Opening another support topic about AP+ fuel, but this time it is about excessive fuel burn and the inability to calculate accurate fuel consumption during AP+, especially with the F18.
This was the third time this happened, so I captured data to support this.
Aircraft ran out of fuel with 48 mins ETA. Quick maths makes that ~4,800kg p/hr (12000 / 2.5hr flight time). That’s 2.6 times MORE than when I enabled AP+.
The fuel issue is mainly due to head/tailwinds. If tailwinds are present, the fuel flow is much lower, as there is less airspeed and thus throttle needed to keep the same groundspeed, which is the determining factor of speed for AP+. If headwinds are present, though, the opposite is true. The plane will need more thrust to keep the same ground speed, meaning it burns much more fuel. Hope this helps your understandment!
Further testing on solo mode where wind would definitely not be a factor has shown that fuel burned over 30 mins in AP+ approximately aligns with the stated flight time in the fuel menu.
Calculation
Ap+ started at 12000kg and 30 min timer set.
Flight resumed 30 mins later, 7185kg fuel remaining.
AP+ burned 4815kg in 30 mins, or 9630kg p/hr
IF fuel menu states 1hr 22mins (1.33 hrs) for a full tank of fuel (13631kg) which calculates as 13631/1.33 = 10,248kg p/hr.
This is completely inaccurate for the F-18 where you can easily stretch 8 hours flight time on a full tank.
GS does change bc of winds. Wind is not taken into account for AP+ as stated by some in this thread, and as shown w evidence in another persons comment. I’m not sure how u think the idea that GS is not associated w wind. Fuel consumption on IF is solely based on wind, type of plane/engine, altitude, speed, weight and the amount of throttle.
If you read my message thoroughly, I was saying that since GS is the way AP+ determines how fast to fly, it changes the airspeed and throttle input according to any head/tailwinds.
GS of course changes due to winds in normal flight, I am aware of that, but not in AP+.
English is my second language since I am Dominican born and raised, but I try to make my messages make the most sense. If you want me to explain further or in layman’s terms, then I can do so.
I’m not sure how you think this is wrong. To keep the same groundspeed in changing wind speeds, you need to manipulate the throttle. You can try this yourself. Cruise at a set altitude and air speed in solo mode, and change the wind speed. You should see your throttle levels change.
You are flying an airplane, not driving a car; and when you fly, you fly with reference to your airspeed. Trying to keep your groundspeed constant is a recipe for disaster.
U can use translator, there’s no shame in trying but ur getting lost with complicated words for ur level of English. Just try to explain in simple words, you don’t have to explain things w complicated words j to sound logical, with a couple sentences with simple words ur okay.
Also I’m telling you in the second answer u gave to the other person I’m not talking abt ur first answer. Try explaining in more simple terms so u don’t lose yourself and others. However yes u gave answers to some of what I have said in ur first response but u seem quite confusing on ur reply to the second person. I just have given more reasons as to how fuel consumption is affected by other factors.
For this part I’m pretty sure that IF calculate the endurance based on a fixed throttle or n1 percentage (I would say it can be at or above 80% throttle) and for the F-18 this mean it’s in Afterburner and with that the unreal time, it can be seen also in other plane but the fact that airliner doen’t have Afterburner doesn’t change that much.
for this part I would say that is not correct because as said before, Laura has responded that AP+ doesn’t consider wind at this time, and to change throttle to maintain a constant GS would mean that AP+ use wind data to calculate the corresponding IAS and set a different Throttle and so the statement of Laura would be False, a little problem of logic. But I could be wrong, I like to know if it’s logical for you
Do you have anything to support this? Could you run a few tests to see if this holds any weight?
While I appreciate the attention that this topic is getting, none of this is actually the answer. Please can we stop sharing guesses and opinions about what “might” be happening based on what people “think”. It’s not beneficial and it’s distracting from the original topic.
My aim for this thread was to highlight the lack of information about AP+ fuel burn and, through testing, try and work out what it currently is. I don’t actually care about how it is calculated, I just want to know what it is so that I can plan accordingly and so that others can benefit from it.
with the new update you can now easily be able to do 60 hour flights with almost all widebodies, I did 19.5 hours on the 789 (nutorious for the bad range in IF) and only used 30% of the fuel, to my estimations, you could theoretically fly up to 60 hours with passengers.
