Pilot information
The pilot's last aircrew medical examination was conducted on 18 May 1995. He held a valid Class 1 medical certificate. His commercial pilot licence was current and he was endorsed to fly tail-wheeled aircraft. His pilot's logbook and aircraft records showed that he had flown fewer than 70 hours in the preceding two years.
Records showed that the pilot had not undertaken an aeroplane flight review within the previous two years. His last documented aeroplane conversion training (which the Civil Aviation Safety Authority accepts as equivalent to an aeroplane flight review) was completed on 17 November 1993.
The instructor who conducted the conversion training said that the pilot's aircraft handling met the minimum required standard and that he had limited flying experience. The instructor advised the pilot to operate under an experienced chief pilot until he gained further flying experience. The pilot declined, saying that he wanted to run his own operation.
Within the preceding five months, several fellow pilots had on separate occasions observed the pilot flying his aircraft in an excessively steep climb after takeoff, followed by an early, low-speed turn. When they mentioned the implications of his conduct to him, the pilot responded by saying that the aircraft was designed for short takeoff and landing. He had been alone in the aircraft on these occasions. The impression given to people close to the pilot was that he regarded his aircraft as very stable and forgiving.
In early June 1995, the pilot was identified flying below 500 ft along the City Reach and the Toowong Reach of the Brisbane River in his distinctive aircraft. Neither the pilot's takeoff practice of climbing steeply, nor the low flying occurrence, was reported to the Civil Aviation Safety Authority.
The pilot worked from 0100 to 0500 EST as a cleaner at a supermarket. He had worked this shift schedule on at least four consecutive mornings the week of the accident, including the day of the accident. He had also flown a charter flight on the afternoon before the accident. On a typical work day, he normally slept after returning from work until about 0900, and again from about 2000/2100 until after midnight, then rose in time to go to work.
The postmortem examination report did not reveal any pre-existing physiological problems which could have affected the pilot's ability to fly the aircraft.
Air operator's certificate
On 16 February 1994, the Civil Aviation Authority (now the Civil Aviation Safety Authority) issued an air operator's certificate authorising the pilot to conduct charter and aerial work flights in his aircraft. When the certificate was issued, the Authority's policy was to inspect each operator once in every 12-month period. The inspection specified is limited to an examination of records, recording systems and facilities. The policy was changed in October 1995, requiring an inspection once in every 18-month period. An inspection of the pilot's operation had been scheduled for September 1995 but this was deferred indefinitely due to a high workload in the Authority's Archerfield office. In addition, the pilot had not been available for an inspection on an opportunity basis when the flying operations inspector's schedule permitted.
The inspection policy change, coupled with delays in scheduling, resulted in a lack of any periodic inspection of the pilot's operation. The flying operations inspector in charge of overseeing the operation said that, had he known of the pilot's potentially dangerous flying habits and the low-flying occurrence, he would have investigated. In addition, the Authority was unaware that the pilot's aeroplane flight review was not current. Legislation does not require notification that a review has taken place. The responsibility of keeping the aeroplane flight review valid rests with the pilot.
Aircraft information
The aircraft was manufactured in Poland and first registered in Australia on 1 November 1989. It was designed as a light utility aircraft for the short take-off and landing role. It was a fixed landing gear, tail-wheeled aircraft, equipped to carry a pilot plus three passengers. Available aviation literature and flight test reports highlighted the docile, power-off stall characteristics of the aircraft.
The aircraft's logbook showed that it had undergone a periodic maintenance inspection on 15 November 1995. The current maintenance release was invalid due to an omission by the licensed aircraft maintenance engineer. He had been unable to document the aircraft hours limitation as the pilot had not given him the expired maintenance release as proof of total hours flown. The new maintenance release was partially destroyed in the fire. As a result, the number of hours flown since the last periodic inspection could not be determined accurately, but was estimated to be in the order of 6 to 10.
No evidence was found in the maintenance records to suggest that the aircraft was not fully serviceable before the flight.
The managing director of the aviation firm which imported four PZL-104 had extensive experience flying the type. He said that the aerodynamic stall characteristics in level flight, power off, were very docile. Control could be regained by releasing the back pressure on the control stick. The aircraft stalled at about 38 knots with take-off flap selected. However, when the aircraft stalled in the take-off configuration with flap and full power, it rolled rapidly to the left, adopting a distinctly nose-low attitude. The altitude lost in the recovery was significant but would depend on how far the nose dropped below the horizon before the pilot reacted and regained control.
Wreckage examination
The wing structure was largely intact with only the centre section burnt. It was separated from the fuselage. The left wingtip struck the ground first and ground marks revealed that the aircraft was rotating left at impact. Take-off flap (21 degrees) was selected. The destruction pattern of the wooden propeller indicated that the engine was producing a significant amount of power at impact. Witnesses said that the engine noise did not seem to vary during the entire take-off /accident sequence. The engine was dismantled in an engineering workshop. Nothing was found which could have prevented normal engine operation.
The cabin area was destroyed by the impact and subsequent fuel-fed fire. All flight controls were checked and found to be free of pre-existing defects. Information received from the public initially cast doubt on the integrity of the pilot's seat/seat rail. Apparently, in several occurrences in Poland, the pilot's seat had been known to slide back on its rails, leaving the pilot unable to move the control stick far enough forward to regain control. Detailed examination of the seat-lock mechanism and rail found that the seat had not moved from the forward position.
