KLMBlue From United States of America, joined Nov 2000, 267 posts, RR: 0 Posted (13 years 6 months 18 hours ago) and read 1468 times:
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.
Prebennorholm From Denmark, joined Mar 2000, 6389 posts, RR: 54
Reply 3, posted (13 years 6 months 16 hours ago) and read 1407 times:
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, Preben Norholm