He appears to be buttoning-up the access panel after having successfully started the engine using the hand cranked inertia starter. The crank handle has been passed down to the next recruit. Probably a training exercise, all under the watchful eye of the old man in the back.

These planes are still in use as water bombers for firefighting. They were the long distance and endurance champs of the day when equipped with extra tanks. An interesting read on them is "The Sky Beyond" by Sir Gordon Taylor.

Is a PBY Catalina.

What the person's looking into is probaly the throttle control cables for the engine to get the right setting for speed control.

[Well you know that was a joke. Ha ha! It's a seaplane. And the thing that stops a wheel is, to get all technical-jargony, a brake, not a "break." - Dave]