what are these objects on A-10 gear nacelles?

On the underside of an A-10 Thunderbolt II, at the rear of the nacelle that holds the main landing gear, there is a device that I have not yet been able to identify.  It looks at first glance like a grate or vent, but various pictures of A-10s show parts of the device on one or both nacelles as a bright red color.  I am trying to understand what it is and what it does, so I can model it appropriately.  The kit I'm using (Italeri's 1/72 version) does have the features modeled but does not call out any painting instructions for them.