Doing a near Max Takeoff Weight from Dubai to Auckland 16 hr flight taking off from 12R with an OAT of +39 the Takeoff Calculator when set to optimum gives me flaps 2, flex takeoff with packs on.

If I use the calculated numbers I will go off the end of the runway before VR.

I attempted the same takeoff three times using the exact numbers it provided all three times failed takeoffs.

It wasn’t until I removed the flex temp for full TOGA, set Flaps 3 with Packs Off was I able to get off the runway in time.

I think the T/O calculator needs to be looked at.

Yeah I’ve had a similar experience although did make it off out of Sydney (YSSY) for Dubai (OMDB), only 513 tonne but it gave me a flex of 74 and boy oh boy did we use some runway, I’ve never come that close to the end of a runway ever before, it did feel off.

Can confirm, it‘s really Bad!

Flew out of JFK RWY 04L with Head Wind, 24 C Temperaturen, TOW 536T, Flex 56C, Flaps 1+F and straight into the trees

I think, the calculator especially has the Problems with higher weights above 500T!

Try using the simbrief calculator, it gave me also flaps 1 but Flex 43, Not 56

Edited 12 hours ago12 hr by Matthias0412
Typo

Confirmed! I have a TOW of 1,198,000 (543 tonnes) and when I sync the weights and compute the numbers (that I got from simbrief), I get "NO VALID DATA".



UPDATE: This might be a SU7 beta issue (in regards to TOW) but like the other users above, I almost go off the end of the runway with the take-off numbers. I'll do another flight in SU6 to confirm.

Edited 12 hours ago12 hr by Veldetta

Another issue with the calculator I've found so far is the issue that it isn't able to compute V speeds for TOGA thrust. When selecting TOGA thrust in the calculator, it simply displays the same V speeds and even a flex temp as if you selected flex thrust.

I just tested this example from the original post... Also Dubai but runway 30L, I manually set weather to clear skies and OAT 40°C.

I loaded the aircraft vie EFB to exactly MTOW.

As you can see, the calculator only suggested me TOGA (I tried this 3 times) with Flaps 2. No Flex temp. to be seen anywhere (and you also wouldn't expect so).

As a result, I used about 70% of the runway before achieving actual lift-off.

What I noticed during some calulation trials is that the performance calculator doesn't give much variance in output values, especially for Vr, when at MTOW. I tried lowering the temperature gradually until about -10°C, there was almost no difference in the Vspeeds, only TOGA and always Flaps 2.

This only started to change when I also lowered the takeoff weight.

What would be important to know @oledurt which FLEX TEMP did it provide you? I find it really curious that your T.O Perf. suggest you a FLEX T/O at 39°C OAT at MTOW... When mine understandably doesn't. Also knowing your calculated Vspeeds would be helpful.

regarding @Veldetta I just looked at the SimBrief numbers, it shows TORA for 24L KLAX at 10285ft, not sure why you got 9541ft. That's less than 3000m. Maybe faulty sim scenery?

Depending on which variant you used, SimBrief says No-Go for the EngineAlliance variant. Also with RR it's only possible with bleeds off, TOGA and Flaps 3. Even with SimBrief's runway numbers (10885ft runway and TORA 10285ft) it's a very close call. Vr is reached just before the piano keys on the other side. You also have a slight tailwind, which doesn't help :D

What I also noticed is that the CG seems to be quite far forward by default, at least if you deliberately try to max out your load. In my tests I saw that you almost can't depart at MTOW without the CG being out of limits (forward). Depending on how accurately this is modeled, it would be something to consider. If your CG is out of the forward limit on takeoff, especially at MTOW, you'll have a hard time lifting your nose.

Maybe the envelope depiction on the EFB is wrong but anyway it would be great to have a possibility to manually adjust the CG by moving loads between compartments @iniBuilds (or maybe I'm stupid and didn't see it 🤔). If you load Cargo and Pax full, your ZFW CG is at the very forward edge of the envelope. Like I said, not sure how accurate all of these numbers already are but going by the current state of things, takeoff at MTOW is basically impractical in most cases because the CG is not in limits.

Sorry for this long post but I found this to be a very interesting topic, especially since many other people and myself included don't seem to have this issue.

