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

The design of Area Alpha was negotiated between the gliding clubs and ATC. It was intended to provide suitable airspace to cater for the traffic density, and to meet the needs of the training syllabus for glider pilots. For example, the average 1,500 ft between ground level and the base of the 2,000 ft step is insufficient for spin recovery training which is mandatory for all glider pilots.

The gliding clubs have a record book adjacent to the telephone in the club house to record details of the release of the airspace and have an 'Alpha Open' sign at the launch point to advise pilots when release approval has been obtained from ATC.

During the launch of the three gliders the 'Alpha Open' launch point sign was displayed although no request for release had been made to ATC, and no approval had been given. The glider pilots were not aware that Area Alpha had not been released. ATC routed the B767 through the area in the belief that glider traffic was conforming to the area step restrictions. Weather conditions at the time were such that the gliders were able to climb to 4,000ft.

There was no indication in the record book adjacent to the club house telephone that any contact had been made with ATC, and ATC did not have any record of telephone calls received from the clubs.

The gliding clubs were not able to determine who had displayed the sign that day and were not sure that the sign had been removed after the previous day’s flying.

The B767 had been correctly routed through the area. The crew was alert to the high-density traffic and was maintaining a heightened visual scan during the descent into Avalon.

Significant factors

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

1. The 'Area Open' sign was displayed when an ATC clearance was not available.
2. ATC was not aware that the gliders were operating in controlled airspace.

SAFETY ACTION

During the investigation, Airservices Australia revealed that as part of the implementation of the ICAO Airspace structure on 20 June 1996, the upper limit of the airspace available for gliding OCTA ('G' airspace) will be 3,500 ft over Bacchus Marsh and 4,500 ft to the west of Bacchus Marsh.

The following safety actions have also been taken.

The gliding clubs have:

1. alerted all glider pilots operating at Bacchus Marsh to the circumstances of this incident;
2. tightened up the mandatory recording of telephone requests for the release of Area Alpha airspace;
3. manufactured a sandwich board indicator of 'Area Open' that shows the date, the name of the person who obtained the clearance and any conditions attached to the clearance;
4. required that the sandwich board be placed in the club house adjacent to the telephone at the completion of each days flying; and
5. required that during the first launch after the sandwich board is placed at the launch point the tug pilot is to call ATC to confirm that Area Alpha is open.

The pilot reported that the engine lost power at a height of about 500 ft, shortly after take-off. As he was unable to return to the runway he carried out a forced landing in an open area. During the landing roll the nosewheel entered a ditch and the aircraft overturned. The pilot was able to exit the aircraft without injury.

No defects were found which were likely to have contributed to the loss of power. The engine ran normally during subsequent ground testing.

The crew of PAL210 transferred from Melbourne Control (Sector 6) to Brisbane Control (Sector 5) at 1523 hours. On first contact with Brisbane Control, they advised an estimate of 1527 hours for Cunnamulla. The Brisbane controller had not received co-ordination from Melbourne Sector 6 on the prior position of the aircraft. He only held an estimate based on the departure time and the flight plan time intervals. That estimate was 1534 hours.

Investigation revealed a breakdown had occurred at Melbourne Sector 6, the control position responsible for the co-ordination. This had happened at the time of hand over of responsibilities at the end of a shift. The controller going off duty indicated to the controller coming on duty the need for co-ordination in respect of PAL210 but the manner in which he did this was misinterpreted by the on-coming controller and the required co-ordination was not done.

Significant Factor

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

1. A misunderstanding occurred between the controller going off duty and the controller coming on duty.

The pilot had been undergoing dual instruction and had been practicing autorotational landings onto a dry mud flat.

One exercise was for the instructor to hold the anti-torque pedals firmly in the neutral position simulating jammed pedals, the pilot terminating the exercise with a run on landing. He made an approach to a larger, and clearer area of the mud flats, but his initial pass was too slow, and he was unable to maintain directional control. The instructor took over and completed the exercise as a demonstration, touching down in a straight and level attitude, with a ground speed of approximately 10 kt.

