Re: Virgin 747 birdstrike

From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
Date:         27 Dec 95 21:43:55 
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>The Pratt & Whitney engines UAL and other airlines use on their 767s are
>virtually identical to the engines they use on their 747s ...
>United keeps only one engine type "in stock" for their 767/747 fleet.

Close, but you missed one significant detail.  United has both old and
new 747s and 767s.  These statements are only true for the newer ones,
the 747-422 (and -451) and 767-322(ER), which use the PW4056 and PW4060
engines, respectively.

The older aircraft use various versions of the JT9D:

    747-122, -123	JT9D-7A
    747-238B		JT9D-7A
    747-222B		JT9D-7R4G2
    767-222		JT9D-7R4D

The JT9D-7R4D and -7R4G2 have one more compressor stage than the
JT9D-7A, and have a greater diameter and slightly shorter length,
so clearly the JT9D-7A can't be interchanged with the other two.
The JT9D-7R4G2 is several hundred pounds heavier than the JT9D-7R4D,
so I suspect they aren't interchangeable either.

Karl Swartz	|Home
Moderator of sci.aeronautics.airliners -- Unix/network work pays the bills