LOP GUY POURS ON THE COAL SURPRIED BY RESULT

[Bob - S50]

10 hours ago, MyNameIsNobody said:

Wow.  Never mind.  Don't beat the dead horse on my account Bob.

What I was referring to was that we were all trying to convince you that you were not LOP.  You already knew that.  It appears that what you were really asking was why your G3 still said you were LOP when you knew you weren't.  So I tried to give a possible explanation of why that might have happened.

[Bob - S50]

10 hours ago, MyNameIsNobody said:

So what have I learned?

1) From Economy to Power fuel setting (LOP to ROP) in my plane at 5500' I realized a 20 knot gain.  

2) The G3, when set to monior 15 LOP and set up for one altitude will give erroneous readings.

3) Cylinder Temps were not significant + or - 320 with power cruise setting.

4) There are times when burning $10 an hour more in fuel is worth it.

5) Going fast can be addictive...in addition to burning < fuel.

6) Owning a plane that can do both is awesome.

 

I still don't think you can gain 20 knots of true airspeed by going from 15 LOP to 50-100 ROP.  5 knots? Probably.  10 knots?  Maybe.  20 knots?  Maybe if you went from 150 LOP to 100 ROP, but not when starting from 15 LOP.  I still think you gained maybe 7-8 knots TAS and another 12-13 knots groundspeed due to changes in the wind.  I would encourage you to go out and set up 15 LOP at some altitude.  Then stay at that altitude and go to your ROP setting and see how much airspeed you gain.  Let us know what you find.

[MyNameIsNobody]

42 minutes ago, Bob - S50 said:

What I was referring to was that we were all trying to convince you that you were not LOP.  You already knew that.  It appears that what you were really asking was why your G3 still said you were LOP when you knew you weren't.  So I tried to give a possible explanation of why that might have happened.

Fair enough.  Yes, the entire time I was trying to establish why I was not getting a ROP indication on the G3 AND my surprise at the volume of speed increase.

[MyNameIsNobody]

34 minutes ago, Bob - S50 said:

I still don't think you can gain 20 knots of true airspeed by going from 15 LOP to 50-100 ROP.  5 knots? Probably.  10 knots?  Maybe.  20 knots?  Maybe if you went from 150 LOP to 100 ROP, but not when starting from 15 LOP.  I still think you gained maybe 7-8 knots TAS and another 12-13 knots groundspeed due to changes in the wind.  I would encourage you to go out and set up 15 LOP at some altitude.  Then stay at that altitude and go to your ROP setting and see how much airspeed you gain.  Let us know what you find.

Fair enough.  Is it possible that a headwind suddenly became a benign or tail wind at the moment that I added fuel and went from LOP to ROP...Yes.  I had been flying an hour at that point and speeds were consistent.  I hadn't seen any significant loss/gain in ground speed at 5500 vs. 7500 UNTIL I increased fuel flow.  I agree that 20 knot increase of ground speed is huge.  THAT is why I was so surprised and thought (damn, I have been missing out on some big speed gains by always flying LOP vs 100 ROP).  I will definitely be doing some more flights LOP and then resetting lean-find to 100 ROP on G3 and seeing what difference in ground speed is for my plane.

[MyNameIsNobody]

I wonder why there are not some charts created by people that own Mooney's with this information?  With engine monitors it is easy to plug in different LOP and ROP settings.  The only good data I could find was the % chart (that is theoretical) due to differences in props and airframes etc....But it IS something.  I will definitely be checking what speed difference is at different power/fuel settings at different altitudes and recording the info.  Bob, have you ever done this with your plane?  You speak to the 7-8 knots going LOP to ROP is this what you have generally seen?  If it is only that, not worth the fuel burn penalty, BUT 20 knots?  Hell yes on some days when headwind is keeping ground speed in the sub 130 knot range...and it is hot down low...and a little choppy...

Anyway, thanks for input and clarification.

Does anybody else have some data on the increase from LOP to ROP or are people all like me.  Firmly in one camp or the other?  My cylinder temps were not significantly different LOP to ROP.  I will stay below 70% power in the future.

[AH-1 Cobra Pilot]

1 hour ago, teejayevans said:

Best economy is ROP? Where did you get that from?

Never mind, I found it, I read this as pull mixture to 25° less than peak:

I guess I kind of mixed terms, taking Economy Cruise as Best Economy.  Mine explicitly states ROP.  Page 5-23 of POH (Issued 1-96, REV. A 5-97).

