FACTUAL INFORMATION

Sequence of events

An Aerospatiale AS350B (AS50) helicopter had been hired by the Civil Aviation Safety Authority (CASA) to perform a flight test of a recently installed precision approach path indicators (PAPI) system. The airport owners, the Cairns Port Authority, had asked CASA to conduct the tests as part of the acceptance procedure prior to the commissioning of the pilot-interpreted approach aid. The PAPI site was located clear of the sealed runway surface but within the runway strip.

A CASA pilot had submitted the flight plan to air traffic control (ATC) via a phone call direct to the Cairns ATC Centre using a number that was provided for the notification of local flights. This procedure did not require flight planning via the regional briefing office in Brisbane.

The helicopter had been hired on the morning of the occurrence and there was insufficient time for the CASA pilot to be rated for solo flight in accordance with company procedures. Therefore the helicopter was operated by a company pilot as pilot in command with the CASA pilot as co-pilot. The CASA pilot briefed the company pilot as to the requirements as each test run transpired.

Runway 15 was the duty runway, and the crew of the helicopter commenced operations by testing the runway 15 PAPI system, conducting several runs to the runway centreline. On each occasion the helicopter landed on the runway, even though some parts of the approach were conducted off the centreline. After landing, the crew air-taxied the helicopter to a position near the PAPI site and conducted briefings with the ground party to ascertain their requirements for future runs. These manoeuvres sometimes resulted in the helicopter being held clear of the runway strip, but on occasions it remained within the strip boundaries. Other runway movements took place during this time, including periods when the AS50 was within the runway strip.

After completing the runway 15 tests, the crew were asked to hold away from the aerodrome while a B727 departed. They were then cleared by ATC to land on runway 33 to initialise the global positioning system (GPS) equipment with the ground party prior to commencing the runway-33 PAPI flight tests. The brief to ATC had indicated that the crew would require an approach to the centreline and then position the helicopter abeam the PAPI site, but remaining on the centreline, for initialisation. The crew entered a hover in this position, approximately 2 ft above the runway.

A Cessna 182 (C182) had just completed a parachute drop and the pilot had been instructed to make a visual approach to runway 15. He had continued this approach until over the runway threshold when, as no landing clearance had been issued by ATC, he reported short final. The aerodrome controller (ADC) then gave a landing clearance. The pilot then requested permission to "land long" to facilitate taxi to his company apron. This request was approved by the ADC. The crew of the helicopter heard these transmissions but elected not to question the ADC as they were unsure of the runway being used by the C182.

As the pilot of the C182 was about 20 ft above the runway surface and about to flare, he noticed the helicopter approximately 100 - 150 ft in front of him and commenced a go-around. The C182 passed immediately above the AS35 and came within 15 ft of that helicopter.

Both aircraft subsequently completed their operations without further incident.

Flight test requirements

The Cairns Port Authority had conducted several meetings with CASA's Cairns District Office in the months preceding the test flight regarding the requirements for a flight test of the PAPI systems. On 21 June 1996, the Cairns Port Authority had written to the Cairns District Office requesting the flight test be conducted on Monday 22 July 1996 and specified the personnel and equipment that they would provide. This date was agreed by the Cairns District Office.

At 1000 EST on the morning of the flight, the Cairns Port Authority contacted the Cairns District Office to inquire about the final arrangements. None had been made. A Canberra based CASA pilot was in Cairns on unrelated CASA business and, at approximately 1130, was asked to conduct the test flight. Shortly after, arrangements were made for the CASA pilot and a member of the CASA ground party to provide a general briefing prior to a scheduled departure of 1500. No ATC representatives were asked to attend this briefing.

Flight planning

The team briefing was given at about 1500, after which the CASA pilot phoned Cairns ATC and submitted a verbal flight plan for a local flight. This included information of a generally non-precise nature such as the requirement to make several runs from 2,000 ft and approximately 4 NM, and the need to initialise the GPS while hovering on the runway next to the PAPI sites. The pilot stated that he informed ATC of the need to make each approach to the runway centreline and of the possible requirement to use the runway strip after landing. Although all parties agreed that such a conversation did take place, the investigation was unable to obtain evidence of the exact details contained in the flight plan notification.

A CASA ground party member had, in the month preceding the flight test, obtained a sample flight plan from the Melbourne-based flying unit. This plan detailed the procedures and requirements to conduct such a flight test.

