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An Embraer E120 (Brasilia) aircraft had departed from Cairns for Bamaga. The crew were maintaining flight level (FL) 220 in controlled airspace under the control of Brisbane Sector 10. They had reported their position as over Lockhart River at 1211 EST with an estimate for Bamaga of 1236. At about 50NM from Bamaga, the crew requested clearance to descend.

A de Havilland Dash 8 aircraft had departed Horn Island for Cairns at 1207 and the crew had reported to flight service (FIS 7) their intention to climb to FL210. The flight service officer instructed the crew to contact the Sector 10 controller when approaching controlled airspace for an airways clearance.

At 1220, the flight service officer passed traffic information regarding the Brasilia to the crew of the Dash 8.

At 1226, the controller instructed the crew of the Brasilia to leave the control area on descent and to report passing FL200, which was the base of controlled airspace in that vicinity. The crew commenced descent at that time and set up a rate of descent of 2,000 ft/min. Shortly after, the controller advised the crew that the Dash 8 aircraft was conflicting traffic for their descent and authorised them to transfer to the FIS 7 frequency.

The pilot in command was the handling pilot of the Brasilia while the co-pilot was performing the radio tasks. When they received a clearance to leave controlled airspace they commenced descent immediately and this action was followed by the receipt of traffic information regarding the Dash 8. The pilot in command quickly assessed that this traffic was in direct conflict and instructed the co-pilot to make a specific call to the crew of the Dash 8 as soon as he had transferred communications to the flight service frequency, rather than the general traffic call normally transmitted.

The co-pilot was waiting to report leaving FL200 as instructed by the sector controller. As a result of the instruction by the pilot in command, he made this report early using the phrase "approaching FL200" and selected the radio to the FIS 7 frequency as the aircraft was passing FL205.

Further delay was then experienced as the FIS frequency was congested. The aircraft was passing the base of controlled airspace and, as the weather was consistent with visual meteorological conditions (VMC), the pilot in command elected to continue visually rather than to level off in the control area. He was confident of seeing the Dash 8 and, in fact, saw the aircraft before the co-pilot could make his initial radio transmission on the FIS frequency.

At 1228, the crew of the Dash 8 contacted sector control for an airways clearance while passing FL188. The controller was unable to issue a clearance at that time because the altitude of the Brasilia was unknown and it was not clear if that aircraft had passed the Dash 8.

At the same time, the co-pilot of the Brasilia was attempting to contact the Dash 8 crew on the FIS 7 frequency to establish their respective altitudes. The crews eventually determined that the Dash 8 was climbing through FL190 while the Brasilia was descending through FL180. The Dash 8 crew had not seen the Brasilia but had seen a shadow pass over their aircraft. Having established that the aircraft had passed, the crew of the Dash 8 returned to the sector control frequency where they were cleared to enter controlled airspace on climb to FL210.

The point of conflict was outside of radar coverage but calculation indicated that the aircraft passed with no more than 2,000 ft vertical separation and no discernible horizontal separation.

 

Air traffic control

Brisbane Sector 10 was operated by a trainee controller under the supervision of a rated training officer. The trainee had obtained a rating on sector 11 approximately eight months earlier and had been operating that sector prior to commencing training on sector 10. The training officer was not the trainees regular training officer.

The trainee passed the Brasilia's Lockhart River position information to the FIS 7 officer at 1217 and during this coordination process, accepted the responsibility to pass traffic information on the Dash 8 to the crew of the Brasilia. The trainee discussed the passing of this traffic information with the training officer and correctly calculated a time of passing, which would be near to the point of descent for the Brasilia. The trainee felt comfortable with such confliction in controlled airspace and had prepared a plan for such an eventuality. The training officer would have preferred the trainee to ask for the Dash 8 crew to be transferred to the control frequency and perform the separation task in controlled airspace. However, the trainee decided to instruct the crew of the Brasilia to contact FIS 7 early, which would allow the two crews to arrange their own separation.

