The EMB-120ER Brasilia was cruising at Flight Level 190, en route from Darwin to Tindal. Just prior to top-of-descent, the crew reported that they heard a loud bang from the right side of the aircraft, and the aircraft simultaneously yawed to the right. Suspecting an engine failure, the pilot-in-command disconnected the autopilot and re-trimmed the aircraft, noting that a considerable amount of rudder trim was required to maintain directional control.

Observation of the engine instruments by the crew confirmed a right engine failure, with the right engine torque gauge indicating 1%. A burning smell and fine smoke then became evident in the cockpit, and the crew put on their oxygen masks. Communications between the two pilots proved difficult with the masks fitted, due to a faulty right oxygen mask microphone. The crew positioned the right engine power lever to flight idle and commenced a descent. The flight attendant also indicated to the crew that smoke had begun to enter the cabin area.

The smoke immediately began to dissipate, following the reduction in engine power. The crew then shut down the right engine in accordance with company operating procedures, and broadcast to Air Traffic Control requesting that emergency services be made available on arrival at Tindal. Air Traffic Control declared a distress phase.

The crew removed their oxygen masks as the smoke had dissipated from the cockpit, however, they still fitted the masks intermittently due to the residual strong burning smell.

By that time the flight attendant had completed the company emergency plan actions, and following approval from the pilots, conducted the emergency briefing. During the briefing, some of the passengers indicated that they were experiencing difficulty hearing the details of the pre-recorded instructions, and the flight attendant had to stop the presentation several times to repeat unheard information. After the flight attendant's briefing, the pilot in command used the public address system to inform the passengers of the right engine problem.

After the single-engine landing, the crew stopped the aircraft on the runway. Emergency services indicated that there was a fuel leak from the right engine cowling. As a precaution, the crew shut down the left engine and instructed the flight attendant to disembark the passengers onto the runway through the main cabin entrance door.

The operator conducted an initial inspection of the failed Pratt and Whitney PW118A engine. This inspection revealed extensive damage to the engine's power turbine and a jammed low-pressure compressor. The reduction gearbox also appeared to have decoupled from the engine, with internal damage to the reduction gearbox case. The engine oil filter bypass indicator had activated, with evidence of metal contamination in the oil filter and on the reduction gearbox chip detector.

The Australian Transport Safety Bureau (ATSB) then quarantined the engine, and delivered it to Pratt and Whitney Canada (PWC) for an investigation supervised by the Transportation Safety Board of Canada. The PWC investigation found that the in-flight shut down had occurred due to the decoupling of the reduction gearbox drive from the power turbine rotor. This was considered to be a direct result of the fracture of the reduction gearbox input shaft by torsional overload. (Refer to Annexes A and B attached to this report).

Maintenance

The following PWC Service Bulletins (SB's), were considered to be relevant to this investigation:

* SB 20246 - Replacement of reduction gearbox (RGB) oil transfer tube arrangement; modification of RGB housing set.

* SB 21323 - Replacement of RGB input shaft.

The aircraft was maintained in accordance with the operator's Civil Aviation Safety Authority (CASA) approved system of maintenance; the operator utilising the engine manufacturer's `high utilisation' periodic inspection requirements as detailed in the maintenance manual.

Listed in those periodic inspection requirements was an engine reduction gearbox input shaft (pinion) borescope inspection, which was required at an interval of 3,000 hours maximum since new, or total time since overhaul, or since input shaft (pinion) replacement. Thereafter, the shaft was to be subjected to an ongoing borescope inspection at a maximum interval of 600 hours. If `unacceptable spalling' was detected on the gear teeth surface, an inspection was to be carried out at an interval of 300 hours maximum. A description of `unacceptable spalling' was included in chapter 72-00-00 of the manufacturer's maintenance manual.

A `Note 5' that applied to the borescope inspection, had been placed in the maintenance manual by the manufacturer in May 1996. This note indicated that the borescope inspection was not required for `non floating layshaft' type reduction gearboxes with SB 20246 incorporated. `Note 5' applied to the reduction gearbox assembly fitted to the failed engine.

The first stage input shaft had been installed in the engine, during the last overhaul in May 1997, after having been assessed as serviceable in accordance with PWC's, Cleaning, Inspection and Repair manual requirements. The shaft had previously been removed from another engine, following the incorporation of SB 21323 into that engine. SB 21323 introduced a new input shaft to the system, with a larger tooth fillet radius and an increased carburised case hardening depth on the shafts' surface. This service bulletin had been issued following the fatigue failure of some reduction gearbox input shafts with insufficient carburised case depth. When the shaft was removed from the previous engine it had accrued 10,180 hours time in service.

