On Tue, 04 Nov 2003 17:00:12 GMT, Rick wrote:

Steven Shelikoff wrote:

Yeah, right. But not over and over

Well, duh ...

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.

Not true. But that was the point of my original statement, that the
tires are more likely to be heated by the wheels and brakes than cooled
by them.

... 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.

Not really apples to apples. RTO's at V1 are rare in any event and when
they do occur it is likely because of a tire, or multiple tire failures
so there is little braking available in any event.

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.


They are aerodynamically most efficient at high speeds but they do not
provide the majority of braking nor are they required to be used or even

They really only work well at high speeds, not low speeds.

desired at all times. They cannot be used until the engine is at idle,

They may not be used or desired at all times, only about 99% of the
time.

there is weight on the wheels, they buckets have cycled open, and the
engine spooled up again. By this time the autobraking has slowed the
aircraft considerably. They must not be used below around 60 knots to
prevent compressor stalls and sucking up garbage. They are useful only
in a very narrow range, not at the highest speed where brakes are needed
most or at the rollout when autobraking is off and manual braking is
used. They are hard on engines and the modern design trend is toward no
reversers, depending instead on carbon brakes.

None of that changes the fact that aircraft braking requirements and
capabilites and tire heating have nothing to do with race car or boat
trailer braking or tire heating. While it may be true for aircraft
braking that the tire is more likely to be heated by the brakes then by
the heat from tire friction, that's not true for most types of racing
and especially NASCAR restrictor plate racing, when the brakes aren't
even used but the tires still get very hot and might benefit from
cooling through the wheel.

Steve