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Freighter Take-offs  
User currently offlineA388 From Netherlands Antilles, joined May 2001, 9720 posts, RR: 11
Posted (5 years 2 months 1 week 1 day 4 hours ago) and read 5193 times:

Hi,

I was wondering, I always was under the impression that cargo aircraft are heavier compared to passengers aircraft. However, an example is the 747-400. Their MTOW as per the Boeing website shows similar MTOW values. So how do cargo aircraft compare to passenger aircraft when it comes down to their weights? Is one or the other indeed "heavier" or how should I interpret this?

A388

15 replies: All unread, jump to last
 
User currently onlineBMI727 From United States of America, joined Feb 2009, 15718 posts, RR: 26
Reply 1, posted (5 years 2 months 1 week 1 day 3 hours ago) and read 5080 times:

The MTOW is about the same. The difference is in loading. Pax flights are generally lighter anyway, and airlines may take restrictions to make a nonstop flight. Cargo operators on the other hand, will stuff their planes and make a stop if they have to. So, they are generally heavier on takeoff than their passenger carrying counterparts. After all, you probably wouldn't take too kindly to a stop in ANC, but that laptop you ordered couldn't care less.


Why do Aerospace Engineering students have to turn things in on time?
User currently offlineSeaBosDca From United States of America, joined Sep 2007, 5312 posts, RR: 4
Reply 2, posted (5 years 2 months 1 week 1 day 3 hours ago) and read 5029 times:

In general, purpose-built freighter versions will have the same MTOW as the corresponding passenger version, but their maximum landing weight will be higher. This allows the airline to use more of the takeoff weight for cargo and less for fuel, trading range for payload. This is why (for instance) the 777-200LR can fly 7400+ nm with its maximum payload, while the 777F (which has the same MTOW) can fly less than 5000 nm at maximum payload.

The increase in MLW generally requires strengthening of the floors and landing gear, at a minimum.


User currently offlineRutankrd From United Kingdom, joined Sep 2003, 2963 posts, RR: 7
Reply 3, posted (5 years 2 months 1 week 1 day 3 hours ago) and read 5005 times:
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Well its depends

The cargo carrier will have a reinforced floor and extra under floor beams, integral rollers for ease of movement/positioning of containers and additional load bearing strapping points
It will also need the addition doors suitable for handling containers.
In the case of the 747F a hinged nose door may be added.
ALL these add weight to the basic structure.

However galleys seating separation screens, cinema screen toilets and associate plumbing. Fitted stairs to the upper level and several intemediate bulkheads are stripped out Saving weight.

Oh and in the case of factory built 744F/748F use of the original sized hump saves significant weight on the final design as well !

BMI727 the best power departures I see regularly are from JAL B744Fs (Factory built).
They have a flight each weekend through LHR that goes on to Amsterdam (Currently virtually empty)
Must be air-born within 1000Ft and passing 3000Ft before end of 27R !


User currently offlineRFields5421 From United States of America, joined Jul 2007, 7605 posts, RR: 32
Reply 4, posted (5 years 2 months 1 week 1 day 3 hours ago) and read 5005 times:

While the MTOW will be very near the same - the big difference is the empty weight of the aircraft.

All those seats, galley's, overhead bins, carpet, entertainment systems, interior bulkheads, lighting, speakers, emergency oxygen - weigh several tons.

With that weight out of the plane - those tons can be used for paying freight.


User currently onlineAA777223 From United States of America, joined Feb 2006, 1232 posts, RR: 6
Reply 5, posted (5 years 2 months 1 week 1 day 3 hours ago) and read 5005 times:

I wrote a thread on this exact same topic recently. It seems that despite the MTOW being the same, cargo operators dedicate more of it to the payload than fuel. Therefore, theoretically, a freighter could have exactly the same range as its passenger counterpart aircraft, if it were just loaded with the same weight of payload as the passenger version with a full fuel load. You can search for my thread in tech ops.


Sic 'em bears
User currently onlineBMI727 From United States of America, joined Feb 2009, 15718 posts, RR: 26
Reply 6, posted (5 years 2 months 1 week 1 day 2 hours ago) and read 4971 times:



Quoting Rutankrd (Reply 3):
BMI727 the best power departures I see regularly are from JAL B744Fs (Factory built).
They have a flight each weekend through LHR that goes on to Amsterdam (Currently virtually empty)

747s, (or any plane really) do look like hot rods when empty.

Quoting AA777223 (Reply 5):
I wrote a thread on this exact same topic recently

And I think I wrote the same thing in that thread too.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 7, posted (5 years 2 months 1 week 1 day 2 hours ago) and read 4961 times:



Quoting A388 (Thread starter):
So how do cargo aircraft compare to passenger aircraft when it comes down to their weights? Is one or the other indeed "heavier" or how should I interpret this?

Well, no one has hit the nail on the head yet. Although there are some good answers but they aren't totally correct.

The main difference between a factory built passenger life and freighter is the MZFW, Max Zero Fuel Weight. The aircraft normally have the same MTOW some even have the same landing weight.

