As it's visible from the images below, when looking at the plane from the top, the engines point outwards and they are banana-shaped, why is that?

(unfortunately I couldn't find a real photo straight from the back of the airplane, from that angle it is way more noticeable),

https://upload.wikimedia.org/wikipedia/commons/9/93/De_Havilland_Comet.svg enter image description here

enter image description here

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    $\begingroup$ Welcome to aviation.SE! Does this answer your question? $\endgroup$ – Pondlife Jun 6 '20 at 15:53
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    $\begingroup$ I don't think that answer does it because the engine are buried well back in the wing so that flow orientation is controlled at the front of a long duct. I'd say it has something to do with angling the thrust line slightly closer to the center of mass for engine failure purposes, or to direct the exhaust flow away from the fuselage perhaps. $\endgroup$ – John K Jun 6 '20 at 17:04

The engines were mounted well inboard to reduce the hazard of asymmetric thrust.

Four turbines are placed so close to centerline of plane that even if two on one side cut out, pilot has little trouble maintaining straight, level flight. [photo caption, p. 101]
The Comet's engines are snugged in so closely to the fuselage that there's no need for the customary trim tab on the rudder. [p. 102]

-- Francis, Decon. "I Saw This Jet Liner Fly 500 m.p.h." Popular Science, 156(5), May 1950, pp. 98–104.

Protecting against that hazard also explains the deflection of the engines' exhausts, which places them closer to a line intersecting the airplane's center of mass.

Another reason for the deflection could be to prevent jet blast from overheating or otherwise damaging the fuselage's skin just aft of the exhaust. The dH Ghost turbojets were built a decade before the first high-bypass engines, so their hot exhaust had no surrounding cooler air.

A third, faint, reason might be to facilitate egress from the over-wing emergency exit windows, sliding aft and down instead of climbing forwards. But avoiding asymmetric thrust is the reason that is documented in the literature of the time. (By the way, that entire Pop Sci article is a hoot.)

  • $\begingroup$ It is a very cool answer, but don't you loose a lot of thrust if you vector it a bit sideways instead of all backwards? And how is it acceptable to lose it just for the reasons you stated? $\endgroup$ – Salomanuel Sep 13 '20 at 10:08
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    $\begingroup$ @Salomanuel: The loss is negligible, as it is proportional to the cosine of the toe-in angle. $\endgroup$ – Peter Kämpf Sep 13 '20 at 12:24
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    $\begingroup$ Asymmetric thrust does not appear to be pertinent to the question. It explains the lateral position of the engines, but not the orientation. The next-to-last paragraph in this answer seems plausible, but a good answer would include some reference that actually documents the claim. This reads more like speculation. $\endgroup$ – Peter Duniho Sep 13 '20 at 18:34

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