Immediately after ground contact the landing skids broke through the firm top layer of the mud crust, causing the helicopter to pitch forward allowing the main rotor blades to contact the ground. The helicopter then cartwheeled and came to rest on its left side, facing back along the approach path.

Approval was given to Melbourne Sector 12 by Sydney ATC for the Nomad to climb clear of the Sydney 230 radial for parachute dropping from FL125. At about the same time, an Airbus was inbound to Sydney from Melbourne via a Rivet STAR. As the Airbus was passing FL130 on descent, the Nomad was observed on radar by Sydney Arrivals, near the inbound track climbing through FL110, in potential conflict with the descending Airbus.

The Arrivals Controller contacted Melbourne Sector 12 who confirmed that they would be separating the two aircraft. Although this was accepted, a short time later the aircraft were observed to pass within 4 NM of each other at the same level, when the minimum lateral separation required was 5 NM.

A subsequent investigation did not reveal any reason for the lack of positive control by Melbourne Sector 12. The incident was also the subject of a separate ATS Quality Assurance investigation.

FACTUAL INFORMATION

History of the flight

During the pre-flight inspection, the pilot in command noticed that the elevators were drooping. He checked that the control lock was engaged and found that while the aileron and rudder systems were locked, the elevator system was not. He attempted to lock the elevators but was unable do so, nor could the engineer on tarmac duty. The engineer assured the pilot that, as the control lock system was rendered inoperative in flight, it would be safe to fly the aircraft and that the defect would be rectified when the aircraft returned to Brisbane later that day. The engineer was correct as the control locks are rendered inoperative in flight. The defect was then correctly deferred in accordance with Sunstate CAA approved Volume No.1 procedures, and the aircraft was subsequently despatched.

Soon after the aircraft became airborne, the co-pilot, who was the pilot flying the aircraft, notified the pilot in command that he believed there was a control abnormality in that more aft elevator than normal was required to rotate the aircraft. Upon reaching cruise altitude, the pilot in command took over the controls and confirmed that the control column was aft of its normal position when the aircraft was in level flight. Following a controllability check in the landing configuration, the aircraft returned to Brisbane. A subsequent inspection revealed that a rudder control rod had been fitted to the elevator control system, altering the geometry of that system and causing the abnormal control column position.

Maintenance aspects

The elevator and rudder control rod systems run parallel to each other and are routed through the ceiling of the aircraft in the area above the galley. Each system has a number of interconnecting rods which run fore and aft between roller guides. The elevator and rudder control rods are similar in appearance, but the elevator control rod is 35 mm longer than the rudder control rod.

On 3 October 1994, a licensed aircraft maintenance engineer had raised a deferred maintenance control sheet for replacement of the "elevator control rod L/H above toilet cabin dividing wall". (When facing forward in the aircraft, the left rod is the rudder control rod). A parts order form was submitted to order a new elevator control rod.

On 11 November 1994, another maintenance engineer found that the elevator control rod referred to on the deferred maintenance control sheet did not require replacement. Consequently, the elevator control rod which had been ordered was not required and was returned to the parts store. However, this engineer noticed that the adjacent rudder control rod was excessively worn so he raised a deferred maintenance control sheet for that item. A replacement rudder control rod was ordered on 15 November 1994 and arrived on 9 December 1994.

A periodic maintenance inspection was carried out on the aircraft during the weekend of 10 and 11 December along with maintenance which had been deferred. On 10 December work was started on the control rod change as required by the deferred maintenance control sheet form SA113. The form was part of a work package which detailed the tasks to be carried out during the maintenance period. The engineer who recorded the elevator control rod defect on 3 October assigned himself to the task of changing the rod.

The word "RUDDER", approximately 100 mm long, was pencilled on the old rudder control rod and the elevator rod was marked with the letters "ELEV". During discussions, the Maintenance Manager indicated that the wording may have been placed on the rods in order to prevent confusion at aircraft assembly. It has since been noted that various rods throughout several aircraft have the particular system name pencilled on them. This appears to have been an unofficial factory procedure. The local Short Brothers Technical Representative was advised by the factory that "the operator should read the part number".

