Re: B747 technical questions

Date:         28 Jul 97 01:13:27 
From:         kls@ohare.Chicago.NOSPAM.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
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>To my knowledge, the only time a fifth engine has been added to the B-747
>is during testing of new engine designs; a la B777. In this case, the
>fifth engine can be and is used during flight.

As noted in other posts, fitting a fifth engine for ferry purposes is
a relatively routine, if not common, operational situation.

For testing, the engine being tested almost always replaces one of the
standard engines.  This was certainly true for GE's 747-100 engine
testbed, used to flight test the GE-90, and for the original 747-100
which Boeing used to flight test the 777's other PW and RR engines.
To do otherwise would require substantial structural modifications --
in these cases, an engine with substantially greater thrust than the
original engines was being tested, and you couldn't just stick that
on the wing at any old place.

There are probably several counter-examples, but the only one I can
think of is a 720 (or maybe a 707) that PWC used to flight test small
engines.  In this case, the test engine was mounted near the nose of
the plane.

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