Thursday, February 01, 2007

Also - I've only just found this, the ATSBs investigation into GNSS non-precision approaches. If you don't know what that means, think Lockhart River, Benalla, Mount Hotham. If none of those placenames mean anything to you, perhaps you are on the wrong website.

Area navigation global navigation satellite system (RNAV (GNSS)) approaches have been used in Australia since 1998 and have now become a common non-precision approach. Since their inception, however, there has been minimal research of pilot performance during normal operations outside of the high capacity airline environment. Three thousand five hundred Australian pilots with an RNAV (GNSS) endorsement were mailed a questionnaire asking them to rate their perceived workload, situational awareness, chart interpretability, and safety on a number of different approach types. Further questions asked pilots to outline the specific aspects of the RNAV (GNSS) approach that affected these assessments. Responses were received from 748 pilots, and answers were analysed based on the aircraft performance category1 . For pilots operating Category A and Category B aircraft (predominantly single and twin-engine propeller aircraft), the RNAV (GNSS) approach resulted in the highest perceived pilot workload (mental and perceptual workload, physical workload, and time pressure), more common losses of situational awareness, and the lowest perceived safety compared with all other approaches evaluated, apart from the NDB approach. For pilots operating Category C aircraft (predominantly high capacity jet airliners), the RNAV (GNSS) approach only presented higher perceived pilot workload and less perceived safety than the precision ILS approach and visual day approach but lower workload and higher safety than the other approaches evaluated. The different aircraft category responses were likely to have been due to high capacity aircraft having advanced automation capabilities and operating mostly in controlled airspace. The concern most respondents had regarding the design of RNAV (GNSS) approaches was that they did not use references for distance to the missed approach point on the approach chart and cockpit displays. Other problems raised were short and irregular segment distances and multiple minimum segment altitude steps, that the RNAV (GNSS) approach chart was the most difficult chart to interpret, and that five letter long waypoint names differing only by the last letter can easily be misread.

When the initial report came out, I was disappointed that the issue of there being a possible problem with these types of approaches was never mentioned, what was mentioned was that one of the crew members was not qualified to fly them. This gave the impression that the crew members were at fault by flying the approach in the first place, despite the fact that the company was responsible for creating the rosters, despite the fact that the cockpit voice recorder wasn't functioning and so we don't actually know who was flying the approach, and despite the fact that CASA had audited the company a few weeks previously and passed them with flying colours.

This report has huge implications for aviation in this country, and possibly overseas. I hear that the GNSS non-precision approach is enormously popular in the US and Canada. Hopefully, now the issue is being taken seriously, some very smart people can get to work and make these things a bit safer for everyone, instead of pulling out the hoary old 'pilot error' chestnut.


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