Loss of control

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.

While taking off for parachute dropping operation, directional control was lost and the aircraft ground looped. The left main landing gear collapsed, substantially damaging the aircraft. All six occupants evacuated the aircraft without injury.

The pilot subsequently reported that, as take-off power was applied, the aircraft started to swing to the left. He applied right rudder to correct the swing, but the aircraft then swung rapidly to the right. He was unable to counteract the swing and closed the throttle to stop the take-off. However, the left wheel ran into a culvert and was torn off before the aircraft could be stopped.

The pilot was conducting circuits to gain familiarization with the aircraft. Late in the landing roll he encountered a willy-willy, which caused the aircraft to swing. Using right brake, the pilot was unable to control the swing, and the right wheel assembly broke off. The right wing fell to the ground and the pilot exited the aircraft when it stopped.

The aircraft was not fitted with an electronic locator beacon.

The pilot reported that he departed Mareeba in company with another R22 helicopter at approximately 1645 EST. The flight was intended to proceed from Mareeba to Cairns via Stoney Creek. The pilot stated that approaching Stoney Creek (5NM west of Cairns aerodrome) they landed to assess the weather further. After consultation with Cairns approach they were advised that Stoney Creek was visible from the control tower. Both helicopters then took off to continue to Cairns. The pilot said that shortly afterwards, and before reaching Stoney Creek the weather ahead deteriorated suddenly, and the pilot decided that they would return to Mareeba. A turn to the right was commenced, and shortly afterwards the helicopter began to yaw uncontrollably to the right and descended into trees. The passenger was uninjured and was able assist the pilot from the aircraft. The pilot then used his mobile phone to call for assistance and guide the Queensland Emergency Services rescue helicopter to the crash site. The passenger and pilot were winched from the site and flown to the Cairns Base Hospital.

Subsequent examination of the helicopter revealed no technical defect which may have contributed to the accident. The pilot described the control loss as an uncommanded yaw to the right, indicating loss of tail rotor authority. The pilot said the last time he observed the indicated airspeed it was 40 knots and was unable to explain the uncontrolled yaw right. Although there was no discernible horizon at the time, the pilot said he was flying towards a clear area, was visual with the ground, and was clearly visible from the other helicopter which was slightly higher and to his right.

The recently rated agricultural pilot was conducting circuit and landing practice in a Cessna Ag wagon. Whilst landing on runway 04 the right brake lost effectiveness, resulting in the pilot losing directional control. The aircraft ground looped to the right, damaging the right landing gear and right wing, before coming to rest adjacent to the runway. The weather was CAVOK with light winds.

The Cessna 210 was engaged in flying tourists between Broome and Cape Leveque. The pilot had been with the company for one and half months and had flown eight hours in the Cessna 210. A substantial portion of his previous flying experience was in Cessna 172 and 182 aircraft. The pilot flew the aircraft to the Cape Leveque landing area at approximately 0930 WST. At around 1100, he loaded the aircraft and embarked his passengers; four adults and a five month old baby being held by his mother. The weather was fine with a light south easterly breeze. The pilot then attempted to start the engine but the starter would not energise. After consulting with the company's chief pilot, the pilot successfully started the engine.

The pilot completed his pre-take-off checks and began the take-off run. After approximately 200 metres, the pilot's side window opened. The pilot stated that the sudden noise surprised him and that he was concerned about dust entering the cabin and upsetting the passengers. He attempted to close the window whilst continuing the take-off run. The pilot stated that he managed to close the window but it immediately opened again. He recalled noticing in his peripheral vision that the aircraft was veering left. Evidence indicated that the aircraft veered approximately ten degrees left and continued in a straight path diverging from the runway centre.

The pilot returned his attention back to the take-off and believing the aircraft had sufficient airspeed, attempted to continue the take-off. He stated that just as he was pulling back on the control column to take off, the aircraft seemed to decelerate. Evidence indicated that the aircraft wheels struck freshly graded sand on the edge of the flight strip. Witness evidence and the wheel tracks in the sand indicated that the aircraft had pitched nose up and banked right with the right landing gear remaining in contact with the ground. With the throttle open, the aircraft continued for approximately 72 metres towards scrub adjacent to the runway.

The left wing struck a tree, slewing the aircraft left. The aircraft then continued sliding right before travelling forward into the scrub, impacting trees and stopping. The pilot and passengers evacuated through the right door. The aircraft's ELT operated correctly. It is probable that the pilot was distracted from controlling the take-off by the sudden and unexpected noise created by his window opening. There was sufficient available runway length for the pilot to discontinue the take-off and secure the window once stopped. The pilot could have also continued the take-off and attended to the window once safely airborne. He decided, however, to close the window while continuing the take-off. With his attention diverted in attempts to latch the window, he did not keep the aircraft tracking along centre of the runway. After the pilot realised that the aircraft had diverged left, he decided to continue the take-off without regaining the runway direction. The aircraft failed to become airborne, possibly slowed by the sand along the runway perimeter.