c5load
Topic Author
Posts: 344
Joined: Tue Sep 16, 2008 9:40 pm

Cargo Aircraft Efficiency

Sun Jun 13, 2010 1:05 am

Why are some models of airplanes more efficient for carrying cargo than others? For example, the A332F is better than the A333F (if there ever was one) as far as weight-carrying capability. The 763ERF is better than the 764F. But in both of those examples, the larger airplane has more room inside than the other, so why wouldn't manufacturers build the larger model of that series to suit the needs of a cargo carrier. The 744F is capable, the MD-11F is capable, so why can't the 764 be capable or the A333 be capable?

One last example is the new Boeing KC-X tanker, which IIRC is built on a 762 frame with winglets. But wouldn't a 764 with the raked winglets and longer fuselage hold more cargo and fuel and still be able to go just as far if not further?
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BMI727
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RE: Cargo Aircraft Efficiency

Sun Jun 13, 2010 4:56 am

Quoting c5load (Thread starter):
A333F (if there ever was one)

There might be on a conversion basis, but it would most likely be used for hauling packages.

Quoting c5load (Thread starter):
But in both of those examples, the larger airplane has more room inside than the other, so why wouldn't manufacturers build the larger model of that series to suit the needs of a cargo carrier.

Because most of that extra room would be wasted on a flight of any length, as the aircraft would reach its maximum weight at a lower volume. This is why the 777F is built off of the 77L airframe, as it allows it a large payload and a greater range.

Quoting c5load (Thread starter):
But wouldn't a 764 with the raked winglets and longer fuselage hold more cargo and fuel and still be able to go just as far if not further?

Not likely for two reasons. First I think that there was a field length requirement that the other 767s would have trouble meeting, and second, using either of the longer 767 models could leave insufficient boom clearance on rotation.
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sunrisevalley
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Joined: Tue Jul 06, 2004 3:26 am

RE: Cargo Aircraft Efficiency

Mon Jun 14, 2010 12:50 am

Quoting c5load (Thread starter):
Why are some models of airplanes more efficient for carrying cargo than others?

There are a number of considerations. Very important are the Uniform Load Devices ( ULD's) that the industry has grown up around and that are interchangeable from carrier to carrier. Do a search on Google under "ULD's" to get some idea of all that are in use. IATA have a spec sheet on the various sizes. The Emirates brochure at http://www.skycargo.com/Images/B777F%20A4%20Brochure_tcm79-421138.pdf shows how efficiently the 777F space can be used with just a few ULD types. The ability of an aircraft type to be loaded as close to the max available volume with these contributes greatly to it's efficiency.
Cargo density is another issue. Different carriers haul different types of cargo and the density varies greatly starting as light as about 120kgf/m3 of ULD space for packet carriers. Another group are in the 150 to 170kg/m3 density for package carriers and so forth. At the other end of the scale is the example that one of the subscribers to the list quoted ; he flew for SQ Freight and one particular load was a one piece propeller shaft for a bulk freighter. I don't remember what it weighed but it was substancial.
 
Viscount724
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Joined: Thu Oct 12, 2006 7:32 pm

RE: Cargo Aircraft Efficiency

Mon Jun 14, 2010 1:03 am

Quoting BMI727 (Reply 1):
Quoting c5load (Thread starter):
But wouldn't a 764 with the raked winglets and longer fuselage hold more cargo and fuel and still be able to go just as far if not further?

Not likely for two reasons. First I think that there was a field length requirement that the other 767s would have trouble meeting, and second, using either of the longer 767 models could leave insufficient boom clearance on rotation.

Another issue for the tanker is the ramp space required for parking, so overall length and wingspan are important criteria.
 
thegeek
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Joined: Mon Nov 26, 2007 7:20 am

RE: Cargo Aircraft Efficiency

Mon Jun 14, 2010 4:03 am

Not only would the extra hold space be wasted, but the extra fuselage weight would contribute to MTOW (and MZFW) and therefore actually reduce the amount of cargo which could be carried. It all comes down to the fact that cargo is denser than pax. Not sure why the 742F didn't work better based on the shrink 747SP either. Perhaps it was a too radical shrink.
 
XT6Wagon
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Joined: Tue Feb 13, 2007 4:06 pm

RE: Cargo Aircraft Efficiency

Mon Jun 14, 2010 6:53 am

Quoting thegeek (Reply 4):
747SP either. Perhaps it was a too radical shrink.

747SP was a very comprimized design. Its only benifit over the 747-100 was extra range. The shorter fuselage cut lower cargo hold volume, and the wieght savings doesn't translate to payload. Oh and the 747 was designed around a fairly heavy cargo density so cutting volume to cut wieght isn't approprate.

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