Re: The Sporty Game -- Boeing 757

From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works
Date:         24 Mar 93 21:43:39 PST
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In article <airliners.1992.43@ohare.Chicago.COM> gregory@bcstec.ca.boeing.com (Greg Wright) writes:
>In article <airliners.1992.27@ohare.Chicago.COM> kls@ohare.Chicago.COM (Karl Swartz) writes:

>>I'm *still* surprised that Boeing hasn't made much noise (maybe none)
>>about plugging this obvious hole by offering a 757-100 or whatever --
>>a shortened 757 like the original proposal and a real replacement for
>>the 727-200.  Even with United it never seemed to come up, instead all
>>the discussion focussing on a massively stretched and pulled and re-
>>designed 737-600.  True, a 757 is more expensive (~ $45 million versus
>>$30 - 35 million) but the changes embodied in the 737-600 would surely
>>have added tremendously to the price.

> I think that you will find that every attempt at a shortened version
>of one of our planes has had limited success. Take the 747SP for example.
>Airlines tend not to like the sorted versions very much. In $/seat or $/mile
>these versions are too expensive to run. There is a real problem having
>too much engine or wing with them. We find it is better to stretch if
>anything....

I agree that the shortened Boeings haven't done all that well.  But
look at them carefully and I think you'll find it has more to do with
the fact that these planes filled only a small market niche or missed
what the market really wanted.

The 720 was the first shrunken Boeing, if you'll accept that it was a
707 shortened and modified for medium-range work.  The airlines wanted
something cheaper to operate than the 707 and the 720 didn't make that
significant a dent in operating costs -- it couldn't with four engines.
Boeing knew that, but perhaps hesitated to do the right thing because
the airlines were not sufficiently confident in jets to accept only
two engines and the compromise of three was too weird.  Of course the
compromise ultimately *was* produced, in the form of the 727, and was
a very successful aircraft indeed.

The 747SP, in contrast, simply never had a large market, at least not
as far as I can see with 20-20 hindsight.  The DC-8-62 had already
shown that, while a market existed for a really, *really* long range
jetliner, it just wasn't that big.  Small wonder tht only 45 instances
of the 'SP were produced.  (I would expect the A340-200 to be somewhat
less than a stellar success for similar reasons.)

The only other shortened version of a Boeing that comes to mind is the
737-500.  I'm not sure if it's better to think of it as a shortened
-300 or a new technology 737-200, with the -300 as the stretched
version which just happened to be built first.  In any case, I don't
have any references handy but it wouldn't come as a great surprise if
the -500 hasn't done as well as the larger -300, even factoring out
the fact that the -300 has been around for a much longer time.  On the
other hand I suspect the -500 has done better than the largest 737,
the -400.

In contrast to at least the 720 and the 747SP, there would seem to be
a huge market for an efficient 727-200 replacement, or if you prefer a
150-seat airliner with a trans-continental range.

The question, then, is whether or not a shortened 757 (let's call it
a 757-100) could efficiently fill this role.  My first impression was
that since the 757 started off at this size, and was stretched to the
180-seat range primarily to secure British Airway's launch order, the
150-seat version would be easy, much like doing the 737-500 well after
the 737-300 came out.  Any fool can guess, though, and this fool ;-)
wanted some hard numbers to back up such an argument.

After tracking down said numbers, I put my response on ice (note that
the original exchange took place last autumn) as the number said the
job of shrinking the 757 would really be quite an undertaking.  For
comparison, here are a few key figures:

    model	pass	range	MGTOW	w.span	w.area	engines		thrust
    -----	----	-----	-----	------	------	-------		------
    737-200(A)	120	 2840	128.6	  93.0	  980	2 JT8D-17A	16000
    737-300	141	 2950	139	  94.8	  980	2 CFM56-3B2	22000
    737-400	159	 2800	150.5	  94.8	  980	2 CFM56-3C1	23500
    727-200(A)	145	 2240	191.5	 108.0	 1560	3 JT8D-15A	15500
    757-200	186-220	 4550	220	 124.8	 1951	2 PW2037	38250

where range is maximum still-air in miles, weight is in pounds, and
wing span and area are in feet and square feet, respectively.  For the
727 and 737 I listed the heaviest version for each series; the 220,000
lb. 757 is the *lightest* for that type.  All numbers are from a spec
chart in AW&ST (March 16, 1992).

Clearly the 757-200 is a *much* larger aircraft than the 727-200 in
every regard.  Creating a 757-100 to replace the 727-200(A) would most
likely entail significant redesign of the wing (reduced span would
probably be an operational requirement due to gate space, while the
much larger area suggests greater drag -- producing greater lift to
permit the higher weights and range, but the higher performance would
not be necessary and thus the drag wouldn't be acceptable).  Landing
gear would most likely be redesigned too, at least the mains, to use
two-wheel mains to save some weight.  And then there are the engines:
as discussed elsewhere in this group, shrinking the RB.211 and PW2000
doesn't seem likely, yet switching to the CFM56 or V2500 has quite a
few liabilities as well.

Working from the other direction, a 737-600 would probably need a new
wing (but so might the 757-100) and new landing gear (the 737-400 is
already at the length limit with the current gear) but the engine
options seem more reasonable.  Given the price difference the 737
would probably be much more attractive to airlines.

I'm still not convinced a further stretched 737 is the right plane to
address this market, but a shrunken 757 doesn't seem feasible.  (The
prospects for a wholly new airframe would likely be even worse.)

--
Karl Swartz	|INet	kls@ditka.chicago.com		
1-415/854-3409	|UUCP	uunet!decwrl!ditka!kls
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