5 ms·

I haven’t read the article. But I thought it was well-known that the death of the 3 engine plane was because the FAA dropped the requirement for 3 engine plans

I haven’t read the article. But I thought it was well-known that the death of the 3 engine plane was because the FAA dropped the requirement for 3 engine plans for over ocean flight. The rule made sense at the time as propeller engines are far more likely to fail. Overtime it became apparent that modern jet engines are extremely reliable and the need for the third engine wasn’t necessary.

t0mas88 5y ago
There are also two engine aircraft with the engines mounted at the tail instead of under the wings. The change there is that larger diameter engines are more fuel efficient and those fit better under the wing than at the tail.
- Robotbeat 5y ago
  Y’all should just read the article. It addresses these things.
Clewza313 5y ago
That's the ETOPS (Extended-range Twin-engine Operations Performance Standards) rule: https://en.wikipedia.org/wiki/ETOPS https://en.wikipedia.org/wiki/ETOPS It's mentioned in the article, and it didn't just kill off 3-engine planes, but 4-engine planes like the 747 as well. The Airbus A350 XWB has a ETOPS-370 rating, meaning it can fly up to 370 minutes (over 6 hours) on a single engine, or between any two points across 99.7% of the world.
- mikro2nd 5y ago
  Also (I'm told) colloquially referred to as, "Engines Turn Or Passengers Swim"
- tialaramex 5y ago
  > meaning it can fly up to 370 minutes (over 6 hours) on a single engine It can fly almost indefinitely† on one engine. Performance is reduced, but it can even still climb. That ETOPS rating means this plane is allowed to fly routes planned at up to 370 minutes over water with two engines in the expectation that when sooner or later it experiences an engine failure the one remaining engine can get them to safety so often that regulators are willing to accept the residual risk. If you call up the regulators and say "OK, I have an A350 here, but one of the engines doesn't work, can I fly that over an ocean to get it fixed?" they're not going to issue you a ferry exemption justified by ETOPS, they're going to say "No". ETOPS is about what you can do with two engines knowing what will happen if one fails. † Obviously it will eventually run out of fuel. And engines can fail, although that's rare, the core idea of ETOPS is that so long as these failures are rare enough we don't need three engines.
  - nemetroid 5y ago
    ETOPS planning ensures that the aircraft will always be able to reach a suitable alternate airport, even if the aircraft experiences loss of an engine and loss of cabin pressure, at the worst possible time during the flight. It’s not a ”so often” thing.
    - tialaramex 5y ago
      Loss of an engine. If you lose both engines mid-way across the Atlantic, I assure you that your twin engine ETOPS qualified airliner is not going to reach to an airport. The Azores Glider made it over 100km after losing its second engine which sounds very impressive -- until you look at a map of typical ETOPS authorised routes. If they'd continued on their original course when they at first didn't understand what the problem was, instead of diverting, they'd have been forced to ditch in the ocean. Now, ditching an airliner in the ocean isn't certain death. But it's very dangerous and there is no margin for error. While the Hudson River is not exactly a welcoming experience, being very cold and more than deep enough to drown, it's much more favourable than an ocean. So, ETOPS is focused on the very low but non-zero probability of losing another engine and so likely loss of life from what may then become a forced ditching of the aircraft.
tobmlt 5y ago
You reminded me of the tale of the Ford trimotor. The way I recall it from aerospace design class (20 years ago) was that any single engine out meant the aircraft couldn’t climb. Hence, the probability of a serious incident was 3 times as likely as for a single engine design. I tried to google this just now and came up blanks. Oh well, I thought it was going to be entertaining and factually accurate enough. Now I am questioning my memory.
- pininja 5y ago
  They still fly these 92 year old planes out at Oshkosh, and I took a short flight in one while I was there. Now I wish I’d asked more questions since their volunteers are pretty knowledgeable.
- sk5t 5y ago
  Also interesting to note that a two-engine craft ordinarily has 200% the power it needs to operate, whereas a three-holer might only have 150%.
  - tobmlt 5y ago
    That might have been what I am mis-recalling then, thanks! Our proff. still managed to turn it into something like a proverb of wisdom. (More engines not necessarily = more reliability)
WalterBright 5y ago
Ironically, the more engines the more likely engine failure and collateral damage is.

t0mas88 5y ago

There are also two engine aircraft with the engines mounted at the tail instead of under the wings. The change there is that larger diameter engines are more fuel efficient and those fit better under the wing than at the tail.

