While returning to Adelaide from Moomba, the crew of a Dash 8 detected smoke coming from around the weather radar. They immediately turned off the equipment, donned oxygen masks and made a PAN call requesting RFF services to be placed on standby. To dissipate the smoke, the crew requested a descent to 10,000 feet where the aircraft was depressurised and the forward outflow valve was opened. After ensuring that there was no smoke or flame coming from the radar unit, the crew made the decision to continue to their destination and briefed the passengers accordingly. Upon arrival in Adelaide the aircraft made a normal approach and an uneventful landing. The flight attendants were later sent for medical attention due to the effects of smoke inhalation. Maintenance investigation by the operator traced the fault to the radar indicator unit. This was replaced and the aircraft returned to service.

CIRCUMSTANCES

VH-AZX, a Beech 76, was taxiing for take-off at the same time as VH-NJU, a British Aerospace 146. Both aircraft had made the appropriate mandatory broadcast zone (MBZ) calls. While lining up for take-off, the crew of NJU noticed AZX at taxiway E approaching the runway. The crew of NJU broadcast "rolling" and AZX stopped. Immediately, another voice broadcast that AZX had infringed the flight strip and suggested that the pilot should take off. This broadcast was acknowledged by the pilot of AZX, who taxied onto the runway and took off.

The crew of NJU had only just commenced the take-off roll and rejected the take-off. The other voice was that of the airport safety officer, who was in a vehicle near taxiway E. He saw AZX cross the holding point and enter the flight strip. He believed that the crew of NJU had not seen AZX, and that a dangerous situation existed. This was the basis for his radio transmission to the pilot of AZX. The investigation found that there were no published procedures or guidelines for airport safety officers to follow in situations perceived to require immediate action. On this occasion, the safety officer made a radio transmission which the pilot of AZX interpreted as an air traffic control instruction and which he subsequently followed.

SAFETY ACTION

The Bureau of Air Safety Investigation is currently investigating a perceived safety deficiency that has been identified as a result of this occurrence. The deficiency involves the lack of published information available to airport safety officers on recommended radio usage. This information is necessary in order to provide safety officers with phraseology they can use to alert pilots to safety hazards, without using terms that could be interpreted as controlling or suggesting. Any recommendation issued as a result of this investigation will be published in the Bureau's Quarterly Safety Deficiency Report.

FACTUAL INFORMATION

The pilot of the Cessna 206 was conducting repetitive parachute jumping exercises at the Dale River drop zone. He was operating in Class C airspace and communicating with the air traffic controller at Perth Approach on the radar advisory frequency. He advised his intention for the parachutists to jump and was cleared by the controller to operate to a ceiling of flight level (FL) 110. Soon after the pilot of the Cessna received his clearance to drop, the pilot of an Airbus A320 contacted Perth on the approach frequency, advising that he was on descent to FL120. The Airbus was inbound to Perth from the south-east on a track that passed close to the Dale River Drop Zone. The Cessna pilot reported that he had the Airbus sighted. The air traffic controller then assigned the pilot of the Cessna responsibility for maintaining separation visually from the Airbus but the Cessna pilot did not respond. Because the two aircraft were on different frequencies, the pilot of the Airbus was unaware of the Cessna and that the pilot of the Cessna had been assigned a requirement to remain visually clear of the Airbus.

At the time of the incident, the Cessna was tracking southbound and had just turned left with the Airbus passing about 1.25 NM to the North. The controller then cleared the Airbus to descend to 8,000 ft. As the Airbus left FL120 on descent, the crew received a traffic alert and collision avoidance system (TCAS) traffic advisory (TA) closely followed by a resolution advisory (RA) instruction to reduce sink rate with which the crew complied. The crew of the Airbus reported sighting the Cessna 400 ft below their aircraft and climbing. Radar evidence indicated that the nearest the aircraft came to each other was approximately 700 ft vertically and 1.25 NM laterally.

The Aeronautical Information Publication (AIP) Air Traffic Rules and Services (RAC) noted that air traffic control (ATC) will provide separation between instrument flight rules (IFR) and visual flight rules (VFR) flights. In this situation, ATC would have normally been expected to direct the aircraft such that a minimum separation of 5 NM laterally or 2,000 ft vertically between the aircraft was maintained. However, it also stated that "under certain conditions, the pilot of one aircraft may be given the responsibility for separation with other aircraft". The Manual of Air Traffic Services (MATS) section 8 prescribed the application of visual separation and there was no requirement for the pilots of aircraft that had not been assigned separation responsibility to be advised that visual separation standards applied. There was also no requirement for the aircraft to be on the same frequency.

