The pilot of VH-NPD, operating IFR and tracking from Port Augusta to Adelaide at 7,000ft, requested Adelaide Flight Service for a change of altitude to 9,000ft. Adelaide Flight Service arranged the altitude change and advised there was no other IFR traffic in the area.

VH-JVN, another IFR aircraft, had been cleared direct from Adelaide to Leigh Creek at 9,000ft, and therefore not assessed by air traffic control as traffic for NPD. The flight route was later changed to via Ardrossan, which put it on a reciprocal heading to NPD. The possibility of a conflict was not recognised by the sector controller before the two pilots had become concerned about the situation and arranged their own separation.

The aircraft passed each other within 1km at the same altitude.

Following touchdown, the aircraft bounced twice and veered to the right, before the left main gear collapsed. The aircraft came to rest on its left wingtip. The wind conditions during the landing were not favourable for the tail-wheeled aircraft.

The wind strength was 10 kts and all crosswind from the right. The pilot lost directional control of the aircraft, probably due to weather cocking.

Factual information

Description of the airspace layout near Brisbane

Controllers are each responsible for pieces of airspace, called sectors. In general, aircraft within each sector were required to have radio communications with the controller responsible for that sector. Airspace involving coastal airways to the north of Brisbane was in sector 3B. Airspace in a similar area to the south of Brisbane was in sector 2G. The boundary between these two sectors was a line between Amberley, Archerfield, Brisbane and the 091 VHF Omni-directional Radio Range (VOR) radial from Brisbane. Sector 4M controlled airspace beyond 30 NM to the east and west of Brisbane, including the Amberley control zone and airspace above. The area up to and including FL200 within 30 NM of Brisbane, excluding the Amberley control zone, lay in the Brisbane Approach area.

History of the flights

Kiwi 185, a Royal New Zealand Air Force C-130, was tracking from the west of Brisbane to overhead Brisbane and then eastbound along the 089 Brisbane VOR radial at FL290. Its estimated time of arrival overhead Brisbane was 1345 hours local time. When near Brisbane, the aircraft should have been handled by sector 4M until about 20 NM west, then sector 3B until 30 NM east of Brisbane, before being handed back to the sector 4M controller. Because the aircraft would be in sector 3B airspace for only about 50 NM, that controller elected to leave the aircraft on sector 4M's frequency. Due to crossing traffic in a sector to the east of 4M, east of Brisbane, FL290 would not have been available. The aircraft was given a requirement to descend to FL270 before 1400. The sector 4M controller passed this instruction to the aircraft at 1335, after checking with the sector 3B controller and confirming that there were no other requirements for the aircraft. Some time later the sector 4M controller also informed sector 2G that Kiwi 185 had been assigned FL270, with a requirement to reach that level by 1400.

VH-TAF was to track from Maroochydore via TRIKI (32 NM on the 010 radial from Brisbane VOR) to Brisbane and then towards Sydney. The aircraft departed Maroochydore at 1337, on climb to FL350. Initially the aircraft would pass from Maroochydore airspace to sector 3B airspace, however the sector 3B controller had the aircraft call Brisbane Approach instead. After leaving Maroochydore the aircraft should have been handled by sector 3B until 30 NM from Brisbane, when it should have been handed off to Brisbane Approach. If the aircraft then climbed above FL200 before reaching overhead Brisbane it should have been handled again by sector 3B until overhead Brisbane, at which time it would have come under the control of sector 2G. At 1340 the aircraft was at TRIKI, and passing FL130, when the crew called Brisbane Approach. After this time the sector 3B controller discarded the flight strip for this aircraft. The climb performance of the aircraft was such that it was above FL200 before reaching Brisbane, in which case the aircraft should have again been under the control of the sector 3B controller. At 1342 the approach controller noticed the track of Kiwi 185 at FL290 and imposed a climb restriction of FL280 on VH-TAF because of the approach of Kiwi 185. The controller informed the sector 2G controller that the aircraft was being held at FL280 until a stable return was received on Kiwi 185. As the sector 2G controller assumed that the sector 3B controller was separating the two aircraft, and that descent clearance for Kiwi 185 would not be issued until that aircraft was east of Brisbane, the approach controller was not informed that Kiwi 185 was actually assigned FL270.