At the time of failure, the shaft had accrued a further 2,565.2 hours. During that time, the operator reported that they had carried out all required oil filter servicings and completed daily operational checks of the engine and reduction gearbox chip detectors. No contamination had been noted during those checks.

The operator had been conducting a Spectrometric Oil Analysis Program (SOAP) on the engine. However, the program had been discontinued following the receipt of advice from a PWC field representative that it was not required.

The flight crew oxygen mask microphone could not be faulted during maintenance ground testing, however, as a precaution both masks were replaced.

Following this incident, the operator engaged a cabin safety specialist to conduct an audit into the cabin issues highlighted during the occurrence, and the operator's general aircrew procedures. The audit identified several areas for improvement, which were subsequently acted upon by the operator.

A Beech 200 (Beech) was on an instrument flight rules (IFR) category flight from Wilcannia to Adelaide. The flight was to be initially conducted in non-controlled airspace up to flight level (FL) 165, then across a Class E controlled airspace (CTA) corridor (above FL165 between Dubbo and Broken Hill), prior to entering Class C CTA above FL200. The pilot was required to request a clearance from a Melbourne sector controller before entering CTA.

The aircraft departed Wilcannia and climbed to FL190 prior to the pilot requesting a clearance from Melbourne Centre. The sector controller estimated that the aircraft had entered the Class E corridor without a clearance. There were two formations of military aircraft in the area at FL170 and FL180 respectively that could have conflicted with the Beech. A subsequent check established that there had not been an infringement of separation standards.

The Class E corridor had been implemented on 3 December 1998 and was depicted on the Aeronautical Information Publication (AIP) chart L5 (3 December 1998). The width of the corridor was promulgated as 5 NM either side of the Dubbo-Broken Hill air route, and was depicted on the chart to scale. However, the width of the Class E corridor was increased to 25 NM either side of the route by a Notice to Airmen (NOTAM) on 8 March 1999. The chart was not due for amendment until 17 June 1999. Consequently, pilots who used the chart for operations in proximity to the corridor needed to be familiar with the NOTAM, and to draw the increased corridor width on the chart for reference, and/or remember to include the increased width in any navigation calculations.

The pilot of the Beech was undergoing a check on the day of the occurrence and had the appropriate charts, NOTAMs and weather information for the flight. The pilot was aware of the amended width of the Class E corridor and had regularly flown the route taken. A number of flights had been planned for the day but were subsequently cancelled. The pilot was therefore required to submit a new plan for the flight that was subsequently undertaken. Although the pilot submitted the new flight plan by facsimile, this was not received by the Melbourne briefing office. When the pilot departed Wilcannia he was advised by air traffic service staff that there were no details held for the flight. Consequently, the pilot was required to re-submit the plan. It was during this period of the flight that the pilot believed he may not have taken into account the amended width of the Class E corridor when estimating the time and point at which the aircraft would enter CTA. He was using a chart and graduated rule and suspected that he may have used the distance between Wilcannia and the corridor as depicted on the chart (approximately 46 NM) for his calculations instead of that actually available due to the amended corridor width (approximately 15 NM).

The combined demands of cockpit workload associated with the particular phase of flight, some self-imposed stress due to being under check, and having to re-submit the flight plan while airborne, probably resulted in the pilot being near to task saturation. Consequently, despite his previous awareness of the need to consider the amended width of the corridor, he forgot to take that into account in his calculations.

An infringement of the 3NM radar separation standard occurred at 0606 western standard time approximately 5NM to the northeast of Perth. The aircraft involved were a British Aerospace 146 (BAe146) that departed Perth on a RWY 03 BIU2 standard instrument departure (SID) followed shortly after by a Boeing 737 (B737) that departed on a RWY 06 PEPPA3 SID.

The 03 BIU2 SID is designed to provide system separation with military airspace to the north of Perth and, as a consequence joins the 06 PEPPA3 SID at position REDIL, 8NM to the northeast of Perth. Military airspace was not active at the time of the incident.

The aircraft were under the control of the Perth Departures (DEP) controller at the time. The responsibility for the provision of separation of aircraft on these two SIDs was defined in Perth Local Instructions as the responsibility of the DEP controller.

The DEP controller was monitoring a trainee controller on DEP who was approaching the final stages of rating training. The controller did not use an "override" box that would have allowed him to override the trainee and transmit instructions to the crews.

The aerodrome controller (ADC) advised the trainee DEP controller that the B737 was next for take-off. The trainee DEP controller issued the ADC an unrestricted clearance for the B737 to depart.

