777guy

When does Max Takeoff Weight occur?

In other words, if I release brakes and apply takeoff power 200 pounds heavy, have I violated Max Takeoff Weight?

If burn off the excess 200 pounds during takeoff roll prior to rotation, am I legal?

This is a nit-pick question obviously, but one that has come up none-the-less.

Does anyone know where the exact definition of Max Takeoff Weight can be found? And, when does Takeoff occur? At thrust increase or liftoff?

Thanks in advance for your ideas on these questions.

DeltaT

The way I would look at it is this: All the performance figures of how much runway you are going to chew up in the take off roll, V1 point, obstacle clearance, factoring the thrust setting, are going to be based on the start weight prior to putting the throttles up.
The thing is, that its all worked out for one engine (2 engine plane) from V1, so the reality is in a normal take-off you will exceed obstacle heights anyway, but we can't be 100% certain the engine won't fail can we! But that is a side issue.
If you are overweight at roll start, then you will go beyond the V1 point you should have (on the runway), and now if you were to stop at your overweightV1 you may not be able to before the runway end.
Obviously, this can go further, that if you have really exceeded MTOW, you might not get to VR before the runway end!!!

Think of it this way.
Max Structural Weight when at the gate ready for Push.
MTOW when lined up ready to roll/takeoff.

SNS3Guppy

Takeoff performance is predicated on your weight at the start of the takeoff roll.

It's reasonable to plan on burning X amount in taxi, when preparing your takeoff performance, based on the weight you will have when you reach the runway for takeoff. It's not reasonable to plan your takeoff performance based on the weight you think you might have at some point in or after the takeoff roll.

The ability to stop during a rejected takeoff isn't predicated on the weight after the takeoff roll, but the weight at the time of the reject. This means you plan for the weight at the start of the roll...not the middle or the end.

esreverlluf

In addition the Boeing performance limitations books (at least for the 767 and 747-400) define MTOW as "the maximum weight at commencement of takeoff roll - ie Brakes Release Weight".

Doesn't leave much room for argument . . .

411A

Three words.
Brakes release weight...IE: at the start of the takeoff roll.

Old Smokey

Aircraft Performance Certification DOES NOT consider fuel burned following brake release.

I think that that says it all.....................

Regards,

Old Smokey