Collision with terrain

The pilot reported that he had obtained a weather briefing from the Bureau of Meteorology at Cairns, prior to the flight. This information including early morning observations from Mareeba Airport. After selecting a launch site to the south-east of Mareeba, Winds in the area were again assessed using a weather balloon. The departure and flight were uneventful until north-east of Mareeba, when the pilot became aware that the surface wind was a southerly, gusting between 10 and 15 kts.

During the approach to land, at about 90 ft above ground level, the balloon was effected by a wind rotor near some trees. The rotor distorted the canopy and caused it to lose heat. As a result a high descent rate developed. The pilot estimated that about 50 ft of height was lost before he was able to arrest the descent using the burner. During the latter part of the descent, the basket and lower flying wires struck the branches of a tree, causing damage to lower panels of the canopy. A fast landing then ensued. After landing, the canopy was further damage when it became entangled in a barbed wire fence.

The pilot reported that a rain shower was experienced some minutes after the landing. He believed that the unusual localised wind during this accident was due to the approaching rain.

A pilot/aircraft engineer who later assessed the aircraft for recovery purposes reported that the grass was about 60 cm long. The pilot later advised that when he applied full power for take-off, the manifold pressure gauge was indicating 26 inches and tachometer was indicating 2,600 RPM.

As he initiated forward flight the helicopter began to sink and loose main rotor RPM, which he was unable to regain in the time available by lowering the collective control to reduce the main rotor blade pitch angle. He turned the helicopter through 90 degrees to the right, which would have reduced the tail rotor blade pitch angle, but it kept on descending without any rotor RPM increase. He then turned left and tried to find enough room through the trees to afford a recovery, but the main rotor struck a tree about 20ft above ground level and the helicopter rolled to the right before impacting the ground. The pilot and his two passengers evacuated with minor injuries.

The helicopter was 73kg below its maximum take-off weight at departure, and within its longitudinal and lateral balance limits. The temperature was about 28 degrees Celsius and a very high humidity, with the density altitude approximately 2,000ft. In these conditions the helicopter’s performance would have been reduced, but it still had sufficient engine power at take-off to effect a vertical climb, which would have reached its limit when the helicopter was hovering out of ground effect at the top of the climb.

As he changed from the hover to forward flight, the pilot probably increased collective pitch slightly to overcome a loss of height as the cyclic control was moved forward.  This would have started the rotor RPM decay as no more engine power was available to maintain it. There was insufficient height above the treetops for the helicopter to settle and allow time for the rotor RPM to recover when the collective control was reduced, or to obtain airspeed by diving to provide translational lift.

The pilot reported a nil wind condition, but thought he may have experienced a slight tailwind during the climb. In either condition, with the engine power available, he would have had difficulty hovering out of ground effect, then initiating forward flight without some form of translational lift being available, such as a headwind or by diving.

The pilot had planned to conduct a series of tourist flights from the helipad at the rear of the Lodge. A 20 m diameter pad had recently been cleared for the operation. The pad was covered with short grass however, it was surrounded by grass up to 0.5 m high. A shrub-like weed was also woven into the tall grass. Only one passenger was carried on the first of the tourist flights and the helicopter performed as expected. On the second tourist flight, this time with two passengers on board, the pilot flew the helicopter to a 1 m hover and then departed towards the east. As it moved through translational-lift the helicopter descended and the right skid entered the 0.5 m-high grass around the helipad. The grass retarded the helicopter, and the leading edge of the skid made contact with the ground. The helicopter started to roll to the right. The pilot attempted to stop the roll by reducing power. When this was unsuccessful, he increased power to the maximum and attempted to fly out of the roll. This was also unsuccessful, and the helicopter ended up rolling onto its right side.

The helicopter was loaded to just under its maximum weight. The pilot misjudged the amount of excess power that would be available under the prevailing conditions, and he was unable to keep the helicopter clear of the grass during the departure. The scrub-like weed provided sufficient retardation for the right skid to dig into the ground starting a roll to the right. The pilot's description indicates the helicopter had probably entered a condition known as dynamic rollover (Aviation Safety Digest No. 95, 1975, pg. 25) before he started recovery action. As a result, his actions did not work.

The pilot was conducting a swath run parallel to a power line, when the tip of one of the main rotor blade made contact with a power pole. The helicopter was subsequently landed without further incident. This occurrence had not been reported.

The pilot reported that he was conducting mustering operations with a second person on board. While operating at about 50 ft above ground level and at 15 kts indicated airspeed the pilot realized that the helicopter was moving downwind. He immediately increased power, however the main rotor over-pitched, causing the helicopter to land heavily. The wind was from the south-east at 5 kts.

The Air Tractor 502 was conducting spraying operations late at night in fine conditions, with scattered cloud, no moon, and a barely discernible horizon.  After levelling at approximately 200 ft from a pull up and procedure turn, the pilot reported that his attention was drawn to another aircraft which was spraying a nearby property.  Whilst the pilot was watching the other aircraft the Air Tractor struck the ground at an estimated airspeed of 95 knots.

Wreckage distribution and pilot evidence indicated that, following the initial impact, the aircraft became airborne for a further 200 metres, with no engine or electrical power, before again striking the ground and sliding to a stop. The pilot, who had been wearing a full harness, escaped without injury.  The aircraft was destroyed.

The pilot reported that it was the first time he had flown the type of glider, and it had been over 3 years since he had flown a glider with water ballast. Prior to the flight he had forgotten to drain the water, and he had departed with the ballast tank about half full.

As he made his approach to land, during an out-landing, the water shifted causing one wind to drop suddenly. The wing tip hit the top of a fence, yawing the aircraft to the right. The landing gear was torn off on touchdown and the left-wing tip then dug in causing the aircraft to ground loop to the left.

The pilot reported that on arrival over the landing area he noted there was a south-easterly wind of about 30 knots. He therefore planned to land into the south-east. He conducted a low pass in the planned landing direction at about 50 ft above the ground and observed there was no turbulence. He then made an approach at 80 knots with 20 deg of flap selected. At approximately 40 to 50 ft above the ground the aircraft encountered a high rate of sink Despite the application of full power and backstick the aircraft hit the ground heavily, dislodging the nose gear. It then slid for about 25 metres before turning over and coming to rest inverted.

The pilot said there was a hill to the south of the landing area, and he was aware this hill could cause turbulence when there was a southerly wind blowing. However, on this occasion he encountered very strong shear which he now believes is unpredictable in that he did not encounter it when he made the low pass prior to his landing approach.

The aircraft was taking off from an agricultural strip for a rice sowing flight, carrying 1,000 kg of rice seed. The aircraft became airborne momentarily before settling back onto the strip. The pilot was unable to stop the aircraft before it collided with a low fence and a contour bank.

There were active thunderstorms reported in the area at the time, and it is likely that the aircraft encountered adverse windshear during lift-off.