Loss of control

The pilot reports that he intended to conduct a practice flight to rehearse for an upcoming air display. His intention was to activate the aircraft's display smoke system on the runway threshold and complete a tight turn through 360 degrees, prior to commencing the take-off roll. This would be followed by a steep climb out to position the aircraft for commencement of the airborne display routine. A gusting crosswind was blowing across the runway being used for departure.

The pilot indicates that after turning left through approximately 90 degrees, the aircraft accelerated sideways across the grass and the right main wheel began to skip. The pilot was unable to maintain control of the aircraft and the right wheel appeared to dig into the grass runway surface. The aircraft was observed to nose over, before toppling onto its back. The pilot was not injured. The pilot states that the loss of control was most likely a combination of the gusting crosswind conditions and the right main wheel digging into the soft runway surface.

The pilot reported that he descended to approximately 150 ft AGL as he was approaching Bellburn airstrip, and decided to overfly the windsock. He noted that the wind was an easterly breeze of about 7 knots. The pilot then intended to carry out a left turn, fly a downwind leg, and terminate into wind. He then rolled on about 50 degrees of bank, and shortly afterwards the helicopter began shaking violently. The helicopter then rotated through 180 degrees and adopted a nose down attitude. The pilot said he applied full power and full collective control, but was unable to prevent the helicopter striking the ground.

A witness located near the parking area saw the helicopter bank steeply and then begin to descend. The tail rotor then hit a patio attached to an office building and the main rotor struck a tree just before the helicopter impacted the ground.

The pilot of the aircraft reported that the helicopter was being used to spray a sugarcane crop when he attempted to avoid a bird. As he banked the helicopter to the right, he heard two bangs and decided to land the helicopter in an adjacent fallow paddock. During the attempted landing, the helicopter yawed right, and the right skid dug into the ground, rolling the helicopter onto its right side. The pilot was not injured. Examination revealed that the right spray boom had struck the crop during the attempt to avoid the bird.

A portable ELT was carried in the cabin, but it was not activated by the pilot.

The Hughes 269 helicopter had completed a 100 hourly servicing during which, the main rotor abrasion strips were replaced, main rotor damper hydraulic fluid levels replenished, and the landing gear oleos checked to ensure that they were within limits. Ground and hover flight checks were then conducted to adjust blade weights and damper settings. The pilot and licensed aircraft maintenance engineer (LAME) reported that the wind was strong and gusting to about 30 kts. All the landings were made either crosswind or into-wind onto a hard bitumen surface. The LAME reported that, on each occasion, he made only small adjustments to the main rotor damper setting and blade track.

The pilot reported that on each of the flights prior to the accident flight, the helicopter had a significant vibration. At the end of each flight, the pilot would land the helicopter and disconnect the main rotor from the engine so that the LAME could make adjustments to the rotor head and blades. During the flights, the pilot occupied the right seat and the LAME operated the vibration and tracking equipment from the left seat. The LAME reported that during the accident flight, the helicopter's vibration levels and main rotor track had been adjusted to being well within limits, but soon after the pilot had made a very light and gentle landing, the helicopter entered ground resonance.

The pilot reported that after he landed the helicopter and as the engine speed decayed through approximately 2,500 to 2,300 RPM, the helicopter entered severe ground resonance. He forced the collective fully down and wound back the throttle setting. He also attempted to operate the rotor disengage switch but his attempts were hampered by the helicopter's severe vibration experienced during the ground resonance. A witness reported that about 5 seconds after landing, the helicopter rocked three times alternately on each of the two skids. It then spun through 360 degrees before disintegrating. Ground resonance occurs when unbalanced forces in the rotor system cause the helicopter to rock on the landing gear at or near its natural frequency.

Unless corrective action is taken, the amplitude of the vibration increases until the helicopter disintegrates. Corrective actions include immediately becoming airborne as ground resonance can only occur when the helicopter is in contact with the ground or stopping the main rotor as quickly as possible to remove the vibration source. After the helicopter had come to rest, the crew was unable to shut down the engine which continued to operate. A bystander reached into the cockpit to secure the engine and electrical equipment before he and others assisted the crew from the wreckage. There was no fire but the pilot was seriously injured. The LAME received minor injuries. No bystanders were injured.