No written flight plan was submitted.

Air traffic control

There were five controllers in the tower at the time of the occurrence. A rated ADC had controlled the initial runway-15 PAPI checks and had instructed the crew of the helicopter to track towards runway 33 and then handed over to a rated ADC who was undergoing familiarisation following a period of leave. The current ADC remained at the console supervising the familiarising ADC and, although feeling a little tired, considered himself fit to undertake the task.

The familiarising ADC issued a clearance for a B727 to depart and then cleared the helicopter to land. In doing so, he wanted to refer to the PAPI site in his transmissions but became confused as to the name of the PAPI during his instructions to the helicopter crew. Consequently the supervising ADC moved away from the console and picked up the instructional material on the equipment for the familiarising ADC to read. The helicopter then landed on the centreline, next to the runway 33 PAPI site, and commenced initialisation. Both ADCs were then of the opinion that the helicopter had manoeuvred to a position outside the runway strip markers, even though the clearance to land authorised the crew to use the runway and runway strip. No transmission clarifying this situation was made.

As the familiarising ADC was reading the PAPI documentation, the pilot of the C182 reported short final. The ADC looked up, saw the C182 over the threshold, made a quick scan of the runway and, believing the helicopter to be clear of the runway strip, issued a landing clearance. He then approved the long-landing request because there were no other aircraft needing to use the runway.

The pilot of the C182 then reported that he was going around due to a helicopter on the runway.

Neither ADC saw the C182 until the pilot reported short final because its approach had been across the setting sun, which severely restricted their observations in that sector. They had used the radar to monitor its position relative to the aerodrome. All the controllers thought that the helicopter had operated outside the runway strip markers during its work on the runway-15 PAPI site, even though the initial approach was on the centreline.

Although the two ADCs believed that the helicopter was hovering outside the markers, some of the other controllers believed that the helicopter was within the runway strip. They were each attending to their own tasks at the time and did not look specifically at the runway until after the clearance for the C182 to land long was given. Although two of the controllers saw what they considered to be a conflict, they had insufficient time to speak before the pilot of the C182 had commenced his go-around.

The flight progress strip for the helicopter was in the sequence bay at the ADC console, a position that indicated authorisation for the use of the runway.

Meteorological information and tower location

The incident occurred at approximately 1730, when the sun was low on the horizon and the sun shields in the tower were deployed to minimise the effect of the brightness. This situation made it difficult to see the C182 as it made its turn onto final and the controllers did not see the aircraft at all until short final.

There were many areas of shade and sun covering various parts of the runway, but the position of the helicopter was such that it was in one of the better situations for sighting purposes. However, the comparatively low aspect of the control tower cabin, when combined with the hover height of 2 ft, enabled the ADCs to see grass from the far side of the runway strip under the helicopter skids. The controllers stated that this caused a visual perception of the helicopter being beyond the grass and therefore clear of the runway strip.

Helicopter crew

The helicopter was equipped with a communications system that allowed only the pilot in command to use the radio and consequently, all communications with ATC were performed by the company pilot. However, the flight-test requirements were being specified by the CASA pilot who was the flying pilot for the majority of the tasks. This system therefore required a relaying of requests through both pilots with a resultant increase in workload.

Even though a flight plan had been notified, each test run was slightly different, and the company pilot was unaware of the changes until briefed by the CASA pilot immediately before the run commenced. These briefings included requests from the ground party prior to each run.

During the runway-15 PAPI tests, the crew had made their approaches to the runway centreline and had remained on the runway for most of the time between runs. They had received a landing clearance in each case and that entitled them to remain on the runway until commencing the departure phase of each run. They usually hovered over the grass area when co-ordinating with the ground party. During these manoeuvres, the helicopter hovered both inside and outside the runway strip markers while runway operations continued.

Pilot of the C182

The pilot had received a clearance to make a visual approach and considered it normal to call short final over the threshold and with the speed of the aircraft approximately 130 kts. It was also normal to ask for a long landing in order to minimise taxiing distances to the company dispersal area.

After receiving a clearance to land, he scanned the runway twice but did not see the helicopter. As he was about to touch down, he did see the helicopter and commenced a go-around.

ANALYSIS

Flight planning

Despite agreeing to a date for the flight test a month earlier, the Cairns District Office did not organise the operation until the morning of the test. The CASA pilot just happened to be available at short notice and was not briefed on the requirements until approximately 4-5 hours before the flight.