The engineer who replaced the rod incorrectly identified the worn rod as the rudder control rod. He then removed that rod, which was in fact the elevator rod, without positively identifying it. After obtaining the new rudder rod from the parts store, he did not compare it with the old rod because he was called away to do another job and placed the new rod, still in its container, on a workbench. When he returned to the task, he removed the new rod from its container and fitted it to the aircraft. He did not notice that the old rod had a different part number printed on it, had the letters "ELEV" pencilled on it, and was longer than the new rod.

On completion of the work another engineer was asked to perform a "dual inspection." This inspection was required by the maintenance control manual volume one, the manufacturer's maintenance manual where it is referred to as a "duplicate inspection", and Civil Aviation Regulation 42G (1) where it is referred to as an "independent inspection". The engineer who performed this inspection had been multi-tasked and was doing unplanned work when he was asked to carry out the duplicate inspection. After being shown the rod that had been changed, he checked it for security and freedom of movement. He subsequently countersigned the duplicate inspection certification sheet.

The duty senior engineer reported that towards the end of his shift, when he was compiling the paperwork, he found that the signatures on the duplicate inspection sheet had been incorrectly placed in the aileron column at the top of the sheet. He said that he had pointed this out to the engineer who performed the inspection, who subsequently took the sheet to the engineer who had changed the rod. The inspecting engineer returned the sheet to the senior engineer with the word 'aileron' crossed out and the word 'rudder' written above it. The work was completed by 0830 hours on 11 December.

As a result of the incorrect rod being installed in the elevator system, the elevator control lock was rendered inoperative due to the altered geometry of the control system.

At about 1745 hours on 11 December, the aircraft was towed from the hangar for an engine run. The flying controls are required to be locked during towing, when the aircraft is parked, and when it is taxied by engineers. The engineer who towed the aircraft from the hangar did not notice that the elevator control could not be locked.

Standard company procedure is to engage the flight control lock prior to commencing an engine ground run. The elevator system could not be locked so the engine run was commenced with the elevator control lock disengaged. The control lock must be disengaged if ground runs in excess of idle are required in order for power levers to be advanced past the control lock baulk.

A daily inspection certificate was signed on the Maintenance Log of the day at 0300 hours on 12 December, certifying that the items on the daily inspection schedule in the maintenance control manual volume two had been carried out. The last item on the schedule states: "Flight controls and trim controls full and free and correct operation". The certifying engineer for this inspection did not notice that the elevator control lock could not be engaged.

The aircraft was then towed from the hangar to the apron on the opposite side of the airport. The fact that the elevator control lock could not be engaged was not noticed.

Maintenance manuals

The Shorts SD3-60 maintenance manual, the Civil Aviation Regulations and the operator's maintenance control manual volume one, contain specific details regarding maintenance practices with control rods. Both engineers involved in the rectification work indicated that these publications had not been consulted before or during the performance of the work.

A new version of the operator's maintenance control manual volume one was approved by the Civil Aviation Authority on 11 February 1994 and was implemented by the operator thereafter. Copies of the maintenance control manual volume one were located in the company's technical library and also in the hangar at a workstation which houses other paperwork and forms. Investigation of staff awareness and training revealed that both engineers had undergone familiarisation with the maintenance control manual volume one on Tuesday 15 March 1994.

Personnel information

The engineer who performed the rudder rod replacement was appropriately licensed and endorsed to perform the task. He joined the airline in March 1991 and held airframe and engine ratings. He had two rostered days off immediately prior to the occurrence but had worked three-night shifts before that. He indicated that, despite the two days off, he still felt tired on the day of the incident and thought this was because he had not fully recovered from the three-night shifts. He did not at any time advise his immediate supervisor or senior managers that he was fatigued. The engineer had been involved in three car accidents which affected his ability to work on stands, operate some tools, and write legibly. The company had not at any time been made aware of the car accidents. The management was aware of the engineer's unsteadiness whilst he was working on stands, and the engineering manager had discussed the problem with him some weeks prior to the incident. He had agreed to see a company doctor.

The engineer who performed the dual inspection was correctly licensed and qualified to carry out the task. He held engine and airframe ratings. He had been rostered off for four days prior to the occurrence.

