FACTUAL INFORMATION

The Boeing 747 (B747) was maintaining flight level 350 (FL350) when the crew received a traffic alert and collision avoidance system (TCAS) resolution advisory, warning of conflicting traffic crossing their track at an altitude 400 ft below. They were able to contact the other aircraft, which was a Douglas DC8 maintaining FL330 in accordance with air traffic control (ATC) instructions.

Both crews were able to maintain their respective levels and no evasive action was required. When the DC8 departed Auckland, ATC verified that the secondary surveillance radar altitude readout had correlated with the reported altitude from the crew. However, on arrival at Honolulu, ATC noted a 1,500 ft difference in the altitude reported by the crew to that showing on the radar display. The aircraft transponder was providing an erroneous altitude, but the crew had no flightdeck display to enable them to check what information the transponder was emitting.

The equipment failure had occurred between departing radar coverage at Auckland and the point at which the B747 crew received the TCAS alert. Initial maintenance action by the company indicated a faulty encoder, but an ongoing investigation in the USA revealed that the central air data computer had been providing faulty inputs to both transponders.

SAFETY ACTION

As a result of this occurrence, the Bureau of Air Safety Investigation is investigating a perceived deficiency involving the lack of information available to flight crews regarding the serviceability of altitude encoders. In addition, the Bureau is investigating the lack of information displayed to crews regarding altitude information being transmitted by transponders. Any recommendations issued as a result of these investigations will be published in the Bureau's Quarterly Safety Deficiency report.

The student with an instructor was practising autorotative landings onto the grass in the helicopter training area in the NE corner of Moorabbin airport. With the student at the controls, the helicopter touched down gently with about 10 kts forward groundspeed. During the ground slide the landing gear skids encountered a patch of sandy loam and dug in. The helicopter lurched nose down. The instructor took over the controls and raised the collective. The helicopter momentarily became airborne before landing firmly. The combined effect of the lurch and the subsequent landing bent the skids, dislodged the aft cross tube supports and caused the main rotor blades to dent the cover to the tail rotor drive shaft.

The instructor had taught students to perform autorotations at Moorabbin for many years. He was surprised at finding a sandy patch in the grassed area commonly used for autorotative touch downs. He has since advised the FAC of the sand hazard. Since the accident, as the grass has progressively dried out in the summer heat, the instructor has noticed several other sandy patches scattered around the airport.

While returning to the airstrip to reload for another spray run, the aircraft experienced severe engine surge with associated rough running. The pilot selected the fuel boost pump on, but with little improvement. He then elected to make a forced landing. While stretching the glide, the aircraft stalled at about five feet AGL and landed heavily in a soft earth paddock. This resulted in the left main landing gear failing, followed by the nose impacting with sufficient force to tear the engine from its mounts. Inspection by the company found the main fuel filter not lock wired allowing the filter assembly to come loose and starve the engine of fuel.

The pilot reported that on approaching the paddock to be sprayed he did a circuit to observe wires and obstructions. He observed two sets of wires, one set running along a main road and another set running along one side of the paddock to a bore. The pilot decided to carry out some clean up runs along the bore wire first, to make the spray runs on the paddock safer. On the fourth run the pilot was intending to go over the road wires, but the landing gear snagged them, and brought the aircraft down to the ground some distance away. The pilot stated that there was a crop of tall sunflowers growing in the corner of the paddock, which made it too dangerous to go under the wires.

The pilot reported that on departure from Pormpuraaw he selected gear up and the gear cycled normally. Passing approximately 2,500 ft on climb to 9,000 ft he noticed the left hydraulic flow light illuminate. Shortly after, the right hydraulic flow light illuminated. The pilot recycled the gear and nothing happened. He then noticed hydraulic fluid leaking from the top of the cowl on the right engine. The pilot realised that there was no hydraulic fluid remaining in the system and that he would have to use the emergency system to lower the gear. The pilot said he continued towards Cairns due to the fact that there were no maintenance facilities at Pormpuraaw, the aircraft was operating normally, and Cairns was better equipped to handle any emergency situation.

On arrival in the circuit at Cairns, the pilot pulled the emergency gear extension handle after performing all the necessary cockpit checks but the gear did not extend. Further attempts to lower the gear were also unsuccessful. The pilot subsequently landed the aircraft wheels-up about 90 minutes later.

Subsequent investigation revealed that a burst hydraulic hose had allowed the contents of the hydraulic system to escape. The emergency gear extension system blow down bottle was fully charged, but the releasing mechanism did not function. When at full travel, the emergency gear extension operating handle (which was attached to a cable) failed to operate the release valve on the bottle. This appeared to be due to distortion of the cable casing when the cable was placed under tension.

The pilot reported that the engine faltered briefly when he applied full power while rolling out of a procedure turn during an aerial seeding operation. He then deliberately stalled the aircraft into the tops of trees when it was clear that it was losing performance. The aircraft rolled right and struck the ground in a nose down, inverted attitude. The pilot and station manager occupied the front seats, the seed dispatcher was tethered by a lanyard in the rear cabin from which the seats had been removed. All three occupants were taken to hospital, two with minor and one with serious injuries.