I also see that we may just be using C vs. F to add to confusion.  I will definitely be careful of that.

[Bartman]

51 minutes ago, MyNameIsNobody said:

Does anybody else have some data on the increase from LOP to ROP

I have verified and can reproduce at 2,500 RPM and 8,500 MSL in smooth air I gain an honest 7 knots going from 15 LOP to 100 ROP, and vise versa.  It can vary a knot or so depending on W+B. 

1977 J

[ArtVandelay]

I have verified and can reproduce at 2,500 RPM and 8,500 MSL in smooth air I gain an honest 7 knots going from 15 LOP to 100 ROP, and vise versa.  It can vary a knot or so depending on W+B. 
1977 J

Do you recall the fuel flow numbers?

[Bartman]

Don't remember exactly for that day, but I'm around 8.6 when LOP at 9,000 ft in summer midatlantic weather.  Don't remember ROP fuel flow and I don't usually fly that profile. I have found 8.6gph is easy target for about 65% power LOP in my IO-360 at that altitude.

[AH-1 Cobra Pilot]

I had to go back to the Engine Monitor topic from a while ago to find this from Bob:

"I lose about 6% ktas (155 to 145) while reducing fuel flow by 22%. (10.5 to 8.2)."

Doing the Math, this is almost perfect.  P=FV, and since F= ½ρSC_DV² , Power depends on V³.  So (155/145)³ = (10.5/8.2) = 1.2.  A 6% drop in airspeed equates to a reduction of 20% in power, or equivalently, a 20% reduction in fuel consumption.

[jaylw314]

3 hours ago, teejayevans said:

Best economy is ROP? Where did you get that from?

Never mind, I found it, I read this as pull mixture to 25° less than peak:

Admittedly, that's a misreading the people writing the POH probably did not think of 30-40 years ago, but you're right, in retrospect the wording is a potentially ambiguous

[Hank]

3 hours ago, teejayevans said:

Best economy is ROP? Where did you get that from?

Never mind, I found it, I read this as pull mixture to 25° less than peak:

No wonder my numbers never match the POH...

 

That clearly states "Lean to peak EGT, then enrich mixture (push lever forward) until EGT is 25° below peak." 

That is 25°ROP. How do you get LOP out of this??? Or did I misunderstand you?

[Bob - S50]

2 hours ago, MyNameIsNobody said:

Fair enough.  Is it possible that a headwind suddenly became a benign or tail wind at the moment that I added fuel and went from LOP to ROP...Yes.  I had been flying an hour at that point and speeds were consistent.  I hadn't seen any significant loss/gain in ground speed at 5500 vs. 7500 UNTIL I increased fuel flow.  I agree that 20 knot increase of ground speed is huge.  THAT is why I was so surprised and thought (damn, I have been missing out on some big speed gains by always flying LOP vs 100 ROP).  I will definitely be doing some more flights LOP and then resetting lean-find to 100 ROP on G3 and seeing what difference in ground speed is for my plane.

Sorry for all the misunderstandings.  I was under the impression you were LOP at 7500' then dropped down to 5500' and ROP.  I was ...not... under the impression that you changed from LOP to ROP while level at altitude.

[MyNameIsNobody]

1 hour ago, Bartman said:

Don't remember exactly for that day, but I'm around 8.6 when LOP at 9,000 ft in summer midatlantic weather.  Don't remember ROP fuel flow and I don't usually fly that profile. I have found 8.6gph is easy target for about 65% power LOP in my IO-360 at that altitude.

Thanks Bartmann.  Another vote for the "crazy" ground speed increase.  So, I plugged in your numbers into the IO360 AP using 9000feet and 65%.  Numbers showed (for Economy cruise) 2600RPM 20"MP and 9.3GPH.  A power setting for 65% was 2500RPM 20"MP and 11.0 gallons/hour.

[jaylw314]

28 minutes ago, Hank said:

That clearly states "Lean to peak EGT, then enrich mixture (push lever forward) until EGT is 25° below peak." 

That is 25°ROP. How do you get LOP out of this??? Or did I misunderstand you?

I get it.  The Lycoming operating manual lists procedures for leaning with and without an EGT gauge.  The procedure with an EGT gauge starts with leaning to peak EGT, then enrichening.  The procedure without an EGT gauge starts with leaning to the point of roughness, then enrichening.  I could see people familiar with both procedures conflating them by leaning past peak to roughness and then enrichening to 25 F below peak, which may still be LOP.

