Charles Oppermann wrote:
I disagree that this is true generally. Everything I've read about
anti-lock braking systems suggests that they will outperform humans under
all but a few special conditions. The special conditions are the cases
where locking the wheels is beneficial to a short stop.


This is good info, thanks. Here's a nugget from the NTSB report on the SWA
accident at Burbank:

"At the request of the Safety Board.s Airplane Performance Group, Boeing ran
stopping distance simulations for this accident wherein maximum, medium, and
minimum 737 autobrake applications, as well as maximum manual brake
applications, were simulated for wet runway conditions after the 182-knot
touchdown. These data indicate that the accident airplane would have
required about 5,000 feet of runway length after touchdown to stop using
maximum autobrakes and about 4,700 feet of runway length after touchdown to
stop using maximum manual brakes."

These were simulations, though, and not tests. It would be curious to
see actual test data to see if the simulations are relatively accurate.


Still, that's not to say that manual braking would always result in shaving
off 300 feet of the ground roll. I guess it depends on the exact conditions
and pilot experience and technique.

Yes, every situation is somewhat unique.


My current opinion is that stomping on the brakes would have been worse than
allowing the Autobrake system, but that's just a WAG.

Impossible to know for sure. This is one case where it actually might
have been better if the airplane had left the runway earlier and got
into some grass or softer area. That might well have allowed a shorter
stop than did staying on the runway. Then again, if they'd have hit
something more solid by doing this, they might have saved the child's
life, but lost lives on the aircraft. No way to know.


Matt