It was not until 1226, after the Brasilia crew had commenced descent, that the trainee finally communicated this traffic information. This broadcast was only made after a prompt from the training officer. The trainee had not written any prompt on the flight strip and was not required to do so. The callsign of the conflicting traffic was notated on the flight plan strip for the Brasilia after passing the information, which was in conformance with the procedures designated in the Manual of Air Traffic Services (MATS).

This was the first time that the trainee had been required to communicate traffic information in a situation where one aircraft was in controlled airspace and the other outside controlled airspace and did not feel confident about doing so. The trainee had intended to perform the task but became distracted by other work related matters.

Training

The trainee had not witnessed or trained for such a scenario since leaving the training college over 12 months before.

The Sector 10 training program was incomplete and the simulator exercises that were available did not contain any scenarios dealing with traffic conflict near the base of controlled airspace. Although more simulator training was scheduled, the trainee had only received two sessions due to simulator unavailability.

The procedures for flight strip annotation did not require any notation prior to passing traffic information and the trainee did not make any. However, the training officer's usual method was to make such a notation in order to provide a memory jogger, in case he became distracted prior to completing the task.

As the trainee was nearing the end of the training period, the training officer was prepared to give the trainee as much scope as possible to work unprompted. He had seen the trainee perform tasks satisfactorily to that point and felt confident that the information would be passed as required. He was surprised when the trainee issued descent instructions without passing the traffic information. Consequently, he prompted the trainee to make the necessary transmission.

Flight service

The flight service officer had correctly assessed the conflict between the aircraft when he received the coordination from the Sector 10 controller. The coordination included the phrase "calls you top of descent" which the flight service officer thought was exactly what would happen. He passed traffic information on the Brasilia to the crew of the Dash 8 and planned to pass information to the Brasilia crew when they first called on the FIS 7 frequency. However, the trainee controller volunteered to pass the information for him. He had calculated that the 2,000 ft difference between the cruising level of the Brasilia and the base of controlled airspace would have given him sufficient time to pass this information to the crew before they departed controlled airspace.

The flight service officer had made a judgement in relation to the rate of descent of the aircraft when there was no performance data provided for his reference.

At the time the Brasilia crew first attempted to make radio contact on the FIS 7 frequency, the frequency was congested. This situation resulted in the Brasilia crew being unable to make a broadcast on the FIS 7 frequency between 1227:30 and 1228:16.

Crew of the Dash 8

Having been given traffic information on the Brasilia shortly after departure, the crew of the Dash 8 elected to initially maintain FL190 while contacting sector control for an airways clearance. They expected the Brasilia crew to descend to FL200 outside controlled airspace to facilitate discussion between the crews in order to agree on a suitable method of separation.

On passing FL180, they changed to sector control frequency as planned. As they did so, they received a call from the crew of the Brasilia, on the FIS 7 frequency, asking for their height. They did not communicate with sector control immediately in order to converse with the Brasilia crew. By the time they had established their relative altitudes, the two aircraft had passed.

Documentation

Aeronautical Information Publication (AIP)

A pilot flying under the Instrument Flight Rules (IFR) may use Visual Flight Rules (VFR) procedures if flying in visual meteorological conditions. A regular public transport flight must proceed in accordance with IFR but this does not preclude the change to VFR procedures which allow a pilot to proceed on a "see and avoid" basis.

The AIP requires aircrews to establish communication on the relevant FIS frequency prior to descending from controlled into non-controlled airspace.

Manual of Air Traffic Services (MATS)

Chapter 3 of this document gives basic guidance to flight service officers in relation to passing traffic information and recognition of potential conflicts. It states, in part, that "when in doubt, advise". Although it contains the most likely circumstances for traffic assessment, it does not contain any guidance on aircraft performance.

Aircraft company procedures

Company documentation for the Brasilia operation reflected AIP requirements but allowed individual pilot interpretation. This situation did not necessarily reflect company policy in the area of radio communications when transiting from controlled airspace into non-controlled airspace.

The company operating the Brasilia were in the process of developing appropriate standard operating procedures when this incident occurred.