I hope I could put some things into perspective, maybe you have time for some further testing. I wish you good luck ☘️

7 hours ago, MR.TX said:

Another issue with the calculator I've found so far is the issue that it isn't able to compute V speeds for TOGA thrust. When selecting TOGA thrust in the calculator, it simply displays the same V speeds and even a flex temp as if you selected flex thrust.

This can actually be correct, especially for such a large aircraft. In order to actually prove miscalculations though, it would be essential to provide the exact parameters (weather, weight etc.) and runways you used. The A380 takes up a lot of runway by default and the Vspeeds are calculated with lots of preconditions like runway condition, OAT, wind conditions but also obstacle clearance criteria (not sure if this is modeled here) or noise abatement procedures. So it can absolutely be the case that at certain weight/weather conditions for a specific runway, the Vspeeds don't change because the calculator deems it necessary for a certain required climb performance.

The A380 is also a 4-engine aircraft, which means losing an engine on takeoff roll at exactly V1 is not as hindering to acceleration as for a 2-engine aircraft. In the latter case, you'll lose 50-70% of your thrust, which prolongs the distance and time it takes to get from V1 to Vr. On the A380 it's maybe 25-30%. This is all taken into account when calculating V-speeds. So naturally, as V1 and Vr are only a few knots apart most of the time, I could imagine that the A380 doesn't really make a difference between FLEX and TOGA in terms of V-Speeds at higher takeoff-weights. As long as the runway isn't too short to begin with, the speeds don't need to change :)

52 minutes ago, SiebAir said:

I just tested this example from the original post... Also Dubai but runway 30L, I manually set weather to clear skies and OAT 40°C.

I loaded the aircraft vie EFB to exactly MTOW.

As you can see, the calculator only suggested me TOGA (I tried this 3 times) with Flaps 2. No Flex temp. to be seen anywhere (and you also wouldn't expect so).

As a result, I used about 70% of the runway before achieving actual lift-off.

What I noticed during some calulation trials is that the performance calculator doesn't give much variance in output values, especially for Vr, when at MTOW. I tried lowering the temperature gradually until about -10°C, there was almost no difference in the Vspeeds, only TOGA and always Flaps 2.

This only started to change when I also lowered the takeoff weight.

What would be important to know @oledurt which FLEX TEMP did it provide you? I find it really curious that your T.O Perf. suggest you a FLEX T/O at 39°C OAT at MTOW... When mine understandably doesn't. Also knowing your calculated Vspeeds would be helpful.

regarding @Veldetta I just looked at the SimBrief numbers, it shows TORA for 24L KLAX at 10285ft, not sure why you got 9541ft. That's less than 3000m. Maybe faulty sim scenery?

Depending on which variant you used, SimBrief says No-Go for the EngineAlliance variant. Also with RR it's only possible with bleeds off, TOGA and Flaps 3. Even with SimBrief's runway numbers (10885ft runway and TORA 10285ft) it's a very close call. Vr is reached just before the piano keys on the other side. You also have a slight tailwind, which doesn't help :D

What I also noticed is that the CG seems to be quite far forward by default, at least if you deliberately try to max out your load. In my tests I saw that you almost can't depart at MTOW without the CG being out of limits (forward). Depending on how accurately this is modeled, it would be something to consider. If your CG is out of the forward limit on takeoff, especially at MTOW, you'll have a hard time lifting your nose.

Maybe the envelope depiction on the EFB is wrong but anyway it would be great to have a possibility to manually adjust the CG by moving loads between compartments @iniBuilds (or maybe I'm stupid and didn't see it 🤔). If you load Cargo and Pax full, your ZFW CG is at the very forward edge of the envelope. Like I said, not sure how accurate all of these numbers already are but going by the current state of things, takeoff at MTOW is basically impractical in most cases because the CG is not in limits.

Sorry for this long post but I found this to be a very interesting topic, especially since many other people and myself included don't seem to have this issue.

I hope I could put some things into perspective, maybe you have time for some further testing. I wish you good luck ☘️

Notice how i manually selected toga and it still gave me a flex temp. I also manually changed it to flaps 3 packs off it originally was packs on and suggested a flaps 2 takeoff.