Neuquén

Impact of the aircraft against a mountain slope while attempting an evasive manoeuvre during a steep left turn. Decision of the crew to fly over hilly terrain below the minimum safe altitude under VFR mode. A contributing factor was the possible distraction of the crew during the last part of the flight over the canyon.

For unknown reasons, the crew was approaching the airport at an insufficient altitude. The following contributing factors were reported:
- Failure of the operator to consider the restrictions at the destination airport,
- Possible windshear on short final.

The exact cause of the accident remains unclear. The crew did not send any distress call prior to the loss of control. It is believed that the accident was the consequence of a possible in-flight fire or toxic fumes emanating in the cabin due the presence of polyethylene stored in several boxes that were not properly packed according to dangerous goods transportation procedures.

The accident was the result of detachment of the right hand wing in normal flight, through structural failure of the wing in the area between stringers 3 and 12 and in the area of the engine outer rib. Within the area indicated, one may identify among the origins of the fatigue the reinforcing plate, and especially, the holes in it for rivets. The cause of these fatigue cracks, since the material of which they were made was satisfactory, must be attributed to stress concentration in the area concerned due to geometry of the design, these cracks becoming critical sooner than had been estimated. The cracks remained undetected and became critical because the manufacturer's inspection programme for the area concerned was insufficiently precise and made it possible for the operator not to detect and correct them in time.