 

Air traffic control

The trainee had never communicated traffic information under these circumstances before and was unsure of exactly how to do so. The trainee had also not had to pass any traffic information during the training period on sector 10. This situation may have contributed to the delayed transmission.

The fact that the training officer and trainee had different preferred methods of notating flight strips and dealing with traffic conflictions near the control area boundary, may have caused some misunderstanding between the trainee and the training officer which, in turn, may have led to the delay in the training officer's prompt.

Flight service

Had the trainee controller not volunteered to pass the traffic information, the decision of the flight service officer to wait for the Brasilia crew to make their general broadcast on the FIS 7 frequency before passing traffic information on the Dash 8, may have resulted in the Brasilia passing through the level of the Dash 8 before the crew received the traffic information.

The predication that the crew of the Brasilia would contact him at "top of descent" did not allow for any of the delays that occurred. It did not allow for the fact that air traffic control generally obtain a pilot report of "leaving" a level before instructing that crew to transfer to the FIS frequency and that a pilot may wait up to one minute after leaving a level before making that report to air traffic control.

Crew of the Brasilia

Due to the short notice given to the pilot in command of the Brasilia about the Dash 8, he had to make a decision on whether to continue the descent. His choice to continue visually, even though he had not yet sighted the Dash 8 or made radio contact with the crew, was made when there was no separation assurance provided by the manoeuvre. However, the pilot in command of the Brasilia had sighted the Dash 8, while still in controlled airspace, and elected to continue descent on a "see and avoid" basis until radio contact was achieved.

This decision also meant that, due to the frequency congestion, the required broadcast on the FIS 7 frequency was not made until the Brasilia was outside controlled airspace.

Documentation

Aeronautical Information Publication

The AIP allows a pilot of an instrument flight rules aircraft to proceed on a "see and avoid" basis under visual flight rules when in visual meteorological conditions. These procedures were designed when the majority of aircraft were comparatively slow and operated at altitudes below 10,000 ft and may not be appropriate at 20,000 ft with aircraft closing speeds in the region of 500 knots. Whether this option should be allowed in all circumstances may need to be reviewed.

Manual of Air Traffic Services

The guidance for air traffic service officers in relation to traffic assessment in class "G" airspace was not specific in regard to the timely passing of traffic information and coordination. Judgement was left to the experience of individual officers and tended to vary from person to person.

 
  1. The sector 10 trainee had not received adequate training in the control of conflict situations near the base of controlled airspace.
  2. The sector 10 training officer was not familiar with the performance of the trainee and allowed the delay in passing traffic information to become significant.
  3. The sector 10 trainee did not pass traffic information on the Dash 8 to the crew of the Brasilia in a timely manner.
  4. The pilot in command of the Brasilia did not establish a positive separation procedure with the Dash 8 while on descent from controlled airspace.
  5. The crew of the Brasilia did not make the required radio broadcast on FIS 7 frequency prior to leaving controlled airspace.
  6. The pilot of the Brasilia decided to proceed visually and use "see and avoid" principles.
  7. The company procedures of the Brasilia crew did not specifically cover the radio procedures for flight from controlled airspace into non-controlled airspace.
 

Following investigation of the procedures relating to the use of "alerted see and avoid" and the provision and issuance of traffic information by air traffic services the Bureau of Air Safety Investigation issued interim recommendations (IR) 970175 on 30 January 1998 and IR980005, IR980020 and IR980021 on 25 March 1998 to Airservices Australia. Also, IR970155 was issued on 30 January 1998 to the Civil Aviation Safety Authority.

Subsequently, Airservices Australia responded to IR970175 in a letter dated 17 March 1998 and to IR980005, IR980020 and IR980021 in a letter dated 27 May 1998. The recommendations and the respective responses were:

IR970175
The Bureau of Air Safety Investigation recommends that Airservices Australia in conjunction with the Civil Aviation Safety Authority:

Review aviation regulations and instructions, with the aim of maximising the use of "separation assurance" procedures in conjunction with "alerted see-and-avoid" procedures by pilots of flights in Class G airspace.

