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AA777223
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Freighter Ranges

Mon Mar 23, 2009 5:00 pm

All this business with the crash of the FX MD-11 in Tokyo has caused me to ask a question I have wondered for a long time. Why do freighter variants of aircraft have such diminished ranges? I realize that people need much more personal space, and cargo can be packed into a plane with much greater density, but at the end of the day, the MTOW of freighter aircraft is typically identical or very similar to their passenger counterparts. If this is the case, a fully laden passenger 744 (for example) or MD-11 (as it is in the news today), shoud have the same range as its freighter counterpart. Any more info would be greatly appreciated.

As a sidenote, I am very sorry about the accident in Tokyo this morning. My best to those affected.
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Stitch
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RE: Freighter Ranges

Mon Mar 23, 2009 5:07 pm

Freighter aircraft can carry much heavier payloads then passenger planes, so they dedicate more of their TOW to payload instead of fuel, resulting in lower range.

A 747-400F, for example, can lift 46t more payload then a 747-400 (113t vs. 67t). So with both planes at maximum payload with identical TOWs, the 747-400F will carry 46t less fuel then the 747-400 and that "missing" fuel is worth many thousands of kilometers in range.

[Edited 2009-03-23 10:14:30]
 
wilco737
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RE: Freighter Ranges

Mon Mar 23, 2009 5:08 pm



Quoting AA777223 (Thread starter):
Freighter Ranges

The MD11 can carry about 93 tons of cargo that would be pretty much like 930 passengers. And I haven't seen an MD11 with so many seats yet.
And the more you loaded, the more fuel you need. So less range.

wilco737
 
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AA777223
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RE: Freighter Ranges

Mon Mar 23, 2009 5:19 pm

Well, do they have the ability to carry as much fuel- meaning similar tank sizes? or is it just that the AC is packed with as much freight as possible, and only enough fuel is loaded for the trip?
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wilco737
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RE: Freighter Ranges

Mon Mar 23, 2009 5:21 pm



Quoting AA777223 (Reply 3):
Well, do they have the ability to carry as much fuel- meaning similar tank sizes? or is it just that the AC is packed with as much freight as possible, and only enough fuel is loaded for the trip?

You can load the same amount of fuel as the passenger version. You put in as much cargo as you can and then the fuel and when you find out you are too heavy to reach your destination you can either land somewhere or you offload cargo.

wilco737
 
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AA777223
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RE: Freighter Ranges

Mon Mar 23, 2009 5:30 pm



Quoting WILCO737 (Reply 4):
You can load the same amount of fuel as the passenger version. You put in as much cargo as you can and then the fuel and when you find out you are too heavy to reach your destination you can either land somewhere or you offload cargo.

I meant only load sufficient fuel for the trip, plus the neccesary safety margins, and then load freight at a significantly high density to reach max TOW.

So, in theory, a 77F loaded with the same cargo payload as a passenger 77L, filling all fuel tanks to the same levels on the both aircraft, they will have the same range?

They have the same fuel capacity, same max TOW, etc. So, using your theory, no matter whether its passenger or freight, both aircraft are designed completely the same, and should therefore have the same range?
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wilco737
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RE: Freighter Ranges

Mon Mar 23, 2009 5:35 pm



Quoting AA777223 (Reply 5):
So, in theory, a 77F loaded with the same cargo payload as a passenger 77L, filling all fuel tanks to the same levels on the both aircraft, they will have the same range?

If both have the same payload on board: yes. If you can compare 77F with 77L from the aerodynamics and fuel load.

For the MD11. Take the F and PAX version. Both loaded with 40 tons, same CG, same amount of fuel, then you have the same range.

wilco737
 
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AA777223
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RE: Freighter Ranges

Mon Mar 23, 2009 7:09 pm



Quoting WILCO737 (Reply 6):
If both have the same payload on board: yes. If you can compare 77F with 77L from the aerodynamics and fuel load.

For the MD11. Take the F and PAX version. Both loaded with 40 tons, same CG, same amount of fuel, then you have the same range.

Great. I had always wondered this. Why then are the advertised ranges so much shorter than their passenger counterparts? If an airline wanted to severely limit their fuel load and increase their payload, they could do the exact same thing that freight operators are. I suppose that Boeing, airbus, MacDac and all the others are simply advertising range at max payload. Is this correct?
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haynflyer
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RE: Freighter Ranges

Mon Mar 23, 2009 7:23 pm

I compared all passenger aircraft and their feighter variants and came up with the same question as the OP. I have deduced that the answer lies in marketing.

