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rivalarrival t1_ja9z706 wrote

ETOPS is (was) for planes with two engines. The thinking was that if one engine failed, you only have one engine in reserve. If it, too, fails, the passengers will be swimming for hours or days before help can arrive. Overland, the loss of both engines leaves the pilots with one final option before passengers are endangered: A dead-stick landing on the ground (See: "Gimli Glider"), or near enough to land for the passengers to be quickly rescued (See: "Miracle on the Hudson"). Flying out to sea, you can't expect a quick rescue after a forced landing. Regulatory authorities don't like it when you are operating with no redundancy left. They really hated the idea of twin engine aircraft flying over the ocean, just two failures away from catastrophe.

ETOPS initially said that If you wanted to fly a route that took you more than 60 minutes from land, you couldn't use a twin-engine plane. You had to find a plane with more than two engines.

You don't want to fly a three engines plane because it is less economical, but you are required by law to use at least three engines. You could use four, but that's even less economical. There was no practical need for three-engine aircraft (outside of extraordinarily rare double-emergency situations), but the law regulating twin-engine planes prohibited them from making these flights. Airlines needed three-engine planes to bypass this law.

ETOPS certification was incrementally expanded from 60 minutes to 370 minutes for some twin-engine aircraft and airlines. If you could prove your engines were reliable enough, and your maintenance program thorough enough, you could acquire additional certification to fly farther from land. With such certification available, more routes can be legally operated with twin-engine aircraft. Fewer routes legally require three engines. Presently, 99.7% of the Earth's surface is within 370 minutes single-engine flight time of a major airport. 99.7% of all possible flights can be undertaken with twin-engine aircraft. There was never much practical use for a three-engine aircraft in the first place; now there is only 0.3% of a legal requirement left. It's now cheaper to slightly alter one of the few remaining routes that twins can't legally perform than to maintain fleets of tri-jets to perform them. (Basically, they have to fly around the south pole, rather than directly over it, so they stay within 370 minutes of airports in South America, Africa, Australia, etc.)

Even 4-engine aircraft are being replaced with twins. Boeing ended production of the four-engined 747 in favor of the twin-engine 777 with nearly the same capabilities, because carriers prefer jets with two huge engines instead of jets with four smaller engines. Twins are simply more efficient to operate. The only thing that stopped them from using twins was the law, and the law has stepped out of the way.

You are correct that I don't understand your point, but I think the problem is that I failed to adequately explain the law. Your criticism doesn't seem to address a situation the law was trying to regulate.

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