Re: passenger stairs in aircraft tail

From:         rdd@netcom.com (Robert Dorsett)
Organization: Netcom Online Communications Services (408-241-9760 login: guest)
Date:         27 Jun 95 01:43:14 
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In article <airliners.1995.873@ohare.Chicago.COM> Martin Fiddler <entmlf@staffs.ac.uk> writes:
>Certain aircraft - the DC9 / MD80 family, and the british BAC-111, have
>stairs that lower from beneath the tail.   Obviously these are very useful
>at remote airfields, as portable stairs are not needed for the passengers
>to enter and exit.  Possibly there are other aircraft with the same
>facility too.
>
>Why don't all aircraft have them?   Is it something to do with the rear
>mounted engines on the above two models?    I guess it's much more complex
>from the rear pressure bulkhead aspect, but that doesn't explain why, say,
>the B737 doesn't have them but the DC9 does.

The DC-9 does not have arstairs.  You are confusing it with the 727, which
lowers airstairs out the back.

The DC-9 does have an emergency exit in the back tailcone, but it is not
used for normal operations.

Both the 737 and DC-9 have had miscellaneous other options, such out pop-
out stairs in the front entry.

The reason they exist at all is for remote field operations.

The reason they are not used is because they are heavy, which translates into
money, and they are not needed: it is very rare for an airliner in the United
States, for example, not to be greeted by a jet-tube, and even rarer still
for an airliner to land at an airport which can't scare up some stairs (al-
though I was once on a 747 which diverted to Windor Locks, and the best they
could do was some rickety air-stairs for a 737: it was about a 6-foot jump
for the crew, so they opted to exit through the electronics compartment :-)).

The reason you see the 727 stairs down all the time is as a counter-balance,
so the airplane doesn't rock back on its tail with a light fuel load.  You
will often see a supporting rod  as well.





--
Robert Dorsett                         Moderator, sci.aeronautics.simulation
rdd@netcom.com                         aero-simulation@wilbur.pr.erau.edu
                                       ftp://wilbur.pr.erau.edu/pub/av