The pilot reported that the circuit and landing were normal. After about 200 metres of ground roll the nosewheel began to shimmy and the nose gear collapsed. The aircraft came to a stop on the runway and all occupants evacuated without injury.

The maintenance organisation which recovered the aircraft advised that they have identified and changed an intermittently faulty down lock microswitch. A detailed rigging check was carried out and all dimensions and tolerance were found to be in accordance with the manufacturer's specifications. The maintenance organisation was unable to duplicate the unlock condition during multiple retractions on the ground.

After finishing four hours of commercial sling loading operations, the pilot loaded one passenger to conduct a brief non-commercial operation. He took off and flew past the helipad a couple of times so that photographs could be taken, after which he returned to the same helipad for a landing. The pilot advised that he performed a normal approach to land on the helipad. The helipad was 1300 feet above sea level. At the time the temperature was about 17 degrees Celsius, and the wind was almost calm. From about 15 feet the pilot was unable to fully stop the rate of descent despite the application of full power.

The helicopter landed heavily on the helipad. During the touchdown the tail rotor contacted a rock which was protruding slightly at the edge of the helipad. As the helicopter was quite capable of performing a safe landing in the prevailing conditions, it is probable that the pilot inadvertently approached the helipad too quickly; this is consistent with his inability to arrest the rate of descent. The tail rotor strike occurred as the pilot was pre-occupied trying to avoid an excessively heavy landing.

Significant Factors

The following factors were considered relevant to the development of the accident:

1. It is probable that the pilot approached the helipad too fast to arrest the rate of descent.

2. The tail rotor strike was probably the result of the pilot being pre-occupied with the heavy landing.

The aircraft was engaged in mustering operations and was returning to refuel before continuing the task. At about 30 feet, with about 10 knots forward speed, the engine hesitated once and then stopped. The pilot had insufficient time to enter autorotation or significantly cushion the descent before the aircraft landed heavily.

Aircraft under the control of Brisbane Approach (North) in the period leading up to the occurrence included:

- VH-TNG which was on left downwind at 3000 feet for a runway 01 ILS approach.

- VH-CZL which was about 20 nm final for runway 01 ILS approach.

- VH-JEX, a VFR aircraft out of Brisbane, heading north-west on climb to 4500 feet.

- An Army helicopter transiting Approach (North) airspace south of the aerodrome.

- A number of aircraft inbound from the north-west.

As VH-JEX climbed, it experienced problems maintaining visual flight and required a number of clearance amendments with respect to both heading and altitude. During this process, the Approach (North) controller became aware of another aircraft, VH-CFQ orbiting Archerfield at 1000 feet awaiting clearance into Approach (North) airspace. The controller involved said that he was not sure how long VH-CFQ had been airborne at Archerfield but was aware of feeling under some pressure to issue a clearance.

He cleared VH-CFQ to enter controlled airspace on climb to 3000 feet west of the Mt Coot-tha TV towers and returned his attention to VH-JEX and the inbound traffic from the north. A short time later, he looked to check the progress of VH-CFQ and saw a conflict with VH-TNG developing. He instructed both aircraft to turn left. However, this resulted in VH-TNG conflicting with VH-CZL. The controller then told VH-TNG to turn right for separation with VH-CZL. The 5 nm separation standard was infringed in both instances, the radar recording indicating the minimum distance to have been 3.5 nm each time.

SIGIFICANT FACTORS

1. Controller workload was significantly increased by the clearance amendments necessary for VH-JEX.

2. The controller felt under pressure to clear VH-CFQ from Archerfield into controlled airspace.

3. The clearance given to VH-JEX was inappropriate and led to the losses of separation.

The aircraft departed Kununurra for Perth using rated take off power and 30 flap. Shortly after reducing power via the Thrust Management System to 800 degrees and raising the flap to 18 degrees, a fire warning for No 3 engine was indicated in the cockpit. As the captain commenced to move the power lever towards Flight Idle, the fire warning stopped. The captain analysed the indication and assessed the warning as false.

As the aircraft was too heavy to immediately land at Kununurra, he elected to continue the flight towards Perth, after having ensured that he had suitable landing points available enroute if required. Engineers discovered that a fire detector on the recently fitted engine had come into contact with the engine, and the prolonged, higher power setting on take-off had tripped the detector and triggered the warning.

The inexperienced pilot was on a solo visual flight rules (VFR) navigation exercise from Essendon, tracking via Moorabbin, Kyabram, Calivil, Melton South and returning to Essendon. After passing Kyabram the pilot observed cloud developing to the west and decided to amend his route. Before reaching Bendigo, he turned south and, as there was cloud ahead, the aircraft was climbed to 4,000 ft, on top of cloud. The pilot then established communications with Melbourne Radar Advisory Service (RAS) and requested navigation assistance.

A short time later, RAS advised the pilot that he had just passed Trentham. At about this stage the aircraft was inadvertently flown into cloud. The pilot experienced control difficulties, because of the turbulence in the area, and reported to RAS that he was "descending quite fast", but that he was trying to climb. Another pilot advised the pilot of VH-JAC to "just keep your wings level." Less than a minute later, the pilot of VH-JAC reported he was upside down and going to crash.

The aircraft broke out of cloud, below the cloud and close to the ground, in a steep nose-down attitude. The pilot managed to regain control and avoid trees. Visual flight was then continued, and the aircraft was diverted to Bacchus Marsh where a landing was made.

The helicopter flew through a flock of birds. The pilot felt and saw a number of birds strike the main rotor and also saw bird remains travel rearwards after this main rotor contact. After a short time of further flight with no apparent problems, the pilot heard a "bang" from the rear of the aircraft. He saw that the rear of the aircraft was vibrating so elected to land immediately. During the landing, the tail rotor contacted the ground.

