The Australian Transport Safety Bureau (ATSB) does not expect to release a final report into the country's worst civil aviation accident since 1968 until next March as it continues to investigate the complex incident. All 13 passengers and two crew on the Transair Fairchild Metroliner III died when it crashed into terrain on an RNAV (GNSS) approach on 7 May 2005, 11km (6nm) north-west of Lockhart River aerodrome in Queensland.
The ATSB acknowledges that the investigation is taking a long time, but it has been hampered by the destruction of the aircraft in a post-crash fire and the lack of cockpit voice recordings.
The bureau released a third factual report into the crash last week and says a draft final report is expected by the end of November, after which parties involved will have 60 days to comment.
The investigation will include further work on the operator's management processes, standard operating procedures, flightcrew training and checking, document control, regulatory oversight of operator's activities, and design and chart presentation of RNAV (GNSS) approaches.
The investigation has already resulted in implementation of a number of recommendations. Australia's Civil Aviation Safety Authority has amended its civil aviation orders, requiring all instrument rating holders to hold an endorsement for any navigation aid being used to navigate an aircraft. The co-pilot on the Lockhart River flight was not approved for RNAV (GNSS) approaches, which at the time was not required.
CASA has also implemented an ATSB recommendation to review maintenance requirements for cockpit voice recorders (CVR) and flight data recorders against international standards. The ATSB was unable to recover any usable data from the Metroliner's CVR due to an unknown malfunction. CASA is also reviewing Australia's policy on the fitment of autopilots after the ATSB recommended that all civil aircraft operating scheduled services are fitted with reliable autopilots.
On approach to Lockhart River the aircraft descended below the minimum safe altitude of 2,060ft (630m) at a rate of 1,500ft/min (7.62m/s) over the 70s before the impact. The Metroliner was fitted with a Honeywell Mark VI ground proximity warning system (GPWS), which should have generated alerts and warnings. The lack of CVR data means the ATSB has been unable to determine whether the GPWS was working correctly.
The ATSB has conducted research studies as part of its investigation, comparing fatal accidents in the far north of Queensland with those elsewhere in Australia and surveying pilots on their perceptions of pilot workload and the safety of RNAV (GNSS) approaches. The RNAV (GNSS) study investigated pilot workload, situational awareness, ease of approach chart use and the safety of approaches.
Of the 748 surveys completed, 49 respondents had been in an incident involving RNAV (GNSS) approaches and the most common incident involved starting the descent too early due to a misinterpretation of position.