Loss of control

Because of deteriorating lift conditions, the pilot elected to make an outlanding. The paddock selected had been recently ploughed and the surface was soft. Almost immediately after touchdown the glider yawed, then groundlooped through 90 degrees, resulting in a compression fracture of the fuselage. It was likely that the glider had been affected by a sudden wind gust shortly after touchdown, and the pilot had been unable to maintain directional control.

The pilot was making a landing approach in moderate crosswind conditions. Touch-down was made in a three-point attitude at an airspeed of about 40 knots. Immediately afterwards, the pilot experienced difficulty in preventing the into-wind wing from rising. He elected to go around and applied full throttle, but was unable to maintain directional control. The propeller struck the ground and the aircraft cartwheeled before coming to rest. Recorded aerodrome information received by the pilot indicated that the surface wind was gusting above the aircraft maximum demonstrated crosswind component. On final approach, the pilot became aware that a significant crosswind existed, but he continued the approach, using a short field landing technique. When directional control was lost after touchdown and a go around was attempted, the combination of an uncontrolled turn downwind, the low airspeed and a gusty wind caused the aircraft to stall.

Circumstances:

The helicopter was operating onto a floating pontoon situated adjacent to a reef area. The pontoon was 30.65 m long and 9.32 m wide and consisted of a wooden platform mounted above two steel floats. A series of hardwood joists 295 mm x 85 mm and approx. 950 mm apart were mounted between the floats and 35 mm x 110 mm hardwood decking was nailed to the joists to form the platform surface. The decking ran lengthwise along the pontoon. The pontoon was constructed in 1985 and had been in operation almost continuously since then. While mainly skid equipped helicopters operated onto the pontoon, it had also been used by wheeled helicopters, including the Agusta 109. It was established that Agusta 109s had landed on the pontoon on some hundreds of occasions prior to the accident. Company pilots reported that they had observed decking planks bend when subjected to the weight of the Agusta 109 through its mainwheels. For this reason, the general practice for Agusta 109 operations onto the platform was for the mainwheels to be positioned over the joists when landing along the pontoon parallel to the decking. At the time of the accident, there was a northerly wind at about 15 kts and the pontoon was pitching some 25-30 cm in the swell. The northern end of the pontoon was occupied by another company helicopter which had just landed and was parked across the pontoon with its engine running and passengers still on board. VH-LHJ approached into wind to land along the pontoon. The helicopter was being flown by the pilot in the left seat. Shortly before the wheels contacted the decking, the pilot in the right seat opened his door to check the position of the mainwheels in relation to the joists. As the mainwheels touched the surface, he reported to the pilot flying the aircraft that the mainwheels were 6-8 in behind the beam. As the weight of the helicopter was transferred to the wheels, the right-seat pilot saw the decking beneath the right mainwheel flex slightly and then crack and break. The helicopter rolled rapidly to the right and the main rotor blades began impacting the pontoon and the water. The helicopter eventually came to rest on its right side, having veered about 130` to the right adjacent to the southern edge of the pontoon. The impact forces destroyed the main rotor blades, substantially damaged the rotor head, and broke the tail boom. There was no evidence of any fault in the helicopter which might have contributed to the accident. There was also no evidence of a hard landing or any other pilot-related aspect which might have caused excessive loads to be placed on the decking during the landing sequence. The investigation therefore focused on the pontoon itself, and a study was commissioned to examine the strength of the pontoon decking with respect to the helicopter types known to use the pontoon. The results of the evaluation of the pontoon decking were as follows 1. The condition of the decking timber was such that deterioration due to exposure to the elements was concluded not to have been a factor in the deck failure. 2. The failure of the decking when subjected to Agusta mainwheel loading was due to grossly excessive bending stress. The overload factor was calculated as 8.39 and readily explained the failure. The only pontoon design documentation which could be located concerned the general structure and dimensions of the pontoon and contained no details on deck strength considerations. No comment can be made, therefore, as to whether the wheel or skid loadings of the various helicopter types using the pontoon, and particularly those for the Agusta 109, were considered during the design of the pontoon.

Significant Factors:

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

1. The strength of the pontoon decking was inadequate for Agusta 109 operations.

2. The pontoon decking failed due to excessive bending stress when subjected to loading through the right mainwheel of the helicopter.

Recommendations:

The helicopter operator and the pontoon owner, along with the Civil Aviation Authority (CAA), were notified of the progress of the investigation. This included information contained in a preliminary report followed later by the complete testing details, technical analysis, and stress calculations concerning the pontoon decking. The analysis concluded that the strength of the decking was inadequate for all helicopter types which used the pontoon and steps were instituted by the operator and the pontoon owner for the deck to be strengthened.

