TopJet001
Topic Author
Posts: 9
Joined: Mon Jul 17, 2006 2:25 am

Why No More Large Twin-jets?

Thu Aug 10, 2006 6:24 pm

Why are manufacturers moving away from the DC9, MD80/90 and B717 design. As we all know Boeing ended production of the 717 in May, and as far as I can tell the only manufacturer to continue production is Embraer with their ERJ family.

It seems that manufacturers (including Embraer with their newer 170/175/190/195 models) want to stay with the traditional - engine-under-wing design. Why is this? More efficient, better aerodynamics...?

I'm sorry if a similar topic has been posted before - I'm fairly new to Airliners Net.


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Andy  Smile
 
BA380
Posts: 1441
Joined: Mon May 17, 2004 9:59 pm

RE: Why No More Large Twin-jets?

Thu Aug 10, 2006 6:30 pm

the title is a little confusing... I thought the A350XWB, 777 and 787 were all twin jets  Wink
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viv
Posts: 2953
Joined: Tue May 31, 2005 5:17 pm

RE: Why No More Large Twin-jets?

Thu Aug 10, 2006 6:31 pm

Quoting TopJet001 (Thread starter):
seems that manufacturers (including Embraer with their newer 170/175/190/195 models) want to stay with the traditional - engine-under-wing design. Why is this?

The weight of the engines offsets lift-induced stress on the wing.

Rear-mounted engines generally necessitate a T-tail, which brings its own problems of structural integrity, masking of the tail surfaces with risk of deep stall at high angles of attack - in turn necessitating the installation of a stick-pusher, etc.

Large-diameter fan engines do not make for easy rear-fuselage mounting.
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CRJ900
Posts: 1940
Joined: Wed Jun 02, 2004 2:48 am

RE: Why No More Large Twin-jets?

Thu Aug 10, 2006 7:00 pm

Quoting Viv (Reply 2):
Large-diameter fan engines do not make for easy rear-fuselage mounting.

The MD90 had to be extended 1,5 meters ahead of the wing to avoid the aircraft tipping on its butt due to the new and heavy IAE V2500 engines.

Quoting Viv (Reply 2):
Rear-mounted engines generally necessitate a T-tail, which brings its own problems of structural integrity, masking of the tail surfaces with risk of deep stall at high angles of attack - in turn necessitating the installation of a stick-pusher, etc.

Could this be one of the reasons why the stretched CRJ900X is still not launched? The engines will be the same (with same weight?) as on the CRJ900, though...
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Glareskin
Posts: 1002
Joined: Fri Jun 03, 2005 9:35 pm

RE: Why No More Large Twin-jets?

Thu Aug 10, 2006 7:16 pm

Fuse mounting saves on the landing gear. The 737 is an intermediate solution: engines with flat-bottom nacelles. The 757 shares the 737 fuselage but due to the bigger engines it needed a higher landing gear.
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