The crew of a Boeing 737 (B737) received a traffic alerting and collision avoidance system (TCAS) resolution advisory to reduce climb when passing 800-1,000ft on departure from runway 34R at Sydney. This was immediately followed by a TCAS instruction to descend. As the crew commenced descent, the clear of conflict command was heard and a Kawasaki BK 117 helicopter sighted passing to the left in the opposite direction at a distance of about 1 NM.

The investigator reviewed radar data and air traffic control automatic voice recordings to establish the sequence of events. The investigation found that the aerodrome controller East was controlling the B737 and the helicopter was being controlled by the aerodrome controller West. Through a comprehensive coordination process, both controllers were aware of the other controller's traffic.

The helicopter was inbound from the north on a Medical Category 2 flight to Prince Henry Hospital and was cleared by the West controller to track via the runway intersection at 2,000 ft. The West controller had provided this advice to the East controller, who agreed with the clearance and advised that the helicopter was not required on his frequency.

Prior to clearing the B737 for take-off, the East controller alerted the West controller of his intention to launch the B737. The West controller advised that he would keep the helicopter to the west of the B737. The B737 was departing from runway 34 R and was cleared via an ENTRA TWO standard instrument departure (SID). The SID required a right turn after departure to intercept the Sydney 023 VOR radial. Because the aircraft had been cleared for take-off and was on an unrestricted climb, there was the potential for conflict with the helicopter, which was inbound to Sydney from the north at 2000 ft.

Approximately 30 seconds after the B737 had been cleared for take-off, the West controller asked the helicopter pilot to report sighting a 737 on departure roll on runway 34R. The pilot reported sighting the B737. The West controller then advised the helicopter pilot of the B737's intentions and assigned the pilot the responsibility for separation. The pilot acknowledged this.

The TCAS on the B737 activated with a resolution advisory some 20 seconds later and the two aircraft passed each other with 0.9 NM horizontal and 500 ft vertical separation.

Visual separation of air traffic was a valid method to use in these circumstances. However, the criteria for its application were clearly detailed in the Manual of Air Traffic Services (MATS) Part 4 Section 5. In particular, MATS 4.5.1.10 stated: "In circumstances where an aircraft has been instructed to maintain separation from, but not follow, an IFR aircraft, traffic information shall be issued to the IFR aircraft, including advice that responsibility for separation has been assigned to the other aircraft". The B737 was an IFR aircraft but was not provided with the required traffic information.

A Cessna 340 (C340) was maintaining 8,000 ft while tracking direct to Williamtown from a position bearing 020 degrees at 25 NM. A Royal Australian Air Force Macchi was conducting a Tacan approach and intended to perform a missed approach procedure before climbing to 10,000 ft to continue the training sortie. The sector controller had issued the approach controller with a restriction for the Macchi to maintain 7,000 ft on departure to ensure separation with the C340. The approach controller was a trainee being supervised by a rated officer.

While the Macchi was on final approach to runway 30, a further restriction of 2,000 ft was placed on the departure due to other conflicting aircraft. The crew of the Macchi contacted the approach controller on departure and advised that they were maintaining 2,000 ft. The controller took appropriate action to resolve the confliction and then cleared the crew of the Macchi to climb to their planned level of 10,000 ft. The controller had omitted to issue the 7,000 ft restriction even though it was still a requirement to ensure separation with inbound aircraft.

As the Macchi climbed through 8,000 ft, while approximately 6 NM south of Williamtown, it passed within 1 NM of the C340. There was an infringement of separation standards.

The investigation by the Directorate of Flying Safety - Australian Defence Force revealed that the Australian Defence Air Traffic System (ADATS) was being trialled at the time but that the older surveillance radar (SURAD) equipment was actually in use by the approach controller. The SURAD did not have identification labels or height information (facilities that were available on more modern equipment) and that limitation increased the workload on the controller. Additionally, the SURAD was unreliable in its ability to provide constant, accurate position information within 10 NM of Williamtown. The controllers were aware of those restrictions as they were documented in aeronautical publications.

The military sector controller was using the Interim Radar Display System (IRDS). Although that system had labels and a Mode "C" height reading capability, the Macchi was not equipped with a Mode "C" capability. Consequently, the sector controller did not have a radar indication of the height of the Macchi.

The airspace was divided vertically between approach/departures and sector control with ground level to 5,000ft being owned by approach/departures, and sector control the airspace above. The coordination had been adequate but flight progress strip management made the task of remembering an additional restriction more complicated. Consequently, the trainee approach controller forgot to issue the 7,000ft requirement to the crew of the Macchi. The rated officer did not pick up the error until the Macchi was actually passing the level of the C340. The training officer said that he looked at the radar and the strips but was feeling tired and may have missed the information.

