Airservices Australia should note the safety deficiency
identified in this document and take appropriate action.
SUBJECT - INSTRUMENT APPROACH DESIGN
INTRODUCTION - REGIONAL AIRLINES SAFETY STUDY
Between October 1995 and July 1997 the Bureau of Air Safety
Investigation undertook a study of the safety of Australian
regional airlines. The objectives of this BASI safety study were
to:
(a) identify safety deficiencies affecting regional airline
operations in Australia; and
(b) identify means of reducing the impact on safety of these
deficiencies.
For the purposes of the survey, regional airlines were grouped
according to the number of passenger seats fitted to the largest
aircraft operated by that airline in January 1997. The groups are
defined as follows:
(a) group 1: 1-9 seats;
(b) group 2: 10-19 seats; and
(c) group 3: more than 20 seats.
The Regional Airlines Safety Study involved analysing data
obtained from:
(a) responses to a survey of Australian regional airline
employees;
(b) discussions with Australian regional airline employees and
managers;
(c) air safety occurrence reports involving regional airlines over
a 10-year period (1986-1995) from the BASI database.
This Safety Advisory Notice addresses one of the safety
deficiencies identified as a result of this study.
SAFETY DEFICIENCY
Some instrument approach procedures require an aircraft to fly a
missed approach toward high terrain when an alternative track is
available that would provide greater terrain clearance.
Survey Results
In their answers to questions related to instrument approach
procedures, six respondents stated that the missed approach track
for specific approaches was towards high terrain and that
alternative tracks would provide greater terrain clearance. The
airfields mentioned were Ballina, Lismore, Mt Gambier and Port
Lincoln.
"The missed approach paths [from the NDB and VOR approaches at Mt
Gambier] take you towards the only hill in the area - Mt Gambier!
For guaranteed performance (i.e. turbine aircraft) this is not a
problem, but what about piston twins?"
- Pilot, respondent 371.
ANALYSIS
The four airports that were identified by survey respondents as
having missed approach tracks directed towards high terrain are all
serviced by small- or medium-piston or turbo-propeller engine
aircraft. Generally, the performance capability of these aircraft
is limited, particularly during single-engine operations. The
missed approach is one of the more hazardous phases of flight as
aircraft are likely to be in close proximity to terrain and
operating in instrument meteorological conditions. In addition, the
crew may also be dealing with an emergency such as an engine
failure. A redesigned missed approach track at Ballina, Lismore and
Mt Gambier would provide maximum terrain clearance during the
missed approach for both normal and emergency operations.
Note: The Port Lincoln instrument approach chart was amended on 21
May 1998. This amendment revised the procedure so that the missed
approach track is now directed away from high terrain.
Airservices Australia should note the safety deficiency
identified in this document and take appropriate action.
The suggested changes to the missed approach paths for the
instrument approach procedures into Ballina, Lismore and Mount
Gambier airports have been examined by our procedure design staff
and their comments are outlined below.
BALLINA: The published NDB procedure calls for a right turning
missed approach onto a heading of 060 degrees. The reason a right
hand turn was chosen was because a left turn would have infringed R
622, Evans Head Bombing Range. It should be noted that the
published circling minima of 800 FT for Cat A&B aircraft will
ensure a minimum of 300 FT of obstacle clearance in the turn
area.
LISMORE: The straight ahead missed approach provides for the
lowest circling minima. A turning missed approach would require an
increase in the circling minima in view of the increased obstacle
clearance requirement for obstacles in the turn areas. It should be
noted that the published circling minima is already very high at
1180 FT or 1145 FT above the airport and any increase of that
minima would make IMC operations into Lismore airport marginal.
Also, because the airport is surrounded by terrain, a straight
missed approach up the valley was considered the best and safest
option.
MOUNT GAMBIER: Although the published missed approach meets all of
the PANS OPS missed approach design criteria, it is agreed that a
slightly turning missed approach away from the terrain to the south
of the airport would improve the procedure. Accordingly, the missed
approach paths will be redesigned and the revised procedures
published at the earliest opportunity.
You can be assured that all of the factors identified in your
safety study are taken into consideration during the development of
these procedures. If you have any further questions on this topic
or on the responses given above, please don't hesitate to contact
the Procedure Design Section Manager, [name supplied] on [number
supplied].