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 October 19Oct 19 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 Tuesday at 07:33 PM5 days by Gungnir

Hi Gungnir

This calculation its been done based on numbers from the testflights before it got the redy to go from the gowerments.

Waigth

temprature

Wind

QNH

Runway slope

Runway attidue

All this listed things have inbact on the take off performence including terain around the Airport. It have no point to take off if the aircraft not are able to climb above high tarain. (a fix in the SID) Exs: D543 at 3200ft ore above.

In the earlig days the crew used tabels to calculate this take off settings. Today computers inside the aircraft own systems, ore on a tablet in the cocpit are used.

Your finding between using LBS ws KG its intresting. I am prety sure the your results on the OIS when using LBS is more likly the corect one.

What about the company T.O. Perf? Do they give you the same values?

9 hours ago, klusik said:

What about the company T.O. Perf? Do they give you the same values?

215Tons are 215tons at any airlines in the world. I get my ZFW from Viturale Emirates and the pax numbers to. I putt in paxnumbers and ZTW into simbreef when i create the flightplan. Company T O Perf. referare to the standar weight on bags and pax. If my weight on pax in simbreef is wrong, and i have given simbreef the ZFW and pax numbers, will the weight on bags and cargo be adjusted to mach my given ZFW. So in this case have that nothing to say.

Edited 5 hours ago5 hr by SteinarG
Added more details.

13 minutes ago, SteinarG said:

215Tons are 215tons at any airlines in the world. I get my ZFW from Viturale Emirates and the pax numbers to. I putt in paxnumbers and ZTW into simbreef when i create the flightplan. Company T O Perf. referare to the standar weight on bags and pax. If my weight on pax in simbreef is wrong, and i have given simbreef the ZFW and pax numbers, will the weight on bags and cargo be adjusted to mach my given ZFW. So in this case have that nothing to say.

I just meant if there is any discrepancy between V1/VR/V2 from TO from the APP (OIS), or if the T.O. PERF gets the same values if you fill the ZFW and so on. :-) Trying to find the core of the issue :-)

I mean now it's obviously late for that, but next time please just try to compute from INIT page where you can put ZFW and block fuel, you can compute the fuel there by "T.O. CPNY" or something like that, it leads you to a menu, where you fill up all values and hit compute and it just computes the values for you. If you could compare the values from this and from the OIS computed and from the Simbrief from Takeoff Performance tab :-)

Edited 5 hours ago5 hr by klusik
Just another paragraph explaining my reasoning

3 hours ago, klusik said:

I just meant if there is any discrepancy between V1/VR/V2 from TO from the APP (OIS), or if the T.O. PERF gets the same values if you fill the ZFW and so on. :-) Trying to find the core of the issue :-)

I mean now it's obviously late for that, but next time please just try to compute from INIT page where you can put ZFW and block fuel, you can compute the fuel there by "T.O. CPNY" or something like that, it leads you to a menu, where you fill up all values and hit compute and it just computes the values for you. If you could compare the values from this and from the OIS computed and from the Simbrief from Takeoff Performance tab :-)

Its not to late for me😁

T.O performence calculated at simbreef, OIS and via INIT page in the fmc, and 3 difrent results.

OIS:

V1: 131

VR: 140

V2: 147

FLEX: 57

FLAPS: 2

INIT PAGE:

V1: 135

VR: 138

V2: 146

FLEX: 47

FLAPS: 1

SIMBREEF:

V1: 135

VR: 141

V2: 147

FLEX: 52

FLAPS: 2

Airport: VTSP

RW:27

TEMP: 25

WIND: 290/08

QNH: 1011

Takeoff Weight: 229.2 TONS

OIS still give the higest FLEX temp, but the difrens from my findengs at HAAB some days ago are alott smaller now than that time i did the HAAB_OMDB flight. But we must have in mind that this product have got 1 main update and 1 hot fix in the mean time. I have no clue if the team have hade time to look at the problem at all before wee go this updates. I did some tast at ENGM after my flight from HAAB, and that test allso give me 2 totaly difrent results. Tonights test show results with only smal variation in the T.O Perf.