[Don Corleone]

Hey you Typhoon pilots...what’s that scorch at the center of the left wing root?

[Jewbacca]

There is a vent there, used for engine redirect, I believe.

(I have never flown a typhoon)

[Yo-Yo]

Hey you Typhoon pilots...what’s that scorch at the center of the left wing root?

Not a Typhoon pilot, but that is the exhaust for the Auxiliary Power Unit (APU,) a small jet engine that provides emergency power for the aircraft if the engines go out for any reason, and provides ground power for engine starts.