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Trimeresurus wrote:Currently, there's an ANA 77W squawking 7700 and flying circles over lake Michigan, presumibly dumping fuel before it can land. But seemingly it has been doing that for the past hour or so, and if it's a medical emergency on board, I'm afraid it might already be too late for that. Does it really take an hour of fuel dumping to reach the landing weight from an 12 hour fuel load?
And what's the consequences of a landing above that weight? Surely some damage to landing gear suspension and brakes wouldn't be worth more than human life?
Starlionblue wrote:While certainly you want that medical emergency on the ground ASAP, this should be weighed against the additional threats of an overweight landing. Normally there isn't any damage but it isn't really about the risk of damaging the aircraft. Threats would be high brake temperatures, which can lead to a fire, the potential of runway overrun, and poor go around performance. If you do end up with a brake fire or overrunning, you may have to evacuate, and during an evacuation injuries are commonplace.
In most cases, you would not consider an overweight landing for a medical emergency. The FCTM states that overweight landings "can be performed in exceptional conditions" (emphasis mine). Look at it this way: They could have been over the North Pacific, two hours from a diversion port when the person became ill.
Adding to this, long haul aircraft have a fairly comprehensive stock of emergency medical equipment. Cabin crew are medically trained, and have access to doctors via satphone.
Fuel jettison system is optional both on the A330 and on the A350. However, I don't know if any operator has ordered the A350 without it.
Horstroad wrote:Example for the 777-200LR:
MTOW: 347,500 kg
MLW: 223,168 kg
-> Maximum amount Fuel to dump: 124,332 kg
Maximum jettison rate with both nozzle valves open and all jettison pumps operating: 2,449 kg/min
Jettison rate with only one nozzle valve open and only wing tank jettison pumps operating: 1,224 kg/min.
So dumping the maximum amount of fuel could take between 51 and 102 minutes.
The jettison rate with only one nozzle valve open and all jettison pumps operating is probably the lowest possible flow rate in a scenario where you want to dump the maximum amount of fuel, as the jettison/override pumps of the center tank need to be operational in order to be able to dump that amount of fuel.
This gives a minimum jettison rate of 1,406 kg/min and a maximum time of 89 minutes.
889091 wrote:Don't you have to account for the fuel that is burned during that 51 or 102 minutes? I don't think it'll be a linear correlation.
889091 wrote:Horstroad wrote:Example for the 777-200LR:
MTOW: 347,500 kg
MLW: 223,168 kg
-> Maximum amount Fuel to dump: 124,332 kg
Maximum jettison rate with both nozzle valves open and all jettison pumps operating: 2,449 kg/min
Jettison rate with only one nozzle valve open and only wing tank jettison pumps operating: 1,224 kg/min.
So dumping the maximum amount of fuel could take between 51 and 102 minutes.
The jettison rate with only one nozzle valve open and all jettison pumps operating is probably the lowest possible flow rate in a scenario where you want to dump the maximum amount of fuel, as the jettison/override pumps of the center tank need to be operational in order to be able to dump that amount of fuel.
This gives a minimum jettison rate of 1,406 kg/min and a maximum time of 89 minutes.
Don't you have to account for the fuel that is burned during that 51 or 102 minutes? I don't think it'll be a linear correlation.
Starlionblue wrote:While certainly you want that medical emergency on the ground ASAP, this should be weighed against the additional threats of an overweight landing. Normally there isn't any damage but it isn't really about the risk of damaging the aircraft. Threats would be high brake temperatures, which can lead to a fire, the potential of runway overrun, and poor go around performance. If you do end up with a brake fire or overrunning, you may have to evacuate, and during an evacuation injuries are commonplace.
In most cases, you would not consider an overweight landing for a medical emergency. The FCTM states that overweight landings "can be performed in exceptional conditions" (emphasis mine). Look at it this way: They could have been over the North Pacific, two hours from a diversion port when the person became ill.
Adding to this, long haul aircraft have a fairly comprehensive stock of emergency medical equipment. Cabin crew are medically trained, and have access to doctors via satphone.
Fuel jettison system is optional both on the A330 and on the A350. However, I don't know if any operator has ordered the A350 without it.
BoeingGuy wrote:Starlionblue wrote:While certainly you want that medical emergency on the ground ASAP, this should be weighed against the additional threats of an overweight landing. Normally there isn't any damage but it isn't really about the risk of damaging the aircraft. Threats would be high brake temperatures, which can lead to a fire, the potential of runway overrun, and poor go around performance. If you do end up with a brake fire or overrunning, you may have to evacuate, and during an evacuation injuries are commonplace.
In most cases, you would not consider an overweight landing for a medical emergency. The FCTM states that overweight landings "can be performed in exceptional conditions" (emphasis mine). Look at it this way: They could have been over the North Pacific, two hours from a diversion port when the person became ill.
Adding to this, long haul aircraft have a fairly comprehensive stock of emergency medical equipment. Cabin crew are medically trained, and have access to doctors via satphone.
Fuel jettison system is optional both on the A330 and on the A350. However, I don't know if any operator has ordered the A350 without it.
The one time I can think of that Boeing recommend landing ASAP even if overweight is in the case of an unidentified or uncontrollable smoke or fire.