Both aircraft were in communication with Townsville Arrivals and being tracked to the west of Townsville on approximately reciprocal tracks. The northbound aircraft at FL390 (39,000ft) and the southbound aircraft at FL370 (37,000ft). The Arrivals Controller had some six aircraft under his jurisdiction and was moderately busy. When the two aircraft were within a few minutes of passing each other, a co-ordination message was received from the Cairns Arrivals Controller with descent instructions for the northbound aircraft.

The instructions specified a higher than normal descent speed and involved delaying the time of descent. The controller was aware that the crew of the aircraft needed the information as soon as possible to allow the reprogramming of the flight management computer. If there is no conflicting traffic, descent instructions are normally passed to the aircraft together with a clearance to descend. The controller passed the information to the aircraft and also gave a clearance to descend to FL230 despite the lower opposing traffic.

The crews of both aircraft realised that the controller had made a mistake and commented as they passed and saw each other. It was then that the controller realised that he had made an error. The higher aircraft did not descend until six minutes later, at its designated descent point. There was no breakdown in separation. Later, the controller could not explain his mistake, commenting that it was probably force of habit that he passed the clearance at the same time as the descent instructions.

Both aircraft were operating scheduled regular public transport flights on crossing air routes within controlled airspace under the jurisdiction of Sydney control sector 5 (SEC 5). 5W-ILF was maintaining FL330. Although SEC 5 was providing control and separation services, Sydney Flight Information Service, International (FS INT) was responsible for providing communications on high frequency (HF) aeromobile facilities. Subsequently 5W-ILF requested FL370 via FS INT. This request was co-ordinated with, and approved by, SEC 5 for a descent to FL270. 5W-ILF was then instructed to descend to FL270 and report when maintaining.

At approximately 1627 EST, 5W-ILF acknowledged the level change and read back maintain FL370. A short time later, a level check of 5W-ILF was initiated by SEC 5 and the pilot of 5W-ILF reported maintaining FL370. It was then realised that 5W-ILF had climbed to FL370 instead of descending to the amended level of FL270 as cleared. SEC 5 calculated that 5W-ILF may have entered the lateral conflict area of crossing traffic, which was VH-EBR at FL350, at 1631. It has been established that 5W-ILF would have taken approximately four minutes or less to climb from FL330 to FL370 and reached FL370 at approximately 1631.

It was not possible to determine if the prescribed separation standards of at least 2,000 feet in altitude or 10 minutes prior to crossing were actually infringed. The pilot-in-command was performing all communications duties and believed that the clearance instruction, which was mutually confirmed by the co-pilot was 5W-ILF, recleared FL370. However, neither pilot could recall hearing the phraseology to descend used in the clearance provided. The aircrew had an expectation for a control instruction to climb.

This aircrew expectation was further compounded by the absence of any challenge to indicate that an incorrect level had been readback to FIS INT, who, expecting to hear FL270, misheard FL 370. The pilot-in-command of 5W-ILF had also omitted to report vacating FL330 and was not queried by FIS INT. It is probable that aircrew operating through differing Authorities may have become conditioned to expect variations and incorrect applications of standard operating procedures and phraseology used by air traffic service officers.

For example, anecdotal evidence suggests that some Authorities are using phraseology such as recleared for level change instructions in lieu of the correct phraseology for climb and descent manoeuvres. The importance of using correct phraseology which clarifies change of level instructions such as climb, descend (for vertical manoeuvres) compared to change of route instructions which contain the phraseology recleared (for horizontal manoeuvres) is evidenced in this occurrence. Analysis The air traffic system safety defences had been progressively breached.

The first system failure was when the FIS INT operator misheard and co-ordinated an incorrect change of level request. The next system failure was the expectation for the requested level (FL370) and readback of that level by the aircrew. The incorrect readback expectation of FIS INT was the final system failure. The departure from published standard operating procedures and phraseology combined with the absence of a standard phraseology which indicates the vertical manoeuvre being executed renders the system fail unsafe. This is particularly relevant when vacating previously maintained flight levels and exposes the air traffic system to the potential for incorrect level assignment expectations by both aircrew and air traffic service officers.

Significant Factors

1. The FIS INT misheard and co-ordinated an incorrect change of level request.

2. There was an expectation for the change of level request to climb to FL370 by the aircrew to be approved.

3. FIS INT did not detect the incorrect level readback by the aircrew nor the absence of advice that the assigned cruising level had been vacated.

4. There is no standard phraseology specified to verify the vertical manoeuvre associated with a change of level.

SAFETY ACTION 

In relation to this and two other occurrences (BO9102639 near Mount Isa and BO9301823 north of Brisbane), the published procedures and phraseologies did not prevent poor listening technique, by both ATS officers and pilots, leading to a breakdown in separation. In this occurrence a flight service officer and two pilots all misheard the flight level given by the other.

Incorrect phraseologies were used, and no indication of climb or descent was included by either party. This resulted in a safety net being absent and the aircraft climbing when ATC expected it to descend.

In occurrence 9102639, four controllers all either misheard the co-ordinated flight level or did not recognise that an amended level had been given. In this case two training officers did not notice the error.

In occurrence 9301823, the trainee inadvertently gave descent instructions to an aircraft without realising that he had given such descent, even though the pilot correctly read back the assigned level. The training officer did not notice the error.

The pilot was landing with a crosswind from the left of 10-15 kt. As the aircraft touched down, the left wing lifted, causing the right wingtip to contact the ground. The aircraft veered right for a short time before the propeller struck the ground, causing extensive damage to the nose section of the aircraft.