The verbal pre-brief was not sufficiently adequate for the complexity of the task and did not specify the particular and unusual requirements of the test flight.

The phone facility to ATC was designed for general operations of local flights and not for "one-off" specific tasks of this nature. The complexity of the test was such that it required a specific pre-brief of ATC and a full flight plan, so that all parties were aware of the requirements. The phone plan left the controllers unsure of exactly what was going to happen. This situation resulted in control being based on individual descriptive requests from the helicopter crew as they happened and the belief that the runway was not going to be used after the initial approach.

Aircrew

While both aircrews complied with their respective clearances, each could have been more proactive in putting into place some form of safety net.

The pilot of the C182, by not reporting short final until over the threshold, did not give the ADC time to compensate for any error that may have been made.

The crew of the AS50 heard a landing clearance being given to the C182 but were unsure which runway was being used. They elected not to question the ADC as to the status of the runway.

Aircraft markings

The AS50 helicopter was painted in generally dark colours which made it difficult to see from above, especially above and behind. The lack of contrast between the grey blur effect of rotating rotor blades and the grey of the runway surface gave few visual cues to the pilot of the C182 as he approached to land.

Air traffic control

The controllers believed that the helicopter was operating clear of the runway strip most of the time and considered that the runway-15 PAPI tests were conducted on this basis. While it was unclear how many runs were made to the runway-15 PAPI site, there were in fact, several. However, each one resulted in a landing on the runway centreline and subsequent taxi to the grass areas inside the strip markers. That situation meant that during these runs, ATC were not providing a positive runway separation service between the helicopter and other runway users. However, due to the airborne phase of the test runs involving the centreline, airborne separation was provided at all times. No controller sought clarification of the status of the helicopter following its approach to the runway-33 PAPI site, nor during the previous manoeuvres involving the runway-15 PAPI site.

The belief that the helicopter was operating clear of the runway strip was reinforced by the sighting of grass below the skids and the fact that helicopters rarely use the runways at Cairns. It is normal for helicopters to arrive and depart via a taxiway or helipad and remain clear of the runway at all times.

Because of the late call on final from the pilot of the C182, the ADC had insufficient time to adequately scan the runway for any unexpected obstructions. The fact that he was reading at the time, albeit about the PAPI approach aid, further diminished the amount of time available to perform this duty. It may have also led to a short-term loss of situational awareness.

The supervising ADC had been lulled into a false sense of security by the fact that the familiarising ADC was a rated controller who had been away for only 18 days. He was a bit tired and may have allowed himself to relax more than the circumstances warranted. He had also just left the console momentarily to find the PAPI information, and he thought that this action may have led to some loss of situational awareness.

SIGNIFICANT FACTORS

1. The preparation by the Cairns District Office did not contain an adequate plan for the flight test.

2. The CASA representatives did not adequately brief ATC.

3. Neither ADC maintained an adequate situational awareness.

4. The ADCs did not ensure that the runway was clear prior to issuing a landing clearance; contributing to this situation was the late "short final" call by the pilot of the C182.

SAFETY ACTION

As a result of the investigation:

1. The operator of the AS50 has painted white markings on the rotor blades to improve sighting opportunities from above.

2. The operator of the C182 has issued instructions for pilots to initiate a "final" call at least 300 m prior to the threshold.

3. Airservices Australia has replaced the tower blinds with a better quality product that reduces glare effect.

A Boeing 737 (B737) aircraft was being radar vectored onto final approach to runway 16R at Sydney from a right base, whilst another B737 aircraft was already established on a straight-in approach from 4,000 ft to runway 16L. The aircraft being radar vectored was given an initial instruction to turn right onto 060 degrees and descend to 3,000 ft, followed by a further instruction to turn right onto 130 degrees to intercept the 16R localiser.

However, this instruction was given late, resulting in the aircraft passing through the runway 16R extended centreline at 3,500 ft, conflicting with the leading B737, already established on final to runway 16L. The crew of the following aircraft had the other aircraft in sight at all times. At their closest point, separation was reduced to 1.2 NM laterally and 700 ft vertically. Instructions were then issued to both aircraft to resolve the confliction.

Details of the flight were forwarded to Bankstown Tower, and both Sydney and Brisbane Air Traffic Control centres.  As the plan was considered to be for the following day, it was held at the Aviation Data System Operators' desks in the two centres, and flight progress strips were not issued to the appropriate sector controllers. 

