As sad as it may seem, the FMC (744/777) is pretty limited. It doesn’t have an obstacle database built in to it as and
Feather #3 has pointed out the Runway Length is part of the Navigation database and not the Performance database.
If ATC offers an intersection takeoff, the FMC has no way of calculating the
takeoff weights , so unless the crew have predetermined takeoff weights from that intersection or are ACARS equipped, the intersection can’t be used.
JTR , the chronological is something like this….
- Enter a tailored takeoff chart for the airport/runway/surface condition/MEL/ Flap Setting/ Thrust Setting.
- Read the limiting takeoff weight at the actual temperature
- If the actual weight is equal or lower than the limiting takeoff weight, enter the Actual Weight in the FMC. The FMC will produce takeoff speeds. Over write the V-speeds for any necessary corrections, such as wet / contaminated or MEL reductions.
(CAA certified aircraft has the option of Wet V-speeds on the FMC, FAA certified aircraft do not.):confused
The main place where this is limiting is for intersection takeoffs, we therefore add new runway’s (36* / 36# or similar) based on the takeoff distance from commonly used intersections. The end result is a lot of pages, therefore some are carried on the aircraft and others such as MEL Takeoff charts can be produced on demand in dispatch.
That’s our way of doing it, I’m sure that other airlines have totally different methods that suit them. If someone does know of a way of doing intersection takeoffs in these aircraft, I’d be interested in learning how.
Boeing has brought out a laptop computer program to allow crews to calculate takeoff weights in the cockpit. This was primarily designed to assist BBJ operators, but is now available for other aircraft types. (For a fee, of course..)
Twistedenginestarter, if you are doing a derated takeoff, you still have the same range of V-speeds.
Mutt. 
[This message has been edited by mutt (edited 29 September 2000).]