The crew of the BAe146 heard the B737 being cleared for take-off and realised that the two aircraft were on conflicting departure routes. The crew asked the trainee DEP controller for a clearance direct to Ballidu in an attempt to resolve the situation. The controller advised the crew that he "would advise" when the direct clearance was available.

The B737 departed and the crew contacted DEP control and advised that they were leaving 1,800 ft. The crew of the BAe146 monitored the proximity of the B737 visually and on the Traffic Alert and Collision Avoidance System (TCAS). The TCAS equipment did not provide a traffic or resolution advice.

The DEP controller did not intervene directly and prompted the trainee to turn the BAe146 away from the B737. The trainee then issued an instruction to the crew of the Bae146 to cancel the SID and track direct to Ballidu. The DEP controller then instructed the trainee to give the crew of the BAe146 a heading in order to resolve the situation. The trainee responded by instructing the crew of the BAe146 to turn left heading 360 degrees for separation. The trainee then instructed the crew of the B737 to turn right heading 090 degrees for separation.

Traffic information was not passed to either crew, nor was the word "immediate" used in passing heading instructions. There was no relay of the urgency of the situation to either crew by phraseologies used by the trainee. At that time the training officer utilised the APP console handset to contact the ADC on the hotline. The ADC was asked by the DEP controller "can you just monitor", to which the response from the ADC was "Yes I'm monitoring". The DEP controller later reported that in his mind it was a request for the ADC to provide visual separation between the aircraft. He also reported that the response received from the ADC indicated to him that the ADC had been providing separation throughout the event by visual monitoring of the aircraft.

The ADC was monitoring a trainee controller by use of a headset. The "B", or training system handset, was not being utilised. The ADC was unable to override the trainee without actually taking over the ADC handset from the trainee.

The DEP controller was not aware of the training on the ADC position and the ADC controller was not aware of the training on the DEP position.

Recorded radar data indicated that separation reduced to 1.4NM with a vertical separation of 200ft. The aircraft were separated by 1.5NM while at the same level. Minimum required radar separation for these aircraft while not 1,000ft vertically separated was 3NM.

The procedures in use were the standard procedures applicable for the use of runways 03/06 for departing aircraft prior to first light. These procedures required the issue of departure instructions for aircraft departing at night or in IMC to be in the form of a SID. It was not permissible for a controller to cancel a SID and issue a radar departure instruction while the aircraft is on the ground prior to first light. It was only permissible in these circumstances to cancel the SID after the aircraft was airborne and had reached the Minimum Vectoring Altitude (MVA). In the case of the 03 BIU2 SID, this situation provided a very short window of opportunity between the aircraft reaching the MVA and commencing a right turn off runway heading. Reliance on controller intervention to cancel this SID and issue a maintain runway heading instruction in order to maintain separation with SID departures from RWY 06 provided no separation assurance.

The crew of the Boeing 747 received a provisional load sheet for the flight while they were carrying out their pre-flight checks. The information on the load sheet was close to the crew's expectations. However, when the final load sheet was subsequently delivered to the crew the computed centre of gravity (CoG) had moved forward significantly, from 25% mean aerodynamic chord (MAC) to 16% MAC.

The captain immediately queried the change. The load controller reported that the load computer program was corrupted, and that he had completed the computations using a manual backup method. He added that he was confident the information was correct.

While the aircraft was taxiing, air traffic control advised the crew to contact their company, who reported that the CoG figure stated on the final load sheet was incorrect, and provided a revised CoG figure that was closer to that shown on the provisional load sheet. However, when the crew entered that figure into the flight management computer (FMC) they received a "> STAB GREENBAND" warning from the engine indicating and crew alerting system (EICAS). The warning indicated that the stabiliser trim setting was incorrect for the CoG position, as sensed by the nose landing gear pressure switch, and that the aircraft was therefore "out of trim". The crew discussed the problem with the load controller, without resolution. The captain decided to return the aircraft to the terminal.

The crew requested company engineers to investigate the problem. In addition, they asked the load controller to investigate the distribution of passengers, baggage and freight. Engineers fitted a new nose landing gear pressure switch, and the load controller assured the crew that the computed figures were correct.

The crew again received a "> STAB GREENBAND" message from the EICAS when the aircraft commenced to taxi. After further discussions with company engineers, the aircraft returned to the terminal. The load controller subsequently informed the crew that further investigation had revealed that 50 passengers in "B Zone" had not been considered in the load calculations. The aircraft had therefore been "out of trim".

