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.

On rotation for take-off the crew heard a noise. As landing gear retraction was normal and the aircraft continued to operate normally the flight was continued. The aircraft had reached about 220km from Darwin when the crew were advised by a company ground engineer that a section of main gear tyre tread had been found on the runway. The Captain briefed the crew for a possible emergency landing and the flight continued to Brisbane where emergency services were put on standby.

A safe landing was made and the aircraft taxied to a parking bay where investigation revealed that the right hand inboard tyre tread had separated, causing damage to the landing gear door clamp. The tyre was a level 6 retread (having been re-treaded 6 times), the occurrence being similar to earlier problems with this make of tyre. The company removed all re-treaded tyres above the level 4 retread status for inspection.

Simultaneous runway operations were in progress at Sydney when VH-MJH was cleared to land on runway 34, with a requirement to hold short of runway 07. After the aircraft had landed the aerodrome controller (ADC) instructed the pilot to take the first available taxiway to the right. This was taxiway 'Hotel', located about 238m from the runway 07 simops lights. VH-RMN, a Boeing 727 which was lined up on runway 07 was then cleared for take-off. VH-MJH was then observed to have passed the taxiway and was told to hold short of runway 07. The aircraft continued rolling and when the ADC became uncertain that the aircraft was going to stop before runway 07, he instructed the aircraft to stop.

The aircraft did not stop, and the ADC then cancelled the take-off clearance for VH-RMN which was now rolling for take-off. Another aircraft was sent around from a 2-mile final approach for runway 07. VH-MJH came to a stop mid-way between the stop lights (holding point) and the edge of runway 07. After VH-RMN had stopped VH-MJH was cleared to cross runway 07 and vacated runway 34 on taxiway Bravo 6. The first officer was the pilot flying VH-MJH until after the aircraft had touched down. The captain then took the controls during the landing roll, and the first officer turned his attention to the after landing checks. The captain stated that he had not heard the transmissions to stop.

It was not until he noticed that the first officer was transmitting that he realised that he was not monitoring the tower frequency. After he had received a landing clearance, he had intended to deselect the company frequency and had inadvertently deselected the tower frequency. The first officer had subsequently acknowledged the transmissions from the tower and was not aware that the captain was not monitoring the tower transmissions. The first officer realised that the captain was not following the towers instructions when the aircraft passed the taxiway and he instructed the captain to stop using both verbal and visual signals. By this time the aircraft was nearing the runway intersection.

The captain misidentified the position of taxiway Hotel due to the position of a large mound of earth which had previously been located south of runway 07, but which was now located north of runway 07. This gave him a false impression as to the location of the taxiway and was not aware that he was approaching the runway until after it was too late to stop before the holding point lights.

Significant factors

1. The captain inadvertently deselected the tower frequency just prior to taking control from the first officer.

2. After handing control of the aircraft to the captain, the first officer diverted his attention to the after landing checks.

3. There was a breakdown in crew co-ordination procedures.

The student was making a practice glide approach to land, with the throttle in the closed position. Sink developed late on the approach with the airspeed reducing, and full power was applied. The aircraft touched down about two metres short of the sealed surface in a soft area. As the aircraft rolled forward the wheels contacted a 'step' at the start of the sealed area. The contact with the 'step' collapsed the main gear legs and the aircraft slid to a stop.

Significant Factors

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

1. The pilot under supervision misjudged the approach.

2. The instructor was late in assessing the situation and did not ensure power was applied in time to correct the sink rate and descent path.

The nose gear collapsed on touchdown. The repair organisation was unable to find any mechanical fault that would have allowed the nose gear to collapse. Later advice was received that during a crosswind landing, the pilot allowed the aircraft to touch down on the nosewheel while the aircraft was yawing to the right.

Qantas 10 was one of four south-east bound aircraft estimating overhead Curtin reporting point at approximately 0000 WST. Lauder Air 2 was north-west bound and estimating Curtin at approximately 0100 WST. Several other aircraft were also due to enter the airspace around Curtin during this period. Lauder Air 2 was maintaining FL350 (35,000 feet). Qantas 10 was maintaining FL310 and had requested FL370. The duty Air Traffic Controller (ATC) cleared Qantas 10 to climb to FL330, at Curtin, with an expectation that a clearance to FL370 would be available later. The complexity of the traffic situation required the duty ATC to co-ordinate traffic with Melbourne Sector and to make a number of calculations associated with the "time of passing" between Qantas 10 and other aircraft.

During this process the ATC, incorrectly, wrote the "time of passing" between Qantas 10 and another aircraft on the Lauder Air 2 flight strip. The correct "time of passing" between Qantas 10 and Lauder Air 2 was 0029 but the duty ATC wrote 0047 on the Lauder Air flight strip. A "time of passing" of 0047 was also entered on Qantas 10's flight strip. Following advice from Melbourne, at 0026, that Qantas 10 would be accepted at FL370 the duty ATC checked the "time of passing" written on the flight strip (0047) to ensure that sufficient time for the climb was available, (ten minutes for the climb and ten minutes for the buffer), and cleared Qantas 10 to climb to FL370. As Qantas 10 commenced climbing the crew observed the lights of Lauder Air 2 directly ahead. Qantas 10 stopped its climb at FL340 and reported the situation to the duty ATC who then instructed Qantas 10 to descend again to FL330. Lauder Air 2 passed directly overhead and 1500 feet above Qantas 10.

The investigation determined that the duty ATC, who was assessed as very experienced and competent, had also made other procedural errors during his time at the console. Evidence was available which indicated that the errors were probably the result of accumulated fatigue brought on by a lack of sleep and disrupted sleep patterns, a lack of adequate rest breaks over both the long and the short term and pressure caused by the additional tasks associated with his position as a Team Leader.

The aircraft was on a test flight following maintenance. The pilot called Cairns Approach for clearance and a clearance instruction was issued. However, no acknowledgement of the clearance was received, and the aircraft did not appear on radar when expected. When further attempts to contact the aircraft failed, search and rescue action was initiated. Approximately 40 minutes after radio contact with the aircraft was lost, the pilot telephoned Cairns Tower advising that the aircraft had suffered a communications system failure (including the transponder) and that he had landed at Cairns after following the loss of radio procedures.

Investigation revealed that there had been a failure of the Cairns Approach primary radar around the time communications with the aircraft were lost. Cairns Approach was not aware of the failure and saw neither a primary, nor a secondary return from the aircraft on the radar displays. The Cairns Tower controllers were conducting a visual search in the expected approach sector of the aircraft and did not see it land. Primary returns are represented by a small cross which appears in the centre of the circular symbol representing the aircraft. The disappearance of this cross was the only indication to the controllers that the primary radar had failed.

The size of the cross is such that its disappearance might not be noticed unless close attention was being given to that particular part of the radar display.

Then factors considered relevant to the development of this occurrence were:

1. The aircraft suffered a communications system failure which included the transponder.

2. There was a failure of the Cairns Approach primary radar of which the controllers were not immediately aware.

Safety Action

A SADN was submitted shortly after the incident concerning the primary radar failure and recommending the fitting of an alarm system to alert controllers of a primary radar failure.