A380 Useable Fuel Capacity

[Evan]

I have a general question regarding the total useable fuel load of the A380. In a Flight International article dated 14/06/05, Frank Ogilvie, aerodynamics director and deputy head of overall aircraft design for the A380 made this statement:

“When the wing was full of fuel we got a ‘bowing’ of the wing, and our flight- dynamics people calculated that we would have unacceptable inertial loads on the ground.” To counteract this, the fuel in the outer tanks is pumped inboard and aft to the tailplane trim tank for take-off, providing bending-moment relief to the outboard wing. In flight, the fuel is gradually pumped back into the wing tanks, while also allowing an aft centre of gravity to be maintained for cruise drag reduction. Each wing contains five transfer pumps, while a further two are housed in the trim tank. Overall fuel capacity is 315,292 litres (83,190USgal), of which almost 23,700 litres is held in the trim tank. Each outer wing tank holds 9,524 litres, while the outer engine feed tanks each hold around 26,975 litres.

In Airbus publication STL 945.1380/05 Issue 2, Flight Deck and Systems Briefing for Pilots, page 153 lists overall useable fuel capacity at 324,540 litres. It arrives at this figure by adding up all the tank capacities. But, as Ogilvie has stated, the aircraft cannot take-off with the outer tanks fueled. Is the Airbus publication in error? What is the actual useable fuel capacity for the A380?

[guamainiac]

The optional refueling probe and drogue system went out with the buggy whip leaving Airbus high and dry. Worse yet it was only offered with the optional white sidewall tyres and with costs of petrol on the rise white sidewalls were out of the question.

Actually Evan there is a very cool shot of three aircraft refueling with the old probe and drogue system in a "doggy style photo op". Google up ... aerial refueling ... and there is a staged shot of an A-3 Skywarrior (whale), that is gassing up another A-3 Whale that in turn is fueling an A-4 Skyhawk. I have a warm spot in my heart for those slow goons.

[brianw999]

Best person to ask this question of would be Frank Ogilvie don't you think ?

[Evan]

Best person to ask this question of would be Frank Ogilvie don't you think ?

Brian, it would appear that Mr. Ogilvie has already given his answer. That was in 2005, however, and perhaps before the final production design. The Airbus website lists fuel capacity at 310,000 Litres, which sounds more reasonable. So now we have three different figures from three different Airbus sources. Kind of strange, isn't it?

Adding to the confusion, Wikipedia says 323,546 Liters. I think this was also calculated by adding up all the tank capacities, which you can't actually do if you expect to leave the ground.

So, again, what's the right figure?

[WILCO737]

LH A380s have a tank capacity of: 323,546 or 258,837 kgs.

wilco737

[Evan]

LH A380s have a tank capacity of: 323,546 or 258,837 kgs.

wilco737

Are you sure they can actually take-off with that much fuel (based on Mr. Ogilvie's remarks about wing design at the top of the thread)? Or is that just the collective volume of the tanks?

[WILCO737]

Are you sure they can actually take-off with that much fuel (based on Mr. Ogilvie's remarks about wing design at the top of the thread)? Or is that just the collective volume of the tanks?

I dont know if it can take off with that fuel load. I just checked for the possible tank capacity.
But how stupid would it be to have that capacity but because of the design it ia not possible?!
I cannotcomment on that as I havent heard of it. 285 tons of fuel is incredible... Loooong flight...

[MCM]

285 tons of fuel is incredible... Loooong flight...

Not when you burn as much per hour as it does

[Evan]

I dont know if it can take off with that fuel load. I just checked for the possible tank capacity.
But how stupid would it be to have that capacity but because of the design it ia not possible?!

If you read the quote in the first post, the problem was with wing droop on those enormous wings being beyond acceptable limits for take-off due to the weight of the fuel in the outer tanks, so the fuel is placed in the trim tanks for take-off, then transferred slowly through the flight to the outer tanks to give a more efficient aft center of gravity.

The thing I find interesting though, is that the Airbus A380-800 Flight Deck and Systems Briefing for Pilots (an informational document not to be used as an official reference) seems to have incorrect data for Total Useable Fuel, adding up all the tank volumes without taking this into consideration.

It does describe the Load Alleviation (LA) Transfers as follows:

The following load alleviation transfers occur in flight:

• After Takeoff:

• Transfer to the outer tanks, until the outer tanks are full.

• Before Landing:

• Transfer from the trim tank, until the trim tank is empty
• Transfer from the outer tanks, until the outer tanks are half empty.

[MCM]

Evan,

I'm not sure it matters very much. Useable fuel in litres is not a figure pilots use.

Pilots deal (for operational purposes) in weight of fuel.

I can tell you how much (in weight at a standard s.g) a 747 can carry, but I have no idea of the actual volume of the tanks.

[Evan]

Evan,

I'm not sure it matters very much. Useable fuel in litres is not a figure pilots use.

Pilots deal (for operational purposes) in weight of fuel.

I can tell you how much (in weight at a standard s.g) a 747 can carry, but I have no idea of the actual volume of the tanks.

Ok, understood, but the same Airbus Flight Deck and Systems Briefing for Pilots chart lists the total useable fuel at 561,660 lbs, which is the equivalent of 324,540 liters, which cannot be possible if those outer tanks need to be light on takeoff.

[Evan]

Unless this beast uses much more taxi fuel than I think...

[WILCO737]

If you read the quote in the first post, the problem was with wing droop on those enormous wings being beyond acceptable limits for take-off due to the weight of the fuel in the outer tanks, so the fuel is placed in the trim tanks for take-off, then transferred slowly through the flight to the outer tanks to give a more efficient aft center of gravity.

I read that post. I just checked for the possible usable fuel load. I didn't check if that is possible to carry or not. But it could be. Although it is hard to believe that one build an airplane with 285 tons of fuel capacity and you cannot carry it? Strange in my opinion. But on the other hand I guess you never need that much fuel. With 285 tons and an average fuel flow of 14 tons per hour, you have an endurance of 20+ hours...

Evan,

I'm not sure it matters very much. Useable fuel in litres is not a figure pilots use.

Pilots deal (for operational purposes) in weight of fuel.

I can tell you how much (in weight at a standard s.g) a 747 can carry, but I have no idea of the actual volume of the tanks.

We use weight, that is correct. But when fueling is finished we get a recepit from the fuel truck driver which only states the litres (or gallons) and the density and then we can double check if enough fuel is on board.

wilco737

[MCM]

G'day Wilco,

Yeah we use the same system for uplift verification as you do - in litres for us antipodeans. I'd get confused using gallons . I was just trying to point out to Evan that we use weight, not volumetric capacity, for most uses.

Evan,

Are you sure that restriction (no filling of outer tanks) actually applies? I've only had a cursory look, but to me it appears that while for a standard load the wing tanks are not filled (until after takeoff when the transfer takes place), you can fill them on the ground if all the other tanks are already full, which means that the usable fuel is indeed the full amount.

Maybe that is a direction to investigate.

[WILCO737]

G'day Wilco,

Yeah we use the same system for uplift verification as you do - in litres for us antipodeans. I'd get confused using gallons . I was just trying to point out to Evan that we use weight, not volumetric capacity, for most uses.

Ah ok, guess I somewhat missunderstood you here. sorry 'bout that.

Gallons confuse me as well, but there are charts and calculators to get it right

wilco737