Recommendation R19980143

Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: R19980143
Date issued: 05 November 1998
Safety action status:



There is currently little or no guidance on effective methods that pilots can use to ensure that radio equipment is fully functional prior to flight. This is a particular hazard when aircraft are operating in mandatory broadcast zones (MBZ) or common traffic advisory frequency (CTAF) areas, where alerted see-and-avoid procedures are intended to provide a higher level of safety. The Bureau continues to receive many reports of serious incidents in MBZs that involve poor usage of radio.


Occurrence summary

The pilot of a Beechcraft 200 King Air reported hearing a radio carrier wave on the mandatory broadcast zone (MBZ) frequency at the same time that he observed a Beechcraft Baron (Baron) taxiing. During its take-off roll, the Baron passed in front of a Fairchild Metroliner that was on final approach for the crossing runway.

Later that day, in heavy rain, the same Baron was on short final approach for a landing while a high capacity air transport aircraft was decelerating through about 80 kts on the reciprocal runway. Shortly before touch down, the pilot of the Baron initiated a go-around and commenced to climb. Witnesses estimated that the Baron passed some 100 m in front of, and 20 ft above, the other aircraft. Again, no radio transmissions were heard from the pilot of the Baron. Poor visibility, and the absence of two-way communication, resulted in a loss of awareness of each other's position and intentions, even though the crew of the airliner and the Baron pilot were aware of each other's presence.

The Baron pilot later reported that he had been making all the required radio calls and that he did not recognise that he had experienced a radio malfunction until he was approaching his final destination.

Related occurrences

The airline operator stated that company aircraft had been involved in 43 air safety occurrences in MBZs since 1 January 1995, in which other aircraft had experienced problems with radio communications, or problems with published procedures. In the same period, the Bureau has recorded approximately 65 reported occurrences relating to problems with communications in MBZs. In May 1998, a regional airline aircraft carrying fare-paying passengers was involved in a near head-on collision with a privately operated Cessna 172 (C172), also in an MBZ. No radio transmissions had been heard from the pilot of the C172. Investigation of this occurrence revealed that the effective range of the radio in the C172 was less than 2 NM.


Civil Aviation Regulation 242-Testing of radio apparatus, requires that a pilot check that the radio apparatus fitted to the aircraft and to be used in flight is functioning correctly, prior to taxiing for takeoff. The regulation does not specify how this is to be achieved. For specific details on correct procedures, pilots refer to a wide variety of other Civil Aviation Safety Authority (CASA) references including the Civil Aviation Orders, the Aeronautical Information Publication (AIP) and its supplement, the Civil Aviation Advisory Publications, and Aeronautical Information Circulars. Other sources of information that may be used by pilots are the documents specific to aircraft, such as Pilots Operating Handbooks, Flight Manuals, and relevant checklists. Pilots that have completed their training may also refer back to various other texts and notes that they had been supplied with or purchased as part of their flying training course. While some of these documents may contain suggested methods to check radio serviceability, the CASA publications that are regularly referred to, such as the AIP, do not contain any procedures, recommendations or guidelines regarding the conduct of such a check.


During the incident flight, the pilot received little direct evidence that the two radios were not functioning correctly. A transmit light was indicating that he was broadcasting. He was also receiving radio transmissions satisfactorily and no radio transmissions were made by others to alert the pilot to his aircraft's radio problems.

The Baron pilot held a private pilot licence at the time of the incident, and had approximately 400 hours of flying experience. His training had been conducted at a variety of training organisations, and had begun prior to 1990. Since commencing this training, numerous airspace and procedural changes had taken place. As the pilot already possessed a licence, the operator of the Baron was not required to obtain the pilot's flying training records from his previous training organisation/s.

In order to obtain a private licence, pilots receive training based on the guidelines in the CASA publications, the Day Visual Flight Rules Syllabus, and the Flight Radio Operators Licence Syllabus. These documents do not detail specific methods that pilots can use to identify radio failures. In order to provide procedural training for pilots that will satisfy the requirements of the syllabus, training organisations also refer to a wide variety of commercially available texts and study guides.

Competency-based training provides specific guidance for training schools in order for them to impart the knowledge and skills that a pilot must demonstrate before being granted a license. Such a system consists of a number of key competencies, such as "Solve Problems", each of which is divided into units such as "Operate Radio". The units would be further divided into specific tasks and skills. To be issued a license, a pilot would be required to demonstrate competency in all the units, and thus fulfil the requirements of the key competencies. As pilots demonstrated each skill a record would be produced of the completed training. As the acceptable standard for the issuing of a license would be detailed, a competency-based training system would provide consistency in training standards across all flying schools.

Aerodrome Frequency Response Unit

Following a serious breakdown of communications in the Bundaberg MBZ in 1997, BASI issued IR970110, which in part, prompted the introduction of aerodrome frequency response units, or beep-back units, at some locations. This is an automated system that responds to a radio transmission on its frequency with either a tone or a read-back of the location. A beep-back unit is effective in informing pilots that they are on the correct frequency, and that they are transmitting and receiving normally. However, the unit cannot distinguish between a carrier wave only transmission and a modulated (voice carrying) transmission. Consequently, the unit responds normally to both types of transmission.


Operating at busy uncontrolled airports requires pilots to utilise alerted see-and-avoid procedures wherever possible in order to decrease the risk of collisions with other aircraft. Pilots, therefore, need to conduct an effective radio serviceability test and be able to recognise a possible radio failure. There is currently no specific mention of these matters in the Day Visual Flight Rules syllabus, nor is there any suitable procedure documented in CASA publications. In addition, knowledge and use of a recommended radio serviceability test procedure may not be receiving sufficient emphasis during initial and ongoing flying training.

