The pilot reported that he was conducting mustering operations with a second person on board. While operating at about 50 ft above ground level and at 15 kts indicated airspeed the pilot realized that the helicopter was moving downwind. He immediately increased power, however the main rotor over-pitched, causing the helicopter to land heavily. The wind was from the south-east at 5 kts.

The pilot decided to sling his helicopter landing trolley a short distance on his own property. He tied two ropes on each side of the trolley so that it would lift evenly from all four corners. The centre point of each rope was then attached to the cargo hook.

With the helicopter in the hover and the trolley airborne about one foot off the ground, one end of the rope on the left side broke where it was tied on to the trolley. The rope recoiled and wrapped around the left skid. As the left side of the trolley dropped to the ground, the right-side rope caught over the heel of the right skid.

The pilot activated the cargo hook release in an attempt to jettison the load but could not free the rope snagged on the heel of the right skid. He managed to land the helicopter precariously partially on the trolley and partially on the ground. Then, after he shut down the engine, and the rotor RPM was decaying, the helicopter settled back on to its tail. As the tail settled on to the ground, the lower end of the vertical stabiliser was damaged, and the tail rotor was destroyed. The main rotors did not strike the ground, but the rope snagged on the heel of the right skid broke the skid off aft of the rear cross tube.

A Major defect Report had been submitted in April 1995 after it was discovered that the nosewheel fork was cracked near the bolt hole, and the nosewheel fork was replaced. The replacement fork was actually a Cessna 150 part, the difference being the size of the axle bolt. The Cessna 150 fork which was fitted had an AN-4 bolt, whereas the correct fork had a larger AN-5 bolt. The pilots reported that after a normal landing the nose gear collapsed. The failure of the bolt at the head appears to be due to fatigue as a result of excessive working loads on the smaller diameter bolt.

A visiting pilot was being trained on the motorised glider over a number of days. During this flight the pilot and his instructor intended conducting several circuits. On the climb out after the second touch and go, the engine stopped at 250 to 300 ft above ground level. The instructor took over and elected to land on a cross runway that was situated behind the aircraft, as the terrain off the end of the strip in use was not suitable for a landing. This decision required that he conduct a 180 degree turn to the left, followed by an 80 degree turn to the right, to align with the runway. The second turn was conducted at a low height, and required all the pilot's concentration. He then realised that the aircraft was lined up on the paddock next to the aerodrome. During the landing roll the aircraft struck a ditch and the landing gear was torn off.

The pilot reported that the engine stopped because the aircraft had run out of fuel. He had logged the fuel state but did not check the log prior to this flight. He had forgotten about flying conducted about two days earlier, during which the engine was used extensively. The clear plastic tube fuel gauge was reported to be inaccurate as it often became blocked at the bottom of the tank.

A portable emergency locator transmitter was carried behind the seats but it was not turned on.

FACTUAL INFORMATION

Two BA146s were inbound to Brisbane from the north. Both aircraft were being processed for landing on runway 01. There were thunderstorms in the area north of Brisbane and the crew of the leading BA146 requested approval to divert east and west of the aircraft's cleared track to avoid weather. These diversions were approved by the sector controller, who advised the crew to divert a specific number of miles left or right of track.

A new air route structure had been implemented the previous week and this had introduced significant changes to the handling of traffic. Controllers were consolidating their understanding of the routes and the processing of traffic. The sector controller was suitably rated and traffic numbers were low. Traffic complexity had increased as a result of the route changes and the weather. In previous years, prior to the start of the summer storm activity, the Airservices' Northern District office had issued a temporary local instruction reminding controllers of the impact of aircraft diversions on safety and co-ordination. The local instruction had not been issued for the current season.

The diversions caused the lead BA146 to eventually be displaced approximately 9 NM east of, and parallel to, the second BA146. To maintain separation between the two BA146s, the Flow controller co-ordinated with the sector controller for the eastern BA146 to track via Maleny for an approach to runway 14. The amended track and runway was issued to the crew of that aircraft. The crew advised the controller that further diversions would be required.

The crews of both BA146s were assigned descent and were being separated using radar. The crew of the eastern BA146 transmitted to the sector controller that they were diverting 10 NM right of track due to weather. The sector controller acknowledged the transmission with "Roger". This was approved terminology but the Manual of Air Traffic Services stated that it should not be used in reply to a question requiring a direct answer in the affirmative or negative. The crew of an aircraft requiring diversion from a cleared route, in controlled airspace, are to obtain air traffic control approval prior to changing track. The crew of the BA146 did not request approval for the diversion. The sector controller did not reply to the crew that the change in the aircraft's tracking was approved or disapproved.

