The plane that made the water landing in the Hudson River was an Airbus A320, with 2 engines on the wings.
Assuming it was geese that caused the problems:
Had the engines been on the back of the plane, instead of the wings, would it have made a difference? Would the geese have hit the wings and not made it back to the rear position engines?
What if it had three engines instead of just 2?
In the case of any engine problems, isn’t a 3 engine plane inherently safer than one with only 2? Why don’t more plane designs have at least 3 engines?
It’s not the location of the engines that’s relevant, but the fact that there’s a large air-intake area in the front of each one that sucks in the air . . . and geese. This is unavoidable.
And you can’t just keep adding engines to a plane. Engines are extremely heavy, and after you already have sufficient power to fly the plane, any additional weight is more problematic (and expensive) than it’s worth.
I don’t think that could be answered as it would depend on the EXACT trajectory of the bird. One could argue that since the engines are mounted under the wings they would have just continued to the back of the plane and been sucked up there, OTOH since in relation to the size of a bird that’s quite a ways away they very well may have changed direction by then. OTOH OTOH OTOH, it’s almost a Butterfly Effect type question.
IIRC greater efficiency of newer & larger engine designs has trumped the old 4 engine motifs (and even more so the 3 engine 727/DC-10/L10111 types), with notable exceptions like the A380. True tho that losing 1 out of 2 is much worse than 1/3 or 1/4; the airline designers obviously feel that the benefits in weight savings etc. trumps the redundancies.
IIRC, one big problem with three-engine designs such as the DC-10 and the Lockheed TriStar, was that the hydraulics controlling the flight surfaces in the empennage (basically the back end of the plain, the tail and stabilizers and everything else) all had to run past the middle engine. If the engine suffered some catastrophic failure (that is to say, if it came apart or blew up) then the flight crew would lose rudder and elevator control entirely. Any redundant hydraulic lines would also have to run past the same engine and thus would often suffer a similar fate.
That said, I’ve only heard of maybe two instances where such a failure happened, and I think they still fly tri-engined planes in many airlines.
But yeah, basically, airliners have to be designed with a certain amount of economy in mind. Having the extra redundancy of more engines is great in an emergency, but emergencies are rare, and redundancy can get prohibitively expensive past a certain point. If your four-engined airliner design has the same performance as your competitor’s somewhat cheaper two-engined design, the airlines will probably be buying from the other guy.
The captain comes on the intercom and says “This is your captain speaking. We have lost power to one engine but this airplane can still fly on three so there is no need for concern, it only means we will take a bit longer to reach our destination.”
Some minutes later:“This is your captain speaking. We have lost power to one more engine but this airplane can still fly on two engines so there is no need for concern, it only means we will take a bit longer than planned to reach our destination.”
Some minutes later:“This is your captain speaking again. We have lost power to a third engine but this airplane can still fly on one engine so there is no need for concern, it only means we will take longer to reach our destination and some of you might miss your connecting flights.”
A while later ““This is your captain speaking again. We have lost power to the last engine…” An impatient and fed up passenger exclaims “This guy’s gonna have us here all day!””
I’ve always liked that joke. The way I heard it, the captain announces the loss of a third engine and the passenger says, ‘If that last engine goes, we’ll be up here all day!’
(‘Story’-type jokes should follow the Rule of Three, IMO.)
Kind of. Twin engine jets tend to have a lot more performance with all engines operating than four engine jets do. The reason is that they need to meet all of the certification requirements on only one engine whereas three and four engine jets are able to meet the requirements with two and three engines respectively and so they don’t need as much performance from each engine. Four engine aircraft can have more marginal performance in normal operations as a result. So twins suffer a bigger performance drop when they lose an engine, but they had more to start with.
Engines are expensive, also from a maintenance point of view.
Also, engines mounted underwing are more efficient due to clean intake airflow. These days, engines are typically only mouted at the back (small regional jets, like the Embraer(?) in the OP’s pic) when there isn’t enough clearance to mount them under the wings.
