3 ms·

The centre tanks are so much larger than the outboard wing tanks. I would be very interested to know if the rate at which the fuel can be pumped up from the cen

The centre tanks are so much larger than the outboard wing tanks. I would be very interested to know if the rate at which the fuel can be pumped up from the centre tank to the wing tanks exceeds the rate at which the engines consume it. If so, is fuel transferred on multiple separate occasions during the flight, or is it instead pumped continuously throughout the flight at a rate approximately matching the rate of consumption by the engines?

readyplayernull 3y ago
The rate at which fuel can be pumped from the center tank to the wing tanks does exceed the rate at which the engines consume fuel, so fuel transfer can occur continuously throughout the flight. The actual rate of fuel transfer and the frequency of transfers will vary depending on the specific flight conditions, such as the weight of the airplane, the distance of the flight, and the amount of fuel remaining in the tanks. The fuel management system on the 747 is designed to optimize fuel usage and ensure that the airplane remains balanced throughout the flight.
- sokoloff 3y ago
  There are two possible interpretations of GP's question. I took the opposite one of the one you did. "Can the fuel be transferred more quickly than engines consume it, such that there is a risk of the wing tanks becoming overfilled from the center tank?" is the one I took. You took "Can the fuel be transferred fast enough such that there is no risk of engine fuel starvation?" which is also valid.
  - kayodelycaon 3y ago
    Fuel tanks have vents to prevent overfilling from damaging them. From one of the Boeing documents I found, the 767-400ER will vent tanks into the fuel dumping system, passively pushing the excess overboard.
    - sokoloff 3y ago
      That fuel was presumably loaded for a reason. Pushing it overboard still represents a risk to the flight.
      - jychang 3y ago
        The alternative would be a burst fuel tank. I think I prefer the “dump fuel” failure mode.
esaym 3y ago
The fuel pump rates are very extreme. A plane can take off heavier than it can land. So if it is fully fueled and shortly after take off it needs to land due to emergency, it will need to dump thousands of pounds of fuel in minutes. The typical design and workflow of a larger jet like this is the engines are feed by the fuel tank nearest them. The flight engineer is on constant duty to continuously pump fuel from the center tank and/or other fuselage tanks to the tanks feeding the engines.

readyplayernull 3y ago

The rate at which fuel can be pumped from the center tank to the wing tanks does exceed the rate at which the engines consume fuel, so fuel transfer can occur continuously throughout the flight. The actual rate of fuel transfer and the frequency of transfers will vary depending on the specific flight conditions, such as the weight of the airplane, the distance of the flight, and the amount of fuel remaining in the tanks. The fuel management system on the 747 is designed to optimize fuel usage and ensure that the airplane remains balanced throughout the flight.

sokoloff 3y ago
There are two possible interpretations of GP's question. I took the opposite one of the one you did. "Can the fuel be transferred more quickly than engines consume it, such that there is a risk of the wing tanks becoming overfilled from the center tank?" is the one I took. You took "Can the fuel be transferred fast enough such that there is no risk of engine fuel starvation?" which is also valid.
- kayodelycaon 3y ago
  Fuel tanks have vents to prevent overfilling from damaging them. From one of the Boeing documents I found, the 767-400ER will vent tanks into the fuel dumping system, passively pushing the excess overboard.
  - sokoloff 3y ago
    That fuel was presumably loaded for a reason. Pushing it overboard still represents a risk to the flight.
    - jychang 3y ago
      The alternative would be a burst fuel tank. I think I prefer the “dump fuel” failure mode.

esaym 3y ago

The fuel pump rates are very extreme. A plane can take off heavier than it can land. So if it is fully fueled and shortly after take off it needs to land due to emergency, it will need to dump thousands of pounds of fuel in minutes. The typical design and workflow of a larger jet like this is the engines are feed by the fuel tank nearest them. The flight engineer is on constant duty to continuously pump fuel from the center tank and/or other fuselage tanks to the tanks feeding the engines.