Consequently, when the crew requested a clearance there was a delay of about 40 minutes to the planned departure as time was spent locating the plan and flight progress strips.  Due to this delay, the crew elected to depart visually from Bankstown, via the lane of entry at 2,000 ft, outside controlled airspace.

The Bankstown tower coordinator controller notified Sydney Flight Service of the aircraft callsign, time of departure, tracking details and altitude.  As the flight had been originally planned to remain within controlled airspace, this was the first time that the Flight Service officer was provided with information about the Citation. The officer annotated a flight progress strip for the aircraft with the details provided.

The crew of a Twin Otter reported departure from Aeropelican aerodrome and indicated that the aircraft was tracking 215 degrees M, on climb to 6,000 ft. The Flight Service officer did not pass mutual traffic information to the crews of the Citation or Twin Otter, as the nominated altitudes of the aircraft provided vertical separation and ensured the aircraft were not in conflict.  When the Citation was north of the lane of entry, the pilot in command initiated a climb outside controlled airspace, anticipating that a clearance would become available which would allow the aircraft to continue climbing to the planned level of Flight Level 330. Recorded radio communications indicated that the Citation crew did not report climbing above 2,000 ft.

Shortly after the Twin Otter departed Aeropelican, the Flight Service officer handed over duty to another officer, a process which took about two minutes to complete.  The new officer then became engaged in coordinating clearances into controlled airspace for the Citation and another aircraft, and responding to a number of calls from other aircraft in the officer's area of responsibility. The Citation was then instructed to contact Brisbane centre for a clearance. Just after the pilot transferred to the Brisbane frequency, the Flight Service officer was advised by the Sydney Departures radar controller that the aircraft had passed in close proximity to the Twin Otter, while outside controlled airspace. Neither crew were aware of the proximity of the other aircrft.

The Flight Service officer handing over was expecting the pilot of the Citation to receive a clearance with little delay. His impression was that the aircraft would soon enter controlled airspace and would therefore remain in his area of responsibility for only a short period. Consequently, he did not request additional tracking information on the Citation such as the next position and estimated time interval. As a result, the Flight Service officer assuming responsibility for the area had limited information to assist in resolving the conflict. The situation was further compounded by the high speed of the Citation, in comparison to other general aviation aircraft, and the rate of closure with the Twin Otter. As the new officer became distracted by other coordination tasks there was insufficient time to appreciate the lack of positional information on the flight progress strip. Without that information the officer was unable to establish if a traffic conflict was likely to occur.

The Flight Service officer may have been assisted in identifying a conflict if the departure report for the Citation, provided by the Bankstown tower coordinator controller, included details regarding the next reporting point and estimated time interval. Current procedures require Bankstown tower controllers to notify only those details which were provided in this occurrence.

The absence of a report by the crew of the Citation, advising that the aircraft had left 2,000 ft and was climbing, was an important cue not received by the Flight Service officer. Without this cue, the officer continued to assume that the Citation and Twin Otter were vertically separated and not in potential conflict. Consequently, traffic information was not provided to the crews of either aircraft.

Safety Action

The Bureau is researching safety issues highlighted during the course of this investigation concerning aspects of Air Traffic Control coordination.  Any recommendations and responses will be published in the Bureau's Quarterly Safety Deficiency Report.

The thrust reverser fault light on the pilot' overhead panel illuminated when the aircraft was approaching top of climb out of Darwin. The crew completed the required check list items and elected to return to land at Darwin. Maintenance locked out the thrust reverser and the aircraft flew to Adelaide where the engine accessory unit (EAU) was replaced.

Thrust reverse control system

The thrust reverser control consists of a thrust reverser isolation valve and a directional control valve for each reverser. Each isolation valve is opened by switches. These switches sense motion of the control stand quadrant to command reverse thrust, and low altitude or compression of the right main gear for normal operation. Also, if a reverser sleeve is sensed to be not fully stowed, the isolation valve is opened and the directional control valve is commanded to the stow position.

Illumination of the reverser light in flight indicates that the reverser isolation valve is open and the directional control valve is in the stow position or vice versa. The light will also illuminate if the stow enabling relays for each sleeve disagree for more than two seconds.  The reverser light illuminates during normal stow and trips the master caution after approximately 12 seconds.

