What an excellent find, sir! Hopefully this data can be put into the simulator so nerds like me can have accurate fuel planning once more. Out of interest, how and where did you find this? It would be interesting if we could find this data for other aircraft.
Not fancy stuff, lots of manual search and scrolling. some of the files, like what I found here, are photocopies, in which I can’t use the search function because all pages are essentially pictures and there isn’t any “text” in the document.
Interesting… I decided to check those figures you gave and I see the IF A330 is significantly more efficient. I did my test at the 240,000kg at Mach0.82, but at 25,000 feet. At that altitude, I got 2337 kg/hr per engine while at 492 KTAS. If we look at the the nm/1000 kg, this would correspond to around 105.3 nm/1,000kg. That’s significantly more efficient than the 67.4 figure they give for that weight at FL330. Over 50% more efficient.
That’s exactly what I found on a recent flight. I was at around 220,000kg and climbed initially to FL320 and saw similar fuel flow to what you have just described. I ended up landing with 15 tonnes extra.
Thrust profile is interesting, because right now the IF ones used way lower N1 per the same weight/alt. But if we go to this, it’s probably going to feel underpowered again
Interestingly enough, if you set 93% N1 at FL350 the burn is 5700 kg/hr, which is very close to the chart’s 5640 kg/hr. Perhaps what the A330 needs then is not a fuel burn reduction but a power reduction, but then we’re back at square one.
That makes sense. If the burn is already close at 93% N1, then it’s probably more of a thrust scaling issue. The old physic already felt underpowered even at 90% N1, so tuning thrust independently should fix that without going back to old behavior
The chart actually looks very similar to what the old A330 physic was aiming for in terms of numbers.
The issue wasn’t the values themselves, but how thrust was being scaled behind those N1 values
If you’re holding 93% N1 at cruise you’re going to need higher than 93% N1 to climb up there. It’s going to feel just as underpowered, unless they tune the curve itself so that 1% increase in N1 near the top gives like 5x as much thrust as 1% near the bottom. That way you’d be able to climb at like 95% and cruise at 93% and fit the fuel curve.
I noticed that as well in the old A330 physics cruising around 91% or 92% N1, but even a small step climb (+500 ft/m) would push it to ~98 ->100% N1
That does feel like the thrust curve near the top isn’t giving enough additional thrust per % N1, which lines up with what you’re saying
What if the A330 is just underpowered? I thought this at the time when the N1 was reduced because I know that in real life it can be pretty slow to climb, especially when heavy.
Personally I do hope that we don’t have to go back to square one; the A330 felt like a dog while climbing prior to the update and now it feels adequately powered, characteristically more aligned with what you would expect from a twinjet without being overpowered. In the ideal situation, the devs can tweak the A330 again to increase the fuel burn (not sure why it’s desired enough to warrant numerous complaints on the forum to be honest) without having to make the A330 underpowered again, but if given a preference between one or the other, I would say keep what has already been done in 26.1 as now the A330 has enough thrust to climb and cruise at higher altitudes more aligned with what SimBrief may suggest, and having more thrust does make for a more pleasant aircraft to fly.
Because people are having to dump fuel to get below MLW on perfectly normal flights. Contingency fuel somewhat scales with trip fuel so longer flights a lot of times that extra 5% can be enough to be a problem
I kind of agree with this but change the curve. For example, high 90s N1 can stay the same as it is now. But cruising at 70-75% makes no sense. You could decrease the power supplied at lower N1s to have it cruise around the 89-90% that the manuals in this topic suggest, which would keep the peak power for climbing but also make the cruise more realistic and fix the fuel burn in one go.
Update some new findings:
People complaining about the lack of power might have used the N1 value displayed on RR engines. Here on an RR engine A332, you can see the cruise N1 is 77%. If you look up the charts above, which are for GE CF6 engines, the N1 should be over 90%.
The problem is that PW and RR engines measure engine power using the Engine Pressure Ratio (EPR), while GE measures it using N1. For some reason I don’t know, the N1 of GE engines is significantly higher than that of RR and PW engines.
The following is the relationship among EPR, N1, and fuel flow for A330-300 RR Trent 772 engines in M0.82 cruise. The three values represent EPR, N1, and FF per engine in kg, respectively.
EPR, N1 and FF Reference Table for A330-300 RR Trent 772 (M0.82 Cruise)
Below is the N1 trend of different engines as the weight and FL increase. You can clearly see that GE engines require a higher N1 than RR engines on every occasion.
Excellent analysis, I’m starting to think the aircraft was more accurate before the N1 was adjusted. It’s also interesting to see how much it differs between the different engine types but, as much as I would like it, I doubt we will get this reflected in the sim. Hopefully we can have the fuel flow updated though as the CEO burning less than the NEO is criminal!
