New MD-80, MD-88 tailcones?

[Philip Papadopoulos]

I noticed on a recent trip that some MD-80's (MD-88's, too) have
"flattened" tailcones (versus conical ones). Could someone give
me some history on this development. It looks like it is
a retrofit product on older MD-80's. Can you find
out why the new design tailcone was adopted (fuel efficiency,
stability?) How much does it cost to refit an older plane and
what are the monetary benefits? When was the "new" tailcone
introduced.

BTW, the flattened and elongated tailcone is very apparent on
American jets, less so on Delta Jets. I saw about 8 Northwest
MD-8x's and none had the flattened cone. All the American Jets
I saw did have the new cone (about 15 examples) and most
(but not all) of the Delta jets had flattened tailcones.

Thanks,
Phil

[Robert Dorsett]

In article <airliners...@ohare.Chicago.COM> you write:
>I noticed on a recent trip that some MD-80's (MD-88's, too) have
>"flattened" tailcones (versus conical ones). Could someone give
>me some history on this development. It looks like it is
>a retrofit product on older MD-80's.

They were installed on all new MD-80 series airliners starting in the late
80's, as part of a weight and drag reduction program.

---
Robert Dorsett
r...@cactus.org
...cs.utexas.edu!cactus.org!rdd

[Hayes N. Press]

In article <airliners...@ohare.Chicago.COM>
papa...@cs.utk.edu (Philip Papadopoulos) writes:

>I noticed on a recent trip that some MD-80's (MD-88's, too) have
>"flattened" tailcones (versus conical ones). Could someone give
>me some history on this development.

The "flattened" tailcones were designed as a replacement/design change
on all MD-80 series aircraft since at least 1986. It was done to decrease
fuel comsumption by both decreasing drag at the tail and by the change
to the use of more composite material. As far as I know, no airline is
actively retrofiting their tailcones but they may replace them with the
newer designed one when and if a replacement is needed.

>BTW, the flattened and elongated tailcone is very apparent on
>American jets, less so on Delta Jets. I saw about 8 Northwest
>MD-8x's and none had the flattened cone. All the American Jets
>I saw did have the new cone (about 15 examples) and most
>(but not all) of the Delta jets had flattened tailcones.

The main reason for your observation probably has a lot to do with fleet
age and mix. American Airlines has the largest fleet of MD-80's with
over 200, and at one time this was the record for the industry of one
airline have such a large fleet of one type aircraft. The Northwest aircraft
you observed were probably all DC-9 series aircraft and these older models
gennerally have not been changed. To the best of my knowledge NW has no
MD-80's in its fleet. And Delta falls right in the middle.

Speaking only for myself and all standard disclaimers apply.

Hayes

[Stefano Pagiola]

Robert Dorsett writes

> > I noticed on a recent trip that some MD-80's (MD-88's, too) have

> >"flattened" tailcones (versus conical ones). (...)

>
> They were installed on all new MD-80 series airliners starting
> in the late 80's, as part of a weight and drag reduction program.

The "flattened" tailcones are usually referred to as `screwdrivers.'
Their design is essentially the same as that of the MD-11's tailcone.
I'm not sure which came first; certainly the MD-80s had them first,
but I vaguely remember a Douglas employee telling me that they were a
result of design work for the MD-11. I believe their advantage is
primarily lower drag.
All new MD-80s have them (I have somewhere the info on when the
switch was made, if anyone is interested). In addition, some
airlines have retro-fitted them to older MD-80s. Alaska is one that
comes to mind.
I wonder if Air Canada's updated DC-9-30s will have them?

--
-
Stefano Pagiola
Food Research Institute, Stanford University
spag...@leland.stanford.edu (NeXTMail encouraged)
spag...@FRI-nxt-Pagiola.stanford.edu (NeXTMail encouraged)

[IanMaclure]

The flattened tailcone came out around 1987(?).
The reason was I believe a 1 or 2% increase in
fuel efficieny.
Retrofitting ought to be relatively easy as the tailcone is
merely an aerodynamic fairing which can be ejected if it
is desired to use the rear bulkhead emergency exit.
Hope this helps.

