On Mon, 03 Nov 2003 17:11:20 GMT, Rick wrote:

Steven Shelikoff wrote:

aircraft brakes are in many cases under engineered since they
depend so much on engine braking to slow down.

Incorrect. The brakes on transport category aircraft are certified to
stop the aircraft on the runway remaining after a rejected takeoff at
the highest speed it would still be on the ground (V1) without using
thrust reversers. Thrust reversers provide little braking at high speeds
anyway.

Yeah, right. But not over and over and if that does happen, i.e.,
stopping the plane with the remaining runway after an aborted takeoff,
you're almost guaranteed a brake fire. No matter how the brakes are
certified, if a heavy gets up to takeoff speed on most runways, aborts
and only has the brakes to stop it, chances are it's gonna go off the
end of the runway.

And I'm not sure where you get the idea that thrust reversers provide
little braking at high speeds. They way they work, they really *only*
provide braking at high speed and very little at low speed. They are
the vast majority of braking at landing speed.

While a jet thrust reverser can be used to back up the plane, very
little thrust is actually "reversed". Mostly, it's just diverted into
an unuseful direction, like up and down or outward, and very slightly
forward for backing up. They slow the plane mostly by engine drag, not
by reversing the thrust forward. And engine drag is greater at higher
speeds. In fact, most of the accidents involving thrust reversers occur
when they are inadvertantly or uncommanded deployed in flight, causing
massive drag on the deployed side and throwing the plane out of control.

Steve