Computations of the aircraft weight found that the maximum allowable take-off weight of 1,300 kg was exceeded by 40 kg. Due to the excess weight, the aircraft loading was outside the limits published in the centre-of-gravity graph.
Weather
A ridge of high pressure established along the coast, directing a moderate to fresh south-easterly airflow onto the coast and islands. The surface wind was estimated to have been a south-easterly at 10 knots. Winds at 500-1,000 ft were stronger at 15-20 kts. Witnesses at the airstrip commented that they noticed the occasional stronger gust of wind.
Aircraft performance
Evidence indicated that the pilot probably initiated a steep climb after take-off. With an excessively steep climb attitude, the aircraft's airspeed decreased rapidly, resulting in an aerodynamic stall, either at the top of climb or when the pilot rolled the aircraft into a left turn. Considering the aircraft's low altitude and the rapid attitude change in a power-on stall, the pilot would not have been able to regain control in time to avoid a collision with the ground. The pilot did not appear to detect or correct the potential problem arising from the aircraft performance in sufficient time to prevent the stall.
Contributing factors to the pilot's actions
Several factors appeared to contribute to the pilot's use of a steep climb attitude and his failure to detect or correct the potential problem in the aircraft's performance.
Firstly, the pilot appeared to believe that the aircraft was very stable and forgiving. This belief may have resulted in the pilot developing an undesirably low perception of the risk associated with some manoeuvres, particularly flying the aircraft with high rates of climb and low speeds after takeoff. After repeatedly flying this manoeuvre without adverse consequences it may have become part of his normal behaviour.
Secondly, the pilot had a relatively low level of overall flying experience, including recent flying experience. This meant that he was probably still encountering a significant workload during the take-off and climb phases. Consequently, he had only a limited amount of information processing capacity available to deal with the detection and resolution of a rapidly deteriorating situation. His low level of experience is also likely to have limited his familiarity with the nature of an impending stall.
One particular area in which the pilot appeared to have had limited understanding concerned the effect that different loads have on the aircraft's performance and capabilities. On the previous occasions in which the pilot was seen to have used a steep climb after takeoff followed by an early turn, there had been no passengers. The aircraft weight was therefore significantly below the maximum allowable take-off weight. However, on the accident flight, the aircraft weight was above the maximum allowable take-off weight. With a heavier than usual aircraft, the performance would not have been what the pilot normally experienced. In addition, the centre of gravity was further aft on the joy flight compared to a pilot-only flight, resulting in a lighter elevator control. The pilot's low level of experience may have meant that he was less able to associate a problem with aircraft performance to the heavier than normal operating weight.
Finally, the pilot was probably suffering from a significant level of fatigue at the time of the accident. Research has shown that working shifts during the critical hours between midnight and 0600 can lead to disruption of the human circadian rhythm. This disruption is due to physiological and environmental factors, as well as the social aspects of trying to sleep during the day when family matters and environmental noise may hamper sleep. Under these conditions the duration of sleep may be similar to that associated with a typical work schedule, but the quality of sleep obtained is usually less than optimal. A lack of quality sleep over a period of several days can be associated with a significant level of fatigue.
If the pilot was suffering from fatigue, many aspects of his performance may have been affected. The effects of fatigue may be exhibited in the form of slower reaction time, decrease in his perception and processing of incoming information, poor judgement, and inappropriate decision making. In other words a significant level of fatigue would probably have influenced the pilot's ability to detect and correct a potential problem with the aircraft performance.
Surveillance by the Civil Aviation Safety Authority
Evidence showed that some fellow pilots made unsuccessful attempts to dissuade him from his questionable take-off habit. The relevant Civil Aviation Safety Authority flying operations inspector had not been made aware of the pilot's technique of climbing steeply after take-off. If these events had been reported, an early investigation may have had the effect of modifying his flying techniques.
Weather
Witnesses at the air strip report that the wind was gusting occasionally. It is possible that a stronger gust of wind exacerbated the handling problem experienced by the pilot.
- The pilot's flying habits probably resulted in the adoption of an excessively steep climb after takeoff.
- The aircraft stalled at low altitude and struck the ground before the pilot could regain control.
At a result of the investigation into this occurrence, the Bureau of Air Safety Investigation forwarded the following interim recommendation to the Civil Aviation Safety Authority on 4 November 1996:
'IR960127
The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority:
- review the Aviation Safety Surveillance Program to ensure that new commercial operators are adequately monitored and inspected until a demonstrated history of safe operation is known;
- align the scheduled surveillance period of the Aviation Safety Surveillance Program to that of the validity period of the air operators certificate;
- reconsider the flight review requirements for Chief Pilots with the view of bringing them into line with the current situation for Chief Flying Instructors, as an additional method of surveillance;
- review the adequacy of the approval and assessment requirements for Chief Pilots who do not have a demonstrated history in flight operations with a commercial operator;
- review the current situation regarding Aeroplane Flight Reviews, to allow for appropriate notification to the Civil Aviation Safety Authority and recording of the results.'
