Israel Aircraft Industries 1124, VH-AJS

The crew was conducting a practice locator/NDB approach to Alice Springs, at night, in clear moonless conditions. The approach involved a stepped descent in three stages using three navigation aids. The pilot in command had earlier briefed the co-pilot that the 'not below' altitude after the final approach fix for the approach (2,780 feet) would be used as 'the minimum' for their purposes.

The flight proceeded normally until the aircraft passed overhead the final approach fix when the pilot in command asked the co-pilot to set the 'minima' in the altitude alert selector. The co-pilot responded by calling and setting '2300 feet'. This altitude was the Category A/B aircraft minimum descent altitude as depicted on the Jeppesen chart for the approach. The minimum descent altitude for the Westwind, which is a Category C aircraft, was 3,100 feet. The 2,300 feet called by the co-pilot was acknowledged by the pilot in command, and the aircraft then descended to that altitude. Shortly after levelling at about 2,250 feet, the aircraft struck the top of the Ilparpa Range and was destroyed.

The crew had descended to the incorrect minimum descent altitude before reaching the appropriate sector of the approach.

The investigation revealed a number of factors relating to the performance of the crew. Also revealed were a number of pre-existing conditions which contributed to the actions of the crew. These ranged from crew experience and training to procedures and policies of the operator and regulator.

The report concludes with a number of safety recommendations.