An open thrust reverser isolation valve will not, by itself, permit the reverser to be deployed in flight: the directional control valve requires ground logic and movement of the reverse thrust lever to move to the deploy position.

Similarly, a directional control valve in the deploy position will not, by itself, permit the reverser to be deployed in flight; the isolation valve also requires ground logic and movement of the reverse thrust lever to open.

System serviceability

The thrust reverse indication system has had a history of intermittent illumination of the overhead panel thrust reverser fault light. The manufacturer has addressed many of the causes through design changes such as the introduction of a spring-loaded proximity sensor, improved thrust reverser control switches located in the isle stand as well as introduction of a six-light engine accessory unit which facilitates trouble shooting.

However, many operators still report problems with troubleshooting the system. These problems have led to a high rate of removal of the EAU, testing of which was unable to confirm any unserviceability within the units. In 1993 the manufacturer introduced a sixteen light EAU capable of monitoring the individual state of each of the thrust reverser indication proximity sensors.

Continuing erroneous fault light illumination was traced to a certain batch of relays fitted to the EAUs. These were failing because of chemical/thermal corrosion of the coil wire, or insufficient clearance between the case and the armature, or cold welding of the relay contacts.

Operators engineering action

The operator is removing the suspect relays on a campaign basis and is having the improved EAU fitted to current delivery aircraft. However, the improved EAU will not be retrofitted to the existing fleet.

A modification that introduces an independent method of locking the stowed thrust reverser is being progressively introduced. So far, the operator has modified 9 out of its fleet of 30 aircraft.

Manufacturers advice

The manufacturer advised that the overhead panel reverser fault light has only one purpose: to inform the crew that the reverser may deploy if another fault develops. No immediate action by the flight crew is required. The manufacturer recommends that the flight should continue to its destination.

The manufacturer is currently assessing whether, with the independent method of locking the stowed thrust reverser installed, it is possible to suppress the reverser light in flight.

During the return leg of a standard joy flight at 500ft, an Osprey struck and penetrated the left windscreen. The front seat passenger was slightly injured by impact and suffered cuts from Perspex shards. Control of the helicopter was not affected, and the pilot was able to land safely.

During short final approach to land at the completion of a local scenic flight, the aircraft encountered excessive sink and a sudden increase in crosswind. As a result, the aircraft bounced heavily on the runway threshold. The pilot then elected to go around and immediately applied full power.

During the climb out he noticed that the wings appeared to be damaged inboard of the tip tanks. Both tanks were full at the time. A decision was then taken to divert to Archerfield where the runway direction would better suit the prevailing wind. An uneventful landing followed.

Post flight examination of the aircraft confirmed significant damage to both wings.

FACTUAL INFORMATION

An instrument flight rules (IFR) flight plan had been submitted for a training flight in a Cessna 172 aircraft departing from Kempsey to Port Macquarie and various other points before returning to Kempsey. The flight was a navigation exercise with a student pilot accompanied by an instructor. The flight plan had been received by the relevant flight information centre. The student pilot broadcast a taxi call on very high frequency (VHF) radio while on the ground at Kempsey,, but he did not receive a response from flight service. The taxi call was in accordance with radio transmissions required for IFR flights and the pilot included the term "IFR" in his transmission. The Cessna was not fitted with a high frequency (HF) radio and the pilot continued the flight using the VHF radio. The Cessna became airborne at Kempsey without the pilot nominating an estimated time of departure for search and rescue ("ETD for SAR") with flight service. The first contact with flight service was after becoming airborne at Kempsey. The pilot then reported departure but did not advise the flight service officer that the flight was operating under the IFR category.

The flight plan had been processed in the flight service centre and a strip posted in the suspense bay on the console applicable to the Kempsey region. However, the flight service officer did not notice the flight strip and assumed the Cessna was a visual flight rules (VFR) category flight because the pilot did not notify the flight as IFR when he reported airborne at Kempsey. Consequently, the officer did not provide traffic information or activate the strip which remained in the suspense bay. During the period between the time the pilot of the Cessna 172 reported airborne and the time he reported his departure from Kempsey, the flight service officer handed over duties to a new officer. The new officer acknowledged the departure report and advised the pilot the area QNH. As there was no strip in the active bay, and the fact that the previous officer had not briefed her on the Cessna during the handover, the new officer also assumed the flight was VFR category. The new officer did not observe the flight progress strip for the Cessna in the suspense bay and did not provide traffic information.

