What is this airplane used for? Every satellite picture I've ever seen of carriers in port usually shows a lot of equipment on the flight deck, presumably involved with servicing and overhauling the ship between cruises.  This example is from NAS North Island in San Diego.



A closer inspection of the stern of the ship shows what appears to be a derelict F-18 airframe parked on the flight deck and stripped of its engines, LE and TE flaps.  



Usually the airwing is launched back to naval air stations on shore prior to the ship reaching port, then fly out again to trap aboard when the ship goes out to sea again and this jet doesn't exactly look flight ready.  What exactly is this aircraft used for?  Is it some kind of training device for shipmates or aircraft handlers or for training on firefighting techniques?
While I'm not sure about the condition of the aircraft, there are uses for a non-flight worthy aircraft in a carrier deck. For example, the crash and salvage team can train salvaging the aircraft, or the sailors can train craning the aircraft abroad the deck.

For example, in the image below, U.S. Navy sailors use a crash and salvage crane to lift a non-functional McDonnell Douglas F/A-18 Hornet during flight deck drills aboard the aircraft carrier USS Ronald Reagan (CVN-76). 



By U.S. Navy photo by Mass Communication Specialist 3rd Class Jonathan Nelson - This Image was released by the United States Navy with the ID 150415-N-WO404-124 (next).This tag does not indicate the copyright status of the attached work. A normal copyright tag is still required. See Commons:Licensing for more information.

It may also be used for firefighting and damage control training, as can be seen in the image below.



Sailors assigned to the crash and salvage crew on USS George H.W. Bush (CVN 77) spray foam on an F/A-18 Hornet training aircraft during a firefighting drill; image from warbirdsnews.com, credited to USN

The article notes:


  Since active jets are precious assets, they use specially-prepared training airframes, like grounded F-18 Hornets ... these former frontline fighters are often antiquated models of current equipment or planes that have been damaged beyond the point of repair. These days the trainers are usually represented by earlier models of the F-18 whose variant has been retired, ... (they serve) as training aids for firefighting and crash retrieval and salvage operations, letting crews hone their skills using real world items, without risking damage to expensive operational flyers