FACTUAL INFORMATION

A Beech 1900 (B1900), callsign SMH, had departed Sydney on a flight to Port Macquarie, NSW. The crew were maintaining the aircraft at flight level (FL) 210 in controlled airspace. The airspace was controlled by Brisbane Sector 15C.

A Swearingen SW4 (Metro) had departed Port Macquarie on a flight to Williamtown, NSW. The crew were maintaining the aircraft at FL140. The base of controlled airspace was 12,500 ft.

At 1433 EST, the crew of the B1900 commenced descent into Port Macquarie but were restricted to FL150 by sector control due to the opposite direction conflict with the Metro.

A second B1900, callsign IMH, was also on the control frequency and had commenced descent into Williamtown. This aircraft was well south of the conflicting aircraft and there were no restrictions for its descent.

At 1436, the sector controller instructed the crew of IMH to contact Sydney flight service (FIS5) on frequency 121.6 Mhz. The reply was broken but included the words "? Mike Hotel". Almost immediately the crew of IMH asked the controller to confirm that the previous transmission was for them. This was confirmed by the controller and the crew transferred to FIS5 as instructed.

The controller then noticed on radar that SMH had descended below its assigned level and attempted to contact the crew to instruct them to return their aircraft to FL150 for separation with the Metro. There was no answer.

The crew of SMH had acknowledged the frequency transfer instruction issued to IMH and had contacted FIS5. The flight service officer had received the correct coordination on SMH and had informed the crew that there was no instrument flight rules traffic conflicting with their intended flight path in his area of responsibility. FIS 5 provided a traffic information service for aircraft travelling outside controlled airspace; that is, at and below 12,500 ft.

The crew of SMH decided that, as control had transferred them to FIS5, the controller was approving their descent from controlled airspace. Consequently, they elected to continue descent from FL150. However, they had not received a specific clearance to descend below FL150.

As soon as the controller realised that the crew of SMH was not on the control frequency, he coordinated with the flight service officer to broadcast on 121.6 Mhz an instruction to the crew to maintain FL150. On receiving this instruction, the crew maintained FL140 because that was the level they were passing at the time. They reported to FIS5 that they were maintaining FL140 and this information reached the controller at approximately 1438, by which time the two aircraft had passed each other. The controller then issued a clearance for the crew of SMH to leave controlled airspace on descent.

Neither crew saw the other aircraft and radar analysis indicates that they passed at 1437 with approximately 2.6 NM horizontal separation and 200 ft vertical separation. The appropriate standard was 5 NM or 1,000 ft.

There was a breakdown of separation standards.

ANALYSIS

The crew of SMH were expecting further descent as they approached FL150 and, hearing such an instruction issued to IMH, misheard the callsign and acted as if the instruction was issued to them. The controller only heard the last two letters of the response and, therefore, did not instantly recognise that the wrong crew had responded. As soon as the crew of IMH questioned the callsign for whom the instruction was intended, the controller commenced action to contact the crew of SMH to re-introduce positive separation that he had observed to have been contravened.

Because they believed that they had been transferred from control frequency, the crew of SMH incorrectly assumed that sector control had no further restrictions for them and descended. They did not receive, nor did they seek, a clearance to descend from FL150.

SIGNIFICANT FACTORS

1. The crew of SMH misheard the callsign "IMH" when an instruction for descent was issued to the crew of IMH.

2. The crew of SMH descended below their assigned level.

Circumstances

The crew advised that the number one engine experienced an uncommanded excelleration to about 84% NI, as the thrust levers were advanced on final approach to land. The engine was shut down in accordance with the requirements of the non-normal check list. The approach was continued for a normal landing. Post flight examination traced the problem to a fault in the fuel flow regulator. The regulator was replaced and after carrying out the appropriate ground runs, the aircraft returned to service without further incident.

The pilot reported that, on a ferry flight back to Hyden from Northam, following a .37 periodic maintenance inspection, he encountered fog ahead along track. As a precautionary measure, the pilot decided to land in a paddock to wait for the fog to clear. He made several passes over the paddock to ensure it was suitable before attempting to land. As the aircraft touched down, the right main wheel struck a rock, hidden in grass, causing the right oleo to collapse from overload.

The pilot of VH-SKN reported that, while cruising FL170 some 52NM from Boulia, a VFR aircraft (VH-FDM) reported 49NM from Boulia, on the same track, leaving FL175 on descent. SKN had been advised of several IFR aircraft by Flight Service but had not received any broadcasts from VFR traffic until the descent call from FDM. The pilot of SKN considered that the three mile separation which existed between his aircraft and FDM compromised safety.

