Interim Recommendation IR19970110

Interim Recommendation issued to: Airservices Australia and the Civil Aviation Safety Authority

Recommendation details
Output No: IR19970110
Date issued: 04 July 1997
Safety action status: Closed


Procedures and facilities to improve the safety of regular public transport (RPT) aircraft operating within an MBZ or CTAF.


The pilots of two aircraft operating low capacity RPT flights to Bundaberg received traffic information on a general aviation instrument flight rules (IFR) aircraft inbound to the aerodrome. The estimated times of arrival for the three aircraft at the aerodrome were within a ten minute period. The pilots of the two RPT aircraft could not establish radio communications with the other pilot on the published MBZ frequency and could not ascertain that aircraft's position. The weather at the aerodrome was instrument meteorological conditions (IMC) requiring the pilots to conduct instrument approaches.

One of the RPT aircraft landed and the pilot observed the general aviation IFR aircraft in the circuit. After further attempts to establish radio communications the pilot was discovered to be operating on an incorrect frequency.


The current procedures for communications in MBZs and CTAFs are not fail-safe. There are insufficient defences to minimise the risk to RPT operations of a failure of communications.


The procedures to enable pilots operating under MBZ or CTAF procedures to establish that their radio is transmitting and receiving on the appropriate frequency are limited to receiving responses from other aircraft on the same frequency. There are no other procedures for a pilot to confirm the correct operation of communication equipment.

Records of reported incidents of a lack of radio calls in MBZs and CTAFs indicate that between April 1996 and April 1997 there was an average of 11 incidents per month Australia wide. It could be expected that this is only a small sample of the communications failures that do occur. Without a definite response by either a ground based radio operator or interrogation device, a pilot cannot be assured that the correct communication channel has been established.

The operation of regional airlines to aerodromes in which MBZ and CTAF procedures apply means that fare paying passengers are being subjected to a reduced level of safety when there are breakdowns of these procedures.

The problem of operations in MBZ and CTAFs, highlighted by the incident, was discussed at a meeting attended by the Bureau of Air Safety Investigation (BASI), Airservices Australia and the Civil Aviation Safety Authority (CASA) on the 7 June 1997. The meeting agreed that BASI would frame appropriate recommendations.

Implementation of procedures and facilities that would ensure that the MBZ and CTAF operations are conducted in a fail-safe manner would improve the level of safety for airspace users and fare paying passengers.

Output text

The Bureau of Air Safety Investigation recommends that Airservices Australia and the Civil Aviation Safety Authority:

1. implement methods for the timely dissemination of the MBZ or CTAF frequency to pilots;

2. implement methods of providing to pilots confirmation of the correct selection and operation of an MBZ or CTAF frequency;

3. examine the requirement for the establishment and operation of traffic alerting services at all aerodromes during RPT operations;

4. examine the provision of additional radar coverage in the Bundaberg area; and

5. examine the provision of surveillance for other locations serviced by RPT operations.

Initial response
Date issued: 11 September 1997
Response from: AirServices Australia
Action status: Closed - Accepted
Response text:

Reference is made to the Bureau's Air Safety Interim Recommendation No IR970110 which relate to communications procedures for MBZ and CTAF.

With regard to Interim Recommendation 1, Airservices have issued a NOTAM instructing pilots to report the frequency to which they are changing as part of the "Changing To" call. The frequency quoted is, whenever practicable, recorded by ATS for the information of other pilots. Airservices do not intend providing the MBZ or CTAF frequency to pilots on an individual basis as a matter of routine. Other methods of disseminating the MBZ or CTAF frequency, e.g. via AWIB broadcast will be taken into consideration.

It should be noted however, that the longevity of this procedure is not great, given the likely directions of Airspace 2000 and introduction of the National Advisory Frequency (NAF) in Class G airspace.

Interim Recommendations 2 and 3 fall within the CASA areas of responsibility for a response.

Interim Recommendations 4 and 5 relating to the provision of additional surveillance in the Bundaberg area and for other locations serviced by RPT will be considered by Airservices.

Last update 01 April 2011