Robotbeat 5y ago
Y’all should just read the article. It addresses these things.

Clewza313 5y ago

That's the ETOPS (Extended-range Twin-engine Operations Performance Standards) rule: https://en.wikipedia.org/wiki/ETOPS https://en.wikipedia.org/wiki/ETOPS It's mentioned in the article, and it didn't just kill off 3-engine planes, but 4-engine planes like the 747 as well. The Airbus A350 XWB has a ETOPS-370 rating, meaning it can fly up to 370 minutes (over 6 hours) on a single engine, or between any two points across 99.7% of the world.

mikro2nd 5y ago
Also (I'm told) colloquially referred to as, "Engines Turn Or Passengers Swim"
tialaramex 5y ago
> meaning it can fly up to 370 minutes (over 6 hours) on a single engine It can fly almost indefinitely† on one engine. Performance is reduced, but it can even still climb. That ETOPS rating means this plane is allowed to fly routes planned at up to 370 minutes over water with two engines in the expectation that when sooner or later it experiences an engine failure the one remaining engine can get them to safety so often that regulators are willing to accept the residual risk. If you call up the regulators and say "OK, I have an A350 here, but one of the engines doesn't work, can I fly that over an ocean to get it fixed?" they're not going to issue you a ferry exemption justified by ETOPS, they're going to say "No". ETOPS is about what you can do with two engines knowing what will happen if one fails. † Obviously it will eventually run out of fuel. And engines can fail, although that's rare, the core idea of ETOPS is that so long as these failures are rare enough we don't need three engines.
- nemetroid 5y ago
  ETOPS planning ensures that the aircraft will always be able to reach a suitable alternate airport, even if the aircraft experiences loss of an engine and loss of cabin pressure, at the worst possible time during the flight. It’s not a ”so often” thing.
  - tialaramex 5y ago
    Loss of an engine. If you lose both engines mid-way across the Atlantic, I assure you that your twin engine ETOPS qualified airliner is not going to reach to an airport. The Azores Glider made it over 100km after losing its second engine which sounds very impressive -- until you look at a map of typical ETOPS authorised routes. If they'd continued on their original course when they at first didn't understand what the problem was, instead of diverting, they'd have been forced to ditch in the ocean. Now, ditching an airliner in the ocean isn't certain death. But it's very dangerous and there is no margin for error. While the Hudson River is not exactly a welcoming experience, being very cold and more than deep enough to drown, it's much more favourable than an ocean. So, ETOPS is focused on the very low but non-zero probability of losing another engine and so likely loss of life from what may then become a forced ditching of the aircraft.

tobmlt 5y ago

You reminded me of the tale of the Ford trimotor. The way I recall it from aerospace design class (20 years ago) was that any single engine out meant the aircraft couldn’t climb. Hence, the probability of a serious incident was 3 times as likely as for a single engine design. I tried to google this just now and came up blanks. Oh well, I thought it was going to be entertaining and factually accurate enough. Now I am questioning my memory.

pininja 5y ago
They still fly these 92 year old planes out at Oshkosh, and I took a short flight in one while I was there. Now I wish I’d asked more questions since their volunteers are pretty knowledgeable.
sk5t 5y ago
Also interesting to note that a two-engine craft ordinarily has 200% the power it needs to operate, whereas a three-holer might only have 150%.
- tobmlt 5y ago
  That might have been what I am mis-recalling then, thanks! Our proff. still managed to turn it into something like a proverb of wisdom. (More engines not necessarily = more reliability)

WalterBright 5y ago

Ironically, the more engines the more likely engine failure and collateral damage is.