The stated ranges have nothing to do with the MTOW but rather the "anticipated" load for the aircraft's mission. Since pax aircraft will have a much lower TOW than freight aircraft, they can fly farther.

What the manufacturer's should do is state range as X,XXXnm at XX,XXX TOW for a true apples to apples comparison.

It's a bit like how auto manufacturers state two MPGs, one for city conditions and one for highway conditions. Same vehicle. Same GVW. But different fuel ratings based upon the anticipated mission of the vehicle.

So in our case, the passenger versions will have the "highway" (longer) range while freighters will have the "city" (shorter) range.

I think that works for me.....
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B777LRF
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RE: Freighter Ranges

Mon Mar 23, 2009 8:11 pm

The answer lies in the smaller difference between MFZW and MTOW that you have on a freighter. In other words, whilst any given freighter and passenger version of the same aircraft type may well have the same MTOW, the freighter will often have a much higher MZFW, thereby allowing for a much higher payload.

Therefore, if you load a freighter up to MZFW and do the same with a passenger version of the same aircraft, the freighter will use a proportionally bigger portion of the available weight (MTOW) for payload than the passenger aircraft. This means that a pax version will have a bigger proportion of MTOW available for fuel, and hence will have more range.

So if an airline markets an MD-11F with a given range, based on max payload (MZFW), it will have shorter range than a MD-11 pax.

However, a 77L will fly longer than a 77L if loaded with same fuel quantity and no payload. This because the Freighter has a considerably lower empty weight, what with the absence of 300ish seats as well as galleys and lavs.
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BMI727
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RE: Freighter Ranges

Mon Mar 23, 2009 8:59 pm

1. Freighters, I think, tend to be heavier due to the extra structure in the floor.
2. Cargo tends to be heavier than pax.
3. Unllike, pax airlines, cargo carrriers generally won't use payload restrictions. After all, your new laptop doesn't care if it has to make a fuel stop in ANC while people would complain loudly.
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tdscanuck
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RE: Freighter Ranges

Mon Mar 23, 2009 11:21 pm



Quoting AA777223 (Reply 7):
Why then are the advertised ranges so much shorter than their passenger counterparts?

Because the advertised range is based off of the expected mission. The payload for a freighter mission is *way* higher than for a passenger mission.

Range numbers, by themselves, are essentially meaningless other than comparing relative range within a type. The payload range curves (in the airport planning documents) are far more informative. Nobody actually buys or flies aircraft based off of the spec range value.

Quoting AA777223 (Reply 7):
If an airline wanted to severely limit their fuel load and increase their payload, they could do the exact same thing that freight operators are. I suppose that Boeing, airbus, MacDac and all the others are simply advertising range at max payload. Is this correct?

The max range value is typically full fuel, then add payload (passengers + cargo) to MTOW. For example, on a 777-200LR (pg. 3 of this PDF http://www.boeing.com/commercial/airports/acaps/777rsec3.pdf) full fuel then payload to MTOW gets you to a range of about 9300 nautical miles, which is what you find as the "maximum range" number here:
http://www.boeing.com/commercial/777family/pf/pf_lrproduct.html

If you start lowering payload beyond that value your range goes up because TOW is dropping, even though you can't carry any more fuel. This is why the ferry range of most commercial aircraft is far greater than their spec max range.

Quoting Haynflyer (Reply 8):
The stated ranges have nothing to do with the MTOW but rather the "anticipated" load for the aircraft's mission. Since pax aircraft will have a much lower TOW than freight aircraft, they can fly farther.

They are related to MTOW because that forms one of the limit curves that define the range-payload envelope. Depending on the payload and range you're talking about, you can be limited by MZFW, MTOW, or fuel capacity. A freighter trades fuel for payload, resulting in the same TOW but a much lower range.

Quoting Haynflyer (Reply 8):

What the manufacturer's should do is state range as X,XXXnm at XX,XXX TOW for a true apples to apples comparison.

This is exactly what they do in the payload-range charts. Any discussion of range should start there, not with the OEM spec range.

Tom.
 
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Stitch
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RE: Freighter Ranges

Tue Mar 24, 2009 12:55 am



Quoting AA777223 (Reply 7):
I suppose that Boeing, Airbus, MacDac and all the others are simply advertising range at max payload.

