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Strange JT9Ds On Some 742s

Sat Jan 05, 2002 8:36 am

So- can anyone explain why there are a few 742 out there (Polar Air Cargo to name one) with JT9Ds that dont look like any other the other JT9Ds on 747s?? What I mean is, they look like the JT9D when used on the DC-10-40 or Airbus A300, they dont have that same look as UAs 742, NW 742s or any other ones I can find!

Whats the reason for the different cowlings and intakes?

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pictured is N921FT with JT9D-70As
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RE: Strange JT9Ds On Some 742s

Sat Jan 05, 2002 8:54 am

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RE: Strange JT9Ds On Some 742s

Sat Jan 05, 2002 10:56 am

The PW JT9D-70A in essence is a 7Q engine however with GE style cowlings.
From a operational view I have experienced two disadvantages, one the aircraft operating weights is a bit higher than traditional 7Q powered planes as the cowl structural design is bulkier and thus adds weight. The second operational problem I have seen is problems with the thrust reversers. The function of the reverser cowls is not as near reliable as the standard PW engine reversers leading to lots of sitautions were one of the reversers were considered inoperative. In addition due the limited success of the -70A engine, reverser repairs could be both time consuming and costly due to a lack of available parts.
From the desert to the sea, to all of Southern California
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RE: Strange JT9Ds On Some 742s

Sat Jan 05, 2002 1:41 pm

The 70A predated the 7Q and did not sell well. SAS, Flying Tigers, Air Madagascar ordered the 70.

I dumped at the gybe mark in strong winds when I looked up at a Porter Q400 on finals. Can't stop spotting.

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