Re: Reverse Thrust

From:         ehahn@fairlite.mitre.org (Ed Hahn)
Organization: The MITRE Corporation, McLean, Va.
Date:         22 Mar 94 09:52:38 PST
References:   1 2 3
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In article <airliners.1994.1026@orchard.Chicago.COM> "Donald A. Hazle" <DAH@PSUVM.PSU.EDU> writes:

   Is reverse thrust used on some aircraft in flight to slow a decent?  I
   thought I had read in this newsgroup that reverse thrust was locked
   out during flight on most aircraft.  However, on a 1968 approach to
   Washington National (from northwest to southeast over the Potomac), the
   flight attendant announced; "the noise you hear are the engines running
   in reverse to control airspeed during our descent".
   The aircraft was a DC-9 an there was a higher amount of noise than normal
   coming from the rear.  I never heard this announced on any other flight.

   Don Hazle  Penn State University
----
For an airliner, reverse thrust is never used to slow an aircraft (in
flight, that is).  In fact, a Lauda Air B767 came apart in flight when
one of the thrust reversers deployed in flight accidentally over
Southeast Asia a few years back.  (The FAA has issued an Airworthiness
Directive about this.)

My conjecture regarding the noise in the DC9 is that the aircraft was flying
with full flaps, thus creating a lot of drag, in turn requiring a
fairly high power setting to maintain airspeed (not an unusual
situation on the River Visual approach to DCA).

In general, aircraft will use wing spoilers (i.e. mid-chord wing
panels that deploy upward - easily seen on B727s) for speed control.

The one exception is the F28/F100 (Fokker), which has a clamshell
spoiler at the tip of the rear fuselage (you can see the hinges
for the shells a few feet forward of the end of the fuselage).  The
wing actuated panels on these aircraft are LIFT DUMPERS, and are ONLY
actuated on the ground for braking purposes.  American Airlines,
USAir, and the new Midway are the primary US operators of this Dutch
twinjet.

Hope this helps, with a minimum of unintentional disinformation...
ed