Hi Captain Lim,
No matter what they say, I can't seem to bring myself to believe that the redundancy of a 4 engine jet is not preferable to a twin when flying over the cold (non survivable) North Atlantic.
Even if 3 engines went out on a 747, you would still have SOME capability to fly a bit further to make land, and as far as I am concerned, quad engines should also fly ETOPS.
It seems to me that while engine failure probability is low for a two engine plane, it is astronomically low for a 3 engine failure even if the twin engines are much more reliable.
A related question... if a pilot had to ditch at sea, would he attempt to locate a ship nearby to ditch so that rescue would be more likely. I recall a story about a 4 engine prop plane long ago that lost either 3 or three engines en route from Hawaii to the west coast, and had to ditch. But at that time there was a ship always stationed at the half way point, I think.
Thanks for your site. I have had difficulty finding this information.
The preference of 4 engines over 2 engined planes would depend on whom you are talking to – the operators or the consumers? The operators would choose a plane that is cheaper to operate for the same seat mile (and still just as safe) whereas the consumer, just like you, would like to have that psychological safety factor of planes with 4 engines.
The benefits of customers that select a four-engined B747-400, A340 or A380 are that they have the ability to continue to their destination after an engine failure and the freedom to overfly remote areas free from the extended range twin-engine operations (ETOPS) limitations.
However, FAA has recently adopted new rules that lifted the restrictions on how far from an alternate airport a two-engined passenger plane should fly and said the evidence is clear that two-engine jets are just as safe as those with four engines.
On your second question about ditching (emergency landing on water), obviously, in planning for one, it would be ideal to do so near to a ship where rescue would be immediate. Where none are available, the pilot’s first priority would be to attempt to carry out a soft touch down onto the water in one piece.
Even though most planes are not designed for ditching, they are however capable of floating on water after an impact – that is, provided the contact with water is well controlled and there is no structural damage. The statistical chances of surviving a ditching are high as seen in this Boeing 737 accident (see image below). In this ditching, all the passengers survived except for a flight attendant who was drown when she fell off the plane when boarding the life raft.
Yes, more survivors are likely to drown after ditching if they are not wearing life jackets. In cold water of 15 degrees Celsius or less, the life expectancy of a survivor in the water is only about one hour.
In an ideal condition, the pilot would ditch into wind because it provides the lowest speed over the water and therefore causes the lowest impact damage. If the ditching was due to impending fuel exhaustion, a powered approach provides for the greatest potential to execute a successful water landing. Further, the pilot should avoid ditching into the face of the swell or into waves because the airplane will behave in a similar manner to one impacting a cliff face.
Well, these are some of major considerations in addition to looking for a nearby ship when faced with a water landing.