Fe wrote:

snip
Also, is there a simple rule-of-thumb relationship between how fast an
aircraft is travelling and how much air friction heats it up (and
therefore how much infra red radiation it gives off)?

IIRC Speed in hundreds of mph squared=degrees C temp rise thus for Concorde
14(00)^2=196C temp rise from a -50 base gives ~150C.

Dont know whether this applies at subsonic speed
--

regards

jc

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