The operator reported that no fault was found in the load control computer system, and that the error had resulted from the load controller incorrectly interpreting computer generated information.

The aerodrome controller cleared VH-CZO for a night-time take-off from the Brisbane runway 01, believing that VH-OGG, after landing, had vacated the runway onto the high-speed taxiway A4S. At the time, CZO was at the A7 holding point. The crew of OGG alerted the controller (and the crew of CZO) that they were on the active runway. Shortly after, the controller asked the crew to confirm that they were on taxiway A4S and was advised that they were not. Aware that CZO had not lined up on the runway, the controller did not cancel the take-off clearance, but monitored the situation until OGG vacated the runway at taxiway A4.

The high-speed taxiway A4S was 1,900 m from the runway 01 threshold, and taxiway A4 was 2,310 m from the 01 threshold. Taxiway A4 required that the crew turn the aircraft through 90 degrees to exit the runway.

Taxiway A4S was equipped with uni-directional centreline lighting, which was not visible from the control tower. This made it difficult in conditions of reduced visibility for controllers to determine that an aircraft had vacated the runway and was on the high-speed taxiway. However, in visual meteorological conditions at night, it was not normal practice for controllers to ask crews to report when their aircraft was clear of the runway.

The Manual of Air Traffic Services (MATS) 6-3-1 paragraph 2 stated:

"When take-off or landing separation is based on the position of the preceding landing or taxiing aircraft and visual determination, particularly at night or in reduced visibility, is limited by poor azimuth resolution or other factors, the pilot of that aircraft shall be instructed to report when the aircraft has:

1. crossed and is clear of a runway intersection; or
2. stopped short of a runway strip; or
3. vacated the runway."

The MATS 6-2-3, paragraph 31 stated:

"Before clearing an aircraft for take-off, and immediately before take-off is commenced, the tower controller shall make a visual check from the control tower to determine as far as practicable, that the take-off path is not obstructed. If the take-off path is obstructed, take-off clearance shall be withheld or cancelled as appropriate, until the obstruction no longer exists."

The prescribed separation standard was detailed in MATS 6-3-4 paragraph 24. The standard required that a departing aircraft shall not be permitted to commence take-off until the landing aircraft has vacated and is taxiing away from the runway.

The controller cleared CZO for take-off using the provisions of MATS 6-2-3 paragraph 32. This paragraph stated:

"Take-off clearance need not be withheld until prescribed separation exists if, in the opinion of the controller, no collision risk exists and there is reasonable assurance that separation will exist when the aircraft commences take-off roll."

The crew of VH-XDZ, a SAAB 340 operating an IFR category flight taxiing at Mt Isa was not passed traffic information on VH-XDA, another SAAB 340 operating an IFR flight inbound to Mt Isa on the same track to be used by the departing aircraft. The flight service officer was not aware of this omission until the aircraft had passed in flight at 1750 EST.

The incident occurred during a peak in traffic movements, with multiple transmissions from aircraft on both VHF and HF frequencies in airspace that encompassed a large and complex geographical area. The work position comprised 2 HF networks, each with three frequencies, as well as four VHF repeaters. Because of the size and complexity of the airspace, the console needed a large chart display on a mobile trolley placed at 90 degrees to the console operator's position to supplement the overhead map display. The flight service officer reportedly had about 15-18 active flight progress strips for aircraft movements within his area of responsibility at the time of the occurrence and 12 aircraft on frequency. Geographical display bays were not used for the flight progress strips; they were sequenced in a chronological order.

The flight service officer had been on duty for five hours before the incident and had worked the position for most of that time. During the previous three days, the officer had worked a 10-hour shift, a 7-hour shift and a 9.5-hour shift, none of which agreed with the planned roster. Staffing throughout the day of the occurrence had been difficult as three staff were on sick leave.

Team leader coverage was required in the centre between the hours of 0600 and 2000 daily. The sole team leader available for duty on the day of the occurrence had worked from 0700 to 1700 hours and was required to stand-down because 10 hours was the maximum shift length allowable. A relief team leader was not available.

The flight service officer elected not to ask for support during the increased workload because of staff availability. Three other flight service officers were on duty. One was absent from the centre preparing a meal; one was working the FIS 3 position; and, the evening shift officer was eating a meal at the utility position. The evening shift officer intended to provide relief at one of the two consoles and had completed a 7-hour night shift earlier that morning.

Earlier that day, all flight service officers on duty at the Brisbane centre were briefed at a meeting on the imminent closure of the flight service function and the potential ending of their employment with Airservices Australia.