VH-COH was inbound to Townsville in instrument meteorological conditions. The tower instructed the pilot that if he was not visual by 6 miles from the airfield he should continue via the final segment of a Sector "D" DME Arrival Procedure and cleared the aircraft to descend to the minimum allowable altitude. The pilot acknowledged the instruction.

At the minima the pilot reported that he was not visual and was instructed to carry out a standard missed approach and climb to 3500 ft. The aircraft was observed to commence a left turn as per the missed approach procedure and the tower then cleared another aircraft, VH-TAV, for take-off.

Just after the VH-TAV became airborne, the tower controller queried the pilot of VH-COV about the altitude and heading of the aircraft. The pilot responded that the aircraft had climbed through 2400 ft and was heading 170 degrees. He was instructed to expediate the turn onto the assigned heading of 290 degrees. VH-TAV was instructed to maintain 1900 ft, to maintain a minimum of 500 ft vertical separation between the aircraft. Within 30 seconds the situation was resolved and the VH-TAV was recleared to its planned altitude.

The minimum separation between the two aircraft was not positively determined but it was probably 2 miles horizontally and in excess of 1000 ft vertically.

The pilot of VH-COV did not have the Townsville DME Arrival Chart open in front of him during the final stages of the approach as he was not expecting to be instructed to carry out that type of approach, and he believed he would become visual before reaching the airfield. However, he acknowledged the missed approach instruction and did not request guidance. During the missed approach some of the passengers reported to the pilot that they could see the airfield and it is possible that the pilot allowed his attention to be diverted and incorrectly turned the aircraft to the right.

VH-RMX was making touch-and-go landings at Avalon and was on the crosswind leg for runway 18 at an altitude of 1400 ft when the pilot reported a helicopter passing beneath him tracking in the opposite direction. Melbourne radar confirmed an aircraft squawking code 2100 half a mile inside the Avalon control zone tracking towards Geelong at 1100 ft.

The helicopter did not respond to calls and faded from radar 90 km southwest of Avalon.

The student pilot with approximately 50 hours experience was undertaking conversion onto a single-seat, higher performance glider.

About one week before the accident flight, the club flying instructor flew with the pilot in a two-seater training aircraft.  During the take-off, the launch cable broke, and the pilot executed a recovery using the correct technique. The flight continued without incident and the flying instructor assessed that the pilot was fully qualified for the conversion onto the higher performance glider.

The accident flight was his second on the type, the first lasting 26 minutes.

The glider was winch launched and was observed climbing in a steep attitude from the start of the climb.  At approximately 100 ft, the glider initially began a turn to the right but then commenced turning to the left.  The nose dropped and the glider was observed to enter a spin before impacting the ground at a steep angle.  Witnesses, experienced glider pilots, observed that immediately before descent the aircraft appeared to be losing speed.

Examination of the wreckage found no deficiencies with the glider, its structure or systems.  Witnesses examining the wreckage on site found the elevator trimmed so as to give the glider maximum nose-up pitch.

Examination of the elevator trim mechanism failed to find any deficiency with the system which would have accounted for the nose-up trim setting. Additionally, analysis of the effect of the impact on the trim mechanism indicated that the impact would have had a tendency to move it into a nose-down trim setting.  The reason for the nose-up elevator trim setting could not be determined.

Findings

1. The pilot lost control of the glider.
2. The glider entered a spin and impacted the ground.
3. There was no indication of any fault in the winch launch of the glider.
4. No pre-existing glider defect contributing to the accident was identified.
5. The elevator trim was found in the full nose-up position.

The aircraft was engaged in a crop spraying operation, and during a procedure turn to the right, with a light downwind component, the pilot allowed the aircraft's airspeed to deteriorate, resulting in a stall.

He was able to partially recover the aircraft close to ground level, but the landing gear wheels became entangled in the crop, causing the aircraft to descend further and contact the top of a drain bank.

Using full power, the pilot attempted to fly away, but the aircraft was unable to clear a line of trees at the perimeter of the paddock which it flew into and came to rest inverted on the ground below.

Circumstances

The pilot had arranged to visit the property of a friend in the Kingaroy area. He planned to arrive at the property at about 0900. At 0930, the pilot rang his friend and advised that he would not arrive until 1200-1230. The delay was the result of maintenance needed on the aircraft which required the pilot to fly the aircraft to Caloundra and return to Redcliffe before departing for Kingaroy.

