Re: B737 Hush Kits

From:         Greg Smith <102040.3106@CompuServe.COM>
Organization: Boeing Commercial Aircraft, Wichita Division
Date:         17 Aug 95 04:58:53 
References:   1
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kls@ohare.Chicago.COM (Karl Swartz) writes:
> >A question that I've not heard answered is whether the 737-200 can either
> >be refurbished to a -300 or otherwise fitted with fanjets ...
>
> You probably want to ask about the -500, which is the same length as
> the -200 whereas the -300 is stretched roughly ten feet.  In any case,
> the heavier engines of the newer models, and especially their forward
> position, necessitated the repositioning of the wing further back on
> the fuselage to maintain a reasonable CG.  There are lots of other
> changes, too, but clearly, upgrading a 737-200 to a -500 (or -300)
> would be infeasible.
>
> The -200 does in fact have fanjets, though not with a very high bypass
> ratio, and certainly not as efficient as those on newer aircraft.  I
> haven't heard of any re-engining programs, though there are several
> for the 727, which uses similar models of the JT8D engine.

			737 Fuselage & Plug Lengths

	      Fuselage	   Forward Plug		    Aft Plug
Model	     Length (in)  Rel. to -100 (in)      Rel. to -100 (in)

-100		1087		N/A			N/A
-200		1163		 36			 40
-300		1267		 80			100
-400		1387		152			148
-500		1173		 26			 60
-600		1173		 26			 60
-700		1267		 80			100
-800		1497		198			212

As you can see from the above table, the only 737 models with the same
lengths are the -300/-700 and -500/-600.  The wing structure was not moved
in the center fuselage and wing structure, plugs were added forward and
aft of the wing, but relative to the nose, the wing is moved on the models.
The wing front spar is approximatly 38% down the length of the fuselage
on the -100 and -200, vs 37% on the -500/-600, 39% on the -300/-700, and
41% on the -400/-800.

I haven't checked the weight and balance loadability charts for the various
models, but I think the main reason for not re-engining the -200s is cost
and scale of the modification, not weight and balance considerations.
The wing attachments and wing internal structure which support the
strut/nacelle/engines is completly different between the -200 and newer
models.  I wouldn't be suprised if you would have to change the entire
bottom wing skin and all of the internal wing structure in the strut area.
You would also probably have to change the leading edge flaps, because
they are tailored to nestle around the specific strut/nacelle
installations.

--
Greg Smith
Weight Engineer 737-700 Program
Boeing Commercial Aircraft, Wichita Division
102040.3106@compuserve.com