At the same time, a DeHavilland Dash 8 aircraft conducting a regular public transport flight (RPT) from Sydney, inbound to Port Macquarie on descent, reported on the flight information area frequency. The crew of the Dash 8 received traffic information on two other IFR flights in the area but not on the Cessna. Nor did the pilot of the Cessna receive traffic information on the Dash 8 or any other IFR aircraft. The crew of the Dash 8, after making an inbound broadcast on the Port Macquarie mandatory broadcast zone (MBZ) frequency, established communications with the Cessna pilot. During the exchange of position information, the crew of the Dash 8 ascertained that the Cessna was IFR category. The Dash 8 crew then queried the flight service officer regarding traffic information on the Cessna and the officer replied that she was unaware of the Cessna. The flight service officer then contacted the pilot of the Cessna on the area frequency, obtained flight details and provided traffic information to, and about, other IFR aircraft. The pilot of the Cessna observed the Dash 8 as that aircraft descended for landing at Port Macquarie. The Cessna did not conflict with the Dash 8 or other IFR- category aircraft. The flight service officer later found the flight strip for the Cessna amongst other strips in the suspense bay.

ANALYSIS

The Aeronautical Information Publication (AIP) OPS NCTL - 3 para. 47.1 states that an "IFR aircraft operating from non-controlled aerodromes must report to ATS before taxiing. If unable to establish contact, proceed in accordance with para. 45.1." Paragraph 45.1 of the AIP indicates that if an aircraft is unable to contact air traffic services on VHF or HF while taxiing, the flight may proceed on a broadcast basis provided:

1. contact is established as soon as possible after take-off, and
2. for non-RPT flights, an estimated time of departure for search and rescue (ETD for SAR) has been established with a maximum of 30 minutes from ETD.

In this incident the pilot of the Cessna was unable to establish communications with flight service but continued the flight on a broadcast basis without establishing an ETD for SAR. The act of nominating an ETD for SAR may possibly have alerted the flight service officer to the fact that the flight was IFR. Also, the incident may not have occurred if the pilot had reported the IFR category of the flight to the flight service officer on first contact, or during the departure report. If the report had been made, the flight service officer would have been alerted that the flight was IFR category and would have provided the appropriate traffic and SAR alerting service. This would have probably been the situation whether the officer observed and used the flight strip or not.

While both flight service officers should have been alerted to the flight by the presence of the flight strip, the lack of IFR category notification in the transmissions from the pilot of the Cessna predisposed both officers to believe the flight was VFR category. Consequently, they did not re-check the suspense bay for a flight strip nor seek confirmation from the pilot. The instructor in the Cessna was aware that the flight service officer had not provided information appropriate for an IFR flight but did not query the officer. Confirmation by the instructor or the pilot of the IFR category of the flight would have ensured that the appropriate service was provided.

Both flight service officers displayed poor work technique on the handover/takeover, which was inadequate. They did not review all the information that was available to them on the console. Had either officer checked the suspense bay on an opportunity basis they may have observed the strip and recognised the flight was IFR category.

The Cessna pilot's adherence to MBZ procedures in broadcasting position information when approaching Port Macquarie was an active defence in the incident and served to break the chain of events. The pilots of the Cessna and the Dash 8 were able to ensure their own immediate separation by providing position reports using the MBZ frequency and to subsequently establish the Cessna's category with flight service. Ultimately, this enabled all IFR aircraft in the area to receive the necessary traffic information and for the Cessna to be provided with a traffic and SAR alerting service.

SIGNIFICANT FACTORS

1. The pilot of the Cessna 172 did not report "IFR" on first contact with flight service.
2. Neither flight service officer adequately scanned the console during the handover/takeover procedure.

SAFETY ACTION

Local safety action

As a result of this incident and other recent minor occurrences, the Manager Flight Service Sydney has:

1. reviewed handover/takeover procedures; and
2. formed a post-incident review committee to vet incidents for deficiencies and to recommend measures to minimise recurrences.

Bureau of Air Safety Investigation safety action

The Bureau of Air Safety Investigation issued interim recommendation IR960096 to Airservices Australia on the 5 November 1996:

"The Bureau of Air Safety Investigation recommends Airservices Australia amend the Aeronautical Information Publication to clarify the requirement for IFR category flights to report "IFR" on first contact with ATS when operating from non-controlled aerodromes."