The pilot and his passenger arrived at the property at about 1230 where they lunched and spent the afternoon. When it came time to leave, the property owner decided to accompany his friend in his own Lightwing aircraft for part of the return journey. They boarded their respective aircraft and the Lightwing became airborne and waited in the area for about 10 minutes for the Skyfox to become airborne. The pilots eventually gained radio contact with each other but the pilot of the Skyfox gave no reason for his delayed departure.

Both aircraft set course for Nanango and the Skyfox, which had been above and behind the Lightwing, overtook the other aircraft and they continued at about 2,000 ft above ground level (AGL). The pilot of the Skyfox then

descended his aircraft, followed by the Lightwing, to overfly an old airstrip at an altitude of between 10 ft and 20 ft AGL, before climbing to a reported 2,000 ft AGL. The Skyfox pilot then advised his friend that he was going to overfly another airstrip and descended. The Lightwing remained at altitude. During the descent the pilot of the Lightwing reported seeing a short then continuous stream of whitish smoke from the rear of the aircraft. He attempted to contact the Skyfox pilot by radio but received no response.

The aircraft was observed by a ground witness to complete two to three orbits of a property homestead before commencing a flypast over the homestead in a southerly direction. The witness stated that he did not observe any smoke from the aircraft. He then reported hearing the sound of the two powerline wires coming together and then observing the aircraft with the wings level but in a shallow descent continue in a southerly direction and impact a tree.  The aircraft immediately caught fire and fell to the ground.  The wreckage was completely burnt out.

Site details

The powerline struck by the aircraft was strung between two poles on the top of ridgelines either side of the homestead. The span between the two poles was 560 m and the wires were estimated to have been in excess of 32 m above the ground at the point of impact. The poles were located in trees of a similar height and would have been difficult to see from the aircraft. The distance from the powerline to the tree struck by the aircraft was approximately 160 m.

Aircraft examination

The aircraft was extensively damaged by the post-impact fire. At the point of contact with the wires, the tip of one propeller blade and a piece of window Perspex had been torn from the aircraft. However, the aircraft appeared to have arrived at the impact point substantially intact. No defects were observed with the airframe that could have contributed to the occurrence.

The engine was removed from the aircraft for specialist examination. The examination did not reveal any defects that could have contributed to the accident. The examination of engine accessories was hampered by the intensity of the fire.

Smoke

The opinion of those experienced in the operation and maintenance of similar aircraft indicates that the most likely source of whitish smoke was a leak of engine coolant. The coolant is used to cool the heads of the four cylinders of the engine and a loss of coolant would result in an increase in cylinder head temperature but would not necessitate an immediate landing. The inspection of the engine did not indicate any signs of a loss of coolant, but the fire damage precluded any determination of the serviceability of the coolant system.

Pilot aspects

The pilot had visited the adjoining property, which is located to the east of the accident site, on the day prior to the accident. Both properties were owned by relatives of the passenger in the aircraft. While visiting the property he had discussed with the owner the upgrading of an airstrip, which was currently used in the operation of model aircraft, to a standard suitable for the operation of the Skyfox. Included in the discussion was a briefing by the property owner to the pilot of the wires surrounding the model airstrip. The briefing did not include the existence of the wires struck by the aircraft on the following day. The property owner was expecting the pilot to overfly his property on the morning of the accident. However, the owner of the property on which the accident occurred was unaware who the occupants of the aircraft were until some hours after the accident.

There was no airstrip in the area in which the aircraft was operating prior to its impact with the wires. The wires crossed a ploughed paddock which was unsuitable for the operation of an aircraft.

Analysis

It could not be positively determined if there was any fault with the aircraft prior to it striking the wires.  Likewise, the purpose of the orbits of the homestead near the accident site is unknown.  It is also unknown if the pilot had been previously aware of the existence of the wires struck by the aircraft but forgot about them on this occasion. Regardless, it appears that the pilot did not see the wires in time to avoid the collision.

Significant factors

1. It could not be determined if the pilot was previously aware of the   existence of the powerline struck by the aircraft.
2. The pilot did not see the powerline in sufficient time to avoid the collision.
3. The serviceability state of the aircraft prior to the accident could not be positively determined.

The pilot reported that during two attempts to land on Runway 08 he experienced handling difficulties with the aircraft. He eventually landed on Runway 05. An inspection subsequently revealed the propeller had suffered a ground strike and the left main landing gear door was open.

