Most (not all) commercial aircraft have 2 jet engines (yeah, I know some have 3 or even 4). Can these things fly on one engine if one fails?
Straight answer: Yes
Smart ass answer: If one engine fails, you still have enough power to fly to the scene of the accident.
Even a 747 can fly on just one of its four engines if it has to.
Pretty much anytime except immediately during take-off, one engine can suffice. During take-off however an airliner is in a very untenable position to suffer a major loss of power. It has to level off, maintain controllability, and not lose so much altitude that it can’t go around the pattern (or make it to the next closest field) and land safely.
Most people are afraid during landings. Landing is a piece of cake. Takeoffs are when a plane (especially a big jet) is at its most vulnerable.
There is no phase of flight in which a twin engined commercial airliner can’t safely cope with an engine failure. If on the ground prior to a certain speed there is enough runway to stop before taking off. Once airborne, there is enough speed to maintain control and climb out on one. Even a light twin poston engine aircraft can technically do this (though the margins are much smaller and it is often safer to land ahead.)
A 747 is flying across the Atlantic when an engine fails. The pilot gets on the PA and assures the passengers that the aircraft is perfectly able to fly on three engines; however, they will be about twenty minutes late arriving at their destination.
A little while later a second engine fails, and the pilot makes the same announcement. This time, he says they will now be about 40 minutes late arriving at their destination.
A third engine fails, and the pilot says their arrival will be about an hour late.
One passenger turns to another and says, ‘If that last engine fails, we’ll be up here all day!’
Just FYI, Broomstick gives a pretty unique account of losing an engine on a commercial flight.
The thread is currently in the pit: Tell me your flying horror stories!
It is a requirement for certification that a plane with 2 engines be able to demonstrate acceptable (i.e. safe) performance with either one not operating.
But in the worst case, the pilot(s) will need to be very sharp to avoid trouble. Airlines devote a lot of training time (and money) to ensuring that pilots are sharp. Most (but certainly not all) of the time, they are.
Private twins don’t have a terrific record. This is partly because their single-engine performance is often not much better than marginal, and partly because their pilots are often not especially sharp (not having frequent training in simulators).
One consequence is that “light twins” have a worse record in engine-out-during-takeoff accidents than do single-engine aircraft. In theory, the second engine lets you cope with a problem. In practice, unless you are sharp it simply offers you more spectacular ways to crash. Many pilots of light twins would have been better off if, on encountering an engine problem during takeoff, they’d simply cut power and landed (crashed) straight ahead.
That is true. The yaw effect of only one engine operating on a light twin is pretty significant and the climbing performance of most of these planes on only one engine is pretty bad so it can be a fatal recipe. Most conscientious pilots are aware of this fact however, and it is possible to pull off consistently as long as you really know what you are doing. I don’t believe the problem is nearly as bad on commercial airliners.
Not only can they fly, sometimes they can fly pretty far and pretty well.
The “default” rule in the U.S. is that a two-engine aircraft can never be more than 60 minutes away from a suitable diversion airport. But if you can prove certain things to the FAA you can get your plane certified for ETOPS. The FAA says that ETOPS stands for “Extended-range twin-engine operations,” but everyone knows it really stands for “Engines turn or passengers swim.” Basically, depending on the basics of your plane and how much work you’re willing to do upgrading your engines, you can get FAA permission to be up to three hours away from a diversion airport. In the U.S., this is important mostly for over-water routes, of course, as there aren’t too many places in the continental U.S. that are fully three air hours away from a half-way decent diversion airport.
Normally, the FAA likes to see a plane fly for a bit before offering ETOPS certification. But the 777 received ETOPS right out of the plant. I think they started them off at 120 and moved them to 180 later, but they might even have received ETOPS 180 right out of the box.
These rules apply to most foreign countries, too.
And of course, some planes can fly without any engines at all.
Somewhat reassuring, when you’re over the Atlantic when it happens.
:eek:
The 777 received 180-minute ETOPS as certified, based on testing and analysis of the engines instead of the operational record normally required. It’s now up to 227 minutes, allowing it to fly anywhere in the world. At least once it has needed almost all the 180 minutes, in a flight over the Pacific. Airbus advertises the A340 in part by pointing out that its four-engine design is not subject to ETOPS restrictions - they make very indirect but unmistakable references to the safety and comfort of four engines over the water.
But most engine failures occur right at takeoff. They’re at max power then, stresses on every part are at their highest, and the likelihood of ingesting a foreign object or a bird is at its highest. Only rarely will something happen at cruise power or at altitude.
One consequence of the engine-out rule is that a twin airliner’s engines are way oversized for normal operation. If you’re ever in a 757 with a light passenger load and little traffic, you’ll have the fun of a very rapid climbout.
One of the reasons that light twins have a worse safety record than singles is that the more engines you have the more often you’ll have an engine failure. The controllability problem is an added bonus, except on a Cessna Skymaster with fore-and-aft engines.