747 question

[Ari707]

this may be a simple question but I was just on theBoeing web site looking at 747-400 details and noticed that the 747-400F has a much shorter range then a pax 747-400 they both carry the same 57,285 gal. of fuel and have the same max takeoff weight of 875,000 lbs, so why the shorter range?

[T-Bird76]

Cargo cans take up far more volume and weigh more then passengers even when fully loaded.

[lijk604]

Cargo cans take up far more volume and weigh more then passengers even when fully loaded.

Just to add to that...
Typical full B747-400...420 pax @ 225 lbs/pax (includes bags) = 94,500

A full cargo B747-400...can typically carry 250,000-300,000 pounds.

[hiss srq]

Payload. Density altitude, engines, payload and fuel combined. It all plays in on that. If you have a 747-400F with tanks full because you need the range and only have say 8,500 feet of runway your going to probably run into issues on a 95 degree day. Payload restrictions. Would you beleive on that note A-320's and A-319's have to be load restricted for that same reason out of airports likme Philly and Charlotte on a regular basis. It is a little complicated to explain but temp. and runway length has a lot to do with what a plane can or cannot take and how it will perform in a given condition.

[PhilDernerJr]

All the answers were right, but Max Takeoff Weight doesn't have so much to do with range, only the weight that the aircraft's structure can handle on takeoff. Once it's in the air, it's ability to MOVE is another story.

Though both might have the same MTOW, that does not mean that they can reach their max range at that weight.

However, I honestly would have thought that an empty 744F, since it has a smaller upper deck and no seats or galleys, would have more range than an empty pax 744.

[N790SW]

Can someone answer why temp effects the plane on takeoff? because I did notice onetime when I was flying it them summer it was ALOT faster then it would be when I flew on a 29 degree day.

[engine46]

Temperature directly affects density altitude. As temperature increases, so does density altitude. Therefore, at higher temperatures, the aircraft cannot perform as well in terms of thrust produced, efficiency, aerodynamic lift, and many others. This is why takeoff rolls in hot temperatures are much longer. Smaller GA aircraft can face serious problems performancewise at high altitudes in high temperatures.

[adam613]

Cold air is more dense than hot air. Because of this, temperature has two effects on aircraft performance:

1) The wing of an airplane provides more lift in dense air. So if it is warmer outside, you need to get the airplane moving faster for the wings to provide enough lift to get you off the ground.

2) Engines perform better in denser air. So if you take off when it's hot outside, you won't get as much thrust from the engines. This leads to longer takeoff rolls, since it takes longer to get up to speed, and reduces maximum takeoff weight because it takes more thrust to move a heavier airplane.

Air gets more less dense as altitude increases. The effects of altitude are well-measured and documented, in that the instruction manual for an aircraft might say that at X altitude above sea level, your engines will operate at Y% of maximum efficiency and your stalling speed increases by Z knots above what it would be at sea level.

Density altitude is a measurement for the effects of air temperature. Say the density altitude is 4000 feet. That means that at the current temperature, your airplane will perform as if it were at 4000 feet at standard temperature. That, in combination with the actual altitude of the airport, allows you to compute the performance of your aircraft in terms of maximum takeoff weight and required runway length.

If you are ever in a city like Phoenix in the summer with a scanner, listen to the ATIS. It often specifies a density altitude. (Not that I recommend being somewhere like Phoenix in the summer. My avatar should indicate why I know this.)

[PhilDernerJr]

As for spotting, cold air can negatively affect locations like Howard Beach, where the planes might get airborne sooner on the runway and turn off before it hits that sweet-spot for yo to take photos, or gain altitude too fast.

[Derf]

Everyone knows that in the summer the temp rises very quickly on the hot tarmac. Due to this reason the airlines need to stock more drinks for the passengers thus more weight and a aircraft uses a longer take off roll in the summer. In the winter the pilots have to make sure they are lightly loaded as during the flight some snow may accumulate on the wings. We all know it is much colder at altitude and the chances of snow on the wings at that high altitude would increase weight. That is really why the F/A throws off the guy who was drinking at the bar but not really drunk.

My Name is Fred and I am a recent graduate from the Cliff Claven school of knowledge.
Glad I could help here with my vast knowledge of everything arodinamic.

[PhilDernerJr]

Fred, I can't tell if you're serious.

But actually, when it comes to weights, the only weights I've seen change with seasons are passenger average weights, which come down in the summer because of the lack of jackets.

[DHG750R]

the 747-400 pax range is higher than the freighter due to the freighter's higher max zero fuel weight (ZFW). 542,500lbs for the pax vs. 635,000lbs for the freighter. Both aircraft have the same maximum structural takeoff weight of 875,000lbs. This means you can carry less fuel before you reach maximum weight, this means less range of course.

It's not unusual for a -400F to carry as much as 273,000lbs of cargo. The typical passenger load with cargo is likely to not exceed 116000lbs (assuming 400pax @ 190lbs with 40,000lbs of bags and freight in the belly)

our -400'Fs are not equipped with fuel tanks in the horizontal stab, most pax -400's are typically equipped for longer range

Zero fuel weight is the weight of the airplane , loaded with everything ready to fly except for fuel.

[PhilDernerJr]

Thanks for those numbers! Certainly clarified some of this for us.

With my experience with weights, the heaviest I've seen for a flight multiplied to 400 pax would still only bring the plane to about 141,000 lbs. That's a lot of extra room for cargo. It also shows how the older, more beat up cargo aircraft are profitable for cargo companies after pax airlines give them up....more weight allowed to make more money.

[Derf]

Fred, I can't tell if you're serious.
.....

ahahahahah rrright, If I EVER make a serious statmenet like that, please ban me! :borat:

Hot long rollouts due to some extra L.I. Ice Tea, and snow accululations on the wing during flight? :borat:

The rest of this post was moved to a new thread

[Idlewild]

As for spotting, cold air can negatively affect locations like Howard Beach, where the planes might get airborne sooner on the runway and turn off before it hits that sweet-spot for yo to take photos, or gain altitude too fast.

Unless it's a A340-200/300.