Payload/weight question.
Posted by DiligentCockroach700@reddit | aviation | View on Reddit | 15 comments
I have a friend who is a conspiracy theorist. He sent me a link to a video basically saying where do they put all the fuel on an A380? I suppose alluding to the conspiracy theory regarding aircraft using some kind of other "secret" propulsion method and/or "chem trails".
I don't subscribe to any of this nonsense so I thought I'd do some research and debunk his theory.
I was somewhat surprised by the result:
Unladen weight of A380: 277 tons
Full capacity Fuel weight: 256 tons
Total. 533 tons
Maximum takeoff weight of A380: 575 tons.
Payload (575-533) 42 tons.
But the maximum payload is quoted as 84-91 tons.
As you can see there's a discrepancy there of 40 odd tons.
Can someone knowledgeable explain the discrepancy?
I can't show him these figures, he'll say it proves what he's saying!
Disastrous-Trash1025@reddit
I hope you reminded him that Covid was so that the government could change the batteries in the birds.
Far-Yellow9303@reddit
An A380 can carry a combination of fuel and payload up to its maximum weight. If it has maximum fuel, they have to leave out some of the payload. If they have maximum payload, they have to leave out some of the fuel. As for where it goes, the wings are over 2 meters thick and almost 80 meters across. They contain a LOT.
ymsv@reddit
There is no discrepancy . It is a bit more complicated , but you can have maximum fuel and less cargo or maximum cargo and less fuel . You choose . Maximum takeoff is the referring point .
DiligentCockroach700@reddit (OP)
Thank you very much for the detailed explanation. I understand now, but I doubt whether my conspiracy theorist friend will, so I'm not going to pursue it with him it's just not worth the effort!
looper741@reddit
He will not.
Young_Maker@reddit
why are you still friends with this dude?
Roger_Freedman_Phys@reddit
Trying to disabuse conspiracy theorists of their beliefs is generally pointless. It’s essentially their religion, and even the most logical of arguments cannot disprove a religion.
747ER@reddit
Most people like this don’t really believe in the stuff they’re saying anyway. They say these things for attention and/or because they enjoy other people arguing with them.
Dont_Care_Meh@reddit
Exactly. Disprove one thing, and they'll move the goal posts. It never ends. Just walk away, OP.
Guadalajara3@reddit
Max zero fuel weight is the most the airplane can weight before any fuel is added. Zero fuel weight = empty operating weight + cargo/passengers. After that, you can add fuel up to your max take off weight or max landing weight, whichever is reached first. If you need more fuel to reach the destination, then zero fuel weight will have to be reduced to accommodate more fuel weight.
Youll never have all the numbers maxed out since its a balance of fuel weight and payload weight to keep within the max allowable weights
bbcgn@reddit
Note that fueling an airliner is done differently than fueling your car. While a lot of people fill up their tanks until they are full, that's usually not done on an airliner (at least since jet fuel became more expensive). Airliners take the amount of fuel they need plus a safety margin. Ever kg of fuel you don't need has to be carried with you to your destination reducing the amount of usable payload or/and increasing fuel burn by having a heavier than necessary aircraft.
In your example: you can choose to fill up the tanks for maximum range, but then you can't use the whole theoretical payload. If you use the whole payload, you can't fill up all the way so you get reduces range at full payload capacity.
derridaderider@reddit
And this is true of ALL modern airliners. You can fill 'er up with fuel but then you can't fill 'er up with passengers, or you can fill 'er up with passengers but then you can't fill 'er up with fuel. Which you do depends on the range you need for that particular flight.
bbcgn@reddit
Thank you for the addition. I think the biggest difference is that the fuel is planned for each individual journey, something most people don't do when they drive. A lot of people just fill up their tanks when they are empty and drive off. Maybe they fill up before going on a long road trip so the first fuel stop can wait longer, but you don't usually plan how much fuel you need to go to work and then only take that plus a safety marging. Also usually people pay way less attention to maximum vehicle weights. Don't know if this is how it works in all countries, buy in my car's papers there is a maximum weight it is allowed to have. It doesn't matter if the car weighs this much because all the seats are occupied by very fat people or if this is due to fewer fat people in the car. The weight of the fuel is also included in this maximum weight. My car has a 70 liter tank, so when filled up the car weighs around 56 kg more than if thr tank is empty. 56 kg is about what some thin women weigh. So if I would put a lot of stuff in my trunk and fill up the car and I would pay as close attention to maximum weights this could mean that I would have to choose between (more) fuel or having an additional passenger. From my experience, unless maybe you drive a truck and are used to having to pay attention to this, the general public probably doesn't care about their cars weight that much.
blackreplica@reddit
"He sent me a link to a video basically saying where do they put all the fuel on an A380?"
Jesus christ these people are stupid, they actually think this is some kind of gotcha
Apprehensive_Cost937@reddit
With maximum payload (maximum zero fuel weight), you can't fill up the fuel tanks, as you would exceed the maximum takeoff weight.
The vast majority of aircraft can't take full fuel and fuel payload at the same time - there's always a balance between the two.