Eli5: why are some airplane jet engines under the wings and some on the vertical stabilizer?
In: 3
There hasn’t been a model designed with an engine on the vertical stabilizer since like the 70s/80s.
As for why, it has to do with reliability and the ability to make an emergency landing if 1 engine fails. Modern jet engines are reliable enough that only 2 of them are needed for the vast majority of airline flights. In the past, 3-engine or 4-engine designs would be used for airline routes that fly over oceans or over isolated areas where the nearest available airport in case of emergency is very far away. For further information about this, search for “ETOPS” (which is what the regulation is called). “4 engines 4 long haul” was also a phrase used in the past by certain airlines which preferred flying 4-engine planes, and by Airbus to market the A340 against competitors such as the Boeing 777.
And of course, with a 3-engine design, the only place to mount the center engine and still be balanced, is the vertical stabilizer.
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