Shift roster

The operation of the airline is dependent on co-ordinating maintenance requirements with operational requirements to achieve the schedule. This involves the conduct of the maintenance at night and on weekends. The shift roster consists of two crews of seven engineers and four crews of two engineers. The seven-person crews work three-night shifts, two days off, two-day shifts, three days off, two-night shifts, and then two days off. The two-person crews work two-day shifts followed by two-night shifts and then have four days off. The two-night shifts commence at 1715 and finish at 0415 the following morning. The remaining seven-person crew commence at 1800 and finish at 0425, while the day shift commences at 0600 and finishes at 1700.

The engineer who fitted the rod incorrectly was on the two-day roster after having worked three nights. He did not consider two days off adequate time to recover after working three 10.4 hour night shifts. Some engineers felt that their health suffered because of the roster, while others indicated that they felt fatigued much of the time because of the interrupted sleep pattern. The matter was an industrial issue at the time, and when the company recently announced that four permanent day shift positions would become available (with corresponding reduction of penalties and allowances) no engineers were forthcoming for the shift change. As a result, company management considered the shift structure was not a serious issue.

The night shift engineers were isolated from the day crews as the shifts did not overlap. Some engineers felt that management did not appreciate their concerns about matters that had safety implications. This latter issue seemed to be more a result of inadequate communication between management and the engineering staff but nevertheless resulted in discontent and attitudinal problems for some engineers.

Working environment

The maintenance facility is approximately 3 km from the airline's apron, and this reportedly caused inconvenience as aircraft had to be towed or taxied from one side of the airport to the other for maintenance. The airline used the parent company's hangar for maintenance and did not have a dedicated area that was close to the parts store and the technical records. This often required engineers to walk long distances from the working area to the other facilities and was an annoying aspect of the work environment.

Regulatory aspects

During the Bureau of Air Safety Investigation's survey of the maintenance facility, some regulatory discrepancies were identified. The discrepancies included aspects of training, daily inspections, and quality assurance.

Training

There was no training program in place in accordance with Civil Aviation Regulation 214. This regulation refers to the training of maintenance personnel, and states that the operator shall make provision for the proper and periodic instruction of all maintenance personnel, and the training program shall be subject to the approval of the regulatory authority.

Daily inspections

Reference copies of the daily inspection schedule were not located in the aircraft or the tarmac office. At ports where engineering staff were not available to conduct daily inspections, pilots signed the maintenance log to reflect that they had completed the daily inspection schedule when the check was actually completed in accordance with a pre-flight check schedule. Consequently, some items on the daily inspection schedule were being signed for when in fact they had not been performed.

Quality assurance

The company did not employ a quality assurance inspector but was subject to periodic inspections from the parent company. This did not facilitate a day to day, hands on approach to quality assurance. However, systems that exceeded Civil Aviation Authority requirements were in place at the time of the incident and both licensed aircraft maintenance engineers had attended a briefing on the Volume No 1 procedures following their introduction.

ANALYSIS

The engineer who had incorrectly identified the rod tasked himself with fitting the new rudder rod. He did not follow basic procedure and practices and fitted the incorrect rod. A "safety net" failed when an adequate duplicate inspection of the system was not carried out. The engineer responsible for the duplicate inspection had been multi-tasked and was doing unplanned work when he was asked to do the inspection. His attention was divided at the time, and this may have influenced the amount of time he spent on the inspection. There was however adequate time to correctly carry out the inspection. The written procedures were not adhered to, and the independent inspection failed to detect that the wrong control system had been worked on.

Training

No formal training course had been conducted for the aircraft type, nor was one required, as it is a 'Group One' aircraft. Familiarisation training had been conducted by the aircraft manufacturer prior to the incident and one of the involved engineers had attended this training. The non-adherence to established procedures may indicate a poor attitude toward compliance with the maintenance control manual and manufacturer's maintenance manuals.

Design

Although the rods were clearly marked with identification numbers, and the attachment fittings were identical, the length of the rudder control rod was not compatible with the design requirement of the elevator control system. A more effective design is necessary to prevent the inadvertent interchange of incompatible components. This could be achieved by the use of dissimilar attachment fittings.