Edited October 3, 2017 by jaylw314

[MyNameIsNobody]

8 minutes ago, Bob - S50 said:

Sorry for all the misunderstandings.  I was under the impression you were LOP at 7500' then dropped down to 5500' and ROP.  I was ...not... under the impression that you changed from LOP to ROP while level at altitude.

I am the one that is sorry as I wasn't very clear in my communication.  This is really making me have questions.  I try to fly at 7500, but often go higher or lower depending on clouds as I am VFR.  I never re-do lean-find with altitude changes.  I will now. I can adjust my find number on G3.  I have set for 10-15 LOP.  I usually have fuel flows that are higher than Bartmann listed.  (9-9.5GPH are common indictated flows) with ALL solid white EGT on four cylinders.  Of course they bounce a little, but I just don't see 8.5GPH flow indicated.  HMMMmmmmm?

[Bob_Belville]

We're on page 3 of this thread so this may have been noted but it is worth pointing out that the power curve is very steep on the lean side of peak meaning that while 20 LOP might result in a loss of 10 KTAS or less vs best power, going to 50 LOP might cost 20 KTAS or more.  

[ArtVandelay]

That clearly states "Lean to peak EGT, then enrich mixture (push lever forward) until EGT is 25° below peak." 
That is 25°ROP. How do you get LOP out of this??? Or did I misunderstand you?

Given I knew about LOP long before reading Mooney POH, I read it as pull mixture, it is ECONOMY cruise after all, I read what I expected not what was written. In my defense, here a page from SR20:

[MyNameIsNobody]

9 minutes ago, Bob_Belville said:

We're on page 3 of this thread so this may have been noted but it is worth pointing out that the power curve is very steep on the lean side of peak meaning that while 20 LOP might result in a loss of 10 KTAS or less vs best power, going to 50 LOP might cost 20 KTAS or more.  

Hmmmmm.  Maybe I was closer to 50LOP and with a mixture increase of over 2GPH moved right into Best Power from deeper LOP.  THAT would explain this, or at least gives some credence to my noted increase in ground speed being so signifigant.  I had leaned for 7500 and dropped to 5500 with no further engine control adjustment prior to mixture/fuel flow increase.

Edited October 3, 2017 by MyNameIsNobody

[Bob_Belville]

Just now, MyNameIsNobody said:

Hmmmmm.  Maybe I was closer to 50LOP and with a mixture increase of over 2GPH moved right into Best Power from deeper LOP.  THAT would explain this, or at least gives some credence to my noted increase in ground speed being so signifigant.  I had leaned for 7500 and dropped to 5500 with no further engine control adjustment prior to mixture/fuel flow increase.

Very possible. My IO360 is happy to run 50 LOP most of the time but it's not the place to be except to do an in flight MAG check. Speed sucks and probably MPG is lower than at 20 LOP. 

[Bob - S50]

2 hours ago, MyNameIsNobody said:

Hmmmmm.  Maybe I was closer to 50LOP and with a mixture increase of over 2GPH moved right into Best Power from deeper LOP.  THAT would explain this, or at least gives some credence to my noted increase in ground speed being so signifigant.  I had leaned for 7500 and dropped to 5500 with no further engine control adjustment prior to mixture/fuel flow increase.

If you descended 2000' without adjusting anything, that means you would have about a 2" increase in MP.  That is about a 7% increase in power.  That combined with going from deep LOP to best power ROP could make the difference.

What I do is set my initial power setting based on ROP settings.  In the J that is RPM+MP=47 gives 65% power.  Every change of 3 is about a 10% difference.  So a total of 50 is 75% and a total of 44 is 55%.  Lately, at lower altitudes I've been using 2600 RPM and 21" of MP for 65%.  I then lean to about 10-30F LOP (richest and leanest cylinders).

When LOP near peak (not too deep LOP), 75% power is 10 GPH.  Each change of about 1.3 GPH is about 10% power.  So 7.4 is about 55%, 8.7 is about 65%, and 10 is 75%.  If I've set 65% ROP and then leaned to LOP, I should be pretty close to 8.7 GPH.

[carusoam]

I duplicated some of this experience flying to Florida last week... I had a few thousand feet of altitude change going above and below the level of clouds. Below was bumpy, above was thinning O2...

1) Altitude changes require re-leaning... to get to the % power settings you had before the change...

