Recommendation

Evidence in support of this recommendation at the time of the
issue of the final report on 4 April 2007 included that Honeywell
had conducted Lockhart River Runway 12 RNAV (GNSS) approach
simulations (using groundspeeds typical of a Category B and C
aircraft) for the constant angle approach along the recommended
3.49 degree profile and a step-down approach along the segment
minimum safe altitudes (see page 68 and Appendix C of the final
report). The simulations indicated that mode 2A alerts and warnings
should be generated during both the constant angle and step-down
approaches at both speeds when in the approach flap configuration.
These alerts and warnings occurred in the vicinity of South
Pap.

The final report also included information on reports received
by the ATSB following the accident involving VH-TFU from the pilots
of two aircraft, that they could not conduct the Lockhart River
Runway 12 RNAV approach without the GPWS announcing 'terrain
terrain pull up pull up'. This was reported to occur in both
aircraft types (one was a Category B performance aircraft and the
other Category C). The occurrence was always after passing LHRWF
inbound and the pilots reported that the warnings had occurred
while the aircraft were on the published constant angle approach
path with the autopilot coupled to the flight management system, in
the approach configuration, and within the appropriate approach
speeds for the aircraft category.

The report also noted the report from a pilot of another
operator who recalled conducting a runway 12 RNAV (GNSS) approach
soon after the procedure was published. He stated that the approach
was flown with the autopilot coupled to the flight management
system, which had calculated a constant angle approach path. The
pilot reported that the GPWS did not generate any alerts or
warnings. The ATSB was unable to confirm the aircraft configuration
or the calculated constant angle approach used on that
occasion.

The ATSB has subsequently received a further report of EGPWS
warnings and alerts being activated when flying the normal approach
profile for the Lockhart River Runway 12 RNAV (GNSS) approach (as
advised to CASA by e-mail on 31 May 2007). Specifically, on 29 May
2007, the crew of a Super King Air 350 was on the approach when the
EGPWS system generated both a 'terrain terrain' alert and 'pull up'
warning when the aircraft was in the vicinity of South Pap. The
crew reported that the published constant angle approach was being
flown with the autopilot engaged in a flight management system mode
which was providing vertical guidance with the crew cross-checking
the altitudes with the approach chart. The crew conducted a
go-around and missed approach manoeuvre and attempted a second
approach. During the second approach, flying the same constant
angle approach, the same alerts and warnings were heard.

Given the evidence gathered during the investigation, the
subsequent report from the crew of the Super King Air 350, and the
results of the test flights conducted by CASA on 22 May 2007, the
ATSB has initiated an investigation into the conduct of Lockhart
River runway 12 RNAV (GNSS) approaches as a transport safety
matter, as defined in Section 23(2) of the Transport Safety
Investigation Act 2003. As part of that process, the ATSB
would appreciate a copy of the Flight Data Recorder (FDR) data
relating the test flights conducted by CASA on 22 May 2007 (Section
32 Notice to be provided separately as per normal procedure through
CASA Corporate Relations).

Noting that CASA is also examining this issue further, the ATSB
has classified the status of this recommendation as 'Monitor'.

The ATSB is concerned that the flight test did not provide a
true validation test as the TAWS Class B (TAWS-B) as fitted to the
test aircraft is a reduced capability system aimed at reducing the
cost of the equipment for use in general aviation. The primary
difference between TAWS-A and TAWS-B is that TAWS-B does not
include the basic GPWS components, which are dependent upon a
height input from a radio altimeter. As such, it is our
understanding that the aircraft was not appropriately equipped to
conduct flying to validate (or otherwise) the activation of the
ground proximity warning system mode 2A warnings that was the
subject of ATSB recommendations R20070005 and R20070008.

The implication of the second paragraph above is that the
TAWS/GPWS warnings are due to incorrect operation of the aircraft
in that they are 'incorrectly configured'. It is the ATSBs
understanding that for many aircraft (particularly those in the
general aviation sector), that it is not normal for the aircraft to
be configured with full landing flap at the final approach fix and
that the flap may not be fully deployed until the aircraft becomes
visual.

The ATSB also makes the following comments in relation to the
recommendations contained in the report attached to your
letter.

Recommendation 1: As noted in Air Transport Communication
(ATcom) issue 2, dated Friday 18 July 2008, APV approaches are
'some time away' and it is our understanding that unless the APV
solution in Australia is compatible with overseas systems (for
example, WAAS) the expense and complexity of such systems will
result in them being feasible for the higher end of the market. The
majority of general aviation will still be dependant upon existing
approach designs, primarily RNAV (GNSS).

There may be an interim solution by redesigning the approach to
the new version of ICAO PANS-OPS that could result in a more
closely runway aligned approach, providing lateral clearance from
the South Pap Terrain feature. The ATSB supports an assessment of a
redesigned RNAV (GNSS) non-precision approach using the new ICAO
standards as an interim measure.

Recommendation 2: The ATSB agrees with this recommendation, with
the reservation regarding the feasibility and availability of the
equipment required for APV approaches discussed above.

The ATSB remains willing to assist CASA in any way possible to
resolve any outstanding issues with our collective aim to improve
safety.

The ATSB is continuing the Safety Issue investigation into the
conduct of Lockhart River runway 12 RNAV (GNSS) approaches as a
transport safety matter.

The ATSB recognises that the revised Lockhart River runway 12
RNAV (GNSS) non-precision approach has now met the intention of the
safety recommendation and has closed this safety recommendation -
Action taken.