Add to that the general engineer’s lament: Increasing redundancy also reduces your mean time between failures because there are more things that CAN fail–fuel systems, hydraulics, control systems.
Better to put your eggs in fewer baskets and just design better baskets.
Also, any flock of geese that was sufficiently dense that striking both engines of an A320 was even remotely likely would also be dense enough to strike multiple engines of, say, a 747.
A320’s engines are 11m or so apart, and have a cross-sectional area of 4.5m2 or so total (both engines combined). 747’s engines are spread over about 40m but have a total cross-sectional area of about 18m2.
For reference, the Boeing most similar to the A320, the 737, has similar numbers to it. As said above, also, the only airliners with more than 2 engines being made these days are the ultra-heavy specialist ones–namely, the A380 and the Boeing 747 family.
Building an aircraft is a compromise anyway. If you design a plane to be percieved as safe as many consumers want it to be, it will be a tank. AFAIR, most crashes are caused by pilot error, not some kind of mechanical failure, so many mechanical improvements in safety (extra safety margin or factor on structural parts, etc.) won’t help anyway.
In addition, they have to look at the probability of such events happening. A birdstrike on 2 engines is extremely rare. Like a meteor hitting a plane. Can you design to reduce the damage? Sure. How likely is it? 99.99999% (roughly ;-), maybe more) of the time, you’ll just be carrying around the extra weight of the armor for nothing.
Also, any extra weight leads to decreased efficiency and reduced carrying capacity, both of which cost the airline more money, which they pass on to the ticket buyers.
If you broaden that to be human error in general (including booboos by Air Traffic Control, mechanics, etc. as well as pilots) then you’re almost certainly right - since a lot of the mechanical failures are caused by people improperly fitting/fastening things, not replacing things when they are supposed to, loading heavy thing in the wrong bit of the plane, and so on.
IIRC planes for flights overseas (i.e. significant amounts of water) were required to have at least three engines. The notion being I guess that the extra redundancy was important when you were in a place you could not possibly land.
I thought it was the 777 which was the first twin engine design approved for overseas flights. Boeing apparently lobbied hard for that certification. I also think it was the first time where computer modeling was used in that certification. Essentially they could simulate thousands of hours of flight and this was sufficient for the FAA.
The 777 was the first twin to get ETOPS certification right from the entry into service, but the 757, 767, and A330 were previously able to get it on an airline-by-airline basis after demonstrating sufficient reliability in service.
(ETOPS can mean either “Extended-range Twin-engine Overwater OPerationS” or “Engines Turn Or People Swim”)
Good point about Lindbergh - he knew that the more engines you have, the more likely you are to have an engine failure. If he’d had one over the Atlantic even in a twin, that would have been the end.
In fact, in the world of light aircraft, twins have a much higher accident rate than singles after engine failure. They’re harder to control, there are more things to do and to be aware of, and pilot training for them is generally inadequate anyway.
What you are referring to is the ETOPS(Wikipedia link)rule. As ElvisL1ves mentions, the triple-7 was the first plane rated for full ETOPS right from initial production; in reality the 767 and Airbus 300 were first to gain the rating.
I feel like the worst airplane geek in the world right now. 24 years of age, and only NOW do I realize that the 767 is a twin-engine jet. I had always assumed it was a larger, four engined version of the 757. :smack:
I believe the 767 allowed smaller airports to have overseas flights. Our local airport had its first overseas flight to Paris with a 767. We now have a London flight instead.
Heh. The main difference, I think, is that the 767 is a wide body while the 757 is narrow.
ETOPS isn’t necessarily for over water flights. It allows flights which take the aircraft a significant distance from enroute alternates. It can be required for over land flights. I believe there are some domestic flights in Australia that require ETOPs approval to fly direct, due to vast areas of the country where no suitable alternates exist.