A Beech 99 aircraft had been cleared to descend to 2,000 feet on approach to Coffs Harbour. As the aircraft was approaching 2,300 feet the pilot heard a radio transmission from VH-ILE which placed that aircraft in the vicinity of his aircraft at an altitude of 2,000 feet. The pilot of the Beech 99 arrested the descent of his aircraft at 2300 feet until he was well clear of VH-ILE.

The pilot of VH-ILE had apparently requested an airways clearance, but this transmission was not received by Coffs Tower and no clearance was issued to the aircraft. The pilot believes he must have mis interrupted transmissions to other aircraft as a clearance from Coffs Tower for his aircraft.

The aircraft departed Oodnadatta with 6 persons onboard. About 15 minutes into the flight, as it reached top of climb at 7000 feet, the fuel pressure to the right hand engine decreased and the engine backfired. The pilot turned the fuel boost pump on, but the engine failed to respond. The propeller was feathered. The aircraft was unable to maintain altitude and the pilot decided to return to Oodnadatta and advised Flight Service of his intentions.

The landing at Oodnadatta had to be made on runway 13 as the other runway was closed due to soft, wet surface. Runway 13 had a crosswind component of about 15 knots at the time and the pilot experienced some difficulty in aligning the aircraft with the runway on final approach. Suffering from some apprehension, and concentrating on the approach and landing, the pilot neglected to extend the landing gear.

The pilot was conducting his first take off on the strip. The fully loaded aircraft did not accelerate to flying speed by the end of the strip. The pilot had looked out of the cockpit to identify another company aircraft operating in the same area whilst his aircraft was accelerating down the strip. When he eventually found the other aircraft and returned his attention to the aircraft performance, the pilot determined that the aircraft would not clear the obstacles at the end of the paddock, so he commenced a load dump. He attempted to fly the aircraft over the obstacles, but it hit the tops of several low trees and a fence before colliding with a more substantial tree which swung the aircraft around and caused the right undercarriage leg to collapse.

The pilot felt that long grass and soft earth combined with the maximum all up weight of the aircraft to reduce its take off performance. He had thought, from his initial inspection, that there was sufficient length available for take off from the point where he commenced his take off roll.

The pilot had been operating from the slightly soft strip for several hours, with a 15 knot crosswind. He was using brake, as well as rudder, to keep the aircraft straight in the crosswind. The pilot had changed direction of take off so that one brake was not overused, but found that if he took off to the West, he encountered unacceptable turbulence, so he resumed easterly take-offs.

At about 50 knots during the accident take off, the left brake failed and the pilot lost directional control. The aircraft ground looped off the runway, causing the landing gear to collapse.

Factual information

VH-TAJ and VH-OJL were tracking via crossing airways T41 and W46 respectively, VH-TAJ maintaining FL350 and VH-OJL initially maintaining FL330. The Sydney air traffic control sector responsible for the airspace in which the aircraft were flying was being operated by a rated officer under familiarisation following a period of absence. This officer was under the supervision of a suitably rated and current training officer. At 1557, the crew of VH-OJL reported passing PARKES with an estimate for ALBEE of 1640 and requested further climb to FL 350. This placed the aircraft in possible conflict with VH-TAJ where the two routes crossed, and the controller initially refused the request until positive separation with VH-TAJ could be assured.

The controller then consulted a lateral separation diagram for the confliction point and decided that VH-TAJ would need to exit the area of conflict before VH-OJL could be given climb. In performing this task the controller misread the reporting point name and the distance specified in the diagram. He instructed VH-TAJ to report 41 NM from reporting point T41B instead of 72 NM from T41A. As a result, the aircraft would still be within the area of conflict with VH-OJL at that point. At 1621 the crew of VH-TAJ reported 41 NM from T41B and the controller, believing that he had established that aircraft clear of the area of conflict, immediately cleared VH-OJL to climb to FL350. As the controllers assessed the current clearances of aircraft under their control, some doubt arose as to the relative positions of VH-TAJ and VH-OJL and distance checks were implemented. At 1622 VH-OJL reported 166 NM west of PARKES, placing the aircraft 21 NM inside the area of conflict and not yet at the crossing point. At 1623 VH-TAJ reported 51 NM from T41B, placing the aircraft 59 NM prior to the exit point, inside the area of conflict and not yet at the crossing point. Calculations placed VH-TAJ at the crossing point at 1624, approximately two minutes ahead of VH-OJL. The point of closest contact was at about 1626 when the aircraft were approximately 10 NM apart. The required standard is 2,000 ft vertically, or one aircraft must clear the area of conflict before the other enters. In this case the area of conflict was 102 NM long on the track of VH-TAJ and 103 NM on the track of VH-OJL. As the vertical separation was less than 2,000 ft and the aircraft were still within the area of conflict, a breakdown in separation occurred.

Neither crew was informed of the situation by air traffic control, no traffic advice was given and no corrective action was implemented by the controllers. VH-TAJ was instructed to report at 72 NM from T41B, a position the controller believed was required to establish that aircraft clear of the area of conflict. In fact this was still within an area of conflict as the controller was still referring to T41B when the position required was in relation to the reporting point T41A. VH-TAJ reported at 72 NM from T41B at 1626 and no further action was taken by air traffic control as they incorrectly believed VH-TAJ to be clear of the area of conflict.