A gusting crosswind of 15 to 25 knots was reported at the time of the occurrence.

Investigation determined that the locking balls were missing from the left main gear door actuator which would allow the door to open if hydraulic pressure was lost. An intermittent open circuit was also detected in the gear extend circuit. This defect caused the hydraulic pump to stop intermittently and may have resulted in the left door opening in flight.

Had the left main gear door opened during the landing sequence it may have contributed to the handling difficulties experienced by the pilot in the gusting crosswind conditions.

The pilot had planned to ferry the aircraft to Rockhampton in accordance with the Visual Flight Rules. He had also arranged to return to Sydney the same day by airline, so as to be able to spend Christmas at home. In order to connect with the return flight, the ferry flight needed to depart before dawn. A weather forecast obtained by the pilot the night before the flight indicated conditions would be unsuitable for visual flight to Coffs Harbour.

The pilot said that when he arrived at Bankstown Airport early the next morning, he assessed the weather as being slightly better than forecast. Consequently, he departed at about 0350, without lodging flight details, and proceeded to fly north up the lane of entry. Passing Patonga the weather started to deteriorate. Light drizzle associated with a decreasing cloud base caused him to consider whether to continue or return. He then noticed that the directional gyro began to malfunction and would not stay aligned with the magnetic compass. Whilst trying to rectify that problem he also noticed that the ADF indications appeared to be unreliable. With his attention diverted by the instrument problems, the pilot lost visual contact with the coastline and decided to return to Bankstown using the magnetic compass as a heading reference. Whilst in a timed turn to the left the aircraft collided with trees and was destroyed.

After regaining consciousness, the pilot managed to extricate himself from the wreckage and walk three kilometres to a farmhouse, over hilly, heavily timbered terrain.

The helicopter was being used for a controlled firebombing and burning off operation. The pilot had been flying very slowly just above the treetops, then after turning onto a southerly heading he believed the engine lost power and was unable to prevent it from striking the tops of the trees. It then descended steeply into the ground, the pilot receiving severe back injuries, and the passenger a broken arm.

An investigation of the helicopter and engine failed to find any fault, or malfunction, that may have caused the engine to lose power.

Weather conditions were very hot with a light northerly wind blowing.

The helicopters weight was calculated to be in excess of its maximum all up weight, with heavy items of equipment stored in the areas below the seats, contrary to the flight manual and placarded instructions.

Being overweight for the operation, and turning downwind, i.e. to the south, the helicopter probably suffered a loss of translational lift with subsequent overpitching of the rotor system by the pilot, giving the impression that the engine had lost power. With no available height margin the pilot was unable to avoid flying into the trees.

On departure the pilot of VH-DXI requested climb to amended altitude 10,000. Due to another aircraft just ahead at 8000 feet the controller issued a clearance to climb to amended altitude 7000 feet. On climb the pilot's attention was diverted when a passenger spoke to him. The aircraft had climbed to almost 8000 feet when the controller queried the pilot on his altitude. The pilot apologised and descended back to 7000 feet. The longitudinal separation at the time was four miles, instead of the required five miles.

Significant Factor

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

1. The pilot inadvertently climbed the aircraft above the altitude he was cleared to.

FACTUAL INFORMATION

History of the flight

Both aircraft were operating scheduled passenger services and were en route from Brisbane to Cairns. JA8104 operating as JAL776, departed Brisbane at 2355 UTC on climb to FL290. VH-CZN departed two minutes later on climb to FL 310.

At 0003, a departure message incorporating the secondary surveillance radar (SSR) code allocation message (CAM) was received by the Cairns aircraft data systems officer (ADSO). The message contained four blocks, each of four numerals representing the departure times and assigned SSR codes for JAL776 and VH-CZN. In preparing the flight strips for the two aircraft, the ADSO inadvertently transposed the codes and departure times, resulting in VH-CZN being planned into the Cairns radar data system against the JAL776 code and departure time, and vice versa.

At 0055, abeam Townsville estimates of 0017 for JAL776 and 0020 for VH-CZN were passed to Cairns Arrivals. At 0118 both aircraft were handed off from Brisbane Control to Cairns Arrivals. The aircraft were handed off using the phraseology "south by two that is JAL776 and Charlie Zulu November". The handoff was accepted by the Cairns Arrivals controller even though the labels showed VH-CZN to be ahead of JAL776.

Subsequent events and relevant times were:

At this point, the Approach controller realised that the radar labels for JAL776 and VH-CZN were transposed. Both aircraft were then processed normally and landed without further incident.