IBM
--
################ No Times Like The Maritimes, Eh! ######################
# IBM # ian_macl...@QMGATE.arc.nasa.gov (desk) #
# aka # mac...@toulouse.arc.nasa.gov (currently) #
# Ian B MacLure # mac...@eos.arc.nasa.gov (internet port) #

[Analytical Methods {NWNet}]

Actually, the "screwdriver" tailcones are not retrofitable onto
older MD-80s and DC-9s. A friend of mine at Douglas tells me that they
went through hell certifying the new tailcone. This was because the
tailcone is jettisonable in an emergency and counts as an emergency
exit. The old tailcone would fall free reliably and not foul the exit,
but the new tailcone wouldn't. Hence modifications were necessary to
allow it to be certified. The screwdriver (we call it a beavertail)
show a 1% improvement in cruise and I once had the idea of selling a
retrofit program for putting them on older aircraft, but this
certification problem killed my idea. However, I would guess that the
MD-11 tailcone is retrofitable on the DC-10.

-Dave Lednicer
Analytical Methods, Inc.

[Geoff Miller]

mac...@eos.arc.nasa.gov (IanMaclure) writes:

>Retrofitting ought to be relatively easy as the tailcone is
>merely an aerodynamic fairing which can be ejected if it
>is desired to use the rear bulkhead emergency exit.

Speaking of emergency exits, were some DC-9s and MD-80s built
without the tail stairway? I don't remember which airline it
was on, but I seem to recall seeing an emergency information
card that either made no mention of the tail stairway or had
separate evacuation instructions for airplanes with and without
it. (The ejectable tailcone seems to be present on all versions,
however.)

Geoff

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Geoff Miller + + + + + + + + Sun Microsystems
geo...@purplehaze.Corp.Sun.COM + + + + + + + + Menlo Park, California
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

[Hayes N. Press]

Reply-To: Geoff....@corp.sun.com

>Geoff....@corp.sun.com (Geoff Miller) writes:
>Speaking of emergency exits, were some DC-9s and MD-80s built
>without the tail stairway? I don't remember which airline it
>was on, but I seem to recall seeing an emergency information
>card that either made no mention of the tail stairway or had
>separate evacuation instructions for airplanes with and without
>it. (The ejectable tailcone seems to be present on all versions,
>however.)

The tail emergency exit is present on all but the DC-9-10 series. All
MD-80's have the emergency exit in the tail, as well as, larger DC-9's
since the extra door is needed to meet the FAA regulation for evacuation
within 90 seconds. The DC-9-10 does not need the tail exit since the exit
rule can be meet without it due to the passenger capacity being so small.

And on Ian's comment (just prior to Geoff's):
>Retrofitting ought to be !!!!! relatively easy !!!!! as the tailcone is
>merely .......
This shows that Ian obviously has never worked on the retrofit of a piece of
hardware (applies to software,too) that is use by scores of airlines in
hundreds of configurations. Nothing is easy when it comes to retrofits
in the commercial airline transport business. Not only do lots of federal
regulations and company guidelines need to be met, but also foriegn
regulations, airline operating procedures, and most of all crew training
changes.

[David S. Wise]

Geoff....@corp.sun.com (Geoff Miller) writes:

>Speaking of emergency exits, were some DC-9s and MD-80s built
>without the tail stairway? I don't remember which airline it
>was on, but I seem to recall seeing an emergency information
>card that either made no mention of the tail stairway or had
>separate evacuation instructions for airplanes with and without

What is worse, I listened to cabin attendants on one airline
(hint: it flew shiny, shiny MD-80s) read instructions verbatim
that said <roughly>
"This plane may [sic] be equipped with a rear exit door; in that case..."

Having heard this quote two or three times,
I pointed out that it would be rather late to check whether
there were actually a rear door, should it ever come time to my needing it.
I suggested that he (SDBCF) toddle on back and look, and then read only
the instructions for the stairs or for the slide---as appropriate.

Apparently, attendants are told to read *exactly* these instructions.
So the victims' estates are free to sue management? Or the FAA?

Sheesh! One would think that the emergency instructions would
be type-specific on "minor" things like the existence of exits! :-|
--
David S. Wise +1(812)855-4866; fax: +1(812)855-4829 dsw...@cs.indiana.edu
Computer Science Dept., Indiana University, Bloomington, IN 47405-4101, USA