UAL747
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Joined: Mon Dec 13, 1999 5:42 am

787 Engine Position - Proportionally Wider?

Sat Dec 31, 2011 10:10 pm

I've been looking at a lot of photos and videos of the 787. The engines seem to be spaced farther out on the wings than other Boeing or Airbus twins. I know that in twins, the closer your thrust is to the centerline of the aircraft, the easier the aircraft is to handle in an engine out scenario. The L-1011's wing engines were very widely spaced in comparison to the DC-10. This had to do with the 2nd engine being closer to (or right on) the centerline of the L-1011. The DC-10, with its 2nd engine positioned higher than the centerline, required the engines on the wings to be closer to the fuselage for better handling capabilities in an engine out scenario. Here are some photos of what I'm trying to describe:

787


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Photo © Bo Kim



777


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Photo © Miguel Nobrega - Madeira Spotters



767


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Photo © Erwin van Dijck



Also, if you watch Jon Ostrower's video of the ANA 787 first flight, at 4:26, you will notice that the engines seem placed much higher from the field of view than any of the other two planes, which leads me to believe that they are indeed farther out on the dihedral.

http://www.youtube.com/watch?v=2V2r3yNxc2I&feature=related

I have also noticed that the 787 seems to have a shorter landing gear than the A330, and has a more squatted appearance, yet it has larger engines. Could this also be because the engines are farther out on the dihedral, allowing for more ground clearance?

Maybe I'm just seeing things, but if this is true, what would allow Boeing to put the engines in this position? I know it is said that the L-1011 engines actually helped alleviate wing stress during flight (assuming wingflex). Anyone have any ideas?

UAL

[Edited 2011-12-31 14:11:41]
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way
 
Ruscoe
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RE: 787 Engine Position - Proportionally Wider?

Sat Dec 31, 2011 11:13 pm

On the 777 the centre of each engine is 31' 6.5" from the midline
On the 787 it is 31' 11" but the 777 fuselage is 1'5" wider making the 787 engines appear even further out

Also the 777 engine is wider so will also appear closer to fuselage than 787 engine

The closest point of contact for the bottom of each engine nacelle (not the front where the air goes in, this is higher) for the 777 is
0.7m to 0.88m depending upon loading and for the 787 is .77 to 1.07m so the engines are higher off the ground in the 787.

The 787 numbers I have used are 2 years old so there may be variances from the current design.

Ruscoe
 
PGNCS
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RE: 787 Engine Position - Proportionally Wider?

Sun Jan 01, 2012 1:35 am

Quoting UAL747 (Thread starter):
The L-1011's wing engines were very widely spaced in comparison to the DC-10. This had to do with the 2nd engine being closer to (or right on) the centerline of the L-1011. The DC-10, with its 2nd engine positioned higher than the centerline, required the engines on the wings to be closer to the fuselage for better handling capabilities in an engine out scenario.

The DC-10 and L-1011 center engines are both on the lateral centerline. The L-1011 engines could go much further outboard because of the larger rudder area available. The L-1011 rudder is VERY effective. As it was the DC-10 required an articulated rudder.
 
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Starlionblue
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RE: 787 Engine Position - Proportionally Wider?

Sun Jan 01, 2012 2:43 am

Quoting PGNCS (Reply 2):
The DC-10 and L-1011 center engines are both on the lateral centerline. The L-1011 engines could go much further outboard because of the larger rudder area available. The L-1011 rudder is VERY effective. As it was the DC-10 required an articulated rudder.

Quite. The L-1011 could have a bigger rudder since the engine was not in the fin.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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bikerthai
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RE: 787 Engine Position - Proportionally Wider?

Sun Jan 01, 2012 3:51 pm

Interesting thing about the 31 ft for both 777 and 787. Wonder if ground support vehicles comes into play when chosing this dimmension?  

bikerthai
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