Read Handling the big jets by Davies. There's a section in there about this. It's a good read if you get the chance.
From the top of my head, there's a bunch of trade-offs with engine placement. One is when one takes a crap you don't want it to affect the other one on that side, so space is good. As well it helps with wing bending moment. Downside is the yaw moment if outer takes a break and max roll angle close to the ground.
4 engined aircraft: engine placement
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Some older designs had the engines up close and personal to the fuselage and were even blended into the wing. The deHavilland Comet and Avro Jetliner come to mind.
I think the use of pylons as opposed to the blended nacelles require some spacing. A pylon mounted engine makes design and maintenance easier.
The separation prevents the engines from physically interfering and minimizes complex interaction between the engines inlet air.
There are a few pylon airplanes that have more than one engine mounted on a single pylon though. The B52 (in the miliatry world) comes to mind.
I think the use of pylons as opposed to the blended nacelles require some spacing. A pylon mounted engine makes design and maintenance easier.
The separation prevents the engines from physically interfering and minimizes complex interaction between the engines inlet air.
There are a few pylon airplanes that have more than one engine mounted on a single pylon though. The B52 (in the miliatry world) comes to mind.
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shitdisturber
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No kidding, if you have a catastrophic failure on the inboard on a tail mounted aircraft you could lose it, it's mate, and if you're really unlucky and the shrapnel goes through the tail, the inboard on the other side. How's that for having a bad day?Big Pratt wrote:Also the VC-10 and the Il-62.
Tail mounted, two per side.
Not good during uncontained failures.
