Snoopy's belly

[jq]

Just wanted to share - an unusual view of the underside of an AC-130U:

The belly of an AC-130U Spooky gunship is seen as the aircraft flies overhead. In addition to the trainable 25, 40 and 105mm guns, the gunship employs three sensor systems, which include the Strik Radar located inside the aircraft's nose, an infrared detection set (IDS) seen just behind the nose and the ALL-TV sensor located below and to the right of the 25mm Gatling gun. (Wikimedia Commons)

Now for the most silly question ever: is it normal that there is so much soot from the engine exhaust on the underside of the wing and flaps?

JimQ