The pilot of VH-CVG contacted Darwin Approach for an Airways Clearance, but due to other traffic in the CTA the clearance was not issued at that time.

A short time later the pilot again contacted approach for a clearance, and the aircraft was then identified at 5,500 ft within the CTA causing a procedural breakdown in separation with the other aircraft. The pilot was not aware that he had entered the CTA steps.

FACTUAL INFORMATION

A formation of four Skyhawk A4 aircraft had been flight planned to depart from Nowra on a low-level jet route flight over central New South Wales and then return to Nowra. The flight was notified in accordance with the Manual of Air Traffic Services (MATS) procedures and included a Notice To Airmen (NOTAM) which had been issued the day prior to the flight. The initial track of the flight was from Nowra, direct to Cowra at flight level (FL) 220, after which the formation would descend to low level, outside controlled airspace. The initial segment of the flight was to be conducted in controlled airspace which was the responsibility of a Melbourne based sector controller. The Melbourne sector controller was required to coordinate the flight with Sydney arrivals and another Melbourne sector.

The formation was to be intercepted by another Skyhawk immediately after departure from Nowra. The intention was for this Skyhawk to depart prior to the formation and to hold overhead Nowra. The pilot of this fifth aircraft would then intercept the formation as it departed Nowra. The intercept was planned to be completed by the time the formation reached a point 20 NM north-west of Nowra. This was just inside the area of responsibility of the Melbourne sector controller. The limit of Nowra military controlled airspace, on the planned track, was 15 NM northwest of Nowra. After the intercept, the fifth Skyhawk would continue on the same route planned for the formation.

Notification of the flight of the fifth Skyhawk was included as a note on the flight plan for the formation. The note advised that an aircraft with a callsign "TBA" (to be advised), would operate within 20 NM of the formation and would conduct an intercept of the formation. The flight plan did not state that there would be five Skyhawks or that the intercept would be conducted in the area between Nowra and 20 NM to the north-west. One hour prior to the Skyhawks' departure, Nowra air traffic control (ATC) contacted Melbourne ATC and co-ordinated the expected use of a block level of airspace from FL180 to FL250 for all five Skyhawks during the intercept. The actual levels requested would be co-ordinated when the aircraft taxied.

This was the first time the Melbourne sector controller had experienced an intercept situation and the degree of co-ordination necessary was significantly different to that which he had previously conducted for flights from Nowra. Another controller offered to assist the sector controller, but the offer was declined. The fifth Skyhawk taxied first and was cleared in accordance with the flight plan at FL220. The Melbourne sector controller co-ordinated this clearance with Sydney arrivals.

When the fifth Skyhawk was ready to depart Nowra, ATC co-ordinated the use of a block level. The block level requested was from FL180 to FL250. Nowra ATC advised that the pilot would remain on Nowra's frequency until the intercept was completed. The Melbourne sector controller requested confirmation of the extent of the area required for the intercept and was advised by Nowra ATC that the Skyhawk may require operations between 20 NM and 30 NM from Nowra. The Melbourne sector controller concurred with the use of the block levels. The sector controller did not issue a clearance limit for the aircraft or co-ordinate the use of the block levels with Sydney arrivals.

The Skyhawk formation taxied shortly after and was cleared via the flight planned route at FL220. The Melbourne sector controller co-ordinated the clearance with Sydney arrivals. The fifth Skyhawk became airborne at Nowra and climbed overhead the airfield. Nowra ATC passed radar identification on the fifth Skyhawk to the Melbourne sector controller. Prior to the formation departing, the Melbourne sector controller twice queried Nowra ATC with respect to the actual levels to be used by the two elements of Skyhawks. On both occasions Nowra ATC confirmed that both the formation and the fifth Skyhawk would be operating in the block level from FL180 to FL250 during the intercept.

The Melbourne sector controller advised both the Sydney arrivals controller and the other sector controller that the aircraft would be conducting an intercept and operating in the block level in his sector before transferring to their sectors. The two other controllers requested confirmation that all the Skyhawks would be maintaining FL220 on entering their airspace. The Melbourne sector controller confirmed that the Skyhawks would be at FL220.