The crew of the BA146 assumed the diversion was approved. They tracked the aircraft to the west towards the other BA146. The sector controller became concerned at the diminishing horizontal separation, between the two aircraft, and instructed the western BA146 to turn right onto a heading of 180 degrees due to traffic to the east. The controller instructed the crew of the diverting BA146 to turn right onto a heading of 270 degrees to enable the aircraft to pass behind the other BA146. The controller issued instructions to the crews of both aircraft in an attempt to establish vertical separation of 1,000 ft before horizontal separation reduced to less than the required standard of 5 NM. The sector controller did not issue traffic information to the crews of either aircraft when the horizontal and vertical separation standards were infringed. The Manual of Air Traffic Services states that when a separation standard does not exist, a controller shall issue traffic information to the aircraft concerned when, in his opinion, their proximity warrants it.

Analysis of the radar data showed that the horizontal separation had reduced to 4 NM when the vertical separation was 700 ft. There was a breakdown of separation.

ANALYSIS

Previous approvals by the sector controller for the crew to divert around weather were quite specific. On the last occasion the sector controller acknowledged the transmission but did not provide a positive instruction to the crew. The terminology used by the controller was ambiguous. The crew of the diverting BA146 assumed that the acknowledgement by the sector controller was an approval to divert off track. The crew were distracted by the need to avoid the weather and did not query the controller before diverting off track.

The sector controller did not use suitable separation assurance techniques to ensure that separation was maintained between the aircraft. The use of these techniques was essential for aircraft that were diverting around weather, due to the potential for random tracking and an increase in cockpit workload.

The non-issue of the local instruction may have removed a prompt to the sector controller of the need to apply separation assurance techniques.

The controller was aware that the separation between the two BA146s was reducing and endeavoured to rectify the situation. The provision of traffic information may have enabled one of the crews to sight the other BA146 and to assist in maintaining separation.

SIGNIFICANT FACTORS

1. The Northern district office did not issue the temporary local instruction regarding traffic management aspects during inclement weather.

2. The sector controller did not use appropriate separation assurance techniques.

3. The crew of the BA146 assumed that their intended diversion off track was approved.

4. The sector controller did not issue traffic information to either crew when the vertical and horizontal separation reduced to below the standard.

SAFETY ACTION

Local safety action Airservices Australia Northern District Office management has noted that controllers need to be aware of the impact of diversions and will re-issue the temporary local instruction each October.

Arriving at the destination the landing gear failed to extend when the pilot selected it down.

His attempts to extend it using the manual hand pump were unsuccessful as he was unable to build up enough hydraulic pressure in the system to operate the gear. Hydraulic fluid was then noticed seeping from behind the centre console which he identified as a serious leak from the power pack He was able to replenished the lost hydraulic fluid with spare engine oil carried onboard the aircraft, but this failed to rectify the loss of hydraulic pressure.

After calculating the aircraft's endurance, the pilot decided to return to Darwin where he carried out a wheels up landing.

An inspection revealed that one of the "O" ring seals located at the joint between the landing gear manifold and the power pack was split, causing a hydraulic fluid leak, and loss of hydraulic pressure.

The manifold had been removed the previous day to change the servo-valve, and it is possible the "O" ring was damaged during reinstallation. Several successful gear retraction tests had been carried out after completion of the work, followed by about 9 gear cycles in flight before the leak developed.

The crew of the B737 were cleared to track via PEPPA for a SPUDO 1 arrival for runway 24 at Perth. At PEPPA the aircraft was observed to turn onto a south-westerly heading instead of continuing towards the west. This turn placed the aircraft in potential conflict with outbound traffic and radar instructions were issued to maintain adequate separation. The crew of the B737 later indicated that they had started to fly a PEPPA 1 (218 degrees) arrival instead of the SPUDO 1 (263 degrees) arrival.

Evidence indicates that the B737 crew misunderstood the clearance. As part of the aviation safety net there is a requirement for crews to repeat a clearance back to the controller to confirm they have received it correctly. The crews read-back on this occasion, indicated they would complete a PEPPA 1 arrival rather than a SPUDO 1. This error was not picked up by the controller. The clearance had been given in an abbreviated form, and it is possible this contributed to the crews misunderstanding, particularly, as the arrival procedure had only recently been introduced (5 December 1996) and was not yet easily recognised by flight crews.

Post-accident engine testing indicated the engine should have been capable of normal operation. Inspection disclosed that the internal wall of the air intake duct, located between the filter and the engine, had collapsed restricting airflow to the engine. The restriction in airflow probably led to the reduction in power reported by the pilot. The ducting consisted of an inner and outer cloth-wall sandwich supported by a wire spiral located between the walls. The duct was also bound with string on the outside. The walls were bonded together on either side of the wire. Some of the bonding between the inner and outer walls had delaminated allowing the inner wall to collapse. The ducting did not have the airframe manufacturer’s part number and was a different type to that approved by the aircraft manufacturer.

