The max take off weight of a 747 is greater than the max landing weight by about 100,000lbs, so if heavily fueled and laden with cargo then they have to dump fuel before landing. It’s the case with a lot of long range aircraft. it’s an issue of structural capability of the airframe rather than landing performance. You don’t want the wings rupturing on landing and spilling fuel all over the runway.
The photo of the landing on BBC news websites seems to show the starboard inner engine shut down. Unless it was a really fast shutter setting so you can see the spiral on the cone without blurring.
And if landing on a broken undercarriage I think I’d want it to be as light as possible.
See how much the plane is leaning right as it comes to a stop? Shut down the #3 engine as that will be the first thing to hit the tarmac if it falls over.
So what happens if they have an emergency during take off (going faster than V1) and have to come straight back in? Surely it is possible to land in that case, hence it’s only a max weight for normal operational landing.
They have to dump fuel. The certification requirements of aircraft demands that an aircraft can take off at v1 and to a go around for a minimum amount of time to enable it to dump fuel before landing. The main reason for an abort at or beyond v1 is the loss of an engine, so the aircraft can fly and perform a go around with an engine out. It only affects the largest aircraft like 747’s, A380’s, 777’s etc. Aircraft smaller than that can land at full weight.
Aracer, you’re right, the max landing weight can be exceeded in abnormal circumstances However, there’s a lot of energy to dissipate (meaning very hot brakes, burst tires, possible brake fires and evacuations) and if you’re not careful you can over stress the aircraft. So it’s not something to be undertaken lightly.
I certainly wasn’t questioning whether it made sense to dump fuel to decrease the weight in this case – clearly if you’re only landing on 3/4 of the normal available gear you want the weight as low as possible (though I’d hope 3/4 of the gear would cope with a full weight landing). Though wobbliscott’s explanation also makes sense, and I was aware of the requirements to cope with “expected” emergencies at >V1.
Aviation is something I know just about enough about to be extremely dangerous 😉
Hmmm, didn’t really follow wobbli’s thinking. Some a/c can’t dump to below max landing weight, decisions become more difficult in that case.
What we can say, is that everyone on that a/c got off safely – although I’m staggered by the number of passengers who thought it better ti video/photograph/take selfies than take up the brace position. I must be getting really old….
The speculation on more informed places then this is that there was a hydraulic failure, which also took out some of the flap deployment as well as some of the undercarriage, hence the hard-ish landing. But still speculation.
A hydraulic failure (bear in mind that a 747 has 3 independent systems) would/should cause the landing gear to gravity drop into its deployed and locked position.
A hydraulic failure (bear in mind that a 747 has 3 independent systems) would/should cause the landing gear to gravity drop into its deployed and locked position.
Yes, but (and I’m just repeating from PPruNe) it may have jammed against the door either on the way up or during the gravity deployment. There is some history of this happening before.
Great videos, that was certainly a pretty hard first touchdown, the starboard inner was very close to the deck and the amount of flex in the wings not what you normally expect on a 747. A B-52 or DC3/C-47, yes; I’ve watched a DC-3 wings waving gently up and down from a passenger window, quite entertaining. 😀
Aircraft call emergencies every day throughout the UK and beyond, what made this one any more special than any other emergency that happened? Media reaction on events like this is terrible, all it does is put the fear of death into people!