The formation of Skyhawks departed Nowra and was transferred from Nowra ATC to the Melbourne sector controller 10 NM north-west of Nowra. The fifth Skyhawk was 8 NM behind the formation and Nowra ATC requested approval to maintain the aircraft on their frequency as the pilot was taking longer than expected to intercept the formation. This was not in accordance with radar control procedures in MATS which require all aircraft being radar separated to be operating on the same frequency. The Melbourne sector controller approved the fifth Skyhawk to remain on Nowra's ATC frequency after confirming that the aircraft was on descent to FL220. Shortly after, the fifth Skyhawk entered the Melbourne sector controller's area of responsibility but remained on a Nowra ATC frequency.

The Melbourne sector controller passed the radar identification of the fifth Skyhawk to the Sydney arrivals controller and advised that the aircraft was on descent to FL220. The Sydney arrivals controller accepted control of the fifth Skyhawk at FL220 and indicated that he was concerned because of a northbound B737 at FL230 that would be crossing the track of the Skyhawks. Traffic information on the B737 was passed to both elements of Skyhawks by the Melbourne sector controller and Nowra ATC. At no stage was the clearance for either Skyhawk element amended to restrict operations, in the block level, to a level that would ensure vertical separation from the B737.

The Skyhawk formation leader sighted the B737, and the pilot of the fifth Skyhawk advised Nowra ATC that he would not climb above FL220. Nowra ATC advised the Melbourne sector controller that the aircraft would not be above FL220. All five Skyhawks then transferred to the Sydney arrivals frequency. The Skyhawks were approximately 50 NM north-west of Nowra.

The pilot of the fifth Skyhawk reported to the Sydney arrivals controller that he was maintaining FL190. This was not the level that had not been co-ordinated by the Melbourne sector controller. The Sydney controller had based vertical separation with other aircraft in his sector on the previously co-ordinated level, FL220. The Sydney arrivals controller instructed the pilot of the fifth Skyhawk to descend to FL180 due to a Saab 340 at FL190. The pilot of the Skyhawk requested FL220 and was subsequently instructed to climb to FL220 by the Sydney arrivals controller. There was no breakdown in separation but there was breakdown in procedures.

ANALYSIS

More specific explanation of the special requirements for the formation flight would have assisted the sector controller to better appreciate the potential separation and co-ordination problems with the flight. This lack of information and the sector controller's lack of experience with this type of operation did not assist in his management of the task. The sector controller compounded the situation by declining the offer of assistance from another controller. This was a further sign of his inexperience.

The expectation by Nowra ATC and the Melbourne sector controller was that the intercept would be completed prior to the Skyhawks leaving the sector controller's area of responsibility. Because of this expectation, the sector controller did not co-ordinate the use of the block levels with Sydney arrivals or the other sector controller. Consequently, as a result of the intercept not being completed at 20 NM from Nowra, the Skyhawk continuing the intercept while remaining on the Nowra ATC frequency and the controller's own co-ordination workload, he was unable to appreciate the developing situation or eventual consequences.

The operation of the two elements of Skyhawks on different frequencies compounded the situation and caused a delay when the Melbourne sector controller attempted to confirm the aircraft were vertically separated from the B737. Retention of all aircraft operating within the particular block of airspace on a single frequency would have provided an improved level of safety for all the aircraft involved.

The lack of specific limits on the airspace to be used for the intercept pre-disposed the controller to losing control of the situation. Despite his obvious apprehension with respect to what was actually planned to occur, he did not impose any limits on the activity. The use of a suitable separation assurance technique or the co-ordination of the use of the block levels with subsequent sector controllers would probably have prevented the occurrence.

SIGNIFICANT FACTORS

1. The Melbourne sector controller lacked experience of this type of operation.
2. There were limited details of the special requirements for the military flight on the flight plan.
3. The sector controller did not co-ordinate the use of block levels with subsequent control agencies.
4. Aircraft did not operate on the appropriate air traffic control frequency.
5. Adequate separation assurance techniques were not used.

SAFETY ACTION

Local Safety Action

The commanding officer of the Skyhawk squadron agreed to issue two flight plans for similar flights in the future and to ensure that more explicit details of the military requirements are provided on the plans.

Two foreign military F18 aircraft entered the Darwin CTA without prior warning, or an airways clearance, 57 km south of Darwin and were observed on radar climbing to 9,000 ft.

A Beech Baron aircraft, in the exact same locality, had just been cleared to descend from 8,500 ft to 3,000 ft. A breakdown in separation occurred as the aircraft passed.

The aircrews of the foreign aircraft were rebriefed on Australian ATC procedures and requirements.