[Boundless]

>> ...abort a takeoff when you are nearing liftoff

> At that point, it's too late; you can't stop inside
> the confines of the runway because you've used most
> of it up and you're going too fast.

That depends on the airport, but generally, the takeoff
decision speed (V1) is lower than the rotation speed (Vr).

Aborting a takeoff below V1 is always theoretically
possible. Aborting above it is usually not recommended
if the runway length is near "Balanced Field Length"
(go around once instead).

> Aircrews check the plane's actual accelleration against
> its calculated accelleration at much lower speeds and
> abort at that point if they don't match.

Military crews do this.
Do civil crews also do it now?
Are civil airports signed for it?

This was raised as an issue when Air Florida flt 90
developed insufficient power on a departure from
Wash Nat (now Reagan), and ended up in the Potomac.

Had they been working an acceleration progress list
against runway markings, they would have realized
they had a problem, and either aborted, or firewalled
the throttles. Either would have saved them.

[Grut]

Military crews do this. Do civil crews also do it now?

Dunno, I'm working from 25-year-old memories of my AF days. An onboard computer probably checks accelleration automatically, now.