ISSUE DESCRIPTION
In career and with A320neo (V2) and A321LR, mission briefing’s fuel prediction (shown on the refuel page before starting the mission) is severely under-estimated (~1/4), leading to User having to cheat in order to complete the flight without running out of fuel.
This appears to be due to the estimated fuel consumption as reported by the aircraft’ checklists being way off what the models actually implement (see details further below).
FREQUENCY OF ISSUE
All the time for A320neo (V2) and A321LR. Did not check for other aircraft, will update accordingly.
REPRODUCTION STEPS
-
Select a A32# career mission flight
-
Refuel the aircraft as recommended with a margin (I tried with a +45% margin for 1000NM trips, which already seems excessive as regards real-world margins)
-
Start the flight and monitor FOB, F.USED and EFOB;
- During Init, EFOB will be negative and the FMGS will alert “DEST BELOW MIN EFOB”
- At some point during cruise, you will run out of fuel and fail the mission if you do not cheat (add fuel mid-flight or exploit simrate bug to lower fuel consumption)
Here are the measurements I made to confirm this issue:
| Flight step | A320neo (V2) | A321LR |
|---|---|---|
| Mission briefing | - checklist fuel consumption = 1133 lb/h = 533 kg/h - checklist range = 3500 NM - dist = 892NM - recommended fuel = 7233 lb - loaded fuel = 10500 lb (+45%) |
- checklist fuel consumption = 1133 lb/h (same as A320neo → error?) - checklist range = 3500 NM (same as A320neo → error?) - dist = 1177 NM - recommended fuel = 8791 lb - loaded fuel = 12793 lb (+45%) |
| Init | - FOB = 4740 kg - Trip = 5.3 T (time = 02:39) - Extra = -2.1 T - EFOB = -0.8 T |
- FOB = 5800 kg - Trip = 6.3 T - Extra = -2.2 T - EFOB = -0.8 T |
| Top of climb | - FOB = 3500 kg - F.USED = 1210 kg - EFOB = -0.6 T |
- FOB = 4640 kg - F.USED = 1130 kg - EFOB = -0.4 T |
| Running out of fuel during cruize | - in-sim time elapsed : 01:56 - FOB = 520 kg - F.USED = 4190 kg - EFOB = -0.6 T |
- in-sim time elapsed : 02:08 - FOB = 1000 kg - F.USED = 4770 kg - EFOB = -1.0 T |
(Nb: because of the simrate bug, those measurements were made with simrate = 1 during the whole flight)
Which leads to the following assumptions:
- A320neo (V2) actual fuel consumption = ~2110 kg/h (instead of 533) → ~4.7 kg/NM
- (yes I know this calculation is very incomplete because consumption is not linearly proportional to distance/time, but it allows to have a rough idea of how much the briefing recommended fuel is off the mark)
- A321LR actual fuel consumption = ~2400 kg/h (instead of 533) → ~4 kg/NM
- -> estimated actual range = ~6600 NM which is significantly off the 3500 number in the checklist (same as A320neo) … surely this is a copy-paste error since the “LR” stands for “Long Range” and thus should have a greater range?
So it appears that the estimated fuel consumption per hour reported in the aircraft checklists are severely off the mark, which may be the explanation why the mission briefing’s recommended fuel is that wrong.
YOUR SETTINGS
[PC Only] Are you using Developer Mode or have you made any changes to it?
No
MEDIA
Irrelevant.