Collision with terrain

The aircraft was engaged in spreading Gypsum from an airstrip with an elevation of 3,200 ft. Take-offs and landings were conducted towards the west, with the wind varying from the northwest to the southwest and increasing in strength. The pilot reported he had encountered high sink rates and turbulence in the treatment area on previous flights.

Acceleration and lift off during the next take off appeared normal but the aircraft almost immediately began to sink. The pilot lowered the nose and activated the load dump system. However, the sink could not be arrested, and the aircraft collided with a fence. The engine and both wings were torn off.

The pilot landed the helicopter in an open grassy area to refuel from jerry cans.

He then decided to reposition the helicopter about 10 metres forward from the original landing point, and after the passenger alighted lifted the helicopter into the air and applied forward cyclic. It suddenly pitched forward sharply as if the front of the skids were caught, the main rotor blades striking the ground before the pilot could regain control.

The landing area was covered with medium height stiff grass that may have fouled the skids as the helicopter became airborne.

The pilot was taking some friends on joy flights. She obtained permission to use a glider parked and ready to fly. Although she had not flown the type before she had flown a type considered to be almost identical. She was also briefed on the altimeter setting procedures in use by the club but was permitted to use her preferred method.

On the first aero-tow the glider released at 4200ft, some 3000ft above the field elevation. This was in accordance with advice received during the pre-flight briefing. No difficulty was encountered with height control during that flight. The second aerotow was terminated at 3200ft, only 2000ft above field elevation. In the latter stages of that flight the aircraft was very low near the landing area. However, the flight was continued in accordance with a standard circuit.

When turning on to the final, the aircraft was just above the trees. Speed brakes were deployed, and the right wingtip struck a tree. The aircraft collided with the ground in a steep nose-down attitude and came to rest inverted. Witnesses assisted in evacuating the occupants.

The gliding community had recently changed altimeter setting procedures from setting zero altitude on the ground (QFE) to setting airfield elevation (QNH). This should have presented no problems to new pilots who would be trained in the new method, but it could present problems to experienced pilots familiar with the old system. This pilot expressed a dislike for the new procedure, saying that it required additional calculations to be made. She was permitted to use whatever system she desired.

For this flight she had set the rear altimeter (she was in the rear seat) using QFE and the front altimeter to QNH. As a result, she should have been quite familiar with the readings on her altimeter and been able to correlate those readings with the external appearance of aircraft height.

Some confusion evidently developed during the flight, leading her to become confused as to the significance of the readings from the altimeter. The result was that the aircraft was much lower in the circuit area than she expected and she did not detect the low height from observation outside the aircraft.

The operation of speed brakes on final approach appears to have been a reflex action which was inappropriate under the circumstances.

It is likely that the whole sequence was initiated when the pilot released from the tow about 1000ft lower than on the previous flight. This was probably unintentional and due to misinterpretation of the altitudes indicated on the altimeters. The false perceptions initiated at that time remained with her for the duration of the flight.

Significant Factors

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

1. The pilot was not familiar with the altimeter setting procedures to be used.
2. The glider was released from the tow about 1000ft lower than intended.
3. The pilot relied upon altimeter readings rather than external reference for height close to the ground.
4. The pilot mis-handled the speed brake on final approach.

The pilot had been spreading superphosphate in a paddock to the north of the strip. To get to the paddock the aircraft had to climb over hills. This was achieved with the assistance of updraughts off the hills. On the accident flight the pilot found the updraughts were not present and the aircraft was not climbing adequately. Concerned that he would not be able to clear trees ahead the pilot dumped the load and attempted to turn left. The aircraft struck a tree and spun to the ground. The pilot escaped from the wreckage, but the aircraft caught fire and was destroyed.

While enroute from Batchelor to Tindal, the pilot encountered deteriorating weather conditions and landed the aircraft in a suitable paddock, on Bonrook Station. The following day he inspected the landing area and judged the length to be 500 metres and that the area was suitable for take-off. However, the weather conditions were still unsuitable for departure.

The next day, after obtaining a weather forecast and being satisfied that the weather was suitable, the pilot decided to continue the flight. He and his passenger boarded the aircraft, and the pilot configured the aircraft for a short-field take-off. During the subsequent take-off the pilot rotated the aircraft at 55 kts. It became airborne and commenced to climb clear of the 10-metre-high trees at the end of the strip. However, the pilot became concerned about a tall tree directly ahead and commenced a left turn to avoid the tree. The stall warning sounded, one wing dropped, and the aircraft impacted the trees. The pilot suffered minor lacerations to his head, probably as a result of being struck by sections of the broken windscreen, and the passenger received minor bruising.