The Airservices Australia letter stated:

"Reference is made to your letter of 30 January 1998 regarding BASI Interim recommendation IR970175. This Interim Recommendation more properly falls within the province of CASA to provide further guidance within the AIP about broadcast arrangements for aircraft leaving controlled airspace into uncontrolled airspace and should be addressed by CASA.

"However, inclusion of text similar to that at OPS CTL - 1 paragraph 14.2 "When determining when to make broadcasts on the Area VHF, the pilot should consider the performance of the aircraft and the possibility of frequency congestion, if the airspace is known to be busy "would appear appropriate in the NCTL section to reinforce the need for timely broadcasts to be made in these circumstances. Airservices would, therefore support the intent of the BASI recommendation."

Response classification: CLOSED-ACCEPTED

IR980005

The Bureau of Air Safety Investigation recommends that Airservices Australia review the guidance in the MATS for the passing of traffic information by ATS personnel to ensure pilots have adequate time to assess the potential for conflict with other aircraft.

The Airservices Australia letter stated:

"Airservices maintains an ongoing process of reviewing the content of MATS and in line with this recommendation the issue of flight progress strip presentation will be reviewed. I must point out that with the advent of the Advanced Australian Air Traffic System (TAAATS) and associated 'Stripless- environment, presentation of traffic conflict and alerts will be vastly different to that which is currently employed. ATS Operational Policy Branch is developing comprehensive procedures for processing traffic information under the new environment."

Response classification: OPEN

IR980020
The Bureau of Air Safety Investigation recommends that Airservices Australia review the MATS in relation to flight progress strip annotations, to assist ATS personnel to provide more timely traffic information to flight crew.

The Airservices Australia letter stated:

"Airservices has revised the methodology and parameters for passing traffic information in its "proposal to amend G Airspace procedures- originally planned for introduction on 16 July 1998. This procedure amendment has been deferred until later in 1998 to facilitate further consultation and development."

Response classification: OPEN

IR980021
The Bureau of Air Safety Investigation recommends that Airservices Australia review ATS proficiency and continuation training requirements with a view to personnel undertaking specific traffic information simulator training on a regular basis.

The Airservices Australia letter stated:

"Airservices has developed its refresher training program for delivery to operational Air Traffic Services officers to emphasise elements dealing with the provision of traffic information and actions to be taken when separation has or may have been compromised."

Response classification: OPEN

IR970155
The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority in conjunction with Airservices Australia:

Review aviation regulations and instructions, with the aim of maximising the use of "separation assurance" procedures of maximising the use of "separation assurance" procedures in conjunction with "alerted see-and-avoid" procedures by pilots of flights in Class G airspace.

The Bureau of Air Safety Investigation further recommends that the Civil Aviation Safety Authority:

Implement an education program for pilots to promote the use of "separation assurance" procedures in Class G airspace.

Local safety action

As a result of the investigation, the companies involved have revised their procedures in relation to radio communications by crews when transiting from controlled airspace into non-controlled airspace.

 
General details
Date: 04 July 1997 Investigation status: Completed 
Time: 1230 hours EST Investigation type: Occurrence Investigation 
Location   (show map):148 km SSE Horn Island, Aero. Occurrence type:Near collision 
State: Queensland Occurrence class: Airspace 
Release date: 01 February 1999 Occurrence category: Incident 
Report status: Final Highest injury level: None 
 
Aircraft 1 details
Aircraft manufacturer: Embraer-Empresa Brasileira De Aeronautica 
Aircraft model: EMB-120 
Aircraft registration: VH-XFH 
Type of operation: Air Transport Low Capacity 
Damage to aircraft: Nil 
Departure point:Cairns, QLD
Departure time:1105 hours EST
Destination:Bamaga, QLD
Aircraft 2 details
Aircraft manufacturer: de Havilland Canada 
Aircraft model: DHC-8 
Aircraft registration: VH-TNU 
Serial number: 203 
Type of operation: Air Transport Low Capacity 
Damage to aircraft: Nil 
Departure point:Horn Island, QLD
Departure time:1207 hours EST
Destination:Cairns, QLD
 
 
 
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Last update 13 May 2014