Analysis

Having decided on the Lateral Separation diagram to use, the controller then misread the figures, transposing the 41 in the reporting point name [T41A] to the distance required and the letter A to a B. This placed VH-TAJ at a point prior to the intersection of the routes, not at the area of conflict exit point as required. Even if the controller had correctly read the 72 NM reference, the error in using B in lieu of A would have still placed VH-TAJ in the area of conflict when he gave VH-OJL climb to FL350. After issuing climb instructions the controllers realised that an error may have been made and checked the position of the two aircraft. When this check revealed a confliction and breakdown in separation, no remedial action was taken. Three minutes elapsed before VH-TAJ reported at 72 NM from T41B but there was no advice to either crew of the confliction or the breakdown in separation. Three minutes should have been adequate time for all these actions to have been instigated. The Lateral Separation Diagrams provided at the console were hand drawn and had many numerals, some of which referred to distance, others to reporting points. This could lead to a situation where a controller may become confused under certain workload conditions. It was also apparent that someone had written 135 T41B on the diagram under the official position of 72 T41A. This is the same point in space but measured from the other reporting point and anecdotal evidence suggests that it is used as much as the official entry/exit point. There is no reason why this position cannot be used to calculate the area of conflict, but it is not on the official diagram.

Significant Factor

The controller misread the lateral separation diagram when determining the area of configuration for the two aircraft.

The aircraft was inbound to Cairns and had requested and was subsequently cleared via a DME (Distance Measuring Equipment) Arrival. When the aircraft was about 45km to the south-east of Cairns the approach controller observed, by radar, that the aircraft had descended below the appropriate level on the arrival procedure. The controller advised the aircraft. However, the crew had realised the error and commenced a climb to the correct level. At the time the aircraft was in visual conditions on top of cloud.

The aircraft captain advised that he was instructing another pilot on this flight. The aircraft was slightly off track (although within the tracking tolerances) and the captain had discussed the matter with the Cairns controller and was advising the other pilot on the method of correcting the track error. He did not immediately notice that the aircraft had descended below the appropriate level but corrected the situation when he became aware of the error.

The crew of VH-KDJ taxied the aircraft for departure from runway 18. Calls were made on both the area and Mandatory Traffic Advisory Frequency (MTAF). From this it was ascertained there were two other aircraft operating in the area. Initially both were to use runway 18, but one of these advised he would land on 36 instead. This did not cause any problems for the crew of VH-KDJ, and they were still able to use runway 18.

Engine power was applied for take-off and as the roll started, they transmitted a call that they were rolling. The pilot of the aircraft using runway 36 called them and said there was another aircraft, of which they were not aware, taking off in the opposite direction. The take off in VH-KDJ was rejected at low speed and the two aircraft did not get close.

The conflicting aircraft on runway 36 was a Jabiru which was being flown on circuits. It was subsequently learned that the radio on the Jabiru was defective. A carrier wave could be heard when the pilot tried to transmit a message, but the pilot's voice could not be heard.

Significant Factor

The following factor was considered relevant to the development of the accident:

1. The VHF radio on the Jabiru was unserviceable.

The crew of VH-FNB flew the aircraft into the circuit area intending to land on runway 06. They then sighted another aircraft on final for runway 24. Calls were made to the other aircraft on the area frequency and the Mandatory Traffic Advisory Frequency (MTAF). No reply was received.

The crew of VH-FNB changed their approach to land on runway 24. The other aircraft made a touch and go landing on runway 24 and then made a radio call. A call from the crew of VH-FNB advised that they were on final approach for runway 24. Radio contact was established with VH-MUF, the other aircraft, and the pilot of VH-MUF advised he had previously had the volume on his radio turned down.

Significant Factor

The following factor was considered relevant to the development of the incident:

1. The pilot of VH-MUF was operating with the radio volume turned down.

VH-JJT was on departure from Ayers Rock climbing through 4000 feet and intercepting the outbound track for Alice Springs when the crew spotted a Cessna in their 2 o'clock position about 800 metres distant. The Cessna was at the same altitude and apparently on descent into Ayers Rock. No avoiding action was necessary but prior to the sighting the crew of JJT were not aware of the presence of the Cessna. They also believe the Cessna was unaware of their presence.

At the time of the occurrence there was a tour group of aircraft at Ayers Rock and the MTAF frequency was being used by tour organisers to arrange aircraft parking and for other non operational purposes. This meant that the frequency was extremely busy. There were a number of other aircraft in the area at the time and the crew of JJT reviewed the traffic situation before take-off but they did not have information on the Cessna that they conflicted with.

Either the Cessna did not make an advisory call or the crew of JJT missed any call that may have been made. It is also possible that any call from the Cessna was over-transmitted by another source.

Significant Factors

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

1. The crew of JJT were not aware of the presence of the Cessna.

2. The MTAF frequency was extremely busy.

3. Either the crew of JJT missed any advisory call made by the Cessna pilot or no call was made.

Overhead Kinglake at 5,500 ft on approach into Melbourne the crew received a terrain proximity alarm and applied emergency climb power, climbing to 7,000 ft.

This is one of a large number of spurious warnings occurring to the world fleet of Boeing 747-400 aircraft. In broad terms, the problem is in the logic of the ground proximity warning system (GPWS) which allows a warning to be registered when the landing gear is retracted, and the number 1 radio altimeter registers an altitude of 2,500 ft (i.e. 2,500 ft above terrain).

The aircraft manufacturer has devised a modification to the antenna and the number 1 radio altimeter that has since been incorporated into the operator's fleet and these spurious warnings no longer occur.