The aircraft reported departing Bundaberg for Monduran Dam on a no SAR flight at 1135 hrs EST with three persons on board and an endurance of 270 minutes. The purpose of the flight was to complete the endorsement of the pilot under check and to assess the suitability of an area of water on the coast to where the passenger, who was the regular pilot of the aircraft, was to fly the aircraft the following day. The pilot in command had flown 27 hours in the previous three months, of which 9 were on type. The pilot under check had flown only one hour in the last three months. This flight had been in VH-BSL. At approximately 1200 hrs, the aircraft was observed in the Lake Monduran area. It flew two left hand circuits, landing into wind towards the dam wall each time. After the second takeoff, it turned left and was seen heading north from the lake. Nothing further was heard or seen of the aircraft. Following an extensive search, the wreckage was located six days later lying inverted in 15 metres of water approximately 2 km WNW of the dam wall in the area of the junction of the main east-west channel and a north-south channel of the lake. Both floats had separated from the aircraft and the right float was severely torn for about half its length. There was substantial water impact damage to the windshield frame/cockpit roof area and to the upper leading edge surfaces of both wings. No fault was found with the aircraft or its systems which might have contributed to the accident. It could not be determined who was manipulating the controls of the aircraft at the time of the accident. Evidence was obtained that it was the habit of the check pilot to have pilots undergoing endorsement or check to fly two circuits landing into wind and then to carry out crosswind landings. The check pilot and the pilot under check had previously operated at the dam and alighted on to both the east/west and the north/south channels. Having been observed to fly two into wind circuits and then head north and not be sighted again, it is possible that the aircraft then commenced crosswind operations onto the north/south arm of the lake, landing in a southerly direction with a crosswind from the left. Information from the Bureau of Meteorology indicated that the surface wind in the area at the time of the accident was 090` magnetic at 15 knots. This information was confirmed by witnesses at the dam wall who observed white caps on the surface of the dam. The north/south channel of the lake was bounded on its east side by steep hills rising to 70 metres above water level. The effect of this high ground was to partially blanket the north/south channel from the easterly wind. The position of the wreckage was in the area where the wind shadow effect would have ended and where the wind would have blown at full strength along the main east/west channel of the lake. The crosswind limitation for the aircraft as stated in the flight manual was 8.7 knots. Commenting in early 1988 on an enquiry regarding the raising of this limit, the aircraft manufacturer emphasised the 8.7 knot limit and advised that any test work to raise the limit should proceed cautiously starting at or below the current (8.7 knot) limit. If the aircraft was conducting crosswind operations in the north/south channel, and suddenly encountered a 15 knot crosswind on exiting the wind shadow area, the control difficulties confronting the pilot could have been significant. The aircraft wreckage was intact except for the floats which had been torn off by water impact forces. The right float was severely damaged while the left was intact. The forward tip of the right float had been severed by the propeller. The remaining forward section had then been forced upwards and outboard and had broken off. This weakened the float support structure, causing it to fail, and allowing the remaining section of the right float to strike the right side of the fuselage just aft of the cabin. Damage of this type an magnitude was most probably caused by the nose of the right float digging into the surface of the lake at relatively high speed. For this to occur, the aircraft was banked to the right at float impact - a possible consequence of encountering a strong crosswind from the left. There was no evidence that the aircraft had hit a submerged object.

After landing in a sheltered gully, the pilot became concerned that the retrieval crew might not have access to the area. He therefore elected to proceed to another area about 3 kilometres away. At this location, a landing was carried out in 10 knot wind conditions. The basket made a hard flat contact with the ground, before being pulled over on its side by the deflating balloon canopy and the wind. Because of the possibility of the balloon making contact with a fence during the landing, the pilot had instructed all passengers to squat below the edge of the basket, which possibly made their stance for the landing unstable. One passenger received a fractured ankle when her leg twisted under her as the basket rolled over.

Circumstances:

The pilot was conducting spraying operations in a large wheat paddock. The aircraft was being flown about two metres above the crop and the pilot intended to pass to the right of a large tree near the end of the particular swath run. The aircraft suddenly swung violently to the left as the wheels entered the crop. By the time the pilot managed to pull the aircraft clear, it was heading for the tree. While attempting to manoeuvre the aircraft, the pilot was unable to prevent it from striking the ground.

Significant Factors:

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

1. Contact with the crop on spray run, reasons undetermined.

2. Aircraft struck the ground during pilot attempt to avoid a tree.

The aircraft had been engaged in spraying cotton fields in generally turbulent flying conditions. Power lines crossed one end of the area at an angle of about 20 degrees to the direction of the swath runs. At their lowest point, these wires were about 10 metres above the ground. The pilot reported that as he approached the power lines, intending to fly underneath at the lowest point, the aircraft ballooned upwards in turbulence. Despite corrective action the cockpit mounted wire deflector struck the lines. The deflector was broken and much of the fin and rudder was torn from the aircraft, which subsequently impacted the ground about 800 metres from the power line.