Kiwi 185 entered the cone of silence overhead Brisbane radar at 1344. The cone of silence is an area above the radar transmitter in which the radar is unable to receive signals from the aircraft. Aircraft in the cone of silence are lost from the radar screen until they are detected on the other side of the cone of silence. VH-TAF entered the cone of silence some 30 seconds after Kiwi 185, shortly before the crew reported approaching FL280. The approach controller held the aircraft at that level until both aircraft had emerged from the cone of silence. Around this time the controller in sector 3B changed. VH-TAF was cleared to climb to FL350 just before 1348, when lateral separation with Kiwi 185 had been achieved. Kiwi 185 commenced descent and reported to the sector 4M controller some 12 seconds after VH-TAF was cleared to climb to FL350.

Analysis

Sector 3B controllers were trained to be aware that some aircraft climbing from Maroochydore can be above approach airspace before passing Brisbane. Their need to check for possible conflictions with traffic overflying Brisbane was, therefore, regular but infrequent. As the controller's attention was normally focussed on the 99% of traffic outside of 30 NM from Brisbane, a positive action to consider traffic inside that distance was required. The two aircraft were the responsibility of this controller overhead Brisbane, but the controller did not recognise the confliction. After VH-TAF had entered Brisbane Approach's airspace, the sector 3B controller discarded the flight strip for that aircraft. It was evident that the controller had not considered the possibility of VH-TAF re-entering sector 3B airspace before reaching Brisbane, nor had the possibility of a confliction with Kiwi 185 been considered. In addition, the controller had not identified Kiwi 185 to sector 2G, nor informed the sector 2G controller of the descent requirement for Kiwi 185. That information was ultimately relayed by the sector 4M controller.

The Approach controller had noticed that VH-TAF and Kiwi 185 would conflict, so took steps to ensure vertical separation between the two aircraft. Both aircraft were outside the Approach controller's area of responsibility. Co-ordination was conducted with the sector 2G controller after this action was taken, but that controller did not mention the descent requirement for Kiwi 185. As a result, the Approach controller was not aware that Kiwi 185 could have initiated a descent at any time. Such a descent would have caused a breakdown in separation standards between the two aircraft. Fortunately, the descent did not take place until other separation standards had been obtained.

The sector 2G controller was aware of both aircraft and the conflict but assumed that the sector 3B controller was providing the separation. This aspect was not positively checked with the other controller, nor did the sector 2G controller warn the Approach controller that Kiwi 185 might descend at any time.

Both aircraft were on different radio frequencies so the crews would not have been aware of each other through radio transmissions.

Significant factors

1. Controllers did not ensure that aircraft were operating on radio frequencies relevant to the airspace in which the were flying.
2. The sector 3B controller did not ensure separation for all aircraft in the sector.
3. The sector 3B controller did not maintain a flight strip to cover the full period for which VH-TAF was in the sector.
4. The sector 2G controller assumed that the sector 3B controller was ensuring separation for traffic near the boundary of both sectors.
5. Co-ordination between controllers was inadequate.

Safety action

As a result of this incident, Airservices Australia Northern District management have recommended the following actions:

1. That aircraft contact the responsible sector for clearance to levels above approach airspace. Such aircraft would be held in approach airspace (maximum FL200) until handed off to the responsible sector. This would provide positive separation to overflying traffic.
2. A review of the terminal area altitude cap (FL200).
3. That the need to retain flight progress strips until an aircraft is clear of a sector's responsibility be reiterated.

The pilot of the Pawnee Brave was conducting a procedure turn to the right, at the end of a spray run. At a height of about 150 ft he heard a loud bang, felt the aircraft shudder, and saw flames passing down the left side of the engine cowling. From the apex of the turn, at a height of about 250 ft, the pilot elected to land in an open field adjacent to the wheat crop he had been spraying. He kept the engine running, as it was still developing some power, until the landing was assured Before he had crossed the boundary fence, the cockpit had started to fill with smoke.

Once the landing was assured, the pilot completed the emergency shut down checks and landed. His vision was obscured by engine oil on the windscreen, smoke in the cockpit and flames and smoke outside the aircraft. After landing, the pilot found that directional control and braking were hampered due to the left brake failing. Once the aircraft had stopped the pilot was able to escape safely but was unable to extinguish the fire with the portable fire extinguisher. The aircraft was totally burnt out within 30 minutes.