For instance, SQ's pax aircraft empty weight is about 180 tonnes, while the freighters are about 160 tonnes. The pax aircraft have a MZFW weight of 244.9 tonnes while the freighters have a MZFW of 288.0 tonnes. What that means is you could put roughly 64.9 tonnes of payload on a pax aircraft and 128 tonnes of payload on a freighter. So, the freighter has roughly 200% payload capacity compared to the pax version of the same aircraft. Max landing weight for the pax version is 285 tonnes while the freighter is 302 tonnes.

Hope that helps.


User currently offlineA388 From Netherlands Antilles, joined May 2001, 9720 posts, RR: 11
Reply 8, posted (5 years 2 months 1 week 1 day 2 hours ago) and read 4917 times:

Okay so the difference in weight lies in cargo aircraft being loaded to the max as I suspected meaning sacrificing the range as less fuel is taken due to the cargo weight. At the same time the weight of the galleys, seating separation screens, cinema screen toilets and associate plumbing, fitted stairs to the upper level and several intemediate bulkheads is almost similar to the strengthening of the main deck floor, cargo door and strengthening of the landing gear in the fullfreighter?

A388


User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 9, posted (5 years 2 months 1 week 1 day 2 hours ago) and read 4865 times:



Quoting A388 (Reply 8):
At the same time the weight of the galleys, seating separation screens, cinema screen toilets and associate plumbing, fitted stairs to the upper level and several intemediate bulkheads is almost similar to the strengthening of the main deck floor, cargo door and strengthening of the landing gear in the fullfreighter?

NO. The Freighters have an empty weight of almost 20 tonnes lower than the pax version. That is quite a difference. I wouldn't call 20 tonnes "almost similar". In addition, the freighters have a much greater (200%) payload capacity than a pax version.


User currently offlineFxramper From United States of America, joined Dec 2005, 7191 posts, RR: 86
Reply 10, posted (5 years 2 months 1 week 1 day 2 hours ago) and read 4833 times:
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Quoting A388 (Reply 8):
Okay so the difference in weight lies in cargo aircraft being loaded to the max as I suspected meaning sacrificing the range as less fuel is taken due to the cargo weight.

There is never a deliberate sacrifice for fuel with a cargo plane. Routes and tech stops are specific and scheduled. A pilot will request additional fuel if a late bulk slip is sent to the cargo a/c.

As stated above it's max zero fuel weight. Cargo a/c don't have all the amenities to make it feel like home, so they weigh less pre-load.


User currently offline413x3 From United States of America, joined Jul 2008, 1983 posts, RR: 0
Reply 11, posted (5 years 2 months 1 week 1 day 2 hours ago) and read 4827 times:

fill an airplane full of passengers and their bags, and some cargo, and you probably rarely are approaching the limits of the airplane. fill a cargo airplane with cargo in the main deck and lower holds, and you are probably around the limits. A lot of freighters fly in full and leave pretty empty, American trade imbalances mean cargo flights from Asia are coming in full, and leaving the states back to Asia with only a few things

User currently offlineA388 From Netherlands Antilles, joined May 2001, 9720 posts, RR: 11
Reply 12, posted (5 years 2 months 1 week 1 day 2 hours ago) and read 4807 times:



Quoting PhilSquares (Reply 9):
NO. The Freighters have an empty weight of almost 20 tonnes lower than the pax version. That is quite a difference. I wouldn't call 20 tonnes "almost similar". In addition, the freighters have a much greater (200%) payload capacity than a pax version.



Quoting Fxramper (Reply 10):
There is never a deliberate sacrifice for fuel with a cargo plane. Routes and tech stops are specific and scheduled. A pilot will request additional fuel if a late bulk slip is sent to the cargo a/c.

As stated above it's max zero fuel weight. Cargo a/c don't have all the amenities to make it feel like home, so they weigh less pre-load.

Okay thanks for the clarification.

Quoting 413x3 (Reply 11):
fill an airplane full of passengers and their bags, and some cargo, and you probably rarely are approaching the limits of the airplane. fill a cargo airplane with cargo in the main deck and lower holds, and you are probably around the limits. A lot of freighters fly in full and leave pretty empty

Okay understandable, thanks.

A388


User currently offlineSEPilot From United States of America, joined Dec 2006, 6832 posts, RR: 46
Reply 13, posted (5 years 2 months 1 week 1 day 1 hour ago) and read 4753 times:



Quoting PhilSquares (Reply 7):
The main difference between a factory built passenger life and freighter is the MZFW, Max Zero Fuel Weight. The aircraft normally have the same MTOW some even have the same landing weight.

Does this mean that the wingbox for a freighter is different than for a pax aircraft? I would think that a higher MZFW would require a stronger wingbox.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 14, posted (5 years 2 months 1 week 1 day 1 hour ago) and read 4731 times:



Quoting 413x3 (Reply 11):
fill an airplane full of passengers and their bags, and some cargo, and you probably rarely are approaching the limits of the airplane.

Actually, on a long haul flight you generally become payload limited if you are looking at full fuel. Or, you have a problem is you reach MZFW you then become fuel limited. On the 400, you can generally take 55 tonnes of payload and full tanks and you will be at MTOW.


User currently offline413X3 From United States of America, joined Jul 2008, 1983 posts, RR: 0
Reply 15, posted (5 years 2 months 1 week 21 hours ago) and read 4497 times:

Yeah I guess I wasn't thinking too clearly. loading 250k lbs of fuel makes almost anything get near the limits! I really love the 744. So jealous you have the honor of flying her.

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