Investigation of the occurrence revealed the following:

The ADSO had been suffering from a headache for two days prior to the incident. It was still present on the day of the incident, but the ADSO felt obliged to attend work as, two days earlier, she had taken the day off because of the headache.

In the ATS system in use at the time, aircraft SSR codes were entered manually by ADSOs on receipt of code allocation messages from adjoining ATS centres. There was no cross reference of aircraft levels and codes, either by the ADSO, or by any air traffic controller.

Although code allocation messages usually referred to only one aircraft, it was not unusual for two aircraft to be included in one message. In this instance, the four-figure SSR codes as well as the departure times for both aircraft all began with the numerals 23, thus increasing the potential for error when the information was transferred.

For a few months preceding the occurrence, there had been problems concerning the SSR mode-C display on Cairns radar. While these had involved correlation of departing aircraft, there were indications of a level of suspicion among the controllers regarding the reliability of the SSR mode-C display.

During the radar handoff of the aircraft from Brisbane to Cairns Arrivals, there was no bearing and distance given for the aircraft, either with respect to a common position (such as Townsville) or to each other. This resulted in an opportunity for rectifying the misidentification of the codes to being missed.

Paras 6-9 of the Manual of Air Traffic Services (MATS) 9-5-2 address radar handoff. However, they refer to single aircraft handoffs only and do not address multiple aircraft handoffs.

Although the abeam Townsville estimates indicated that JAL776 was ahead of VH-CZN, there were indications that these estimates could be unreliable. It was reported that the day before the incident, two aircraft were handed off by Brisbane with the second aircraft having the earlier estimate. This may have encouraged a climate whereby estimates were considered unreliable indicators of aircraft position.

CONCLUSIONS

Significant factors

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

1. The physiological condition of the ADSO may have reduced that person’s task efficiency.
2. The code allocation message referred to two aircraft.
3. The ADSO transposed the SSR code information for both aircraft.
4. A check was not conducted to confirm that the correct SSR codes had been entered against each aircraft.
5. The radar handoff was such that positive aircraft identification was not assured.
6. MATS procedures did not cover multiple aircraft handoffs.
7. Previous problems with SSR mode-C readouts may have influenced the controllers to assume that the altitude labels for the aircraft were incorrect.

SAFETY ACTION

As a result of the investigation, the Bureau of Air Safety Investigation issued the following interim recommendation

to the Civil Aviation Authority on 13 December 1994.  The response to the interim recommendation from Airservices Australia is also reproduced in part.

IR940300

The Bureau of Air Safety Investigation recommends that the Civil Aviation Authority:

1. review message format procedures to ensure that separate messages are used for departure and SSR code allocation information for each aircraft;
2. review the radar hand-off methods to ensure that individual aircraft validation needs for each unit are appropriate to the equipment and procedures in use at that unit; and
3. introduce a system of SSR code integrity checks between ATS centres and, where appropriate, between individual sectors within the same centre.

Airservices Australia response

Head Office and District Office (ATS) meetings were held to discuss the issues and implications of the Bureau's recommendations, and the following changes to procedures have been implemented.

Message format has been amended so that double spacing appears between all aircraft departure and code allocation advice.  The error rate has been greatly reduced and the problem of "dyslexic" interpolation of callsigns is no longer apparent.

Hand off methods between units have been addressed by the issuance of an interim MATS amendment (IMA) 13A effective 18 August 1995.  This new procedure was installed by local direction pending the effective publication date.

MATS 9-5-2 Para 4.b

Add new second sentence so that sub-para reads as follows:

b. .... by specifying the location of the radar return by a bearing and distance from a known point or fix, together with the observed track or return. When aircraft are within 10 NM, or a distance as otherwise specified in Local Instructions, of one or more other aircraft, relative position information will also be passed to ensure correct relay of identification. The receiving controller may consider identification positive if only one return observed on the display agrees with the information specified..."

MATS 9-5-2 Para 4.f

After existing sub-sub-para f. (3) add new NOTE as follows:

"NOTE: This technique shall not be applied across boundaries of non-linked RDP systems."

Procedures have been introduced into the NDO to provide timely advice of code allocation and insertion into the RDP system, reducing the chances of errors being generated by this work being done at the ATC console.

Hand-off procedures are now considered secure to pick up code-based errors.

Response classification:  CLOSED-ACCEPTED