Loss of control

A number of witnesses observed the aircraft operating in the accident area. A common observation was that it was operating at a lower height (probably between 500 and 1000 feet above ground level) than was usually seen of other light aircraft flying over the area. The aircraft was seen to complete a number of level orbits over a chicken farm and then to head south for about two kilometres. While this was occurring the engine sound died and picked up again a few times, as if the pilot was practising setting the aircraft into a glide. The aircraft then flew a level left turn through about 270 degrees before suddenly entering a 30 to 40 degree dive. At close to tree-top height it abruptly changed attitude and entered a steep, perhaps vertical, climb. Some witnesses felt that the pilot was about to fly a loop. As the aircraft climbed, the speed rapidly decayed. During these manoeuvres, the engine note was heard to die and pick up twice. The aircraft was then observed to fall, nose first and right wing slightly low, into a near vertical dive. Apart from completing one or possibly two rotations, it remained in this attitude until lost from sight amongst trees. The aircraft impacted the ground in a 90 degree nose down attitude. When recovered from the wreckage the airspeed indicator was indicating 105 knots. It was established that the engine was operating at impact. No evidence was found of any abnormality in the aircraft or its systems which may have contributed to the accident. No explanation was found for the apparent operation of the aircraft at a relatively low height, or for the dive to a very low level followed by the steep climb. The carburettor fitted to the engine was equipped with an accelerator pump. A characteristic of carburettors of this type is that rapid or "slam" opening of the throttle can temporarily over-fuel the engine and cause the RPM to fluctuate for a short time. It could not be determined whether this characteristic may have been associated with the engine note dying and picking up twice as heard by witnesses in this instance. Investigation established that the the passenger occupying the front right-hand seat had flown 33 hours dual and 3.5 hours solo on Cessna 152 aircraft during 1983/84. The front seats of the aircraft were adjustable fore-and-aft along rails attached to the floor. Examination of the cockpit revealed the adjustment of the front left-hand seat (occupied by the pilot-in-command) at impact to have been five notches from the front. The front right seat was positioned in the forward-most notch. Tests of these seating positions were conducted in another PA28 aircraft using persons of the same height as those involved in the accident. These tests indicated that the right seat occupant should have been able to comfortably manipulate the engine and flying controls of the aircraft. However, the left seat appeared to be too far to the rear for the pilot-in-command to have been in a normal flying position in relation to the controls. Specific flying techniques are required to recover an aircraft from an extremely nose-high attitude at low speed. The aircraft involved in this accident was observed to develop such an attitude accompanied with low speed, and the low height at which this occurred would have increased the level of pilot skill required to return the aircraft to a safe flight environment. It was established that the pilot-in-command had received no training in the flying techniques required to recover aircraft from unusual attitudes. The seating position tests suggested that the pilot-in-command may not have been manipulating the controls during the final stages of flight, and it is also probable that the person occupying the right-hand seat had not received any training in recovery from unusual attitudes. It is considered probable that once the aircraft had reached the nose-high attitude at low speed, that it was beyond the experience level of either of the front seat occupants to effect a safe recovery, particularly in view of the low height of the aircraft at the time.

Until the day prior to the accident the pilot had not flown for over three months. He was carrying out a period of touch-and-go landings. On about the third or fourth landing the aircraft was apparently caught in an area of sink at the approach end of the strip, and touched down in a flat attitude and bounced slightly. The aircraft was recovered and touched down again in a normal attitude. The pilot lowered the nosewheel onto the strip, then applied power to go-around. The aircraft was observed to become light on the mainwheels and commence a swing to the left. As the swing increased the right wingtip hit the ground and the nosegear leg broke off. The aircraft slid to a halt on the mainwheels to the left of the flight strip.

Circumstances:

During a period of low operational activity, the pilot was contracted to spray a crop in open, flat terrain. Having almost completed the irregular shaped area, the pilot positioned his aircraft to make a run over a very small corner of the crop, towards a clump of trees, some of which were up to 25 metres high. The pilot mis-judged his turn onto the run alignment, necessitating a steep approach. Once settled at spray height, he was faced with a very steep climb-out to clear a large tree. During the pull-up, the aircraft stalled and collided with the tree. The nose pitched down, and the aircraft impacted the ground in a near vertical attitude, before rolling inverted. The pilot extinguished a small fire.