Whilst Civil Air Regulation 163 stated that an aircraft must not be flown so close to another aircraft as to create a collision hazard, it did not prescribe a minimum separation requirement. Therefore, the pilot given the responsibility for maintaining visual separation was at liberty to fly close to another aircraft so long as no collision hazard was created.

Although the air traffic controller had assigned a visual separation requirement in accordance with the AIP and MATS, he had not sought confirmation from the Cessna pilot regarding the assignment of the separation responsibility. However, there was no evidence to indicate that the Cessna pilot did not maintain such separation from the Airbus. Because the aircraft were on different frequencies and the air traffic controller had not advised the Airbus pilot that the Cessna was assigned separation responsibility, the Airbus pilot was unaware of the Cessna and the reduced separation standard being applied. He had no opportunity to accept or reject the reduced separation standards and his first indication of the presence of the Cessna was the TCAS alert to which he properly responded.

SAFETY ACTION

In 1996, a similar event occurred involving a Boeing 767 departing from Darwin and a Partenavia P68C which was conducting aerial work at Darwin. As a result of the investigation into that incident, the Bureau issued interim recommendation IR970027 to Airservices Australia. The interim recommendation stated, in part, that "Airservices Australia should introduce a requirement for a controller to advise the crew of an IFR-category aircraft that the pilot of another aircraft has been assigned visual separation responsibility and to pass traffic information on the other aircraft". On 31 October 1997, the Bureau received a response from Airservices Australia which stated, in part, that "Airservices will seek a review, in conjunction with CASA, of the visual separation standards applicable to aircraft operating below FL125, at the earliest opportunity. On completion of the review, BASI will be advised of any outcomes".

Response classification: OPEN

As at 11 July 1998 the Bureau had received no further advice on the proposed review. As a result of this occurrence (9801510), the Bureau is investigating further safety aspects related to visual separation procedures and responsibilities. Any safety outputs resulting from this investigation will be published in the Quarterly Safety Deficiency Report.

FACTUAL INFORMATION

The crew of an instrument flight rules (IFR) Beech 200 (B200) was conducting a base check which would entail a practice non-directional beacon (NDB)/distance measuring equipment (DME) approach to runway 12 at Williamtown aerodrome. The pilot under check (handling pilot) and the checking pilot briefed for an approach to the minima, followed by a missed approach to 1,500 ft and then join the circuit for circuit training. The missed approach was to be conducted with the aircraft configured to simulate asymmetric operation. While inbound to Williamtown, the handling pilot briefed the approach controller of their intentions and was subsequently cleared to make the NDB/DME approach. The handling pilot then advised the approach controller that, after the NDB, the aircraft would conduct a go around. The check pilot did not hear this transmission due to the aircraft's communications configuration, which prevented his hearing any air/ground transmission by the handling pilot.

Prior to the missed approach point the handling pilot commenced an asymmetric missed approach and reported to the aerodrome controller. The aerodrome controller (ADC) instructed the crew to go around, to maintain runway heading and to maintain an altitude not above 500 ft. The transmission from the ADC was broken and both pilots believed that the assigned altitude was 1,500 ft. The handling pilot readback the requirement to maintain runway heading but did not readback the altitude, which was contrary to Aeronautical Information Publication (AIP) procedures. The ADC did not challenge the lack of the readback of the altitude by the pilot, which was contrary to air traffic control procedures.

The ADC's intention was to limit the altitude of the B200 to establish 500 ft vertical separation with a formation of Macchis that was entering the circuit via the initial point. The Macchi pilots had sighted the B200 as they tracked from the initial point and pitched into the circuit. During the missed approach, at approximately 1,200 ft, the B200 pilots saw the formation of Macchis pass from their left to right in front of and slightly below the level of their aircraft. The Macchi formation passed with approximately 200 ft vertical separation.

ANALYSIS

The misunderstanding by the handling pilot of the B200 in relation to a "go around" and a "missed approach", and the fact that the check pilot did not hear the transmission, created a developing situation that was appreciated differently by the two pilots and the ADC. The minima for the "missed approach" was 570 ft, whereas a "go-around" could have been commenced from a lower altitude.

While the radio transmission quality made communication difficult, the lack of radiotelephony discipline by both the handling pilot and the ADC ensured that the opportunity to resolve any misunderstanding was lost.