A subsequent examination of the wreckage found that a cylinder had separated on the left side of the engine, fracturing a fuel injector line. Fuel had sprayed onto an adjacent high tension ignition lead conductor, which was shorting to the sparkplug body. The left brake failed due to the airborne fire burning through a flexible hydraulic brake line.

FACTUAL INFORMATION

A Piper PA23 aircraft, VH-MBU, on a right base leg for runway 15 conflicted with a Boeing 737 on left base leg as a result of a co-ordination breakdown.

VH-MBU was inbound from Stoney Creek and the Approach 2 controller co-ordinated with the Tower Controller to process the aircraft via right base leg behind a Boeing 747 on final approach for runway 15. The pilot was asked to sight the B747, which he did. The pilot was then told to contact the Tower. There was no co-ordination with Approach 1. The Approach 1 controller had transferred a Boeing 737 VH-TAK, to the Tower and asked Approach 2 what he was doing with MBU and should TAK be following MBU, to which he replied in the affirmative. TAK was turning left base on Tower frequency by this time. Co-ordination with the Tower Controller alerted him to the confliction. The Tower Controller advised MBU to orbit right base and TAK was allowed to continue with the visual approach.

Radar data confirmed that the two aircraft conflicted with a separation of 1.5 NM at the closest point of approach.

ANALYSIS

The Approach 2 controller failed to co-ordinate the landing sequence with the Approach 1 controller. The reason for this lapse in performance was not positively established but the controller's supervisor thought that a desire to provide an expeditious service may have been a contributing factor.

The helicopter was on a scenic flight over the Bungle Bungle National Park. As it passed an outcrop it appeared to be rocked by turbulence. The helicopter yawed to the right and commenced an uncommanded descent. The pilot stopped the descent and checked the engine indications. Although no warning lights were illuminated the rotor and N2 RPM were still increasing. The pilot was able to stop the N2 overspeed at 104 per cent. He turned the helicopter towards the airfield and commenced a cruise descent. As the helicopter descended through 150 ft, on final approach, the engine-out alarm sounded, and the pilot heard the turbine RPM decreasing. He turned the helicopter into wind and completed an autorotational approach, landing short of the airfield. After landing, the pilot observed the engine was still operating at idle RPM.

Post-landing inspection disclosed damage to the tail boom, probably as a result of a heavier-than-normal touchdown.

It was reported the rotor and N2 RPM problems were the result of a sheared engine governor drive shaft.

FACTUAL INFORMATION

The controller started acting as the Aerodrome Controller (ADC) at 1100 local time. Up until 1120, the workload was described as being light. At 1120 the ADC was responsible for one helicopter under the final approach path of runway 32, at three miles from the field and operating not above 500 ft. Another helicopter was flying from the north of the aerodrome towards the same area and had been directed to track to the west of the aerodrome. A third helicopter was waiting at Burleigh for a clearance to enter the zone. A Piper PA28 was about two miles from the runway, on final for runway 32. Two jet aircraft were also approaching final for runway 32, and were about 15 and 22 NM from the airport. An Airbus A320 reported ready at the holding point for runway 32. That aircraft was given a clearance to line up.

Because of the short distance from the parking area to the holding point, the controller was aware that airline aircraft sometimes take a long time to actually line up at the threshold. The cabin crews on the aircraft often need a considerable period of time to complete their briefings and the pilots taxi slowly to avoid stopping the aircraft. The taxiway for runway 32 was situated about 400 m from the threshold of runway 32, with the result that the time taken for aircraft to be ready for take-off could vary. On this occasion the Airbus was reported to have been slow to line up.

The ADC asked the pilot of the Piper if he would accept a landing on runway 35, a 552 m long strip which crossed the main runway about 850 m from the threshold of runway 32. The change was accepted and the pilot was asked to report on final approach. The helicopter under the final approach path was asked how long he wanted to remain there, and was then told to report on completion of his activities. The ADC then cleared the Piper to land on runway 35. Another aircraft reported ready to line up, and the ADC instructed that pilot to hold at the holding point. A helicopter previously cleared to track northbound east of the coast from Point Danger to Burleigh was asked to make an orbit or hold due to a jet aircraft about to take off and turn right.

