Posts: 264
Joined: Fri Nov 17, 2000 5:36 am

Can A 747 Or 340 Do This?

Mon Feb 05, 2001 9:11 am

Can a B744 or a A340 do the following?
1. Say the the two outer engines(the two farthest apart) fail. Can the two inner engines keep the airplane flying, and for how long?
2. Or the two inner engines fail, can the two outer engines keep the airplane in the air?
I know it sounds redundant asking the two different questions, but I am just wondering! Thanks in advance.
Posts: 228
Joined: Mon Feb 05, 2001 8:01 am

RE: Can A 747 Or 340 Do This?

Mon Feb 05, 2001 9:23 am

yes both can fly with any 2 engine out at max gross weight.
Posts: 1232
Joined: Sat Oct 30, 1999 5:01 am

RE: Can A 747 Or 340 Do This?

Mon Feb 05, 2001 9:24 am

The B747, A340 can fly with 2 engines for not so long, but they can fly for 1-2 hours during a declared emergency landing procedures until they land the plane(s).

Baec777  Big thumbs up
Posts: 6595
Joined: Tue Mar 21, 2000 6:25 am

RE: Can A 747 Or 340 Do This?

Mon Feb 05, 2001 10:15 am

They will easily keep flying at low altitude on two engines only.
They will be in somewhat worse condition than a twin which beyond V1 speed actually must TAKE OFF with half of the power lost - with flaps and gear down etc.
Otherwise they wouldn't be able to climb to and cruise at high altitude where the max power is roughly one fourth due to the thin air.
Both planes have a lift to drag ratio around 20 and a power to max weight ratio around 4 at sea level. So even with only one engine operational - if it was placed on the centerline - and consequently power to weight ratio of 16, they would still be able to climb slightly. But that would depend very much on the condition of the disabled engines - what drag they would produce.
But with a light load - a lot of fuel either burned or dumped - they would both easily maintain flight on one inner engine only at low altitude.
Best regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs

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