B737 T/O Performance - V SPEEDS UNAVAILABLE
Hello gents,
ran into a problem recently with the trusty 737... Departure from Nairobi, runway 06, slight tailwind of four knots. B738 SFP, heavy at 78.5 tons estimated TOW, 16°C. According to the T/O performance charts the best bet was a Flaps 1, no bleed, improved climb takeoff. V-speeds in the charts obviously quite high. Entering flaps 1 on the Takeoff ref page blanks the QRH speeds with the 'V SPEEDS UNAVAILABLE' message - so the FMC would exceed the maximum V speed increase to stay above minimum control speeds... The FCOM says 'takeoff is not permitted' - according to the takeoff performance charts allow for a takeoff in this case though, with fitting high V-speeds... Eventually the TOW was nearly two tonnes less on the actual loadsheet, we ended up doing a flaps five takeoff (no bleed again) - the FMC happily provided v-speed suggestions for flaps five.
In any case - if the takeoff performance charts allow for a takeoff (giving own V-speeds) and the FMC gives 'V SPEEDS UNAVAILABLE' - where do we stand? The speeds from the takeoff analysis charts will allow for enough margin to the control speeds, so can that message be disregarded? Any ideas? Reported this to the performance department as well, I will post their answer...
Last edited by STBYRUD; 29th Jul 2013 at 17:07.