2) Descending while LOP really is a slow change as you go deeper LOP.

3) the dramatic loss of power isn't noticeable while descending.

4) When leveled off, adding back the proper fuel flow closer to peak, you will probably feel the acceleration...

For reference... 

IO550...

MP 20" (sets airflow constant)

LOP FF 12-13gph ... 2500 vs 2550 rpm

ROP FF 15-16gph

 

It really helps to memorize a set of these numbers for your plane...

If you are using 12 gph while Thinking you are LOP with your IO360, this is enough to make you check your power chart to make sure of where you are at...

Suddenly, you notice the 12 gph is hovering in IO550 land...

Roughly speaking

O&IO360 uses 10gph leaned ROP, and 8-9 leaned LOP.   (MP is very important to this calculation)

I always tend to fly near 10k' when able... or set an MP of 10k' until I can get the power chart out....

MAPA has simplified this Best using 'key numbers' to define 65% power somewhat independent of altitude.  This gives flexibility to setting rpm and MP without doing all the excessive memorization....

Best regards,

-a-

 

[Hank]

3 hours ago, carusoam said:

I duplicated some of this experience flying to Florida last week... I had a few thousand feet of altitude change going above and below the level of clouds. Below was bumpy, above was thinning O2...

1) Altitude changes require re-leaning... to get to the % power settings you had before the change...

2) Descending while LOP really is a slow change as you go deeper LOP.

3) the dramatic loss of power isn't noticeable while descending.

4) When leveled off, adding back the proper fuel flow closer to peak, you will probably feel the acceleration...

For reference... 

IO550...

MP 20" (sets airflow constant)

LOP FF 12-13gph ... 2500 vs 2550 rpm

ROP FF 15-16gph

 

It really helps to memorize a set of these numbers for your plane...

If you are using 12 gph while Thinking you are LOP with your IO360, this is enough to make you check your power chart to make sure of where you are at...

Suddenly, you notice the 12 gph is hovering in IO550 land...

Roughly speaking

O&IO360 uses 10gph leaned ROP, and 8-9 leaned LOP.   (MP is very important to this calculation)

I always tend to fly near 10k' when able... or set an MP of 10k' until I can get the power chart out....

MAPA has simplified this Best using 'key numbers' to define 65% power somewhat independent of altitude.  This gives flexibility to setting rpm and MP without doing all the excessive memorization....

Best regards,

-a-

 

This is important. Learn the key numbers for your plane.

For my O-360, it's pretty simole6:  the numbers on MP and Tach shojld add to 47. Someine gave the number ab6ive for the IO-360.

When I'm changing altitude, I have three sets of numbers I can use without thinking:

• Low altitude (~3000 msl or less)--23/2300
• Mid-level (4000-7000/7500)--22/2400
• High--WOT minus a bit/2500

Change altitude or power setting, the relean. Can make thise long step-downs aggravating, but it's good for my engine, so I try not to fuss too much.

[MyNameIsNobody]

1 hour ago, Hank said:

This is important. Learn the key numbers for your plane.

For my O-360, it's pretty simole6:  the numbers on MP and Tach shojld add to 47. Someine gave the number ab6ive for the IO-360.

When I'm changing altitude, I have three sets of numbers I can use without thinking:

• Low altitude (~3000 msl or less)--23/2300
• Mid-level (4000-7000/7500)--22/2400
• High--WOT minus a bit/2500

Change altitude or power setting, the relean. Can make thise long step-downs aggravating, but it's good for my engine, so I try not to fuss too much.

Fuel flow is the KEY to power.  You can get economy or Power at 25 squared at 3000 feet.  It is about the flow and watching the cylinders.  The way I have flown my plane (regarding fuel flow) has been EXTREMELY conservative.  Cylinder temps have always been happy.  My digging has re-affirmed this.  Definitely going to explore more ROP power from time to time keeping it below 70%

That thinking is WRONG.  Hank your 47 is key.  Matches up well with theoretical AP.  Thanks for info.

Edited October 4, 2017 by MyNameIsNobody

[jetdriven]

The Lower the % of power the less degrees Lop you want to be. You can hold at 4.0 GPH but it's at 15 ROP.  14" and 2400 RPM  

And the IO360 will happily run at 83% power LoP all day long with cool 330 CHT.  >3000 DA and 11.0 GPH. But it's the airframe. The IAS is so high that you only fly a few knots faster than 75%.