The aircraft carried an emergency locator transmitter (ELT) which was fixed to structure in the rear fuselage. The ELT worked automatically, alerting AusSAR to the accident.

Onsite photographs indicated that the engine was producing high power when the propeller struck tree trunks. The flight conditions were extreme; 43 degrees C, moderate turbulence and a density altitude of approximately 5,200 ft.

The Kawasaki 47G3B helicopter had undergone major servicing, part of which required the removal and re-installation of the tail rotor cables, gearbox and extension tube. The pilot had assumed the ground-running of the helicopter from another company pilot, who had conducted the daily inspection. Following the rectification of some problems with the engine, the ground runs were completed and the tail rotor successfully balanced. The rotor track and balance equipment was then transferred from the tail to the main rotor to conduct main rotor blade tracking and balancing ground runs. The licensed aircraft maintenance engineer (LAME) who had conducted the maintenance work accompanied the pilot during the ground runs.

After the flat pitch track had been checked and found to be within limits on the ground, the LAME requested the pilot to fly the helicopter into a hover to check the main rotor blade tracking. The pilot complied with the LAME's request. However, the maintenance documentation had not been completed in that the independent inspection required on the flying controls had not been certified.

As the helicopter lifted to a 3-ft hover, it began to yaw to the right. The pilot attempted to correct the movement through the application of left tail rotor pedal, but the yaw accelerated to the right. Because the yaw was accelerating despite the pedal input, the pilot concluded that the helicopter had sustained a tail rotor failure. As the helicopter completed the second or third turn, the pilot lowered the collective to place the helicopter back on the ground. The helicopter landed heavily, damaging the landing gear, main transmission system and components of the tail rotor system. Neither of the helicopter's occupants received any injuries. No bystanders were injured.

The tail rotor control cables were subsequently found to have been incorrectly routed onto the tail rotor pitch change drum, causing the tail rotor control to work in the opposite sense to the tail rotor pedals.

The LAME had previously completed similar tasks on the helicopter type. He could not explain why he had incorrectly installed the cables on this occasion, other than to comment that he may have become too familiar with the procedure.

Before disconnecting the cables to conduct the required servicing, the LAME pinned the tail rotor cable pulley assembly to avoid a later requirement to re-rig the tail rotor controls. After the tail rotor gearbox and extension tube had been fitted, the LAME reinstalled the two tail rotor control cables to the tail rotor control drum. The cables ran in parallel along the helicopter's tail boom to the rotary drum that adjusts the tail rotor pitch control. When installed, the cable lengths were similar and both of the cable ends were alike. Instructions detailing the installation of the cables to the drum were in the maintenance and overhaul instruction manual. Although these instructions referred the reader to a diagram that displayed the routing of the cables, the diagram did not highlight the need for the cables to cross over before being connected to the drum. The cables should have been installed such that the inboard cable was connected to the outboard section of the drum and the outboard cable to the inboard section of the drum. However, the cables were not installed such that they crossed over and were, therefore, attached to their respective sections of the drum. Despite the incorrect installation of the cables, the tail rotor pitch change drum still worked, albeit in the reverse sense. Because the LAME had pinned the tail rotor pulley assembly, he decided that the check rigging of the tail rotor detailed in the maintenance manual was not required. As a result, a procedural step that may have detected the incorrect routing of the control cables was missed.

After the LAME had completed the work, he certified the appropriate sections of the maintenance work package even though the secondary inspection of the flying controls had not been conducted or certified. The independent secondary inspection should have detected the incorrect routing of the tail rotor pitch cables. Civil Aviation Regulation 42G detailed the qualifications required to conduct secondary inspections. The regulation permitted a pilot who held a licence that was valid for the aircraft to conduct a secondary inspection. However, the pilot was not required to undertake any relevant specific training on the conduct of such inspections. There was no regulatory requirement for the pilot to check the maintenance documentation other than the maintenance release before flying the helicopter, so he was not aware that the secondary inspection of the flying controls had not been completed.

The LAME's circumvention of the procedures, probably because of his familiarity with the task, was a factor in the accident. Although the maintenance manual specified procedures that should have ensured the correct operation of the tail rotor system, the design of the cables did not preclude their incorrect routing and attachment to the drum. Therefore, the design of the cables was also a factor in the accident. The investigation also found that the maintenance manual description of how to route the tail rotor cables was deficient in that it did not adequately highlight the cable crossover to the drum.

SAFETY ACTION

As a result of this occurrence, the Bureau of Air Safety Investigation is currently analysing two possible safety deficiencies. The deficiencies identified involve tail rotor cable marking and routing instructions in the Kawasaki Bell 47G and the qualifications of people permitted to carry out secondary inspections.