For freighters they do.

For passenger planes it is usually just passengers and bags. Ranges at actual maximum structural payloads for passengers plane are a good bit shorter then what the websites give. You can find the actual ranges in their PDFs.
 
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RE: Freighter Ranges

Tue Mar 24, 2009 1:07 pm

How should I see the new generation of full freighters such as the B777-200LRF, A330-200F and the B747-800F. These cargo aircraft are marketed as having a larger range capability but do the aircraft manufacturers mean that the aircraft can be loaded with cargo to the max and still fly the maximum range (full tanks) the aircraft can take? Can these new generation freighters take-off fully loaded from high altitude airports or do they still need to refuel along the way on longhaul flights if they want to take-off fully loaded from high altitude airports?

A388
 
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RE: Freighter Ranges

Tue Mar 24, 2009 1:17 pm



Quoting A388 (Reply 13):
These cargo aircraft are marketed as having a larger range capability but do the aircraft manufacturers mean that the aircraft can be loaded with cargo to the max and still fly the maximum range (full tanks) the aircraft can take?

There's no way they can be loaded with max payload AND full tanks. That would put any airliner (freight or otherwise) today way above MTOW.

Typically, the only time an airliner is filled to the brim with fuel is for ferry flights, with minimal payload.
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RE: Freighter Ranges

Thu Apr 09, 2009 6:49 pm



Quoting Starlionblue (Reply 14):
There's no way they can be loaded with max payload AND full tanks. That would put any airliner (freight or otherwise) today way above MTOW.

I believe the 747-400ERF disagrees with you. But that is the only example I can think of
 
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RE: Freighter Ranges

Thu Apr 09, 2009 7:24 pm

Another factor is revenue and profit optimization. If you can fly a freighter with full payload shorter distances, stop into a freight hub and offload (e.g. PANC), and then continue with another full load to another hub, you make more money then if you flew payload restricted because you want to fly the maximum range of the aircraft with the reduced payload. The downside would be more airframe cycles but that's part of the trade-off.
 
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RE: Freighter Ranges

Thu Apr 09, 2009 10:02 pm

I believe that one factor is that passengers desire as few stops as possible, while freight, as BMI727 aptly notes, doesn't care. This means that freight operators can make a fuel stop when that is more economical than carrying enough fuel for a nonstop flight, and I suspect most of them do so. The constraint comes when fuel stops delay delivery too much; so you still want reasonable range.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
tdscanuck
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RE: Freighter Ranges

Fri Apr 10, 2009 1:19 am



Quoting 413x3 (Reply 15):

I believe the 747-400ERF disagrees with you. But that is the only example I can think of

According to the Boeing data for the 747-400ERF, MZFW is 611,000 lbs and max fuel is 361,700 lbs. If you went to max payload then max fuel you'd be at 972,200, which is 59,700 lbs over MTOW.

Tom.
 
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RE: Freighter Ranges

Fri Apr 10, 2009 10:44 pm



Quoting AA777223 (Reply 5):
I meant only load sufficient fuel for the trip, plus the neccesary safety margins,

You always just add enough fuel for the trip. Don't get technical here I know we sometimes tanker a little or add for Min landing fuel but generally speaking... Anytime you add more than you need you're going to burn more just because of the extra wgt. We do KIX-MEM and used to do CDG-SFS and 12 hrs is definitely long enough for me.
 
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RE: Freighter Ranges

Sun Apr 12, 2009 4:35 am



Quoting B777LRF (Reply 9):
The answer lies in the smaller difference between MFZW and MTOW that you have on a freighter. In other words, whilst any given freighter and passenger version of the same aircraft type may well have the same MTOW, the freighter will often have a much higher MZFW, thereby allowing for a much higher payload.

I understand that freighters have heavier main decks to support the cargo. Does this deck structure allow for the entire increase in MZFW or are there factors?

Quoting B777LRF (Reply 9):
However, a 77L will fly longer than a 77L if loaded with same fuel quantity and no payload. This because the Freighter has a considerably lower empty weight, what with the absence of 300ish seats as well as galleys and lavs.

