Re: Air Speed

Date:         17 Sep 97 02:49:18 
From:         "JCSFlyboy" <jcs@flyboy.com>
References:   1
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Ruth or Doug Blue <theblues@axionet.com> wrote in article
<airliners.1997.2180@ohare.Chicago.COM>...
> 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.

You heard correct sir. Except that that rule goes for all aircraft...not
just passenger jets. (However, military aircraft operating in an active
Military Operating Area (MOA) can go any speed they wish.) Below 10,000
feet is the most crowded airspace there is. (Not many Cessna 150's go above
10,000.) This rule exists to slow aircraft down so they may better look for
other traffic and to help ATC prepare arriving/departing traffic a smooth
flow in that airspace. Occasionally, ATC will ask or grant you permission
to exceed the 250 knot speed restriction. Also, remember, if you have an
emergency, you can deviate from any ATC instruction or FAR in order to deal
with that emergency (FAR's 91.3 and 91.123). Not only is there the 250
rule, but there's more! Now I'll quote you the obligitory regs:

FAR 91.117        Aircraft Speed

a) Unless otherwise authorized by the FAA Administrator, no person may
operate an aircraft below 10,000 feet MSL, at an Indicated airspeed of
more than 250 knots (288 m.p.h.).

b) Unless otherwise authorized or required by ATC, no person may operate
an aircraft at or below 2,500 feet above the surface within 4 nautical
miles of the primary airport of a Class C or Class D airspace area at an
indicated airspeed of more than 200 knots (230 m.p.h.).  This paragraph
(b) does not apply to any operations within a Class B airspace area.  Such
operations shall comply with paragraph (a) of this section.

c) No person may operate an aircraft in the airspace underlying a Class
B airspace area designated for an airport or in a VFR corridor designated
through such a Class B airspace area, at an indicated airspeed of more
than 200 knots (230 m.p.h.).

d) If the minimum safe airspeed for any particular operation is greater
than the maximum speed prescribed in this section, the aircraft may be
operated at that minimum speed.