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An ATSB discussion paper has found from a large survey of endorsed pilots that a recently introduced type of satellite approach [termed RNAV (GNSS)] used during the May 2005 fatal accident near Lockhart River is perceived as difficult, particularly in bad weather and without automation and vertical guidance instruments.

The Australian Transport Safety Bureau sent the survey to all Australian pilots with aRea NAVigation (RNAV) Global Navigation Satellite System (GNSS) endorsement and received 748 representative responses, a response rate of 22 per cent.

The most difficult RNAV (GNSS) approaches reported by pilots, based on responses adjusted by commercial movements into an aerodrome, were Mt Hotham and Lockhart River.

Pilot workload, including time pressure, was perceived as higher for RNAV (GNSS) approaches, and pilots reported having trouble maintaining situational awareness more often than other approaches, except non-directional beacon (NDB). Poor weather and turbulence were among the largest compounding factors. Responses from high capacity airline pilots differed somewhat and were generally more favourable towards RNAV (GNSS) approaches because their aircraft had autopilots and vertical guidance systems.

Pilots reported a common concern that RNAV (GNSS) approaches did not use distance to the missed approach point references on the approach chart or electronic displays. As with the Lockhart River runway 12 approach, short and irregular segment distances and multiple minimum segment altitude steps were also a concern, as was approach chart interpretability and the use of 5 letter waypoint names with only the last letter differing.

The most common problem trainees had with RNAV (GNSS) approaches was maintaining situational awareness, often linked to confusion as to the segment they were in and distance from runway threshold. Global positioning system (GPS) and waypoint issues were also significant.

49 respondents reported incidents with RNAV (GNSS) approaches: 15 had descended too early due to position misinterpretation and 3 almost did; 5 others lost situational awareness; and 4 descended below the constant angle approach and/or minimum segment steps.

Copies of Research Discussion Paper B2005/0342 can be downloaded from the website, 1800 020 616 and comments addressed to the Deputy Director, Information & Investigations by 3 October are welcome.

Media contact: 1800 020 616
 
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Last update 01 April 2011
 

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