Fuel burn value when LOP

[PTK]

I'm curious as to what fuel burn value you fellow LOP'ers utilize for flight planning purposes in the J. What is a realistic ball park LOP full tank trip in hours with reserves. I used to use 4.5 hours when full tanks, which translates to 14.2 gph! No more!

[FAST FLIGHT OPTIONS LLC]

Take off to touch down average LoP fuel burn is almost exactly 10 GPH

[jetdriven]

Our block fuel burn over 250 hours is 9.0 GPH.  Thats exclusively target climb, and 8-8.8 GPH in cruise LOP.  At altitudes above 8K you can plan for something in the low 8s.  If you are willing to fly at Carson speed then 8.0 might be achievable.

[danb35]

I conservatively plan for 9 gph as a block value.  Since I mostly cruise at 9-10k lately, I find I burn a bit less than this on average, but it's an easy number to work with.

[Lood]

My long term average ROP is 10 gph.

[Bolter]

For quick mental calc's I use 10 gph to include climb and cruise.  Actual is less, but 10 is a "safe" number and very easy math.  I find that actual use varies a lot with how much I climb.  For LA-Oregon last weekend I averaged 8.5 gph total due to LOP and long cruise stretches.  

For detailed planning, I use Voyager (Seattle Avionics) and put in detailed climb and cruise fuel burns for different altitudes.  For example, cruising 12.5k at 152 KTAS I was down to 7.2 gph, but at a more common 5.5k at the same speed is 8.5 gph.

I see a lot of variation here.   I know that ROP I could not average 10 gph, since at typical altitudes I would need 11-12 gph to keep CHT's down.  That may due to higher ambient temps in SoCal.  At 10.5k I was 20-25°C over standard day.

[fantom]

I use a 9.5 block to block average for planning on my IO-360.

A silly question without specifying your model.

[Jeff_S]

Gary, really? Why the hostility? What part of this original question did you miss?

I'm curious as to what fuel burn value you fellow LOP'ers utilize for flight planning purposes in the J.

[fantom]

The 'original' posthaste been edited, Jeff.

No hostility involved....

[fantom]

The 'original' posthaste been edited, Jeff.

No hostility involved....

[Lood]

@Jim: Just for my own interest. Do you set 60% power according to the POH tables, regardless of the actual altitude that you are flying or do you go up to a minimum altitude where the engine will only reach 60% at WOT?

[Jeff_S]

It should be noted that not all (or even many?) engines will be happy at the super-reduced fuel flows, except perhaps at higher altitudes. I generally cruise in the sweet-spot range of 7-9,000', and I can cruise down around 8.5 gph LOP but if I try to go lower than that the engine really complains. Jim, can you get to that low GPH even at lower altitudes, WOT?

[PTK]

Quote: JimR

Lately I've been setting power for 60 percent LOP (8 GPH) and conservatively flight planning for 140 KTAS.  Not accounting for the climb, that provides eight hours of ultimate endurance, or three hours per side and 840 nautical miles with healthy reserves. 

Jim

[PTK]

Quote: Jeff_S

It should be noted that not all (or even many?) engines will be happy at the super-reduced fuel flows, except perhaps at higher altitudes. I generally cruise in the sweet-spot range of 7-9,000', and I can cruise down around 8.5 gph LOP but if I try to go lower than that the engine really complains. Jim, can you get to that low GPH even at lower altitudes, WOT?

[jetdriven]

At low altitude I have found I had to back off on the MP to get FF below 7 to 7.5 GPH.  One way to ensure enough air is run it at 25" or MP, for a 4.5 GPH FF, it takes about 15".  At those super low power settings just run it at peak.

[FBCK]

A little of topic, but when flying a turbo, 360Lb in a 231 for example that number is 13.9 I believe.  So I fly at 30 inches burning 11..5 gallon per/hr so that would be 13.9x11.5/210=76% power, when I advance the throtle to 32 inches I see a speed gain, but I'm still at 76%, how can that be?

[KSMooniac]

Quote: FBCK

A little of topic, but when flying a turbo, 360Lb in a 231 for example that number is 13.9 I believe.  So I fly at 30 inches burning 11..5 gallon per/hr so that would be 13.9x11.5/210=76% power, when I advance the throtle to 32 inches I see a speed gain, but I'm still at 76%, how can that be?

[DrBill]

I'm still playing and learning on my 65 M20E.  Yesterday I flew a Pilots N Paws flight.  Picked up 40 mins away, flew 1.3 hrs, drop-off, then take/off- re-land (door poped open -- let pass "secure" it), and flew home .  Total tach time 3.6 hrs.  Total fuel burn 26 gal. Cruising at 24/24, LOP. 8000 feet (9K on return trip). 145MPH indicated.That's 7.2 average. I'll start keeping track and average it over a few months.  That's way too low !

BILL

 

[Cruiser]

On Wednesday last, at 7000' 16°C WOTx2450 8.9gph I was showing between 148 and 152 KTAS. Two on board with 50 gallons fuel.

[Cruiser]

Quote: MooneyPilot

How is the factor of 15 HP per gallon/hour derived for an IO360?  Is the factor precisely 15 or is that a rounded number?

[PTK]

Thank you Cruiser for the derivation of the calculation. It only applies when lop then am I correct? Because I notice at full rich eg. on takeoff power, my ff is 18.4 gph. Doing the calculation it yields a hp of 138%!

[Cruiser]

You are correct for the 15.17 figure. It works at all settings but you must know the BSFC for each particular setting. If you know the HP and fuel flow you can calculate the BSFC. For ROP it would be 5.92FF/HP = BSFC. As you can see, it changes for each combination of FF and HP. It also changes going too far LOP, going too far LOP will actual be less effective power and BSFC goes up (but only a little). The curve looks a lot like a hockey stick.

[DaV8or]

Quote: allsmiles

Thank you Cruiser for the derivation of the calculation. It only applies when lop then am I correct? Because I notice at full rich eg. on takeoff power, my ff is 18.4 gph. Doing the calculation it yields a hp of 138%!

[Vref]

Did a recent 600 Nm trip 9000 Ft MSL most of the time TAS 147 Kts LOP and burning 34L/HR or tiddle less then 9 US gallons/Hrs this is with 2500RPM and 22 MP WOT (more I can't get..)

This includes a ROP climb when reaching cruise altitude I set for LOP. I am rather new at this LOP stuff so it takes some fiddling before fine tuning the right LOP and smooth engine set-up I notice my CHT temps are 10 to 15 degrees celisius lower then when flying ROP .. drawback when flying with a headwind...it slows down the progress.......

 When heaving a serious headwind I prefer lower altitude <4000 FT and ROP for better power/speed and staying out of the red-box.....600 Nm with a headwind is close up to 5 hours and that is about my limit..

With a tailwind >7000 Ft the LOP is just great and a money saver...the engine runs smoother also

[PTK]

Quote: Vref

 When heaving a serious headwind I prefer lower altitude <4000 FT and ROP for better power/speed and staying out of the red-box.....600 Nm with a headwind is close up to 5 hours and that is about my limit..