1. A recommendation was made to the CAA on 13 September 1991 that the circumstances of the accident be brought to the attention of other organisations involved in operations on to helicopter landing sites with timber decking and that these organisations confirm the design specifications of those surfaces for the particular types of helicopter involved.

2. It is further recommended that the Civil Aviation Authority through surveillance, following the failure and subsequent repair of this pontoon, confirm that the pontoons and other helicopter landing sites which are being used by this operator, have the structural integrity to accommodate operations of the relevant helicopter types.

Circumstances:

The aircraft had taken off on runway 24 towards a range of hills. Wind at the time was reported as a steady 20 knots from the south-west, straight down the runway. After take-off, the pilot retracted the landing gear and reduced power for climb. He reported that soon after, the aircraft encountered a windshear, lost airspeed, and failed to climb. He did not reapply full power. There were no clear areas ahead, so he commenced a left turn; however, the airspeed decayed further, and the left wing dropped. The aircraft struck the top branches of a 15 m pine tree, rolling inverted before coming to rest approximately 15 m from a house. The occupants were trapped in the wreckage until emergency services arrived. The accident site was approximately 1 250 m south-west of the end of the runway. The terrain is below a five percent gradient, but beyond this area it rises quite steeply to a ridge line approximately 5 km from the runway. No fault was found with the aircraft. There was evidence from propeller strike marks on severed branches that the engine had been delivering substantial power at the time of impact. The area is well known for local wind effects due to the terrain. The prevailing wind direction would have been conducive to wind shear in the lee of the ridge where the accident occurred. This is the second of three similar accidents which have occurred within an area of 1.5 km during the last few years. In each case the aircraft failed to outclimb the terrain after taking off from runway 24.

Significant Factors:

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

1. The aircraft may have encountered windshear soon after lift-off.

2. The pilot did not operate the aircraft for maximum performance.

3. The pilot was not able to maintain speed.

Recommendations:

Over the past ten years BASI records indicate at least 16 take-off accidents to fixed wing aircraft attributed in part or totally to the effects of wind over the local terrain and to high density altitude. The following recommendations are made:

1. The CAA consider preparing an educational article to be widely distributed detailing considerations for GA type aircraft operations in areas where flight may be affected by terrain, wind, and density altitude.

2. The CAA bring to the attention of training schools the need to accent these issues in both theoretical and practical training.

Spraying operations were being conducted in generally calm weather conditions. One load had been sprayed successfully, but the pilot later advised that, as he manoeuvred at the end of the second run with the next load, sink was encountered. Although he dumped the remainder of the load, he reported that he had insufficient time to increase power. The aircraft collided with a tree, then struck the edge of a road and groundlooped into an adjacent crop. Weather conditions at the time were unlikely to have produced any sink. It was probable that while turning towards rising ground the pilot misjudged the slope of the terrain. The aircraft had stalled, with insufficient height available in which to effect a recovery.

Circumstances:

The aircraft had been flown twice that day prior to the accident flight. No problems or unserviceabilities had been reported. The purpose of this flight was to take a youth for a joy flight and the passenger emplaned while the engine was still running after the previous flight. After take-off, the aircraft was seen by several witnesses to fly low over the strip and adjoining areas before starting a manoeuvre at low level which resulted in the aircraft apparently stalling. The aircraft was then seen to rotate several times before crashing in a near vertical attitude through several branches of a large tree. Witnesses ran to the aircraft and found the pilot dead, but they were able to free the surviving passenger from the rear seat. It would appear that at the time of the accident, the pilot was carrying out some form of impromptu display at low level or "showing off". The investigation established that the pilot was want, at times, to show off or enjoy "pushing it" or taking an aircraft to its limits. Although it was not possible to determine the exact manoeuvre performed by the pilot which lead to his loss of control, there is no doubt that he carried out a manoeuvre at low level that resulted in the aircraft stalling at a height insufficient for recovery. Such a manoeuvre was apparently induced by the pilot rather than as a result of his experiencing a problem with the aircraft. No faults or anomalies were detected in the aircraft that could have contributed to the accident. All witness evidence is consistent in that the "spin" or spiral occurred after the aircraft entered the turn at low level. During his earlier flight in the aircraft that day, the pilot was reported to have performed aerobatic manoeuvres. The aircraft was not certified for aerobatic flight, and no record was found of the pilot holding an endorsement to perform aerobatic manoeuvres.