Departure instructions for the Airbus were obtained from the Approach Controller and the ADC cleared the aircraft for take-off, followed by a right turn to a heading of 120 degrees. During this process he reported checking the radar screen and runway 32. He did not check the flight strips. The controller then devoted his attention to the helicopter under the final approach path for runway 32. He initially asked the pilot to fly to the west of the final path for about three miles. In response the pilot informed the ADC that he was finished in the area and requested a clearance to track to Surfers Gardens.

When a break in this interchange occurred, the pilot of the Airbus informed the controller that the other aircraft was now clear of his path, and asked to confirm whether he was clear to take off. This was re-affirmed. The pilots of the Piper had heard the Airbus being given a take-off clearance and had been prepared to go around if that aircraft began to roll. The pilots of the Airbus had seen the Piper during their pre-take-off scan and had waited until the aircraft had crossed their runway.

As the Piper was originally to land on runway 32, the ADC had that runway marked on the flight progress strip. When the runway was changed the new runway should have been marked. This was not done. In addition, when the second runway was activated he should have notified the Surface Movement Controller. This was not done, reportedly because the aircraft was close to landing and the second runway would only have been active for a short period of time. The controller workload at Coolangatta was described as becoming busy irregularly. During a normal working week controllers were often on duty in the various positions when activity was low.

The controller estimated that he was only able to achieve about two hours per week when the activity was moderate to busy. As a result, he found it difficult to maintain a system which catered for the busy periods. Most of the time he was able to remember the complete aircraft activity picture without reference to the various systems to aid memory, such as the flight progress strips. The investigation was also informed that tower controllers often did not maintain current information on the flight strips when activity became high. There was a need to retain the activity picture in their mind as well as maintaining the information on flight strips, and this latter aspect often lost priority.

Prior to issuing a take-off clearance the controller reported that he should have scanned the runway, the circuit area, the apron and taxiway, the flight progress strips, the active bay, and the radar. On this occasion he did not do all of these actions. He attributed this to the irregular activity pattern which was not conducive to a regular scan.

No deficiencies in workstation layout or visibility from the control tower were found. Ranges to the west of Coolangatta could have made the Piper difficult to see when it was on final approach and close to the runway. The radar display was "gated" so that aircraft within one mile of the runway were not displayed. This was done to avoid the display becoming crowded with returns of aircraft on the ground. Depending on the position of the Piper aircraft, it may have not been displayed on the radar.

During the four days prior to this incident the controller had been suffering from the effects of a virus. Although he had initially started the day not feeling like going to work, by the time he had arrived he was keen to be working.

ANALYSIS

The term 'mental workload' refers to the difference between the amount of information processing resources required by a situation and the amount of such resources available to the person at that time. The controller was probably experiencing a significant mental workload around the time of the incident. The control situation at the time involved a significant number of different aircraft, producing an unusual task load. Although the controller rated the workload as moderate, there were periods of radio communication without significant breaks. The controller's ability to cope with the situation may have been degraded by a lack of proficiency and his recent health, although the influence of these factors could not be established.

The controller was in the habit of retaining all the relevant information and the operational picture in his memory. This meant that he was not in the habit of conducting a full sequence of checks prior to issuing a take-off or landing clearance. One of these checks involved a scan of the flight progress strips. When his workload became high, he was in the habit of allowing activity on the flight progress strips to lapse, in favour of retaining his mental picture. That was the situation on this occasion. He probably developed a "loop", whereby he did not scan the strips because he knew they were not accurate.

When the pilot of the Piper was asked to use runway 35, the aircraft was not far from landing. As far as the controller was concerned it would not be long before that runway was no longer in use. He did not comply with the procedure to notify the SMC of the runway's activation because of the short time the runway would be in use. This action created another gap in the separation assurance of the two aircraft involved. It also excluded the other controller from any cross-checking capability.

The ADC's workload had become high very quickly and he had some problems, other than the aircraft landing on runway 35, that needed his attention promptly. The evidence indicates that he omitted the Piper from his thinking as soon as it had been cleared to land. When runway 32 was scanned prior to giving the Airbus a take-off clearance, the Piper was not seen as it was not near this runway. When the radar was scanned, the Piper was probably inside the area which was not displayed on the screen. The only other prompts which could have reminded the controller about the Piper were a scan of the strips and a strip indicating that runway 35 was active. It is likely that he would have been reminded about the presence of the Piper if he had scanned the strips, even though he had not kept them up to date.