Circumstances:

The pilot reported that the engine run up checks were normal, with the engine operating for about ten minutes before the take-off was commenced. During take-off, no anomalies were noted by the pilot, however, at about 100 feet the engine lost nearly all power. The pilot attempted to turn back in order to land on the strip. During the turn, control was lost, and the aircraft struck the ground. The area beyond the strip where the power loss occurred was mainly open farmland. The occurrence of a major power loss at low height gave the pilot little time to assess the situation. Inspection of the aircraft did not reveal any mechanical defects which might have caused the engine power loss. The pilot had been using a mixture of Avgas and unleaded motor fuel. This aircraft type was not approved to operate using automotive fuels. Atmospheric conditions were conducive to the formation of significant carburettor ice under all engine power conditions. The use of automotive fuel may have increased the possibility of this occurring. Inspection of the stall warning system revealed that the screws securing the connections to the wing mounted vane assembly were loose, and the system had been inadequately maintained. It was likely that the system was not operating at the time of the accident.

Significant Factors:

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

1. Conditions conducive to carburettor ice formation.

2. Use of non-approved fuel.

3. Engine power loss at a low height.

4. Pilot attempted to turn back to land on the strip from too low an altitude.

5. Poor condition of the stall warning system.

6. Pilot did not ensure adequate airspeed was maintained.

Circumstances:

While taxiing after a normal landing, a rumbling noise was heard from the vicinity of the nose gear, the hydraulic low-pressure light illuminated, and nose gear steering authority was lost. The right hand nosewheel had separated from the aircraft due to fracturing of the axle. As the nosewheel departed it damaged the nose gear uplock assembly with consequent loss of hydraulic system integrity. It then continued under the fuselage causing skin damage. The nosewheel axle was recovered and subjected to metallurgical examination which showed that the fracture was due to fatigue. The fracture resulted from prior long term fatigue cracking which occupied approximately 75 of the cross sectional area of the axle. Stress corrosion cracks were present which were the most likely initiator of the fatigue cracks. A mandatory crack inspection requirement called up for this axle did not cover the specific area in which the stress corrosion was located. Consequently, during the axle refurbishment, the stress corrosion cracks were covered by a layer of electroplated chromium. Upon advice of the failure mode by the Bureau, the operator carried out an inspection of all Inservice and spare axles, to remove any axles with stress corrosion under the electroplated chromium.

Significant Factors:

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

1. The nosewheel axle failed due to fatigue initiated by stress corrosion cracks.

2. The recurrent Non Destructive Inspection for the axles does not address the area where the stress corrosion occurred. Consequently, pre- and post- refurbishment inspections did not detect the cracks.

Recommendations:

1. The Civil Aviation Authority consider extending the current mandatory Non Destructive Inspection for the axles, to address the area discovered in this accident.

Spraying runs were being conducted over a paddock which had power lines along one boundary. The pilot had been passing beneath the lines during each run, however after completing about two thirds of the task the wire deflector on the aircraft snagged and broke the powerline. The pilot carried out a precautionary landing and discovered that the rudder of the aircraft had been substantially damaged by the wire strike. At the point where the wire strike occurred there was less clearance between the wires and the ground than that available during previous swath runs. The pilot was aware of the situation, but had been subject to a visual illusion, which had led him to believe that there was sufficient clearance to allow the aircraft to pass beneath the wires. By the time he realised that the clearance was insufficient he was unable to take avoiding action, and had elected to allow the wire to strike the deflector, rather than risk the landing gear contacting the ground. The anti-snag deflector plate on top of the rudder had failed, allowing the wire to contact the rudder. The upper portion of this component had then been torn from the aircraft.

The flight was intended to provide familiarisation for the pilot on the aircraft type. After loading water into the hopper the pilot took off and carried out a series of turns before positioning for a spray run along one of the flight strips. At the end of the run the aircraft pulled up steeply and began banking to the right. It then appeared to enter a spin to the right and subsequently struck the ground in a steep nose-down attitude with little forward speed. The pilot had been instructed to load 100 gallons of water for the purpose of this exercise. Unsupervised, the pilot loaded 200 gallons of water which resulted in the aircraft being operated at the maximum all up weight approved agricultural overload. It subsequently stalled in a procedure turn at a height from which the pilot was unable to effect recovery before impact with the ground.

The pilot was conducting spraying operations on a pea crop. Swath runs were being made at right angles to a power line and low trees which were located just beyond the end of the crop. On the final run, the aircraft was flown beneath the power line, but the right wing then struck the top branches of a dead tree. The aircraft was seen to climb to about 200 feet, before descending steeply and striking the ground some 370 metres beyond the point of collision with the tree. A fierce fire broke out on impact and engulfed the wreckage. Previous swath runs had almost certainly been made with the aircraft passing above the power line. The reason the pilot chose to fly under the line on the final run could not be established, as there appeared to be no operational reason for this course of action. Expert opinion indicated that after passing below the line, a collision with the tree was virtually inevitable.

The pilot undergoing the check flight had completed a helicopter instructor course about two months earlier and had not flown this helicopter type for nine years. He was being checked for future employment as a Grade 2 helicopter instructor. The early part of the flight was conducted in the training area where various types of circuit and approaches were carried out satisfactorily. On return to the aerodrome the instructor demonstrated an autorotation to touchdown. The pilot under check then conducted two autorotations to touchdown. The instructor reported that during the touchdown phase on the second landing the other pilot applied excessive collective control. He attempted to correct the situation but was physically unable to prevent the other pilot from raising the control. Rotor rpm decayed excessively and the tail boom was severed in the ensuing hard landing. The pilot under check was experienced on another type of helicopter requiring a different landing technique from this one. He was also not used to having another pilot making control inputs and did not give precedence to these inputs. The instructor had evidently made no verbal comment to the other pilot that he was applying corrective inputs to the controls.