Takeoff Obstacle Limit Weight 737
 

Good afternoon!

I digged a little into manual calculation of take-off performance and there is 1 thing I can't understand.

We need to calculate the 'Takeoff Obstacle Limit Weight' using DISTANCE FROM BRAKE RELEASE and OBSTACLE HEIGHT. (FCOM - Performance Dispatch - Takeoff)

Where am I supposed to find the information about those heights and distances? In OPT I can look for this kind information but there are some problems too.

1) OPT distances are calculated from the liftoff RW end (not from brake release as FCOM states)
2) Imagine if we have OPT fault and we calculate all the performances manually so we don't have this access to OPT data, therefore, we have NO information at all

Any ideas?

Thank you!