FDM departed Mt Isa 5-10 minutes before SKN and thus should have been aware that SKN was tracking for Boulia. Both aircraft were King-Air variants, but had a significant performance margin over FDM and it was this which contributed to SKN catching up to FDM during the flight.

An aircraft was approaching to land through a straight-in approach in accordance with the published procedures and criteria. At about 2 NM on final approach, another aircraft reported on base. Although an attempt to contact the aircraft on base by radio was made, it continued and joined final about 500 m in front of the aircraft conducting the straight-in approach. The pilot flying the straight-in approach conducted a go-around and landed off a normal circuit.

The student pilot was conducting circuit training on runway 32. He elected to make the circuit his last for the day due to deteriorating weather. The wind direction was swinging in strong gusts, mainly from the west. The pilot conducted a normal crosswind landing.

However, he later reported that when the aircraft's speed was down to about 30 knots, he relaxed too soon and did not maintain enough aileron pressure to keep the upwind wing down. A strong wind gust then swung around the aircraft around to the left. The pilot was unable to correct the movement quickly enough, and the right-wing tip touched the ground. The aircraft then nosed over onto its back.

Summary: The pilot had submitted a flight plan for the IFR flight at 7,000 ft. The aircraft was limited to 6,000 ft on departure, and this altitude, along with the departure time and the transponder code were mentioned in the co-ordination between the tower and sector controllers. The details read back by the sector controller included 7,000 ft as the altitude. This error was not detected by the tower controller. The pilot subsequently reported maintaining 6,000 ft when contacting the sector controller.

At no time was the altitude prefixed by "amended" or any such phrase to draw attention to the different altitude. Airservices Australia advice was that there is no requirement for the use of the term "amended" when the cleared level is different from the planned level. This incident is the subject of safety deficiency action to investigate the need for the use of the term "amended".

The pilot reported that selection of the landing gear up was followed by a loud noise, which appeared to be associated with the landing gear system. The landing gear in-transit light remained illuminated. The pilot remained in the circuit area and selected the landing gear down. This produced green lights for both main gears but no light for the nose gear. The in-transit light remained illuminated. The pilot then attempted to extend the landing gear manually. However, the manual extension lever was jammed and could not be moved.

Observers on the ground advised the pilot that the nose gear was swinging backwards and forwards as the aircraft flew overhead. The pilot then attempted to force the nose gear into position by manoeuvring the aircraft. However, the landing gear indication remained unchanged. The pilot subsequently selected the landing gear up and landed the aircraft with the main gear retracted and the nose gear hanging.

Examination of the landing gear revealed that the gearbox end of the rear retract rod end for the nose landing had failed. The failure was caused by fatigue crack growth. There was clear evidence of galling between the spherical ball and the outer race. (Galling is adhesive wear between two contacting surfaces and involves localised welding and transfer of materials from one surface to the other.) Under such conditions, then the ball would have been prevented from moving freely during landing gear operation, subjecting the fitting to abnormal operating loads. Advice from the manufacturer indicated that the rod could have been in the aircraft since its manufacture in 1972.

The pilot reported that at 25 DME inbound to Tennant Creek, the appropriate inbound call was made on the CTAF frequency. No traffic responded to this call, nor were any other calls heard until, approaching 5,000 feet, there was an excited call from an unidentified aircraft to "aircraft inbound to Tennant Creek". VH-ANY levelled at 4,500 feet and called the other aircraft. The pilot of VH-NLB responded, saying that he had left 5,000 feet on climb. VH-ANY then continued descent to Tennant Creek.

The pilot of VH-NLB later said that he had made taxy, airborne and departure calls on departing Tennant Creek. He estimated the minimum separation with VH-ANY to have been about 1NM. The crew of VH-ANY did not see the other aircraft.

Shortly after departure from runway 23 at Adelaide for a training flight, the pilot advised ATS that one engine was shutdown. The aircraft returned for an uneventful landing. Post flight examination found that the left propeller had suffered an in-flight separation of a counterweight and retaining bolts. Debris from the separating counterweight punctured the aircraft fuselage. A bolt head and spacer were retrieved from the nose baggage compartment area.

Metalurgical examination of the components was unable to determine the sequence of failure of the counterweights. Due to the inflight loss of failed parts, it is not possible to complete the investigation into the failure.