SIGNIFICANT FACTORS

1. The pilot of the B200 requested a "go around" instead of a "missed approach"

2. The check pilot could not hear the handling pilot's air/ground transmissions.

3. The pilot did not readback the requirement to maintain 500 ft to the ADC.

4. The ADC did not challenge the pilot to readback the altitude requirement.

The crew of a Fairchild Metro 23 aircraft report experiencing difficulty in maintaining directional control as they applied power during the take-off roll. The aircraft seemed to be sluggish in accelerating and was pulling to the left. The difficulty in controlling the aircraft was exacerbated due to the inadvertent deactivation of the nose wheel steering button on the left power lever.

This system had been checked during taxi and was confirmed as serviceable. The crew indicate that this switch was "on" at completion of the pre-take-off checklist but had somehow been released during the early stages of the take-off roll.

The crew detected that the left propeller had not released the start locks, resulting in asymmetric power being produced. A non-standard call made by the pilot not flying is reported to have delayed the crew's recognition of the problem. The crew were in the process of abandoning the take-off when the aircraft veered off the left side of the runway, stopping prior to the runway 10 T-VASIS. The crew taxied the aircraft back onto the runway, switched the nose wheel steering system "on" and taxied normally back to the hangar for maintenance investigation.

The aircraft was not damaged during the incident and all aircraft systems checked out as serviceable. The crew briefed themselves on aspects of the previous incident before departing on the planned flight.

During a property inspection prior to commencing spraying, the engine failed. The helicopter was about 700 ft above ground level at the time. The pilot attempted to dump the load by the electrical system, but this failed to operate. He was too occupied to operate the mechanical dump system.

During the subsequent landing, the helicopter rolled onto its side after a cross tube on one side failed. The failed area had been weakened by corrosion and there was evidence of pre-existing cracks. The engine crankcase was fractured, consistent with a connecting rod failure at no. 5 cylinder. Logbook records indicated that the engine had been over-sped some 200 operating hours earlier. A faulty canon plug had prevented the electrical dump system from operating.

As the aircraft reached approximately 20 kts during the take-off roll, no 2 engine failed. The take-off was rejected. No other damage to the aircraft was reported. The engine examination by the aircraft operator revealed that all first-stage blades had failed adjacent to their blade platforms. The damage was most likely caused by failure of blade No 35, which failed in high cycle fatigue emanating from the blade trailing edge. The operator experienced several similar failures previously. The engine manufacturer was aware of the problem and was undertaking corrective action.

FACTUAL INFORMATION

Inbound to Launceston from Cape Barren, the pilot of a PA-23, VH-JSB, requested a 32L VOR/DME approach. Because of conflicting traffic, air traffic services (ATS) instructed JSB to enter the holding pattern, to maintain 7,000 ft, and report turning inbound in the holding pattern. The pilot acknowledged the instruction, but proceeded immediately into the 32L VOR/DME approach, descending from 7,000 ft. He reported turning inbound, but ATS believed the 'Inbound' call referred to JSB being inbound in the holding pattern. The pilot continued to fly the published 32L VOR/DME pattern and positioned the aircraft to intercept the 319 degrees radial as prescribed on the DAP chart. Minimum altitude specified before being established on the 319 degree radial is 2,800 ft.

Meanwhile, VH-OZV, a PA-31, was in cloud at 3,000 ft, conducting an ILS approach to runway 32L at Launceston. A company pilot occupied the right seat on the flight from Flinders Island. When passing the NILE locator, 7.7 NM DME distance, at 3,000 ft, the aircraft entered a cloud break and the right seat pilot sighted another aircraft about 200m ahead. The flying pilot took immediate action to avoid the other aircraft which was subsequently identified as JSB. JSB continued the 32L VOR/DME approach, and ATS provided OZV with separation.

ANALYSIS

The final approach paths for the runway 32L ILS and runway 32L VOR/DME are slightly different, with the ILS approach requiring the 313 degrees inbound radial to be flown, and the VOR/DME specifying the 319 degrees radial. The inbound turn in the VOR/DME pattern is a right turn to intercept the 319 degrees radial, and this requires the aircraft to fly across the inbound ILS approach track. An aircraft flying a VOR/DME approach would normally be inbound by 8NM, which is almost adjacent to the NILE locator, which aircraft utilise on an ILS approach.

Altitude requirements in the two approaches are also similar. At a distance of 7.7 NM DME, the distance of the NILE locator, an aircraft on an ILS approach would be descending from 3,000 ft, and an aircraft on a VOR/DME should be at about 2,900 ft.

Although aircraft may be carrying out different approaches to runway 32L, they need to be treated as if they are flying the same approach, and ATS apply separation standards accordingly. If a pilot misunderstands an ATS instruction, potential exists for two aircraft to be in close proximity.