The potential for a more serious incident was averted by the crews of the two aircraft. Both crews were aware of the other aircraft and were prepared to take avoiding action. The crew of the Airbus did not commence take-off until the other aircraft was clear of their runway. They also checked again with the controller to ensure that everything was in order for their departure. The crew of the Piper were prepared to go around and take other avoiding action if the Airbus began its take-off roll. For these reasons, a serious incident involving an inadvertent breakdown of separation was not likely.

FACTORS

1. The controller was experiencing a high level of mental workload.

2. The controller was not maintaining accurate flight progress strip information.

3. The controller did not take the appropriate steps to activate runway 35.

4. The controller forgot about the Piper after issuing a landing clearance.

5. The controller did not scan all the available information prior to issuing the Airbus a take-off clearance.

6. The pilots of both aircraft maintained sufficient situational awareness to avoid each other.

SAFETY ACTION

The use of the team concept by Airservices Australia is being examined by the Bureau as a result of previous incidents. The details of this incident will also be considered during that research.

The aim of the flight was to check the front seat pilot's capabilities in assessing and flying slope-lift generated by mountain slopes. The area near the mountain became unsuitable for continued operations due to mist and the presence of other aircraft. As a result, the crew decide to return to their base. The instructor reported that as the glider passed through a saddle, with sufficient height and speed to reach the airfield, it was caught in a series of downdrafts. A significant amount of altitude was lost in the turbulence and the glider continued to lose altitude rapidly once it reached clear air. The air brakes were found in the fully deployed position. They had not been selected by either pilot. The glider was 300 ft above ground level and over trees when the air brakes were selected in. The glider had insufficient performance available to reach the airfield.

The pilots decided to complete an outlanding on a road. The space between the trees on either side of the road was less than the glider's wingspan and the right wing and canopy collided with trees during the landing. The glider came to a stop in the trees at the side of the road.

It is probable the airbrakes were deployed by the loadings encountered during the turbulence.

FACTUAL INFORMATION

History of the flight

The aircraft was scheduled to complete a flight test following major repairs to the left wing and fuselage. These were carried out in Broome to repair damage resulting from a birdstrike which occurred in May 1996 (BASI report 9601590). The crew for the flight comprised two experienced pilots, one of whom was a qualified test pilot, and a flight test engineer. There were no passengers. When the landing gear was selected up, after take-off, the nose landing gear door unsafe and landing gear handle lights remained on. The gear was selected down, and safe indications were obtained. The gear was selected up a second time and it retracted normally. The test flight was continued, with sequences being completed up to the landing gear tests. Landing gear down selection resulted in a safe indication on the main gear (two green lights) and unsafe indications on the nose gear (a red gear light, no amber door light and a light in the gear handle). Actions were completed in accordance with the abnormal and emergency checklist however, the nose gear continued to indicate unsafe.

An inspection by ground engineers, during a fly-past, determined that the nose gear was still retracted but the gear doors were partially open. Positive-gravity manoeuvres and a touch-and-go landing failed to shake the nose gear free. The crew decided to land at Broome once all other traffic was clear, and emergency services were in place. Advice from the manufacturer's representative in Broome indicated that the propellers would remain clear of the runway during the landing. A landing was completed with the aircraft sliding to a stop on its main wheels and nose, 460 m after touchdown.

Nose gear locking mechanism

To release the nose gear, using either the normal or alternate systems, the over-centre up-lock initially moves further away from the neutral position before moving back through neutral to the gear extension position.

Movement of the up-lock causes a corresponding movement in the upper drag strut. Inspection determined that the nose landing gear had been jammed in the up position as a result of a lack of clearance between bolt heads securing a cover plate on the nose leg and the upper drag strut. The lack of clearance prevented the initial unlocking movement. Witness marks were found on the upper drag strut where the bolt heads had been making contact with it.

Nose leg history

The nose leg had been removed from another aircraft following a ground incident some months prior to this accident. As it was damaged, it was sent to an overseas workshop for repair. When the nose leg was returned to the operator a cover plate, which is designed to protect microswitches associated with the nosewheel steering system from dust and stone damage, was missing. The overhaul shop advised the operator to obtain a replacement. The operator believed it already had a suitable replacement in a box in its store in Adelaide and no further action was taken. The original nose leg from VH-JSI was removed, during the wing repair, and fitted to the ground incident aircraft to help restore it to flying status as soon as possible. The overhauled nose leg was fitted to JSI once the wing repair was almost complete.

