Why did big airplanes go from four engines to two engines?
In: Engineering
It’s a number of factors
For context, long-distance flight paths will always put the plane within a certain distance of an airport in case of emergency. These emergency diversion airports can even be located on tiny remote islands in the middle of nowhere
In the early days of jet travel, engines were less reliable. Four-engined planes had the power/thrust needed, and if 1 or 2 engines go out, there would still be enough engine power to get the plane landed
Modern jet engines are incredibly reliable, powerful and fuel efficient. They proved reliable enough to perform long distance flights.
Now let’s talk about ETOPS. It stands for **E**xtended-range **T**win-engine **O**perational **P**erformance **S**tandards, though aviation nerds sometimes call it “Engines Turn Or People Swim.”
You’ll sometimes see the letters ETOPS on the outside of a airplane or on the safety placard inside. The number after the ETOPS rating is the number of minutes the plane can fly on one engine.
The Boeing 777-300ER, a very ubiquitous and popular twin-engine long distance plane, is ETOPS 180, so it can fly for about 3 hours on one engine. When flights are being planned, they’ll make sure the plane is always within that amount of flight time from an emergency airport. The highest ETOPS rating is the Airbus A350, which is certified for 370 minutes on one engine
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