Simbrief V speeds

1st Official Post

    Does anyone else use SimBrief? it works great with the A350, even with an out-of-date Airac; route building works well on most of the longhauls I've done, and fuel burn predictions are amazingly accurate.

    My question is about V speeds (specifically at light weights. The OIS seems to give incorrect V speeds (and possibly wrong To-off trim settings, Simbreif gives correct lower V speeds.

    The issue is that the OIS speeds are so high for the gross weight, the aircraft will want to become airborne before V1 (depending on CG) The speed difference between Aerofly OIS and SimBrief/real world can be as much as 15/20 knots.


    Landing VLS for various gross weights are correct in both the OIS and SimBrief

    This shows the difference in speeds at 249 tonnes

    Simbrief

    V1 - 146
    VR - 150
    V2 - 160

    OIS

    V1 - 160
    VR - 167
    V2 -176


    Edited 2 times, last by 777Driver (January 3, 2026 at 5:43 PM).

    • Official Post

    I still have to check when and how the real aircraft changes the VLS from takeoff to flight phase computations. The VLS we use is the same for both and with that the takeoff speeds must be higher, otherwise you would immediately be in a low speed state after lift off according to the VLS displayed on the PFD.

    The v-speeds can also be calculated and inserted directly by double clicking the MFD text entry fields. The computation works a bit different here, so the values may not be identical to the OIS computations.

    Obviously we also don't know where SimBrief get's its values from and if we can rely on that or if they just happen to work with other addon aircraft for other simulators but are actually incorrect.

    If you have a real world table for the v-speeds for our exact weight variant (as shown on the OIS), then I'd be happy to use those instead. But we're not going copy data from someone else where we're not sure if they are correct and how they obtained them.

    • Official Post

    Like I said, we also base our values on VLS data from the real aircraft but the data may be different for takeoff. Not sure why they do this but perhaps the additional thrust component directed upwards is accounted for here which isn't credited for horizontal flight and stall? I'd have to dig deeper into the logic.