Nose leg cover plate

When the box containing the replacement cover plate was delivered from Adelaide, and opened in Broome on 2 August 1996, it was found that some parts were missing. The manufacturer advised that a 36-week lead time was required to replace the missing parts. Maintenance personnel in Broome then decided to manufacture substitute parts. The operator's engineering staff, outside Broome, were not consulted. The operator's maintenance control manual required all non-approved parts to undergo a design and approval process prior to being fitted to its aircraft. A Brisbane-based contract engineer would have been responsible for this design and approval had it been requested. No action was taken to meet the design and approval requirements.

The cover plate was non-load bearing, and it was reported that it did not appear to be a significant part of the nose leg structure. The original plate was shaped to provide clearance between it and the microswitches. Because of the limited manufacturing capability in Broome, the replacement cover was manufactured from flat plate and spacers were used to provide similar clearance.

The original plate was secured using counter-sunk screws. This aspect went unnoticed by the maintenance personnel although the screws were depicted in the Dash 8 parts manual. The holes in the replacement plate were not drilled to accept counter-sunk screws and it was secured using hexagonal-head bolts and washers. The use of spacers and hexagonal-head bolts and washers meant that the tops of the bolt heads protruded 8.5 mm beyond the normal position of the counter-sunk screw heads. The measured space available between the tops of the counter-sunk screws and the upper drag strut, on a serviceable Dash 8 with its nose leg retracted, was 5 mm. The difference of 3.5 mm was sufficient to cause the landing gear to jam although hydraulic pressure was able to overcome the lack of clearance on at least one occasion after take-off.

The maintenance engineer who fitted the replacement plate to the nose leg reported that, had the holes in the plate been counter-sunk he probably would have recognised that counter-sunk screws were required. Had counter-sunk screws been used instead of hexagonal-head bolts and washers, the plate, with its spacers, would still have protruded 6.6 mm instead of 8.5 mm. That is 1.6 mm beyond the space available.

While the replacement plate was being manufactured the nose leg was refitted to the aircraft and landing gear retraction tests successfully completed. No retraction tests were attempted after the cover plate was fitted.

Organisational issues

Three significant organisational issues were identified during the investigation. These involved project management, pressure and fatigue and loyalty and motivation.

Project management

The repair of JSI was completed by two groups of engineers. The wing and fuselage repair was supervised by an engineer employed by the aircraft manufacturer and completed by an overseas contractor with assistance from the operator's staff. The reassembly and certification was completed by a licensed aircraft maintenance engineer, with Dash 8 approvals, using a mixture of the operator's staff from Broome, Perth and Darwin.

The operator's technical manager, who had ultimate responsibility for the work on JSI, was based in Adelaide and was only able to visit Broome on four occasions, the most resent being between the 12-16 May. It was reported that he departed on 16 May as the reassembly was essentially complete. He was not consulted about the plan to manufacture a replacement cover plate. A Broome-based licensed aircraft maintenance engineer was originally appointed to coordinate the repair, but he was not given any formal project management authority. This engineer did not have Dash 8 approvals, but he did have extensive experience in the maintenance and repair of large airline aircraft and was familiar with the requirement to have the correct approval for all parts fitted to transport category aircraft. The licensed aircraft maintenance engineer, with Dash 8 approvals, who assumed responsibility for reassembly and certification, was sent to Broome on temporary assignment, to provide licence cover, and arrived after the wing repair had started and the coordinating maintenance engineer had commenced his task. It was reported that this led to some conflict amongst maintenance staff. The result was that neither of the licensed aircraft maintenance engineers, or anyone else, exercised any overall responsibility for the project. At no stage was a project manager appointed to supervise the whole job. Although the maintenance personnel were aware of the maintenance control manual's requirements for non-approved parts, action was not taken to ensure that it was complied with.

