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Safety Advisory Notice issued to: Airservices Australia

Recommendation details
Output No: SAN19980115
Date issued: 29 July 1998
Safety action status: Closed
Background:

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.

Output text

Airservices Australia should note the safety deficiency identified in this document and take appropriate action.

Initial response
Date issued: 17 August 1998
Response from: AirServices Australia
Response text:

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].

 
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Last update 01 April 2011