eli5: Why do small jet aircraft, like regional jets and private jets, have engines on the rear, but larger jet planes have engines on the wings?
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Small jets are short, and that’s a design feature
Small jets like private jets aren’t always serviced by a jetway. Private jets in particular want to have a set of stairs they can put down for people to get on and off, this means that you can’t be more than about 3/4th of a fuselage height off the ground, for a Gulfstream G650 that’s 8′ in diameter that means its about 6 feet up.
Jet engines are large, this is another design feature as engines with larger fans at the front end up being more efficient. The engines on a Gulfstream G650 are about 6′ in diameter so to put them under the wing you need to ensure the wing is up quite a ways, it needs to be engine diameter + pylon length + safety margin off the ground andddd now you’re wayyyy above where the stairs can go
Bigger jets are pretty much always serviced by a jetway or a rollup staircase that is as tall as it needs to be to accommodate the plane. The concerns for these planes ends up being that working on an engine 40 feet in the air is kinda sketchy and the weight distribution of the plane ends up being better if they’re low and a hair forward of the wing. On small jets, the wings are set further back to adjust for this change in weight distribution. You always want your plane’s center of gravity to be in front of its center of lift, if it isn’t it will quickly try to correct that for you
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