panais
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Posts: 227
Joined: Mon May 05, 2008 1:50 pm

Airplane Length And Width Relation

Wed Jun 30, 2010 9:47 am

There have been a number of discussions on a plane's width and its suitability to a market. For example, some A.neters say that the CS300 is a better plane than the A319/B737-700 because it has a smaller width and therefore, less drag that its competitors, even if it is longer that them.

Also, you have the A340-600 which is longer and narrower than the B777, but it did not fare well because among other things it was heavier.

The question is how long can a manufacturer go with a certain width before it is too long.
 
rwessel
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Joined: Tue Jan 16, 2007 3:47 pm

RE: Airplane Length And Width Relation

Wed Jun 30, 2010 10:04 pm

I don't think there's a hard-and-fast rule, but longer is definitely worse from a structural perspective, while wider is worse from an aerodynamic perspective.

It's a bit interesting to note that two of the "longest" airliners, the MD-82 and the A346 have similar fuselage length to width ratios, a bit over 13:1. The 773 is about 11% shorter on a width basis than the A346.

The construction matters too - I think many people are expecting CFRP, which is much stiffer, to make longer tubes more practical.
 
dw747400
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Joined: Wed Aug 15, 2001 8:24 am

RE: Airplane Length And Width Relation

Thu Jul 01, 2010 12:55 am

Quoting rwessel (Reply 1):
I don't think there's a hard-and-fast rule, but longer is definitely worse from a structural perspective, while wider is worse from an aerodynamic perspective.

The structure/aerodynamics are definitely the biggest factors, but you also have operational considerations. Increased turning radius, needing a larger parking area, and of course increased turnaround times.

On the positive side, provisioning and servicing the airplane may be easier--on a short, fat aircraft (the A380 as a double decker is a prime example) your personnel and equipment are all competing for a limited amount of plane-side space.
CFI--Certfied Freakin Idiot
 
panais
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Joined: Mon May 05, 2008 1:50 pm

RE: Airplane Length And Width Relation

Thu Jul 01, 2010 7:09 am

Quoting rwessel (Reply 1):
The construction matters too - I think many people are expecting CFRP, which is much stiffer, to make longer tubes more practical.



Interesting point there.

I did a check on two of Airbus's aircraft, the A321 and the A333, both fuel efficient in their category, carry a lot of passengers, medium range and the fuselage length to width ratio was 11.27 and 11.28 respectively.

The other Airbus aircraft that comes very close to this with 11.22 is the A350-900 which is meant to be fuel efficient, carry a lot of passengers but long range.

There seems to be an valid point on the use of the CFRP panels.

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