The pilot of JSB misunderstood the ATS instruction to report inbound in the holding pattern, to mean to report inbound in the VOR/DME approach. Because of this misunderstanding, he commenced the approach and descended below 7,000 ft without a clearance. This action placed JSB in conflict with OZV which had been cleared to carry out an ILS approach to runway 32L. The 'Inbound' call to ATS did not provide a warning of the developing situation, as ATS were expecting the call in the holding pattern.

ATS had advised the pilot of JSB that the instruction to enter the holding pattern was because of other traffic in the area, including some making instrument approaches. Although adequate information was transmitted by ATS, the pilot's decision to descend from 7,000 ft and carry out the VOR/DME approach he originally requested, indicated a loss of situational awareness.

Further investigation showed that four minutes before the breakdown of separation between JSB and OZV, VH-IAM, a PA31, had departed from Launceston for Flinders Island. IAM was held at 6,000 ft to maintain separation from JSB which was thought to have been at 7,000 ft. However, when IAM departed, JSB had descended from 7,000 ft. With JSB descending to the southeast of the VOR and IAM climbing to the northeast, there was probably no breakdown of separation, but there was no separation assurance.

SIGNIFICANT FACTORS

1. JSB descended from 7,000 ft and commenced a 32L VOR/DME approach without a clearance.

2. In a cloud break, the right seat pilot of OZV sighted JSB.

3. The flying pilot in OZV took action to avoid JSB.

The operator and pilot reported that the helicopter struck a single-wire-earth-return (SWER) power line at the beginning of a swath run during a spraying operation. The orientation of the cane paddock being sprayed was north-east / south-west with a major power line running through the north-eastern corner. A SWER power line running east -west joined the main power line over the paddock. The pilot had sprayed the western edge of the paddock, flying the helicopter over the main power line on each spray run. As the pilot moved his spray effort further east on each swathe run, he concentrated on missing and flying over the main power line. On one pass he lost awareness of the SWER line and during descent onto the crop the mast of the helicopter struck the line. The helicopter rolled into the crop. The pilot was not injured

FACTUAL INFORMATION

At 0450 WST, the Bell 206 helicopter departed the heliport on East Intercourse Island to conduct a marine pilot transfer to a ship waiting at the outer buoy in Dampier Sound. The pilot reported that although there was a high overcast, which mostly obscured the moon and made the sky very dark, the horizon was visible. The towns of Dampier and Karratha were to the south-east of the ship. The wind was calm and the sea surface almost mirror-like. The pilot reported that the horizon was clearly discernible during the transit to the ship. The moon set at 0452 and sunrise was at 0633. The helicopter landed on the ship at about 0505 and disembarked the marine pilot. At about 0514, the helicopter departed towards the north-east. The pilot reported that as the helicopter climbed through 500 ft, the tail rotor pedals felt unusual. Whilst he was attempting to determine the nature of the tail rotor pedal problem, he did not monitor the helicopter's flight attitude and performance, and the helicopter descended into the sea. A deck hand on the ship reported to the ship's bridge staff at about 0515 that he saw the helicopter's lights enter the water off the ship's port side. At approximately 0615, a port authority vessel recovered the uninjured pilot. The helicopter sank in about 18 m of water in the main shipping channel to Karratha.

An inspection of the recovered wreckage did not reveal the cause of the reported fault in the tail rotor control system. The pilot reported that although the pedals had felt unusual, there had been no loss of directional control before the impact.

The helicopter was fitted with a radio altimeter that had a low height alert warning light. The pilot reported that the alert was set to activate at 150 ft but did not recall seeing the low light illuminate before the helicopter struck the water. The helicopter was not fitted with an autopilot or height hold facility. The operator reported that the collective of the helicopter had a tendency to fall if not closely controlled by the pilot.

The pilot had recorded approximately 4,200 hours flying experience on a variety of helicopters, including approximately 900 hours on the Bell 206. He had completed 20 hours on this helicopter in the 30 days immediately prior to the accident. The pilot had a valid night visual flight rules (night-VFR) rating and 51 hours night-VFR experience. However, he had accumulated only 5.5 hours instrument flying time and he did not have an instrument rating. The pilot commenced night marine pilot transfer training about 2 months prior to the accident, and had received 21 hours of night-VFR training that included more than 63 landings on ships at night. About half of these landings were to brightly lit decks. About 70 per cent of the landings had been conducted under dark-night conditions but his training did not include practice emergencies or distractions during night departures. He began carrying passengers less than 1 month prior to the accident.