Significant Factors:

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

1. The pilot attempted to spray an area which was only marginally suitable for aerial treatment.

2. The pilot mis-judged his approach to the area.

3. The aircraft stalled during the pull-up.

Recommendations:

The Civil Aviation Authority reassess recency requirements for agricultural pilots to place emphasis on hours flown during the preceding 90 days. This assessment should take into consideration the type of operation the pilot is to return to following an extended break, or period of very low operational intensity.

The pilot had landed at the one-way agricultural strip in order to deliver covers for a load of superphosphate. The subsequent take-off was normal until the point where the tail of the aircraft was raised. At this time the aircraft was affected by a strong wind gust, and the pilot was unable to maintain directional control. The aircraft ran off the side of the strip and struck scrub and a steel fence post. The wind at the time was relatively strong, giving a substantial downwind/crosswind component. Although the pilot had operated from this strip on numerous occasions, he had not worked from it for about 12 months. The strip posed difficulties because it changed direction to the right over the crest of a hill. Due to a strong left tailwind, the pilot had to maximise the take-off run available. The path chosen, combined with the prevailing wind, took the aircraft off the right side of the strip before it had attained flying speed.

The glider was being winch-launched from strip 36. During the launch, the left wingtip dropped into lush vegetation covering the strip. The glider rolled rapidly to the left around the wingtip, until it was inverted. It impacted heavily in this attitude and came to rest 96 metres from, and 15 metres to the left of the take-off point. A 15-20 knot north-easterly wind was blowing at the time and the right wing was seen to lift as the left wing contacted a reasonably heavy cover of dandelions which were 30-40 centrimetres tall. The pilot had activated the manual release and the winch operator stopped the launch when the glider adopted the acute roll angle, but both of these actions were too late for recovery to be achieved prior to impact. Due to soggy conditions, the gliding club had not used the strip for the previous 2 months, and had not mown the surface prior to recommencement of operations.

The pilot was approaching to land in what he believed were light wind conditions. As he crossed the threshold he realised that there was a tailwind component, but elected to continue the approach. Touchdown occurred with about 415 metres of the strip remaining. During the landing roll the pilot became concerned that the aircraft would not stop before the boundary fence, and a ground loop was attempted. The left maingear collapsed as the aircraft came to rest 103 metres from the end of the runway. The landing attempt had been made in 12 to 15 knot downwind conditions. The pilot had assessed the wind direction from the smoke emitted by nearby power stations. He had not noticed the direction indicated by the two windsocks at the aerodrome. It was likely that the pilot was mentally fatigued following a long and difficult day at his workplace, and he may have been pre-occupied with business matters which were related to the reason for the particular flight.

The pilot, who is an approved AUF instructor, was conducting a solo test flight, following complaints by a student that directional control was more difficult than normal. During the takeoff run a rudder lever arm collapsed, directional control was lost, and the aircraft collided with a fence. It was likely that the directional control problems originally reported were related to the rudder lever arm being bent. The reason for the bending was not established, but the lever had evidently been weakened to the point where it failed during the attempted takeoff.

Circumstances:

The student pilot was landing the aircraft during his second period of dual instruction on type. Shortly after touchdown the aircraft was struck by a wind gust. Despite corrective action by the instructor, directional control was lost, and the aircraft ran off the runway, substantially damaging the tail boom.

The pilot was spraying a small paddock, to the south east of which the ground rose steeply. All spraying runs were being conducted towards the south east, with the pilot carrying out left hand orbits at the end of each run in order to reposition the aircraft. However, manoeuvring in this manner was taking the aircraft close to houses in a noise sensitive area. The pilot therefore decided to carry out a procedure turn and conduct a run into the north west. About half way around this turn the aircraft lost performance, probably as the result of a downdraft, and then stalled at about 100 feet above the ground. There was insufficient height available for the pilot to effect recovery and the aircraft struck the ground in about a 30 degree nosedown attitude. The pilot subsequently advised that he was aware that downdrafts were likely to be present in the prevailing conditions. However, he had been concerned to avoid the noise sensitive area, and had not considered the possibility of downdrafts as he manoeuvred over rising terrain. When he was attempting to recover from the stall situation, the pilot had not dumped his load because there were valuable animals in the paddock below the aircraft.

As part of the final phase of the rating test, the pilot was required to spray a paddock. An inspection of the area to be treated was carried out. During the procedure turn at the end of the second spray run, the nose dropped and the aircraft struck the ground in a near vertical attitude. The pilot had incorrectly assessed the wind direction and had carried out the procedure turns at the end of the spray runs in the wrong direction. In an effort to align the aircraft for the next run, the pilot tightened the turn and the aircraft stalled.