Checks of the fuel did not reveal any contamination, and the pilot believes that the engine was operating normally during the take-off.

An inspection of the take-off area revealed that the surface was firm and that the grass had recently been slashed.

The performance charts contained in the flight manual show that the strip distance available was adequate for a take-off from a dry grass runway. However, on this occasion, it is likely that the surface was wet and covered in recently slashed grass and that take-off performance was degraded. The pilot was not familiar with operation from such strips.

The student pilot, returning from a solo training session, carried out a normal circuit and approach for landing, but the aircraft bounced slightly on touchdown. The pilot applied some forward elevator control, but the aircraft veered about 90 degrees to the left and ran off the runway.

The pilot unsuccessfully attempted to control the swing with right rudder, then applied full power to go-around. She then observed another aircraft taxiing and turned the aircraft left to avoid that aircraft. The left wing struck the ground and the aircraft cartwheeled.

The student pilot/owner and an experienced private helicopter pilot, who was not endorsed on type and did not hold a valid medical certificate, decided to ferry the helicopter. Enroute, they elected to enter an autorotation to practise a forced landing from about 1,000 feet above the ground. When attempting a power recovery near the ground, they realised that the engine had stopped. During the autorotative touchdown the main rotor cut through the tail boom. The landing gear skid assembly broke, and the helicopter rolled onto its left side.

No mechanical failure of the airframe or engine has been found which may have contributed to the accident.

At the time of the flight the relative humidity was about 88% and the outside air temperature about 13 degrees Celsius; conditions were ideal for the formation of carburettor icing. The engine is water cooled and is fitted with a water jacket on the carburettor. If the tap adjoining the carburettor is turned on, hot water will circulate to warm the carburettor and thereby counteract carburettor icing. On the standard Rotorway EXEC 90, the tap must be turned on before flight because there is no means to turn it on from the cockpit. On VH-YCP, the tap was turned off.

Subsequent to the accident it has been noted that the carburettor air temperature gauge fitted to the console reads about 10 degrees celsius colder using the external air scoop, which is an Australian modification, as opposed to the original Rotorway design. Since the accident, the Civil Aviation Authority has amended the permits to fly. Until the matter of carburettor heat is resolved, the induction anti-icing system must be turned on for all flights in conditions of outside air temperature below 24 degrees Celsius; and flight in conditions of outside air temperature 10 degrees or below in visible moisture is not permitted.

Significant Factors

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

1. The carburettor heat water jacket was not turned on before the flight.

2. Prevailing conditions were conducive to the formation of carburettor icing.

3. The engine probably failed due to carburettor icing.

The helicopter was cruising at 200 feet above ground level whilst the pilot searched for a vehicle that he wished to rendezvous with. Having sighted the vehicle coming towards him from the right front quarter, the pilot decided that rather than conducting a fly-past to attract the driver's attention he could achieve the same result by landing the aircraft beside the road and in front of the vehicle. To achieve this the pilot placed the helicopter in a hard right turn and entered a steep descent. As the helicopter rolled out of the turn the pilot realised that he had insufficient height available to completely arrest the descent before impact. Although the pilot's attempt to cushion the landing was partly successful, the aircraft touched down heavily and somersaulted.

The pilot reported that shortly after take-off, at approximately fifteen feet above ground level, the aircraft yawed to the right and collided with some low scrub. The aircraft came to a stop clear of the right hand side of the strip. It was also reported that the strip met all requirements and that there were no apparent control malfunctions.

The reason for the loss of control was not determined.

The owner pilot and his wife flew to Cape Naturaliste where a water landing was carried out and the aircraft was taxied on to the beach. On departure the aircraft was positioned for a water take-off into a 10-knot southerly breeze on a slight sea. The pilot reported that the aircraft lifted off after a few bounces at the end of the water run and was held level to build up climb speed. Shortly thereafter the aircraft appeared to yaw violently to the right, rolling to the vertical. The right wing entered the water, and the aircraft cartwheeled coming to rest nose down and inverted. The pilot was flung clear, and his wife was able to extricate herself from the wreckage. Both were supported in the water by their life jackets while awaiting rescue. The aircraft sank and was not recovered.