Clearly with a lower empty weight (OEW?) and a higher MZFW for a given MTOW, payload will go *way* up and range will go down.  smile 
How does this work out in conversions? I can see where a 767BCF wouldn't quite reach the OEW of a 767F but could have the same MZFW. That would give the two the same range with the F carrying a little more payload. Sound about right?  scratchchin 
Thanks,
Cary
 
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Stitch
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RE: Freighter Ranges

Sun Apr 12, 2009 2:12 pm



Quoting Caryjack (Reply 20):
Clearly with a lower empty weight (OEW?) and a higher MZFW for a given MTOW, payload will go *way* up and range will go down.  Smile
How does this work out in conversions? I can see where a 767BCF wouldn't quite reach the OEW of a 767F but could have the same MZFW. That would give the two the same range with the F carrying a little more payload.

Comparing an average 767-300ER with an average Boeing/Aeronavali 767-300ERSF passenger to freighter conversion:

Boeing 767-300ER MZFW: 130t
Boeing 767-300ERSF MZFW: 134t

Boeing 767-300ER OEW: 89t
Boeing 767-300ERSF OEW: 83.5t

Boeing 767-300ER MSP: 41t
Boeing 767-300ERSF MSP: 50t

MSP = Maximum Structural Payload
 
Caryjack
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RE: Freighter Ranges

Tue Apr 14, 2009 5:41 am



Quoting Stitch (Reply 21):
MSP = Maximum Structural Payload

Thank you.
MSP looks like the maximum allowable weight of the payload plus the usable fuel.

Boeing 767-300ER MZFW: 130t
Boeing 767-300ERSF MZFW: 134t
Boeing 767-300F MZFW: 140t

Boeing 767-300ER OEW: 89t
Boeing 767-300ERSF OEW: 83.5t
Boeing 767-300F OEW: 85t

Boeing 767-300ER MSP: 41t
Boeing 767-300ERSF MSP: 50t
Boeing 767-300F: MSP: 55t

I took some 763F specs from the Boeing site and penciled them in. They seem reasonably to me except the OEWs. I would have thought that the F version would have a lower OEW than the SF version.
I could have used a different data sheet or made a conversion error (tonnes right)? It could also be that the same structures that add 10t of MZFW to the 767F also add to the OEW.

Off topic but how much weight can there be between Max Taxi Weight and MTOW on, say a 767? A 20 minute taxi can't use much, right? Maybe 300lbs? It seems like MTW might be one of the lesser referenced specs.

Thanks,
Cary
 
rwessel
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RE: Freighter Ranges

Tue Apr 14, 2009 9:48 am



Quoting Caryjack (Reply 20):
I understand that freighters have heavier main decks to support the cargo. Does this deck structure allow for the entire increase in MZFW or are there factors?

Actually strengthening the main deck won't increase MZFW at all. Typically you need to strengthen the wing root (and/or center wing box) a bit, plus beef up the landing gear if you end up with a higher maximum landing weight.
 
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RE: Freighter Ranges

Tue Apr 14, 2009 10:46 am



Quoting Rwessel (Reply 23):
Actually strengthening the main deck won't increase MZFW at all. Typically you need to strengthen the wing root (and/or center wing box) a bit, plus beef up the landing gear if you end up with a higher maximum landing weight.

Increasing MZFW does not necessarily increase maximum landing weight. It just allows you to use a greater portion of it for cargo instead of fuel, which is what most freight operators want. Upgrading the gear is a very expensive proposition.
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Stitch
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RE: Freighter Ranges

Tue Apr 14, 2009 2:17 pm



Quoting Caryjack (Reply 22):
I would have thought that the F version would have a lower OEW than the SF version.

The dedicated freighter probably has more structure to support heavier floor loads then the converted freighter. They will reinforce the passenger deck, but usually the floor loading varies from section to section and tends to be lower towards the front and back of the plane compared to the dedicated freighter.
 
phollingsworth
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RE: Freighter Ranges

Fri Apr 17, 2009 1:51 pm



Quoting SEPilot (Reply 24):
Increasing MZFW does not necessarily increase maximum landing weight. It just allows you to use a greater portion of it for cargo instead of fuel, which is what most freight operators want. Upgrading the gear is a very expensive proposition.

In most cases if you increase MZFW you will see an increase in MLW. As you change the missions rules in your design the amount of fuel you will be expected to land with will change, but the increase in MZFW often forces and increase in MLW (there just isn't enough buffer in the passenger version's MLW). All of the Boeing widebody freighters on offer now have higher MLWs than their passenger counterparts.

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