Newsgroups: sci.aeronautics.airliners
From: barr@ash.mmm.ucar.EDU (Keith Barr)
Subject: Re: Need Opinion: Possible Mechanical Failure?
Date: 24 Jun 93 13:38:18 PDT

In article <airliners.1993.472@ohare.Chicago.COM> you write:
>I was on a flight from Indianapolis to Washington National on U.S. Air
>flight #1506, June 15th.  About 15 minutes before landing, the lights
>in the plane went out, except for the emergency lights on the floor
>aisle.  The engines became silent, and our downward motion accelerated
>quickly.  The plane remained level.  We eventually landed without incident.

This sounds pretty normal to me.  I don't know if it was an evening or
night flight, but it is normal procedure to turn out the cabin lights so
the passengers eyes can adjust to the darkness, in case an emergency
evacuation becomes necessary.  The rapid, quiet descent can be explained
by the fact that most jets are very "slippery", and can be hard to
slow down while descending.   The best way to slow it down is to pull the
throttles back to flight idle, possibly deploy the spoilers to their
flight position, and point the nose downhill.

>I have been on a few dozen flights in my life, and have *never* experienced
>such a drastic loss of power.  If the pilot's explanation was correct, is
>it acceptable for air traffic control to be giving such short notice that
>such drastic measures need to be taken?

ATC can ask for any rate of descent, but the pilots do not have to accept
the clearance if they feel it is excessive.  The penalty for denying a
clearance, however, could be length delays that would surely cause
pasx complaints.

I have friends who fly for United into Denver, and they complain fairly
regularly about the descents that are given to them here.  In general,
apparently aircraft are handed off to Denver approach at FL220 (roughly
22,000 feet above sea level), at cruise descent airspeed.  Approach then
requests them to cross Keann at FL170 at 250 knots, which is only a few
miles ahead.  To comply with the crossing restriction is sometimes a
problem, but doable if passenger comfort is somewhat sacrificed.

In the tight airspace surrounding IAD and DCA, I would guess that steep
descents would be regularly called for.
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| Keith Barr                  \           \   \__      _____
| barr@ncar.ucar.edu           \___________\   \/_______\___\_____________
| COMM/AS&MEL/IA/A&IGI         /           ( /_/   .....................  `-.
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