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 10 Fuel Burn at Cruise (Read 284 times)
NickL1011
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Fuel Burn at Cruise
Jun 23rd, 2020 at 12:24am
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Does anyone know what the normal fuel burn is for the L-1011 during "normal" cruise which is supposedly Mach. 86? Engines are at like 95% n1 to maintain that empty. Fuel burn gets up to like 19000 pph. It seems too high.
  
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Beardyman
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Re: Fuel Burn at Cruise
Reply #1 - Jun 23rd, 2020 at 6:10am
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Engine data and some drag values are messed up.
Try to change cruise lift scalar to 0.65, fuel flow scalar to 0.91.
Also reduce ridiculous flap drag to 0.5
  
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NickL1011
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Re: Fuel Burn at Cruise
Reply #2 - Jun 24th, 2020 at 8:15pm
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Is this also why I run out of runway on a takeoff roll at 400k lbs? 94 percent N1 .532 epr
  
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Beardyman
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Re: Fuel Burn at Cruise
Reply #3 - Jun 25th, 2020 at 5:03am
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EPR parameter is totally out, so do not use it as reference.
To use EPR and fly by the book CS should make custom engine model, which is not likely.

Is 94% ok ?, we do not know as CS did not provide real world tables.
L1011 without mods flies like a brick, and i think is far from real one.

Do u use V-one gauge ?
  
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Markoz
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Re: Fuel Burn at Cruise
Reply #4 - Jun 25th, 2020 at 3:11pm
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I have never run out of fuel during takeoff, so I don't know how you can unless your sitting at the gate with the engines running flat out for a few hours before taxiing to the runway. Or you started out with too little fuel.

For me, it flies really nicely. Today I did a flight from YMML (Melbourne, Australia) to VHHH (Hong Kong), a distance of 4031nm, with a weight of 429,031lbs (so nearly at maximum takeoff weight), which was a combination of 50% passengers, 6000lbs cargo, and 100% fuel. I flew at FL320 for the first hour, or 90 minutes, then climbed to FL340 for the remainder of the flight. And seeing as Wikipedia* shows the range of the L-1011-1 as 2,680 nmi (4,963 km) for the max passengers + baggage (which I wasn't carrying), and a ferry range of 4,250 nmi (7,871 km) for max fuel (I believe I had enough fuel remaining to do that extra 219nm, or more (~9% fuel remaining)), I think that Captain Sim have it pretty close, unless the latter means with 0 passenger and baggage, and no cargo.

* I know Wikipedia isn't always accurate, but it's all I have to go on. Wink
  

Mark Fletcher



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Beardyman
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Re: Fuel Burn at Cruise
Reply #5 - Jun 25th, 2020 at 5:33pm
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Dear Mark, without real world tables and data, we can only do tea leaves reading here.
L1011 is marked as 'Professional' so please give us tables so we can fly by the book.
  
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NickL1011
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Re: Fuel Burn at Cruise
Reply #6 - Jun 29th, 2020 at 8:54pm
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Markoz wrote on Jun 25th, 2020 at 3:11pm:
I have never run out of fuel during takeoff, [/i]. Wink


To clarify, I didn't say I ran out of fuel, I ran out of runway. I fly pretty much empty, just 2 or 3 pax. It's a private bird. I was also topped off (max fuel) for my TNCM to GVAC flight. I have been going by roughly 15 or 16,000 pph fuel burn to get to .84 Mach. .86 takes basically takeoff power to achieve, which I have to assume drags down fuel economy.

I also know that L-1011s, MD-11s, and 747s fly into TNCM, so the runway is definitely long enough.
  
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NickL1011
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Re: Fuel Burn at Cruise
Reply #7 - Jun 29th, 2020 at 8:56pm
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I was able to get off with some more power for takeoff, so i guess 95 percent+ will need to be used in heavier conditions, regardless of what docs say.
  
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Beardyman
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Re: Fuel Burn at Cruise
Reply #8 - Jun 30th, 2020 at 5:19am
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Yep, sad but flying this marvel in the sim is pure guessing, it is like flying Cessna - u push engine until u fly.
Definitely not the way to fly big tubeliner...
  
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trevors
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Re: Fuel Burn at Cruise
Reply #9 - Jul 1st, 2020 at 4:00pm
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Trevor
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Beardyman
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Re: Fuel Burn at Cruise
Reply #10 - Jul 1st, 2020 at 5:37pm
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Trevor, do u have access to real performance tables ?
  
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Beardyman
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Re: Fuel Burn at Cruise
Reply #11 - Jul 3rd, 2020 at 8:53am
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NickL1011 wrote on Jun 23rd, 2020 at 12:24am:
Does anyone know what the normal fuel burn is for the L-1011 during "normal" cruise which is supposedly Mach. 86? Engines are at like 95% n1 to maintain that empty. Fuel burn gets up to like 19000 pph. It seems too high.


I have found info that fully loaded L1011 burns 8.3T per hour during cruise flight.
To match that number fuel_flow _scalar in aircraft.cfg should have value 1.235 - during testing now.
  
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Beardyman
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Re: Fuel Burn at Cruise
Reply #12 - Jul 3rd, 2020 at 11:17am
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stand corrected, 1.397 is spot on if target is to get 8.3T/h
  
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trevors
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Re: Fuel Burn at Cruise
Reply #13 - Jul 3rd, 2020 at 5:44pm
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The L1011's normal cruise speed was M0.84 (for Atlantic crossing) but they were also flown between M0.82 - M0.85
At FL350 and average fuel flow would be about 11,000 pounds per hour at M0.84
Obviously it depends on temperature, weight etc.
  


Trevor
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Beardyman
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Re: Fuel Burn at Cruise
Reply #14 - Jul 3rd, 2020 at 7:18pm
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RB211 had cruise SFC 0.57 to 0.59, or by some sources 0.6
SFC is a mass of fuel needed to produce net thrust for a given period.
If we take 11.000lb per hour then SFC is 0.275 calculating lower thrust output ( 40.000 ).
Taking SFC as reference looks like 11.000 pounds is way too less.

  

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