Fuel Issues

[PK787]

Hello!

Long time FSpassenger user, first time forum poster! I am having issues with Long Haul Flights and fuel.

Firstly A380 flying from LAX to Dubai, which falls within the max range of the aircraft by around or below 1000 nm, the flight
time is something like 13-16 hours but the fspassenger (this is fs9 by the way) in-flight report shows only 9-10 hours of flight time
based on available fuel, which is always 100% on take off. This inevitably leads to cancelling the destination and diverting
while still a fair while out, usually to Tokyo.

Now the plus one hour is always an hour less that the main value, say I have 5 hours left it will read 4 hours. Silly question but
just to clarify this doesn't mean that the one hour reserve is infact able to last 4 hours, meaning I have 9 hours in total available?

Secondly with the FS9 standard B747, from SFO to Brisbane, again within the max range of the aircraft. There are varying
routes, some the exceed the max range by 1000 nm, but the most direct is around 6100nm, within the 7200nm range of the
aircraft. Yet again the inflight reports that I will run short 2 hours out.

Anyone have any advice? or do I just need to shorten the distances im flying ^^

Best Wishes,

PK787

[PK787]

The flight KSFO - YBBN (Brisbane) I am currently cruising at 330 kts, although the inflight report says 540??? Could that be it? That
I have set too high a cruise speed. The fuel burn seems excessive too, 43433 lbs/hour on a 747, is that normal?

[whiskey-zulu]

Above Fl 180, you should be reading speed in Mach numbers; so at 29.92 mmHg, at Fl360, 540 KIAS will be roughly Mach 0.85. The fuel burn to me sounds
about right for the 744.

If you're in doubt you can always modify the fuel scalar in the aircraft.cfg file of the 744 - there are a couple of threads around on how to.

[gbapache]

I hate to admit this but the only way to make my helicoptors fly more is to change the fuel_scalar to .4



Post Edited ( 05-21-12 02:05 )

[ben_r]

Pardon me if this has been discussed elsewhere, but how does FSP determine how much fuel is sufficient divert fuel to avoid getting pinged for not having a reserve?
With only ~14hr in FSP, I've been flying piston GA singles around. I know the rule is 45m reserve, but what fuel flow rate does FSP use to determine how many pounds
add up to 45 minutes? Is there a formula I can use to calculate this? The difference between 45 minutes at just above stall speed vs cruise speed is not insignificant.

[gbapache]

@ben_r, You have the right idea with the slow vs. fast. The algorithm that FSP uses is the average flow rate for the flight when you close
out. My advice is to not make your flights so long as to worry about the reserve. Proper prior planning prevents piss poor perfomance.



Post Edited ( 06-17-12 18:32 )

[ben_r]

Oh, that makes sense. I just noticed that the in-flight report has a fuel section, so I'll do a few flights at different altitudes/cruise speeds and gather some data points to get
a better understanding of how much buffer I have to work with. The longest flight I've done so far in FSP is KSFO->KPDX because I wasn't sure how much leeway I had,
but I always seem to have enough fuel left that on the approach, I could almost divert back to my origin. I think I might be a little over-conservative with my fuel, but like
you said about prior planning...

I've also been using a nifty 3rd-party gauge for FSX that calculates instantaneous fuel flow, along with time- and range-to-empty, flight time, and some other things like a
door management panel: http://simviation.com/1/browse-FS+Gauges-124-1 (it's the fourth one down that page).

[AKLupine49]

There have been times that I have been more than a little nervous about fuel on long haul flights. However, if you know the average burn rate of
your aircraft and the average speed for east/west flights, you can compute how much fuel you will need for a given flight. As an example, I know that
my Level-D 763 averages 12700 pound per hour fuel burn and averages east flights at 480 kts. With that I can calculate that I need to have 124K just
to make a 4300 nm flight. If I were to look at the inflight report say an hour after departure, the fuel flow would show I was way off in my
calculations and that I would only have enough on board for say two more hours of flight. However, if looking again about an hour out, it would be
much closer to what I figured. The way it works is FSP uses the up to the minute fuel burn for the time remaining calculation which would be skewed
because while climbing you burn 4-5 times the fuel/hour that you do in cruse. I would recommend charting the data of all your flights and after a
while you can start to see the trends and be able to do a long flight and not worry. It may help to look in the more downloads section, I believe
under utilities, for a spreadsheet that was created years ago to chart all the data.

[iflyfsx]

The very cool FSUIPC gives you a ton of real-time information, including fuel consumption and estimated range.

Fuel consumption will vary significantly depending on a number of factors, so any "average" has limited use.

[Captain_Ricadro]

Hi,
Maybe it isn't fspassenger s problem, maybe is it the plane aircraft.cfg, I think it is in generalenigedata like on my is economical

[generalenginedata]
engine_type = 1
fuel_flow_scalar = 0.60 <-------------
min_throttle_limit = -0.23

engine.0 = -6.00, -85.50, -5.50,
engine.1 = 20.00, -49.00, -8.00,
engine.2 = 20.00, 49.00, -8.00,
engine.3 = -6.00, 85.50, -5.50,


[turbineenginedata]
fuel_flow_gain = 0.00135 <------------
inlet_area = 35.00
rated_N2_rpm = 9750.00
static_thrust = 80214.00
afterburner_available = 0
reverser_available = 1

normally it should be 1 and anything that's above 1 change it's range and flight time, on my it is economical of the real data of the RR
engine, I think.
Maybe this help to solved other problem from aircraft.cfg invented or create by head.
Regards