Flying training organisations employ a variety of methods to train students. Subsequently, the content and depth of knowledge imparted to students, and the standard procedures taught, is likely to vary considerably. In addition, when students undertake flying training at a variety of organisations, there is an increased possibility that they will not acquire the required knowledge and skills to enable them to conduct their flying with a high level of proficiency and thus safety. Without an industry-wide, comprehensive and detailed syllabus, student pilots are also more likely to receive incomplete training. A competency-based training system, such as that which is currently being developed by CASA, may address the above deficiency and contribute to reducing the hazard of incomplete training. The system would produce a detailed record of all the training that a pilot has completed and would allow a pilot to transfer from one flying school to another without repeating or missing important aspects of training. As the competency-based training system would require a pilot to demonstrate each skill and procedure that is required, it would ensure that a student pilot learns both the theory and the application of these skills and procedures. Consideration also needs to be given to implementing a system whereby a pilot's flying training record is an accountable record of his/her flying training experience, in the same way that a logbook is intended to be an accountable record of a pilot's flying experience. This incident may have been prevented if the pilot had been required to demonstrate both an effective procedure to check the radio, and the ability to detect partial or complete radio failures, as part of his training.

While aerodrome frequency response units have made a positive contribution toward safe and effective communications in MBZs, this incident would not have been prevented had a unit been installed. Such a unit would have responded normally to the pilot's carrier wave only transmission and would have reinforced the pilot's perception that his radios were functioning correctly. Further defences are needed to reduce the likelihood and consequences of communication breakdowns to an acceptable level.

Output text

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority develop and publish an effective procedure by which pilots can ensure radio equipment is fully functional prior to flight.

In addition, the Bureau has also issued the following recommendation:


The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority consider the need to ensure that knowledge and use of a recommended radio serviceability test procedure forms part of initial and ongoing flying training.

Initial response
Date issued: 07 June 1999
Response from: Civil Aviation Safety Authority
Action status: Open
Response text:

The Authority has not been able to devise a practicable procedure which will guarantee that radio equipment is fully functional before flight. Training in radio operation using competency based standards will assist in establishing serviceability (see below), but circumstances will not always permit voice transmission capability to be confirmed.

Radio serviceability is testable at a controlled aerodrome or one with a certified air/ground operator, but a test transmission at the majority of uncontrolled aerodromes would not provide an indication that the radio equipment was functional unless reacted to by another aircraft. As noted in the occurrence brief, a transmit light does not necessarily indicate that a modulated signal is being broadcast. While the presence of a sidetone is generally indicative of a modulated voice transmission, this may not always be evident when using a hand held microphone.

The occurrence brief also notes that while aerodrome frequency response or "beep-back" units provide an assurance that the correct frequency has been selected, they cannot distinguish between carrier wave and modulated transmissions. Technical advice available to the Authority is that it would not be practicable to modify these units to respond only to voice transmissions.


ATSB response:

The following correspondence was forwarded to the Civil Aviation Safety Authority on 27 August 1999:

Thank you for your responses to the Bureau's recommendations, R19980143 and R19980144. The Bureau considers that the intent of R19980144 has been satisfied and CASA's response to the recommendation has therefore been classified Closed - Accepted.

The Bureau notes that CASA commented that "a test transmission at the majority of uncontrolled aerodromes would not provide an indication that the radio equipment was functional unless reacted to by another aircraft." The Bureau fully agrees with this statement. However, the possibility of other aircraft in the area that may be conflicting traffic is the very reason that pilots are encouraged to utilise alerted see-and-avoid procedures wherever possible. In most cases, other aircraft will be equipped with functional radio equipment, thus providing pilots with the opportunity to establish two-way communication or, alternatively, alert pilots to the possibility that aircraft radio equipment is malfunctioning. The Bureau accepts that there is currently no practicable procedure that will guarantee pilots that aircraft radio equipment is functioning correctly. However, in most cases, a test transmission would provide an additional defence that may prevent a collision.

The Bureau considers that regularly used CASA publications should contain a suggested method by which pilots, where possible and appropriate, can ensure that radio equipment is fully functional. Therefore, the Bureau has classified the CASA response to R19980143 as OPEN and request that it be reconsidered. Another copy of R19980143 is attached.


Further correspondence
Date issued: 27 September 1999
Response from: Civil Aviation Safety Authority
Response status: Closed - Accepted
Response text:

In relation to R19980143, you have requested that CASA reconsider its previous response, and include within CASA publications a method, to be used where possible and appropriate, by which pilots can ensure that radio equipment is fully functional.

Existing procedures for all aircraft require a taxi clearance at controlled aerodromes, and mandatory taxying broadcasts in MBZs and CTAFs; these provide assurance of radio serviceability at all controlled aerodromes and at non-controlled aerodromes where there is a manned radio service such as a Certified Air/Ground Radio operator or Unicom operator. In addition, where an ARFU installed at an aerodrome, a high, but not absolute level of assurance is also provided. AFRUs have been installed at more than 120 aerodromes used by two-pilot aircraft providing RPT services. IFR aircraft are also subject to further communications requirements in regard to contacting Air Traffic Services.

In general terms, therefore, the issue relates primarily to VFR aircraft at uncontrolled aerodromes that do not have such facilities. CAR 242 notwithstanding, whilst CASA supports the intent of R19980143, it contends that it is not practical to provide a defined process whereby pilots always have absolute assurance of the full functionality of their aircraft's radio equipment in every such type of operational circumstance.

Whilst additional 'test' transmissions could be recommended, or indeed mandated, CASA doubts that these would provide any worthwhile increase in the overall safety-of aircraft operations and at the same time could impose operational complexities.

CASA would welcome any specific suggestions that BASI might make which would result in a quantifiable enhancement in surety of radio serviceability in such circumstances.


Last update 01 April 2011