The management of the flight progress strip, which was very crowded and difficult to read, was different from that used in other Australian locations. Local procedures were being taught where level restrictions were placed in box 11, whereas in all other air traffic control units the box for such notation was box 4, as specified in the Manual of Air Traffic Services (MATS). That local procedure had been in use at Williamtown for some time, but the investigation was unable to find any documentation specifying such action. In addition, the strip had been divided into four quarters to cater for four separate approaches that the crew of the Macchi had intended to carry out. That action made the writing very small and difficult to read. The alternate method was to use separate flight progress strips for each approach, resulting in more writing space being available for instructions and, therefore, allowing for larger print.

While climbing through 1,500 ft after take-off from Hobart, the crew of the Boeing 737 advised air traffic services that the number one engine had failed and was being shut down. The crew returned the aircraft to Hobart. There was no evidence of fire.

Disassembly and inspection of the CFM56-3C1 engine, serial number 856135, traced the failure to the loss of a 15 x 20 mm segment of trailing edge from a single high-pressure turbine blade. The passage of the segment through the turbine resulted in extensive damage to all four stages of the low-pressure turbine assembly, rendering the engine inoperative. The subject blade was subsequently removed and examined by the Australian Transport Safety Bureau.

The failed blade, serial number 849M8, had accumulated 26,576 hours and 17,928 cycles since new. Maintenance records indicated that the blade received a "full" repair in the manufacturer's facilities in Singapore in June 1997 and was subsequently installed into the subject engine where it accumulated 10,226 hours and 5,332 cycles. The repair involved the use of Rene 80 alloy. The blade also received a "mini tip" repair in July 1995. On that occasion Inconel 625 alloy was used.

The reason for the "full" and "mini tip" repairs was to rebuild the blade tip area eroded due to the high operating temperatures and pressures. Any thermal cracks in the area were checked and removed at that stage. The "full" and the "mini tip" repairs were carried out in approved repair facilities in accordance with the appropriate manufacturer's repair documents. There was no difference between the repairs as far as the extent of the blade weld repair, materials and techniques used. The only difference was in the area of the blade coating.

The subject blade and the high-pressure turbine were periodically inspected in accordance with the manufacturer's and operator's maintenance programs. Those programs required the high-pressure turbine to be inspected at intervals not exceeding 1,140 hours. The inspection required detailed examination of the convex and concave mid-chord tip areas for radial cracks and of the blade trailing edge for axial cracks. The procedure specified the permissible crack length and imposed engine service limitations if cracks exceeded the limits.

The subject blade had accumulated 660 hours since it was last inspected on 11 August 2000. Following that inspection the high-pressure turbine was certified as serviceable.

The operator advised of a similar failure to a high-pressure turbine blade from another CFM56-3 engine. That item showed the loss of a similar section from the blade trailing tip corner but without the catastrophic consequences for the rest of the turbine and the engine.

The engine manufacturer indicated that that type of blade failure was not new. Although not every blade failure was reported by the engine operators, the manufacturer received reports of a number of similar cases each year. The manufacturer indicated that no formal records of the failed blades, their time in service, and repairs, were maintained.

A Boeing 747-400 (B747-400) was en route from Singapore to Sydney at flight level (FL) 330 on air route A585, and a B747 was tracking in the opposite direction at FL350 from Melbourne to Jakarta on air route G222. The routes A585 and G222 converged at SAPDA, a position approximately 720 NM north-west of Broome on the boundary of the Australian and Indonesian flight information regions (FIRs). Route G222 was north-east of route A585 and the prescribed lateral separation point between the routes was 272 NM south-east of SAPDA. The aircraft were under the control of the Kimberley sector controller of the Brisbane centre.

The B747-400 was estimating SAPDA at 1811 Universal Coordinated Time and the controller approved that crew at 1747 to climb to FL350 at SAPDA. The Kimberley controller was advised at 1806 the B747 was at METUM, a position 252 NM south-east of SAPDA, at 1805 maintaining FL350 and estimating SAPDA at 1836. At 1812, the Kimberley controller received a SAPDA position report from the B747-400 crew and shortly after recognised there was no separation being applied between the aircraft. At 1813, the Kimberley controller instructed the B747-400 crew to descend to FL330, however there was an infringement of separation standards. The B747-400 crew subsequently reported maintaining FL330 at 1819.

The estimated time of passing of the aircraft was 1824. The Kimberley controller needed to establish the vertical separation standard of 2,000 ft between the aircraft before 1809 to ensure separation.