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

During the initial climb after take-off from Runway 07, the pilot saw a large white bird in front and just right of the aircraft. With the aircraft only 50 ft above the runway there was insufficient airspace and time to take avoiding action. The windscreen shattered and shards of Perspex flew around the cabin. The pilot closed the throttle immediately and landed the aircraft on the remaining section of runway.

After taxying clear of the runway, the pilot shut the engine down and attended to a young boy who was seated in the right rear seat. He had been injured by the flying Perspex and was bleeding profusely from a cut above his left eye. The boy later received stitches at the Redcliffe Hospital.

During an inspection of the runway, Perspex pieces and the remains of an Ibis were found 400 m from the threshold.

The aircraft was taking off from runway 16L when, on rotation, a loud engine vibration noise was heard throughout the aircraft. The number two engine vibration indication rose to three units, though all other engine parameters were normal. A Pan call was made and the aircraft was vectored by Air Traffic Control (ATC) along the coast and onto a 10 nm final for landing back at Sydney. During the return to the aerodrome, both engine vibration indications fluctuated to five units but returned to normal on landing.

A subsequent ground inspection of the engines revealed bird strikes to both engines. Four fan blades from each engine displayed leading edge bending although boroscope inspections of both engines revealed no internal damage. Both engine fan blade sets were changed and the aircraft was returned to service.

A seagull carcus was found during a runway inspection after the incident.

Safety Action

In 1996, the Bureau of Air Safety Investigation conducted a review of reported birdstrikes in Australia (report released November 1996). A number of airports, including Sydney, were identified as having a particularly high frequency of reported birdstrikes.

The review generated recommendation R960129. The recommendation was directed to the Federal Airports Corporation (FAC), the Civil Aviation Safety Authority (CASA) and Airservices Australia (AA). It stated the following:

"As a result of this review the Bureau of Air Safety Investigation recommends that:

The Federal Airports Corporation and other airport authorities review 'Bird Management Plans', especially for those locations with significant frequencies of bird-strike occurrences;

The Civil Aviation Safety Authority assess the need for increased oversight of 'Bird Management Plans' to ensure the most effective and efficient reduction in the frequency of bird strikes; and

Airservices Australia assist in reducing the bird-strike hazard by issuing NOTAMs when significant bird activity has been noted or is forecast, and by advising flight crew where specific bird hazards have been observed."

On 20 January 1997, a response was received from the FAC and stated the following:

"Thank you for your letter (B/96/061) of 10 January 1997, accompanying the report 'Reported Bird Strikes in Australia' and addressed to Mr Peter Snelling. In accordance with your Safety Recommendation R960129, we have forwarded a copy of the report to all Federal Airports requesting that they all review their Bird Management Plans. We have further directed that action be taken by those airports listed in Appendix 2, Table 2 of the report to reduce the bird strike hazard.

The opportunity was also taken to remind all airports to take reasonable action to reduce any identified bird hazards. We look forward to cooperating with the Civil Aviation Safety Authority and Airservices Australia to reduce the bird strike hazard to aviation."

On 7 April 1997, a response was received from CASA and stated the following:

"I refer to your BASI Investigation Report 'Reported Bird Strikes In Australia' containing the BASI Recommendation R960129. The following comments are forwarded for your consideration. In order to allow CASA to assess whether there is a need to increase oversight of bird management plans, we have asked our aerodrome inspectors to check that the aerodrome operators have taken all steps to guard against birdstrike, and report any specific actions taken by them to further reduce bird strike hazard. CASA will determine bird management oversight strategy following the review of aerodrome operators' efforts in regard to existing bird hazard management plans, and any proposed changes."

On 11 June 1997, a response was received from Airservices Australia. Airservices considered that their current bird hazard procedures were adequately meeting the intent of the recommendation. These procedures consisted of the inclusion of bird hazard information in the Enroute Supplement of Australia (ERSA), the issuance of bird hazard NOTAMs, and the provision of bird hazard information on Automatic Terminal Information Broadcasts and direct voice contact with Air Traffic Controllers.

A bird hazard workshop was held in October 1997. It included representatives from the FAC, CASA, BASI, airport operators, and local government. An interim committee was formed to summarise the outcomes of the workshop and formulate strategies to address the bird hazard problem. The FAC has employed the services of Birds Australia, consultant ornithologists, to report on a quarterly basis and make recommendations on any further bird management strategies. A follow-up workshop is to be held in April 1998 to reassess the situation, evaluate current strategies and consider alternative bird management plans.

The Bureau will continue to monitor reported birdstrikes, especially at those locations with significant bird-strike occurrences.

The pilot of a Piper Lance was attempting to take-off from a property airstrip. The surface condition was described as being firm to soft. During the latter stages of the take-off roll, the aircraft was reported to have passed through two soft patches of dirt, with a subsequent loss of momentum. This resulted in the aircraft becoming airborne about 27 m before a fence.

The aircraft collided with the top wires of the fence, before flying into the tops of some small scrubby trees. The aircraft was landed in a substantially wings level attitude, however, the right main landing gear was torn off when it struck a log.