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saltysimulations / salty-747

An open-source modification for the default MSFS 747-8, aiming to improve the lacking features and realism of the default aircraft.
GNU General Public License v3.0
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High Fuel Usage #471

Open jamcomp opened 2 years ago

jamcomp commented 2 years ago

Flew with the stock Asobo 747-8i, and then with yours on the way back with a 20 to 30 knot tail wind and fuel usage was way higher with your aircraft. I was able to get from KMSP to PHNL with about 150K Lbs of fuel in the stock airframe. I had 161K Lbs when I took off from PHNL and was at 1K lbs left when landing with higher speeds due to tail wind.

jamcomp commented 2 years ago

I just started a new flight with your aircraft. It is burning 44,000 lbs of fuel per hour at cruise altitude FL400. It should be half that according to Boeing's website.

DesertRick13 commented 2 years ago

I'm curious as to the weight of the aircraft when you were flying at FL400. Even though the 747-8 is listed as capable of even FL430, the plane has to be pretty light by the time you get that high. Do you recall the recommendations in the VNAV section for Flight Level?

runningdavid commented 2 years ago

Same here for me.. It costs me more than half tank of fuel to fly from Singapore to Japan, even if I'm following the VNAV alt recommendations.. Had to refuel halfway in the sky.. I just changed my aircraft.cfg to reduce fuel_burn_rate by half it works much better now.

Rasmus380 commented 2 years ago

Same thing for me. Used the simbrief profile provided on discord for CTP today between KATL-EHAM. According to simbrief I should’ve burned 63 tons but ended up burning 84 tons which made it a very tight trip…

dcherrie commented 2 years ago

To explain a little about fuel burn, I posted this in the reply on Discord, but reading these comments, this isn't expected behaviour. For any flights that you do that you are having these issues, can you please mark down on your Simbrief files, the fuel remaining at each waypoint and post the files? This is the only way we can verify your issue.

I continually do regular short and long haul flights with the aircraft and my fuel burn matches Simbrief within 5,000-10,000lbs at maximum.

This is because the fuel burn from Asobo is linear and doesn't reflect the weight of the fuel. Obviously when you are full of fuel, your fuel burn should be higher because you weigh more, and the less fuel you have should be lower because you weigh less. This doesn't happen with the current fuel flow, so we calculated the fuel flow to be an average. You will find that you will born more fuel than predicted on shorter flights, and burn less fuel than predicted on longer flights. Basically we have found the happy medium where you aren't at risk of running out of fuel, but you also won't be landing with 100,000lbs extra and landing overweight. Is usually about 5,000lbs more on short hauls and 10,000lbs less on long hauls.

avs-code commented 1 year ago

Two flights, two high fuel usage, this is the data from last flight Simbrief resume: imagen LEMDOIIE_PDF_1669195710.pdf

Acars Data: imagen

Version | 1.1.0.2306 (release) -- | -- Simulator | Microsoft Flight Simulator Aircraft | Salty Boeing 747-8i Boeing House Departure Gate | Gate 505 (Gate Heavy) Blocks Off Time (Sim) | 09:46 23-11-2022 UTC Blocks Off Time (Real) | 09:46 23-11-2022 UTC Ramp Weight | 700,373 lbs Taxi Out Time (Sim) | 09:51 23-11-2022 UTC Taxi Out Time (Real) | 09:51 23-11-2022 UTC Takeoff Flaps | 10 Takeoff Weight | 699,069 lbs Takeoff Time (Real) | 09:54 23-11-2022 UTC Takeoff Time (Sim) | 09:54 23-11-2022 UTC Taxi Fuel Used | 1,310 lbs Taxi Out Time | 3m 44s Departure Centerline Deviation | 12.54 ft Departure Heading Deviation | -0.21° Departure Runway | 14R Takeoff Speed | 169 kts Arrival Threshold Distance | 2,165 ft Arrival Runway | 11L Arrival Heading Deviation | 0.18° Arrival Centerline Deviation | 24.94 ft Landing Time (Sim) | 14:58 23-11-2022 UTC Landing Time (Real) | 14:58 23-11-2022 UTC Landing Rate | -367 ft/min Landing Pitch | 2° Landing G-Force | 1.00 g Landing Roll | 0° Landing Heading | 109° Landing Weight | 579,213 lbs Landing Fuel | 13,511 lbs Landing Speed | 154 kts Landing Flaps | 30 Blocks On Time (Sim) | 15:01 23-11-2022 UTC Blocks On Time (Real) | 15:01 23-11-2022 UTC Taxi In Time | 2m 27s Arrival Gate | Parking 134 (Ramp GA Large) Total Flight Time | 05h 15m 10s

P.S: Is there a post in fs2020 forums to vote the fix?

dcherrie commented 1 year ago

@arv187 Thanks! As I calculate you consumed 16.4% more fuel than planned. I'm doing some test flights at the moment and finding it to be anywhere between 12.3 to 14.6% more fuel. Am now testing a change to the fuel flow with a friend to see if this is a fix.

If you could continue posting the planned block fuel and landing EFOB along with the actual block fuel and landing AFOB, can continue you to see how off the fuel burn is and settle at a more accurate fuel burn.