The ducting fitted was Aeroduct SCEET 16, a duct that is often used in aircraft systems such as air conditioning, but not for negative pressure applications. The manufacturer approved ducting consists of Aeroduct SCAT 16, a heavy-duty ducting suitable for engine intake applications.

The aircraft had been engaged in low level survey work in very hot conditions. It is probable this led to a deterioration in the bond between the duct walls. On the day of the accident the partially clogged air filter probably increased the negative pressure in the intake duct sufficiently to cause the delaminating inner cloth liner to partially detach and block off the intake airflow. The weakened inner duct wall probably detached before the negative duct pressure reached a level sufficient to open the alternate air door. From that point on the emergency landing was inevitable. If the correct SCAT 16 ducting had been fitted it should have prevented the occurrence. The fitment of incorrect ducting was brought to the attention of the maintenance organisation that carried out the work and the regulatory authority.

Over a period of four days the aircraft operated twenty sectors with a high pitch squeal emanating from the L2 door. The squeal reportedly occurred at the top of climb and during cruise and stopped when power was reduced and descent commenced. On some sectors the squeal was not reported. On other sectors it was controlled by lowering the cabin differential pressure. At times the squeal was so loud that earmuffs were worn by the cabin crew, and passengers were seated away from the area. The investigation was unable to determine who issued the verbal instruction which resulted in the earmuffs being issued.

After many attempts at rectification the aircraft was removed from service and ferried to Melbourne. During the flight a licensed aircraft maintenance engineer was able to remove some trim and closely inspect the door. He found that above certain pressure differentials and airspeeds the lower door seal was able to flutter. The door was examined and found to be rigged to the upper limit allowed by the maintenance manual. The door assembly was rerigged to the lower limit. During a subsequent verification flight, the seal was found to be secure. The adjustment required was small, the door being lowered less than four mm.

The investigation disclosed that many factors had inhibited the early detection and rectification of the problem.

These included:

• an inadequate system of recording cabin defects,
• flight crews did not always record that the defect existed,
• flight attendants gave incomplete reports to flight crews, - a lack of timely advice to maintenance management, and
• the difficulty in visually identifying the seal flutter.

The investigation also found there had been inadequate communication links between:

• flight attendants and the company's cabin safety management,
• the flight attendants union and the company cabin safety management,
• cabin safety management and maintenance, and
• flying operations, cabin safety management and maintenance.

While it is undesirable to have a defect existing for so many sectors, this particular defect was difficult to detect in normal service and was not found until after the door trim was removed and the seal closely inspected in flight. The major safety concern was that on some sectors the cabin crew wore earmuffs which could have prevented them from immediately responding to some other problem, should one have occurred.

Safety actions taken

The operator is introducing a system of recording cabin defects that will stand alone from the technical report used by flight crews. This will require appropriate certification to transfer technical items into the maintenance log and will also enable cabin crews to have access to a running history of cabin reports.

The operator has also instituted an enhanced communications structure that will allow pilot reports to be rapidly conveyed to maintenance management, ensuring direct contact between operations, maintenance and cabin safety management. The operator's cabin safety management has advised cabin crews to make immediate telephone contact with them in the event of similar problems occurring.

The BAe146 was inbound to Kununurra from Curtin and the crew had been listening on both the area and the MBZ frequencies. They heard the pilot of the C207 make contact with Perth and discuss SARTIME arrangements and give his destination as Broome. This information indicated the C207 might be conflicting traffic for their arrival. They assumed the C207 was still on the ground at that time. As nothing further was heard from the pilot of the C207, the crew of the BAe146 made several attempts to contact him. When contact was established the C207 was 12 NM from Kununurra on the 242-degree radial at 5,500 ft. The BAe146 was 14 NM from Kununurra on the 250-degree radial at 3,800 ft, on descent.

The pilot of the C207 reported that his aircraft was fitted with one VHF set. After making his departure report on the MBZ frequency he changed to the area frequency and became engaged in a discussion with Perth flight service about his SARTIME. The discussion took longer than expected and during that time he could not hear any transmissions from the BAe146 on the MBZ frequency. When he changed back to the MBZ frequency he heard the transmission from the BAe146, and he answered immediately. He had tracked south of the Kununurra - Broome track to remain clear of cloud. He does not believe he came close to the BAe146.

It is likely that the discussion between the pilot of the C207 and Perth flight service, which the crew of the BAe146 assumed had taken place whilst the C207 was still on the ground, was the one that occurred after the C207 had departed. Consequently, the BAe146 crew did not hear the taxi and departure transmissions that preceded that discussion. The fitment of only one VHF set prevented the pilot of the C207 from adequately monitoring the MBZ frequency and, as a result, separation between the two aircraft could not be arranged in a timely fashion.