Re: Air Speed

Date:         17 Sep 97 02:49:18 
From:         Mary Shafer <>
Organization: NASA Dryden Flight Research Center, Edwards CA
References:   1
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"Ruth or Doug Blue" <> writes:

> Several of us (non pilots) have been told that a large passenger jet should
> not descend below about 10,000 feet at more than about 250 knots air speed
> in controlled flight. Should that speed be inadvertently exceeded, what
> sort of problems would arise? We felt that they might be related mainly to
> temperature increase in the denser air, but wondered if anyone had detailed
> information.

The reason is that the FAA doesn't want really fast planes zipping
around down low.  This is a ATC rule, not physics.  It has nothing to
do with how the planes fly.  Should you exceed it without good reason,
you'll hear from ATC.  The plane will just keep flying quite happily.

If you can't fly that slowly for a good reason, then you're allowed to
fly faster.  We have had to fly some of our aircraft faster than the
250 kt limit because the planes don't fly well more slowly.  This is a
sufficiently good reason.  For example, the SR-71 that flew out of
Milwaukee last month was at about 300 KIAS at about 3,000' MSL.  No
problem with ATC.

Mary Shafer               NASA Dryden Flight Research Center, Edwards, CA
SR-71 Flying Qualities Lead Engineer     Of course I don't speak for NASA                               DoD #362 KotFR
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