It's also the attachment point for the parachute for that wing (obviously there is one for each side). (it is at the C of G).
In the event of a sudden, alarming descent which the pilot decides is never going to become controllable, he operates an alarm to tell the CC to open the emergency window, and take the parachute pack out on to the wing and clip it on to the bracket you can see.
The parachute pack is stowed under the exit seat for that purpose.
The same procedure is followed for each wing. As soon as the parachute is secure the CC comes back into the cabin bringing the release cord. The releases for both sides are pulled simultaneously to prevent asymetric uplift.
The aircraft then descends in a stately manner to the surface, while passengers don their lifejackets in the approved fashion if over water, record the video for YouTube, text their families and the press with details of their terrifying ordeal, get their hand luggage ready for leaving the aircraft, go for an emergency pee,and so on.
Last edited by Capot; 24th Oct 2012 at 11:17.