The pilot had been working alternate days for 8 days prior to the accident. The longest shifts had been two of 8 hours duty time each.

Human performance levels vary through physiological cycles of approximately 24 hours. These are referred to as circadian rhythms. The most significant circadian low-point occurs between approximately 0200 and 0600. The effects of circadian dysrhythmia include poor judgement, increased reaction times, mental haziness or lethargy and a general decrement in psychomotor performance. On the day of the accident, the pilot had been awakened by a call from work at 0400 to pick up two marine pilots for a departure 1 hour later.

A constraint in human performance when operating at night is the eye's poor ability to quickly adjust from brightly lit areas, such as a ship's deck, to dark environments, such as over water. The human eye generally achieves a large amount of dark adaptation after 15 minutes with full adaptation occurring after about 40 minutes.

The Civil Aviation Regulations (CARs) permitted the operation of aircraft under night-VFR with certain provisions. Although the CARs restricted single-engine aircraft charter operations, the Civil Aviation Orders (CAOs) provided exemptions to these limitations for marine pilot operations. CAOs also required that operations that were conducted during visual meteorological conditions at night, do so in accordance with the helicopter's flight manual. Although the regulations and orders did not require a visual horizon when flying at night, there was no on-going requirement for a pilot to demonstrate an ability to fly an aircraft with sole reference to the aircraft's flight instruments.

The company operations manual required night-VFR flights to be flown such that flight attitude could be maintained by reference to external objects adequately illuminated by ground or celestial lighting. The helicopter's flight manual required that the pilot maintain orientation through visual reference to ground objects solely as a result of lights on the ground or adequate celestial illumination. Neither publication provided guidance or caution on the human factor limitations associated with night visual flying.

ANALYSIS

The pilot had a visual horizon during the transit to the ship and the lights of the town of Dampier would have provided a horizon to the south-east for the return transit. The ambient and ground lighting conditions would probably have been sufficient to meet the requirements of the company operations manual and the helicopter's flight manual, although it is unlikely that such conditions existed during the departure from the ship. The moon had set 13 minutes prior to the helicopter's arrival at the ship. The transit time to the ship would probably have been sufficient for the pilot to attain a large proportion of his visual dark adaptation and therefore he may have ascertained that there was an adequate horizon to the north-east. However, after landing on the ship, the pilot's dark adaptation would have been substantially destroyed by the ship's lights illuminating the deck area. Although the company operations manual and helicopter's flight manual required sufficient lighting to maintain flight attitude, neither publication provided guidance or caution on the human factor limitations associated with dark adaptation. Consequently, although the pilot thought he had an adequate horizon on which to maintain the helicopter's flight attitude, he had no objective measure with which he could ascertain the suitability of the conditions for continued flight in accordance with the company manuals.

The departure from the ship was unlikely to have been made with any discernible horizon because the moon had set 22 minutes before, the high overcast had obscured much of the celestial lighting and the pilot could not have achieved any dark adaptation in the brief period from the take-off to water impact. Deprived of an adequate external visual horizon, the pilot would have been unable to maintain the helicopter's attitude and departure profile without referring to the helicopter's flight instruments. Given his minimal instrument flying experience, the pilot may have had difficulty transitioning from visual reference to instruments during the departure. When the pilot became concerned at the "feel" of the tail rotor pedals, he diverted his attention from the helicopter's attitude and performance indications for an extended period. While the pilot was not monitoring the helicopter's flight attitude or performance, it is likely that the helicopter's collective control fell and the helicopter descended. Having been awakened at 0400, the pilot was working within the most pronounced low point of his circadian cycle which may have also adversley affected his ability to maintain his situational awareness during the distraction. His relative inexperience at conducting night marine transfers associated with possible circadian dysrhythmia may have reduced his situational awareness because he was unaware that the helicopter was descending until it struck the water.

SAFETY ACTION

The Bureau of Air Safety Investigation is currently investigating a perceived safety deficiency that has been identified as a result of this occurrence. The deficiency relates to:

- human factors involved with operating helicopters over water at night;

- passenger safety provisions for over-water helicopter operations; and

- the adequacy of current night-VFR requirements for over-water helicopter operations.

Any recommendation issued as a result of this investigation will be published in the Bureau's Quarterly Safety Deficiency Report.

Local safety action

The operator has increased the training requirements for pilots operating to ships under night VFR. These requirements include night training under moonless conditions and total cloud coverage, the introduction of basic instrument flying proficiency checking and the introduction of annual written human factors examinations.