|Quoting OldAeroGuy (Reply 20):|
Are the odds on your lotto that improbable? If so, the tickets sales required to have a winner must be very high.
Welcome to China.
|Quoting ZANL188 (Reply 21):|
On the other hand they ignore the enhanced takeoff performance of the ETOPs twin over a 4 engine jet, namely the ability to continue a takeoff and climb on only 50% of the installed thrust.
That is actually false, tri jets and quads have a higher/better certified takeoff gradient/performance than a twin. FYI a twin commercial airliner cannot commence a takeoff on 1 engine, it can only continue a takeoff once at sufficient speed. A tri jet or quad can commence a takeoff roll with one engine inoperative when on a maintenance ferry flight etc.
|Quoting ZANL188 (Reply 25):|
I'd be happy to. 4 engine jets are not required by regulation to survive a loss of 50% of installed engine thrust on takeoff & early climb, ETOPs twins are. As a result there has not been a hull loss of an ETOPs twin following loss of 50% of installed thrust on takeoff. There have been a number of 4 engine jet hull losses (with all aboard killed) in the same case.
ETOPS has nothing to do with takeoff performance (with the exception is looking at a departure alternate).
A loss of an engine on quad gives you better certified climb performance than a twin with no reduction to the systems, a loss of two engines on a quad gives you better climb performance than a twin with a double engine failure, with only mild system changes.
FYI a 340-600 can climb on 2 engines at MTOW, we can even maintain altitude with 3 engines out at a reduced weight. I have not see the 380 charts for that case, I would suggest it will also be able to do it as well.
|Quoting ZANL188 (Reply 31):|
Irregardless of the aerodynamic condition of this aircraft, following the loss of thrust from two engines it would not have been able to climb away and was going to crash. The only question was where.
FYI the El Al case you are talking about did not happen on takeoff, it happened at about 6000', it was not the loss of engine thrust, as far as I am aware both the engines that departed the aircraft were functioning at the time. They had the separation of two engines from the same wing due to a fault in the engine pylon. This was not the last time for that to happen to a 747.
The crash was not for a lack of thrust, it was for a lack of controllability, bit like the Lauda Air 767 crash.
Also trying to compare reliability based upon the number of engines alone it ridiculous, if I were to compare the 707 to 777, the 777 would be better, compare the 737-100 to A340, 340 would be better, if I were to look at a 737-100 to 707, I would still go 707.
As for your E3
case, no aircraft is certified for takeoff into a flock of birds, and a lot of military aircraft do not meet civil takeoff requirements due to all the extra bits they have hanging off them, and the practice of taking off at weights about what a civil version of the same aircraft would, and using "military thrust" settings. In the cold war, jets like the Vulcan and B52 would keep going even if they could not start an engine.
Flocks of birds have taken down single engine, twin engine, tri jets, and quads before, and will do so again in the future.
The technology available today is "statistically safe", the risk level in a modern quad is still less than modern twin. Quads still have more redundancy.
|Quoting Bond007 (Reply 33):|
In most cases, unless you are BA, this requires a diversion to the nearest suitable airfield.
Nope it never has, it depends on the situation, hence the reason why the FAA dropped its case.
Having more engines does not mean you have a higher chance of a failure, the probability of having a failure depends on the age and history of the engine, and any known problems with the design. Failures due to accessories and metallurgical failure can be predicted accurately, and increase with the cycles, and the stress of the cycles.
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