Pressure and fatigue

A deadline had been set by the operator's management team for JSI to depart Broome on         18 August 1996. Reassembly and certification of JSI could not be completed until after the wing repair had been finished. Because of the complexity of the wing repair the contractor declined to give the operator a definite completion date. The wing and fuselage repair was not completed until the week commencing 12 August 1996. As a result, time to complete the whole process was limited. The nose and left main landing gear and left engine and propeller had to be reinstalled. Electrical systems, damaged during the birdstrike, had to be repaired and tested. A test flight was needed, and the aircraft had to be repainted. The local engineers believed that the time required to get the Brisbane-based engineer to complete design and approval of the replacement cover plate would probably have exceeded the limited time available.

The operator's aircraft maintenance personnel were required to work on JSI as well as complete their normal maintenance activities on other company aircraft. These processes resulted in some unusually long shifts (often 15 hours but up to 28.5 hours) and the onset of significant, observed fatigue.

Loyalty and motivation

Discussion with the operator's staff provided anecdotal evidence that there was strong company loyalty and motivation to get the job done. Staff excelled themselves in order to meet demanding deadlines. Whilst this approach is laudable, research and investigation has shown that it can lead to incorrect practices if the appropriate balance is not found.

Other issues

A number of other administrative and procedural issues were noted during the investigation. These were not directly related to this accident but provided supporting evidence that a culture aimed at "getting the job done" existed amongst the operator's staff.

ANALYSIS

It is probable that motivation, pressure and fatigue were the main factors in the decision not to complete the maintenance control manual requirements prior to manufacturing the replacement cover plate. It is likely that the maintenance engineers allowed their desire to get the job done to overcome any caution developed through experience. Limited time availability meant that ordering a replacement part or ensuring the completion of the required design and approval process, would prevent them meeting the deadline. Fatigue may have reduced the maintenance engineer's analytical ability and possibly contributed to the flawed decision.

The lack of a project manager to supervise and audit the complete engineering process meant there was no safety net to prevent incorrect decisions or practices, emanating from the workface, having a detrimental affect on safety. The lack of a project manager and the limited presence of the technical manager also meant there was no one of authority that the maintenance engineers could readily discuss the problem with before they made their final decision.

The fact that the cover plate was not a structural component and was only a protective cover probably misled the maintenance engineers into believing that the manufacture of a similar, but not exact, replacement part would not significantly affect safety.

The ultimate safety net, landing gear retraction tests, failed when the cover plate was not fitted prior to the tests. The plate was not fitted because it was not seen as a significant part of the landing gear system and time pressure probably led maintenance personnel to believe that the tests could not wait until assembly was complete.

SAFETY ACTION

The operator advised it has have taken action to address all of the management, administrative, procedural and maintenance issues noted during this investigation. Amended processes will be applied during the repair of damage sustained by JSI in this accident.

The Melbourne FSO notified Sydney FS that the Metroliner was taxiing at Dubbo and was provided with traffic information on another aircraft. The Metroliner departed Dubbo, and the crew reported their departure to Melbourne FS and broadcast a departure report on the Dubbo mandatory broadcast zone (MBZ) frequency. The Melbourne FSO notified the crew of the Metroliner the traffic information provided by Sydney FS and notified Sydney FS of the departure time of the Metroliner.

As the Metroliner climbed enroute, the crew observed another aircraft approaching overhead Dubbo from the northeast. The crew attempted to contact the pilot of the other aircraft via the MBZ and FS area frequencies. As the Metroliner passed 8,000 ft at approximately 5 NM from Dubbo the crew estimated they went through the level of the other aircraft.

The callsign of the other aircraft was established shortly after when the crew of the Metroliner overheard the pilot of the Mooney report overhead Dubbo at 8,000 ft.  The crew of the Metroliner changed to the Sydney FS frequency and confirmed the other aircraft's callsign and track details with the Sydney FSO.

ANALYSIS

The Melbourne FSO estimated the flight of the two aircraft would not be in conflict based on his experience and understanding of Metroliner aircraft performance. He considered the aircraft to be well separated despite the fact that the flight information on the flight progress strips indicated that the aircraft met the criteria for traffic in conflict detailed in the MATS.

The FSO had recently undergone a performance check and had received favourable comment in relation to his ability in assessing conflicts between aircraft. This may have led the officer to be somewhat over-confident in his abilities and possibly caused him to trust his own instincts in preference to standard procedures.

SIGNIFICANT FACTOR

The Melbourne FSO did not comply with the procedures in the Manual of Air Traffic Services for the provision of traffic information to IFR category aircraft.