so I could be all wet.

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39 minutes ago, Fly Boomer said:

I was just asking for clarification.  I agree with an earlier post that 1600 TIT sounds like a good maximum, but I was trying to understand how more fuel would help bring the temps down.  If you are already lean of peak by 52, 72, 83, or 90 and your TIT is over 1600, it seems to me that more fuel will raise TIT, not lower it.  I would think that, if ALL EGTs go up when you increase fuel, that would verify that you were indeed lean of peak, and to lower EGTs (and consequently TIT), you would need less fuel, not more.  I'm still learning, so I could be all wet.

No you nailed it!

Adding fuel ROP cools down EGTs and TIT

Reducing FF LOP cools down EGTs and TIT, dramatically so when fully leaned!

But adding FF LOP raises EGTs & TIT back up to peak 

Above the comment was made "Someone mentioned adjusting  MP to further affect FF" exactly since FF follows MAP/airflow via fuel metering. Increasing MAP will increase FF.

Probably the original comment about adjusting MAP stems from the fact that with a Turbo we are not limited to lean by FF alone. We can also lean by way of increasing airflow/MAP but when doing so it becomes a 2 handed operation to keep FF constant as we increase MAP to to lean, otherwise we won't be able to measure how much leaner we're getting by adding air alone.   

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  • 2 weeks later...
On 5/4/2024 at 10:48 AM, dkkim73 said:

Yes, to clarify I am trying to understand if I should consistently always lean it a lot further out. 

Someone mentioned adjusting  MP to further affect FF. It isn't clear what the relationship would be to TIT LOP; is the higher mass flow cooling in it's effects?  Or is it going to lean it further despite the mechanical mixture.

And then since FF determines energy flow LOP, one could adjust MP and RPM for whatever gives the best mechanical efficiency. Eg use the POH or do test runs to fill in a matrix of TAS. 

(I am) Overcomplicating this for sure. But ty for verifying the concern re < 1600F.

D

Don’t think so Dave I’m equally confused I’ve been trying LOP for the last year since I purchased the plane but yesterday I flew a two hour flight at ROP I was like 28/2450 19 Gph main observation even with TKS theses are fast planes, anyway flying home finally due the the crummy I can finally get out of the south, back to LOP? Maybe something like 26/2450 at 14.5 should be LOP somewhere I think my temps are. Great generally especially yesterday’s ROP TIT1590, Egts 1500-1580 CHTs 320-345 always had cool CHTs since breaking in. Still the lean find is confusing 

D

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On 5/4/2024 at 11:48 AM, dkkim73 said:

Yes, to clarify I am trying to understand if I should consistently always lean it a lot further out. 

Someone mentioned adjusting  MP to further affect FF. It isn't clear what the relationship would be to TIT LOP; is the higher mass flow cooling in it's effects?  Or is it going to lean it further despite the mechanical mixture.

And then since FF determines energy flow LOP, one could adjust MP and RPM for whatever gives the best mechanical efficiency. Eg use the POH or do test runs to fill in a matrix of TAS. 

(I am) Overcomplicating this for sure. But ty for verifying the concern re < 1600F.

D

When on the lean side, at a constant fuel flow, more air slows the combustion event. This makes for lower peak pressure in the cylinder. There is a point on the lean side of peak for any fuel flow at which the combustion event gets so slow that both power and efficiency start to decrease

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36 minutes ago, Danb said:

Don’t think so Dave I’m equally confused I’ve been trying LOP for the last year since I purchased the plane but yesterday I flew a two hour flight at ROP I was like 28/2450 19 Gph main observation even with TKS theses are fast planes, anyway flying home finally due the the crummy I can finally get out of the south, back to LOP? Maybe something like 26/2450 at 14.5 should be LOP somewhere I think my temps are. Great generally especially yesterday’s ROP TIT1590, Egts 1500-1580 CHTs 320-345 always had cool CHTs since breaking in. Still the lean find is confusing 

D

Have you verified that TIT is a good proxy for EGT? It works fine for as long as all cylinders peak sufficiently close to the same FF.  This is to say that it would be good to know which cylinder is leanest and which is richest and roughly where they peak relative to peak TIT.

 

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On 5/4/2024 at 10:48 AM, dkkim73 said:

consistently always lean it a lot further out

Try these John Deakin articles (Pelican's Perch #63 through #66).  John was one of the principals of the Advanced Pilot Seminars put on by several of the GAMI guys.  The APS website is https://www.advancedpilot.com/

John's Pelican's Perch articles on how to run your engine are at:

https://www.avweb.com/features/avweb-classics/pelicans-perch/pelicans-perch-63where-should-i-run-my-engine-part-1/
https://www.avweb.com/features/avweb-classics/pelicans-perch/pelicans-perch-64where-should-i-run-my-enginepart-2-the-climb/
https://www.avweb.com/features/avweb-classics/pelicans-perch/pelicans-perch-65where-should-i-run-my-enginepart-3-cruise/
https://www.avweb.com/features/avweb-classics/pelicans-perch/pelicans-perch-66where-should-i-run-my-enginepart-4-descent/
 

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26 minutes ago, Fly Boomer said:

Should be required post check ride reading for all private pilots. The fact that I remember reading them when they were originally released, makes me feel very old.  I miss John’s presence in aviation. Not only was the fountain useful information, he was good at communicating that information in a thoughtful and entertaining way.

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2 hours ago, Shadrach said:

The articles below or a good primer for anyone operating turbo charged or turbo normalized engine.

I'll see your four, and raise you two:
https://www.avweb.com/features_old/pelicans-perch-35those-fire-breathing-turbos-part-5/
https://www.avweb.com/features_old/pelicans-perch-36those-fire-breathing-turbos-part-6-and-final/

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Finally think I nailed a good LOP setting , 4-5 hour flight.

After being in cruise for a few minutes set MP 29 RPM 2400, tried lean find again went to 44* LOP Great numbers 11,000 ft Fran didn’t want oxygen

190 TAS. TIT1595 highest EGT 1590 all pretty close CHT lowest 297 highest 330. FF 15.1 gph.

Ill accept these fair speed great temps good economy 

D

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