Aircraft

US investigators have released photographs of clear evidence of fatigue in the wing structure of the Grumman G73 Mallard of Chalk's Ocean Airways that crashed off Miami Beach, Florida.

All 20 occupants were killed in the accident on 20 December which happened when the amphibian aircraft suffered catastrophic structural failure shortly after departure for the Bahamas.

The cause of the failure is not known, but pictures released by the US National Transportation Safety Board show clear evidence of a fatigue failure in a spar.

The NTSB's caption to the picture above reads: "Overall view of the inboard end of the right wing as it was recovered from the water. An labelled arrow indicates the lower spar-cap of the rear spar where fatigue features were observed."

The NTSB captions this picture: "Closer view of the fracture surface at the inboard end of the lower spar-cap of the right wing rear spar. Unlabelled arrows indicate the location of two offset drilled holes."

Concerning this picture, the NTSB says: "Closer view of the fatigure region in the horizontal leg of the lower spar-cap of the rear spar. Unlabelled brackets indicate fatigue origin areas at the surfaces of the fastener hole, and dashed lines indicate the extent of the fatigue region visible on the fracture surface."