The Kimberley sector was a procedural sector operated by a single controller. Communication between controllers and flight crews could be by either:
- very high frequency (VHF) radio,
- controller pilot data link communication (CPDLC), or
- high frequency (HF) radio through a third-party radio operator.

The controller was communicating with the B747-400 crew using CPDLC and with the B747 crew by third-party HF radio. There was no VHF radio coverage in the portion of the sector in which the aircraft were operating.

The controller commenced the shift at 1300 (2300 Eastern Standard Time) and worked till about 1530 when he had a break. He returned to the position at 1610 and remained there until the occurrence. Normally during the period from 1400 to 1800, the number of aircraft in the sector gradually increased and after that time, traffic numbers decreased. The controller reported that there had been a busy period that had finished just before the occurrence. That was the controller's first shift following a 2-day break.

When the B747-400 crew requested approval to climb to FL350 via CPDLC, the controller checked for conflicting aircraft on the air situation display. At that stage, the B747 on G222 was over Western Australia and the controller reported that he might have perceived that aircraft as part of a group of aircraft on a more northerly route. Consequently, he coordinated a change of level with the adjacent Indonesian sector controller, and then instructed the B747-400 crew to climb at SAPDA.

The air traffic system had a flight plan conflict probe (FPCP) function to assist in the early identification of conflicts outside radar coverage. However, the FPCP had not been included in the commissioning of the new air traffic control system during 1998-99 and was not active.

Sequence of events

The Cessna A152 Aerobat aircraft was engaged on an aerobatics training flight with the pilot the sole occupant of the aircraft. The pilot was practising for an aerobatic competition and had been having problems conducting stall turn manoeuvres.

Before the accident flight, the pilot had completed an aerobatic practice flight with an instructor. The pilot then decided to fly a solo flight to practise stall turns without the effect of a second person's weight on aircraft performance in aerobatic manoeuvres. He then intended to practise his full aerobatic sequence, which the instructor later stated was well within the pilot's capabilities. Between flights the pilot refuelled the aircraft and consumed a bottle of soft drink.

After takeoff for the solo flight, the pilot discussed with his instructor by radio, his intentions for the flight and the criticisms of his manoeuvres during the dual flight. The instructor later reported that during the discussion, everything concerning the pilot and the aircraft seemed normal.

Witnesses some distance away heard the aircraft fly over. They later heard a thump and noticed smoke rising from the same direction as the source of the sound. There were no witnesses to the impact.

Wreckage examination

The wreckage was contained within a relatively small area, apart from two sections of fuel tank and the associated wing that were found about 40 m away. Most of the aircraft had been consumed by a post-impact fire.

Examination of the accident site revealed that the aircraft had impacted the ground in balanced flight at high speed in an attitude of approximately 70 degrees nose down. The engine was producing high power at impact. Examination of the wreckage did not reveal any technical defect that would have contributed to the accident.

Pilot

The pilot was 61 years of age and had been flying since 1979. He held a Private Pilot Licence (Aeroplane), and a valid Class 2 medical certificate. He had accrued a total of 893.3 hours flying experience, including 7 hours in the last 90 days, probably all on type. In the last 30 days, he had flown 1.3 hours, all on the day of the accident. Since 1982, the pilot's principal interest had been aerobatics, and in recent years he had become involved in competition aerobatic flying. Since November 1994, he had held a CASA approval to conduct aerobatics down to 1,500 ft AGL. He had completed his most recent biennial flight review on 26 June 2000.

The pilot had a long history of hiatus hernia and taken medication for it but had not undergone surgery. At the time of the accident, he was not taking prescribed medication. For about 10 years, he had been prone to fits of coughing after eating and drinking. During these attacks, his ability to perform other tasks was impaired. About 45 minutes before the dual flight, the pilot had eaten a burger and chips. During the dual flight, he had suffered a fit of coughing during which time his attention to flying the aircraft was reduced.

Toxicological examination of the pilot revealed the presence of the drug doxylamine, at a concentration of 4.7 mg/kg in the liver. The finding was reported as `semiquantitative' with a possible error of 20 percent. However, regardless of any error, the pathologist regarded the concentration as sufficiently high to possibly affect the pilot's ability to fly the aircraft.

Medical information revealed that makers of pharmaceutical products usually include doxylamine with other agents such as paracetamol and codeine in strong analgesic medication for such conditions as migraine. In isolation, doxylamine is classified as an anti-histamine, but it has strong anti-emetic properties useful for treating motion sickness, nausea and similar conditions. It is also a drying agent used in a number of non-prescription cold and flu preparations. However, either alone or in conjunction with other substances, doxylamine can cause drowsiness, visual disturbance and can contribute to disorientation.