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Output Number
R20060019
Approval Date
Organisation
Civil Aviation Safety Authority
Published Date Time
Recommendation type
Recommendation
Status
Closed - No Action
Mode
Aviation
Date released

Safety issue: RNAV (GNSS) approach pilot workload and
situational awareness

Pilot workload was perceived as being higher, and reported
losses of situational awareness were reported as more common, for
the area navigation global navigation satellite system (RNAV
(GNSS)) approach than all other approaches except the
non-directional beacon (NDB) approach, which involved similar
workload and situational awareness levels.

This was especially a concern for pilots operating Category A
and Category B aircraft. Further research into pilot workload and
losses of situational awareness associated with RNAV (GNSS)
approaches is warranted.

Safety Recommendation

The Australian Transport Safety Bureau recommends that the Civil
Aviation Safety Authority address this safety issue.

Organisation Response
Date Received
Organisation
CASA
Response Status
Monitor
Response Text

In respect of recommendation R20060019, CASA will have the
findings of the report considered by the Australian Strategic Air
Traffic Management Group (ASTRA), consult with regulators overseas
and review research findings from other studies (particularly a
recent one by Leeds University in the UK). It would be helpful,
however if the ATSB would provide further clarification on the
additional research that it recommends be undertaken into pilot
workload (especially given the low response rate and limited
available data cited in the present study).

ATSB Response

In response to this recommendation CASA noted that there was
limited available data cited in the ATSB report concerning pilot
workload.  The ATSB study was based on subjective
estimates of workload and other factors by pilots and the results
suggest that follow-up research with objective measures of workload
is warranted. As we point out in our report, there have been very
few other studies conducted on this matter, and the few that have
been published tend to restrict their focus to high capacity RPT
operations, where workload issues may be substantially different
from those faced by pilots in other operational categories and/or
single pilot operations (typically Category A and Category B
aircraft).  ATSB therefore holds the view that additional
research on this topic is warranted to extend the knowledge gained
from our own research, and particularly to better understand the
differences in workload and time pressures faced by pilots of
Category A and Category B aircraft compared with other instrument
approaches and pilots of high capacity, multi-crew airline
operations.

The ATSB acknowledges that CASA has developed important and
useful educational material to assist pilots with the transition to
RNAV (GNSS) approaches, and that this information was recently
updated and reissued.  The ATSB also notes that CASA touched
on this issue in an article in a recent edition of Flight
Safety Australia. 

ATSB Response date
Date Received
Organisation
CASA
Response Status
Monitor
Response Text

In regard to R20060019, CASA will continue to monitor
developments in this area, particularly in the United Kingdom. To
this end, CASA will be meeting staff of the UK CAA shortly to
discuss recent work done by them on RNAV (GNSS) approaches. The
issues raised in your report have also been raised at the recent
ICAO Navigation Systems Panel. At the present time, however, it is
unlikely that CASA will be in a position to commission specific
research, either from universities or in-house. 

Date Received
Organisation
Safety action rolled into AI-2007-2010 Safety Issue investigation
Response Text

This safety action was closed without a redesign of the Lockhart
River runway 12 approach. A Safety Issue investigation
(AI-2007-010) into the design of the Lockhart River runway 12 RNAV
(GNSS) approach with respect to activation of Mode 2A ground
proximity warning system (GPWS) is continuing. This Safety Issue
investigation has established that RNAV (GNSS) approaches can now
be redesigned using the revised obstacle clearance areas released
by ICAO on 31 October 2008. The revised obstacle clearance areas
should enable some RNAV (GNSS) approaches to be re-designed with
simpler intermediate segment lengths and profile gradients. It may
also allow for the moving the Lockhart River Runway 12 RNAV (GNSS)
approach away from 'South Pap' which may remove the current
requirement for uneven intermediate segment lengths and/or steeper
than normal profile.

Date Received
Organisation
Airservices Australia
Response Text

On 18 September 2009, Airservices Australia advised the ATSB
that the Lockhart River runway 12 RNAV (GNSS) non-precision
approach had been redesigned using the revised ICAO PANS-OPS DOC
8168 design criteria for RNAV (GNSS) approaches. The procedure has
been flight validated. The new approach is more direct and allows
for a straight approach to the Lockhart River runway, rather than
the existing five degree off set. The minima, or lowest point for
descent on the approach, has been reduced by around 60 feet and the
approach now largely follows the valley into Lockhart River.
However, due to terrain considerations, the PANS-OPS terrain
clearance criteria did not allow the standard 5-5-5 NM segments to
be included. The new approach will be published in the Aeronautical
Information Publication amendment effective 19 November 2009.

ATSB Response

The ATSB accepts that Airservices Australia has now met the
intention of the safety recommendation. Although it is probable
that the pilot workload associated with this approach is still
higher than for standard 5-5-5 NM segments, as the approach now
follows the valley and the approach chart displays coloured terrain
contour lines, the risks have been reduced as low as reasonably
practicable given the confines of the terrain and PANS-OPS design
criteria. The ATSB has closed this safety recommendation - action
taken.