Re: Development of MD-11?

Date:         11 Feb 98 04:23:54 
From:         mweber@t140.aone.net.au (James Matthew Weber)
Organization: Customer of Access One Pty Ltd, Melbourne, Australia
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>	One disadvantage of mixed engines is that I suppose all engine-out
>performance figures would have to be figured for the worst case, with
>one of the larger engines inoperative. This could result in a lower
>maximum take-off weight for the same airframe.

I doubt this is as much of a problem as it seems to be. In the 1980's
Qantas had a 747-100 with 1 x JT9D-3A's, 1 X JT9D-7A , 2 x JT9D-7F. It
was a leased aircraft, but there is considerable variation in engine
performance there. My recollection is that covers about 40,000 to
48,000 pounds thrust.

I don't know what impact that had on procedures. I imagine it might
have made the autothrottles interesting, but QANTAS had so much
trouble with P&W autothrottles they disabled them quite early on so
that was a non-issue. Given that this was obviously  an early
747-100, I doubt it impacted the MGTOW at all. The thing was probably
certified for the -3A's.

My thoughts anyway.