Significant Factors:

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

1. The pilot was engaged in an unauthorised impromptu display at low level.

2. The pilot stalled the aircraft at a height insufficient for recovery.

3. The pilot attempted manoeuvres beyond his level of experience.

Recommendations:

It is recommended that the Civil Aviation Authority

1. Require evidence of logbook endorsements for aerobatic manoeuvres, Biennial Flight Reviews, and other logbook only entry qualifications to be recorded on the departmental pilot history file.

The pilot had been airborne for about forty minutes when he decided to outland to talk to the ground mustering party. He selected a strip of ground, as an Authorised Landing Area, with sparse low mulga scrub on the sides and a patch at the end of the proposed landing area. Although the pilot overflew the selected area to check for obstructions, he did not carry out his customary low level inspection of the landing surface. The subsequent landing roll was reported to be smooth and uneventful. After talking with the ground party, they departed and the pilot elected to take off in the opposite direction to his landing as there was nil wind. About halfway down the strip on the takeoff roll, the pilot felt the left wheel strike an obstruction and the aircraft slewed to the left. It then ran through some mulga, about 35 metres to the left of the centre of the strip, as it paralleled the takeoff direction. The pilot recalled seeing an airspeed of about 40 knots at this point and as the aircraft was now clear of the scrub, he decided to continue the takeoff. The aircraft was recovered without further incident. The accident was not the subject of an on-scene investigation and the above information was provided by the pilot. Although the pilot's decision to continue with the takeoff did not contribute to the cause of the accident, it is considered that this was an error of judgement on his behalf. Subsequent examination of the damage revealed, amongst other things, that the right elevator balance horn had been torn off. Such damage could easily have led to control surface flutter, component failure and loss of control.

Circumstances:

The pilot was mustering cattle to clear rising flood waters. A second pilot was on the flight to assist and to observe the first pilot's methods of operation. The aircraft was landed near a gate to allow the second pilot to disembark, open the gate and provide further assistance from the ground. The aircraft then took off and the pilot mustered cattle for about the next 15 minutes. The approach prior to the accident was made from the North at about 15 feet with a wind of about 360 degrees at 15 knots. After passing over the cattle, the aircraft pulled up to about 100 feet and levelled for about three seconds. The cattle were now behind and to the right of the aircraft. The left wing and the nose dropped, and the aircraft entered a steep, descending turn to the left until it hit the ground. No pre-accident defects were found with the aircraft. A search of the aircraft logbooks revealed no discrepancies which could have contributed to the accident. Discussions with the observer pilot and pilots who had conducted initial mustering endorsement and subsequent training, indicated a lack of awareness in their own training of airspeed judgement when flying near the ground. Little importance seems to be attached to the different ground speeds when flying into or down wind and the associated perception of airspeed, while the airspeed indicator seems to be largely ignored with wind sound changes used to judge airspeed.

Significant Factors:

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

1. The pilot failed to maintain airspeed.

2. The aircraft entered an inadvertent stall with insufficient height to recover.

3. Pilot training. It is likely that the pilot's training had not placed sufficient stress on the effects of low level manoeuvering in windy conditions whilst relying on airspeed judgement from ground features.

Recommendations:

1. It is recommended that the Civil Aviation Authority surveillance of instructors conducting cattle mustering endorsements, ensure that both ground and air instruction covers the effects of manoeuvering at low level in windy conditions, particularly the awareness of airspeed. Reference CAO Section 29.10 Appendix 1 paragraphs 2(b) (ii) and 2(b) (iii).

The pilot was making an approach in light wind conditions to a 600 metre long strip. Undulations on the surface were such that the slope in the landing direction varied from about 7 up to 4 down. The pilot was using a short-field landing technique. Touchdown occurred just prior to the threshold, and the aircraft bounced. Full power was applied, but the aircraft then touched down heavily 100 metres in from the threshold. The noseleg broke at the fork, the propeller struck the ground several times and the aircraft came to rest at the edge of the strip. The strip did not meet the published requirements for an ALA suitable for Private category operations. The premature touchdown short of the threshold may have resulted from visual illusions associated with the strip slope. The aircraft had stalled during the attempted recovery from the bounce after initial touchdown.

The pilot reported that he had difficulty obtaining effective braking during the landing roll, due to a grassed, wet strip surface. He was able to initiate a groundloop near the end of the landing roll but the aircraft drifted sideways off the side of the strip prior to the upwind threshold. Very heavy rain had fallen during the previous night and up until 30 minutes prior to the landing, and there were areas of standing water on the strip. The airstrip was not suitable for the intended operation.