Does anyone know what these two small variable inlets on top of the engines are used for on the Super Hornet?

enter image description here
Source: navy.mil; cropped

  • 6
    $\begingroup$ That is one tired looking aircraft. $\endgroup$
    – FreeMan
    Commented Mar 23, 2020 at 23:40
  • 4
    $\begingroup$ Navy airplanes at sea just don't have the luxury of periodic baths. $\endgroup$ Commented Mar 24, 2020 at 1:38
  • $\begingroup$ @CarloFelicione It is far easier for a Navy plane to take a bath than for most land-based aircraft... $\endgroup$
    – MikeB
    Commented Mar 24, 2020 at 16:02
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    $\begingroup$ Another luxury they don't have is periodic paint. Aircraft paint and marine paint both have hexamethylene diisocyanate in the resin. Marine paint is formulated for brush or spray. For brush, PPE is wear gloves and cordon anywhere within 6' of the wet paint. For spray, PPE is a moon suit and cordon anywhere overspray could drift to, in short, you will not spray while underway. Hence, brushing. Aircraft paint can't do that. $\endgroup$ Commented Mar 24, 2020 at 16:56

1 Answer 1


These are the auxiliary air inlets for the ECS (Environmental Control System):

F/A-18 cutaway
(image source)

They provide air to the primary heat exchanger (A18), which is then exhausted via the ram air exhaust (A20, the tubes visible behind the inlets in your picture).


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