Flight Details
The aircraft was operating a scheduled freight service under IFR from Darwin to Sydney, with stops at Tindal, Alice Springs, and Adelaide. The flight from Darwin to Tindal was reportedly normal, and the aircraft departed Tindal slightly ahead of schedule at 1834 CST. The pilot in command occupied the left cockpit seat. At 1925, the crew reported at position DOLPI, 200 miles north of Alice Springs, at Flight Level 330 to Melbourne Control. Another Westwind aircraft was en route Darwin–Alice Springs, more than 40 miles ahead of VH-AJS.
Descent and Approach
Cockpit voice recordings indicated the pilot in command was flying. At about 1929, he began instructing the co-pilot to program the navigation system for a locator/NDB approach to Alice Springs. The pilot requested the co-pilot to enter an offset position into the RNAV system for an 11-mile final for runway 12. The co-pilot entered a bearing of 292 degrees (the outbound bearing from Alice Springs NDB to Simpson's Gap locator), while the pilot stated he wanted 296 degrees relative to the runway but allowed the 292-degree setting to remain. The pilot then instructed the co-pilot to set Alice Springs NDB on ADF 1, Simpson's Gap locator on ADF 2, and to preset Temple Bar locator on ADF 2 for selection after passing Simpson's Gap. The pilot indicated his intention to descend to 4,300 feet until overhead Simpson's Gap, then set 3,450 feet on the altitude alert selector, and later set 2,780 feet as the minima for the approach.
At 1940, the co-pilot contacted Adelaide Flight Service (FIS) and received Alice Springs weather including local QNH. At 1945, the co-pilot advised that the aircraft was leaving Flight Level 330 on descent. About 30 miles from Alice Springs, the pilot turned right to track the offset RNAV position. The crew set the local QNH passing 16,000 feet and completed transition altitude checks, including landing and taxi lights. At 1949, the co-pilot advised a frequency change to Alice Springs MTAF. At 1953, the aircraft passed Simpson's Gap at about 4,300 feet; the co-pilot then set 3,500 feet in the altitude alert selector. About 15 seconds later, the pilot instructed the co-pilot to set the minima after passing the next locator. At 1954, the pilot called 3,500 feet. Shortly after, the co-pilot indicated over Temple Bar locator and stated they could descend to 2,300 feet. The pilot repeated 2,300 feet and asked for landing gear down. The pre-landing checks were completed.
Collision
Eleven seconds after the descent call, the co-pilot reported being 300 feet above the minimum descent altitude, which the pilot confirmed. About 10 seconds later, the co-pilot twice called to pull up. Immediately after the second call, the aircraft struck the top of the Ilparpa Range, approximately 9 kilometres northwest of Alice Springs Airport, while heading about 105 degrees at an altitude of about 2,250 feet in a very shallow climb. Witnesses in a housing estate on the northwestern side of the range observed aircraft lights approaching from the northwest, appearing significantly lower than usual. The lights illuminated buildings as the aircraft passed overhead, then the northern escarpment, followed immediately by a fire and explosion at the top of the range.
Probable Cause
The official investigation identified the following factors as significant in the accident sequence: difficulties in the cockpit relationship between the pilot in command and the co-pilot; low level of crew resource management; the unique nature of the Alice Springs locator/NDB approach; inadequate briefing by the pilot in command; an incorrect minimum altitude accepted by the pilot; high cockpit workload from the pilot's technique; and the crew not using the radio altimeter during the approach.