An examination of the wreckage revealed that there appeared to be no pre-existing mechanical faults. The main rotor system vibration level and blade track were well within limits and the landing gear oleos had been checked during the servicing in accordance with the servicing manual. The landing gear oleos were checked after the accident and were found to be serviceable. Therefore, it was unlikely that a mechanical fault caused the helicopter to enter ground resonance. When the pilot reduced the main rotor speed prior to shutdown, the centrifugal force acting on the main rotor blades also reduced.

The main rotor blades would then have had a potential to excessively flap in response to the gusty wind. The helicopter may then have rocked on its landing gear oleos and subsequently entered ground resonance. Because the helicopter had no apparent mechanical faults, the prevailing wind conditions may have been a factor in the accident. The decision to perform the main rotor track and balance in strong and gusty wind conditions would appear questionable considering that the rotor system would have been experiencing varying degrees of translational lift.

Therefore, stable blade tracking and vibration readings from the equipment would have been difficult to obtain. Because the main rotor RPM was decreasing, the pilot was unlikely to have recovered the helicopter from ground resonance because both the recovery techniques were unavailable to him. He was unable to disconnect the main rotor from the engine due to the helicopter's vibration and, the quick development of the ground resonance meant that it was also unlikely that the pilot had sufficient time to re-accelerate the main rotor and take-off.

The pilot was flying a Cessna 185 aircraft on a VFR charter flight from Moorabbin to Peterborough with 2 passengers. On arrival at Peterborough he overflew the strip and estimated the wind to be from 220 degrees at 5 to 7 kts. The strip has an uphill gradient to the east, and, even though this would result in a slight tailwind from the right quarter for the landing, the pilot elected to accept this and make use of the uphill gradient.

The landing was reported to have been smooth and light and was accomplished with a trickle of power and full flap (4 stages). During the roll out the aircraft diverged slightly left and then made a rapid and increasing swing to the right. Application of rudder and brake was not able to stop the developing ground loop. The aircraft left the mown strip with the group loop tightening until the left main landing gear collapsed. The aircraft came to rest pointing back down the strip towards the touchdown point.

After shutting down the engine the pilot and passengers evacuated without assistance or injury.

The pilot considered that he should have used a different technique when landing. A powered approach with 2 stages of flap, raising the flaps as soon as possible after landing, and using power to ensure adequate rudder authority during roll out would have result in control of the aircraft being maintained.

A Cassuit Racer had completed a short flight in the Camden area. The pilot reported losing directional control on touch down, following a normal approach and flare. The aircraft nosed over during the accident sequence, causing damage to the lower engine cowl and propeller.

The pilot had recently purchased the aircraft, and this was his first flight on type. As it is a single seat aircraft, he was completing a self-endorsement under the supervision of another pilot.

The student helicopter pilot was conducting his second solo flight at Hoxton Park. The weather was fine, with almost no wind. Prior to commencing the solo phase, the student had completed a satisfactory dual circuit check.

As the instructor walked away from the helicopter, he heard a "thump'. As he turned around, he saw the helicopter had rolled onto its side, causing substantial damage to the rotor blades. The accident was consistent with 'dynamic rollover'. The student was not injured and was able to exit the helicopter.

As the student had commenced to lift off the helicopter had rapidly rolled to the right. Although he had expected there would be some rolling tendency, the rate of roll was greater than the student had anticipated, and he had been unable to prevent the rollover.

The pilot reported that while he was conducting a turn above some cattle, the aircraft appeared to lose speed and altitude. The aircraft was about 75-100 ft AGL at the time. The pilot pushed the control column forward and applied full power. However, this had little effect, and it became obvious that the aircraft was going to strike the ground. The pilot said that just before impact, he pulled back on the control column. The pilot could not recall looking at the airspeed indicator during the final stages of the flight, and did not recall hearing the stall warning sound. However, he considered it likely that the aircraft stalled during the turn and that there was insufficient height above the ground for him to effect recovery to normal flight.