CONCLUSIONS

Findings

1. The maintenance engineers were correctly licensed to carry out the task.
2. The engineer incorrectly identified the worn rod as an elevator control rod.
3. A new rudder rod was fitted to the elevator control system.
4. The effect of the new rod on control deflections was not checked after work was completed.
5. The engineer responsible for carrying out a duplicate inspection did not recognise that the elevator system had been worked on instead of the rudder system.
6. The duplicate inspection was not carried out in accordance with published procedures.
7. The elevator control lock could not be engaged. This was not detected by the engineer who conducted the daily inspection.
8. The pilot was unable to lock the controls during his pre-flight inspection.
9. An engineer advised the pilot that the malfunctioning control lock was not a major defect.
10. There was no formal SD3-60 training course for engineering staff.

Significant factors

1. The worn control system was incorrectly identified by the engineer who replaced the rod.
2. The new control rod to be fitted was not compared with the old rod which had been removed. The rudder rod and the elevator rod were similar in appearance.
3. The duplicate inspection was not carried out in accordance with published procedures.
4. The elevator control lock malfunction was not diagnosed fully, and to allow the aircraft to be despatched, the item was deferred in accordance with company procedures.

SAFETY ACTION

The Bureau of Air Safety Investigation issues safety advisory notice SAN  960055 to the Civil Aviation Safety Authority.

The Bureau of Air Safety Investigation highlights this occurrence to the Civil Aviation Safety Authority (CASA) with particular reference to the transposition of the elevator and rudder control rods. The Bureau suggests CASA review certification standards to prevent the possibility of incorrect components being fitted to primary flight control systems and bring this to the attention of recognised authorities.

The Bureau also draws CASAs attention to the findings regarding maintenance surveillance and suggests that CASA review its surveillance activities with regard to RPT operators to ensure compliance with Civil Aviation Regulation 214.

The operator has advised that the following actions have now been taken:

1. Basic familiarisation training on the Shorts SD3-60 aircraft for some company maintenance employees. Each employee will have all documentation relating to training placed upon his or her personal file following a particular training exercise.
2. Revision and update of the maintenance control manual and associated documentation including daily inspection schedules for pilots and maintenance engineers. The pilot's daily inspection schedule appears in Part B of the company's Shorts SD3-60 operations manual. Pilots and maintenance engineers certify completion of the daily inspection in the maintenance log form SA102.

Three aircraft were in the landing sequence for runway 34R at Sydney. VH-NEK, on right downwind as number three, was given an ATC instruction to "sight and follow" the second aircraft, VH-DMO, which was on a left circuit. However, VH-NEK was seen to follow VH-SMH, the first aircraft in the sequence which was also on a right circuit. Separation was lost between VH-NEK and VH-DMO before the Approach Controller could contact the pilot of VH-NEK, who had already changed to Tower frequency before being instructed to do so. As a result, the aircraft came within 1 NM of each other before VH-NEK was vectored to follow VH-DMO.

Subsequent investigation indicated that VH-DMO, would have been in the "two o'clock" position from VH-NEK, at a range of about 10 NM, when the pilot of VH-NEK was instructed to follow the second aircraft. The first aircraft in the sequence, VH-SMH, would also have been at "two o'clock" from VH-NEK, but at a range of only 5 NM. VH-DMO was also nearly head on to VH-NEK at the time and would have been difficult to see. As a result, the pilot of VH-NEK mistook VH-SMH for the second aircraft and turned inside VH-DMO, resulting in a loss of separation. In hindsight, the "sight and follow" instruction may not have been the most suitable for this particular situation.

The temperature was about 37 degrees, a light wind was blowing straight down runway 25 and there were thermals in the area. A dual check flight of 30 minutes of circuits on runway 25 was completed with an instructor. The instructor then sent the pilot to do two solo circuits.

On the first approach for runway 25 the pilot made a touchdown in the three point attitude. After a short ground roll the right wing lifted, apparently due to an encounter with a thermal and the aircraft swung right. Left aileron and rudder and a small amount of engine power were applied but this did not prevent the aircraft from overturning.

Significant Factors

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

1. Thermal encountered at a critical time.

2. Pilot probably too slow to react to the effects of the thermal.