Today when i go to fly from HAAB to OMDB the take of calculation give me take off settings some make me run out of runway before i reache V1.

Estimated TOW was: 211,713 kg

Take off performence used 215,000kg to add some extra safty margin with Take off.

The onboard TO Perf calculation give me this:

Flaps 2

Flex 67

v1:163

vr:164

v2:169

RW25L TODA: 3803M.

I have noticed that Flex 67 is given to me at ewery flight i do with the A350. That make non sens at all. Tempratur, QNH, TOW, RV attidue will allways afect the Flex temp, but not in this case.

When i run take off performence on simbreef i got totaly difrent result.

Flaps: 3

TOGA

v1: 131

vr: 131

v2: 139

Edited Monday at 09:41 AM1 day by SteinarG

6 hours ago, SteinarG said:

Today when i go to fly from HAAB to OMDB the take of calculation give me take off settings some make me run out of runway before i reache V1.

Estimated TOW was: 211,713 kg

Take off performence used 215,000kg to add some extra safty margin with Take off.

The onboard TO Perf calculation give me this:

Flaps 2

Flex 67

v1:163

vr:164

v2:169

RW25L TODA: 3803M.

I have noticed that Flex 67 is given to me at ewery flight i do with the A350. That make non sens at all. Tempratur, QNH, TOW, RV attidue will allways afect the Flex temp, but not in this case.

When i run take off performence on simbreef i got totaly difrent result.

Flaps: 3

TOGA

v1: 131

vr: 131

v2: 139

Hi,

Thanks for your detailed feedback. I will forward this thread to the team for further review.

Thanks again!

Hi again.

Its look like that the take off performence is calculated based on that the MTOW are 349.5tons. When i use the onboard take off performencetool this show up: MOTW(perf) 349.5 T. If the system belive that this aircraft have a MTOW at 349.5 tons, change ewerything, and my results in this tools start to make scense.

But that waigth its fare to high. Airbus A350-900 have a MTOW of 283 tons. For the A350-1000 is MTOW 322 tons.

I find quite large differences between the Simbrief tool and the OIS tool too. Here is QNH 1013, 15 degrees and no wind with TOW = 280 T and CONF 1 forced, giving 10 kts difference for the same configuration.

I have no clue which one is more accurate though, or how much arbitrariness is included in this. I would guess that the reason the aircraft does not do its own calculations (it's up to the airline/crew) is because there are many reasonable answers to the question.

Speaking of arbitrariness, switching the weight unit to 1000x lbs (and changing nothing else) gives very different results (a bug I found reported here but not acknowledged):

So something, at least, is broken.

Edited 5 hours ago5 hr by Gungnir