Collision with terrain

The flight was to be a period of solo practice exercises following the completion of a Commercial Licence flight test a number of weeks earlier. The pilot conducted a number of circuits and landings, and on this circuit was carrying out a power termination autorotation landing from 800 feet above the ground. As he commenced levelling the helicopter from the flare, he felt a bump at the tail. He landed the helicopter and shut the engine down. An inspection revealed that the tail rotor had contacted the ground, severing the tail rotor blades. The resultant vibration and imbalance caused the tail boom to fracture and the horizontal stabiliser to became detached. No pre-existing defect was found with the helicopter which could have contributed to the occurrence. It was evident that the pilot had misjudged his height above the ground during the landing flare.

During the flight the pilot encountered gradually deteriorating weather conditions, forcing him to reduce his cruising altitude from 5500 feet initially, to below 3500 feet. Cloud covered the tops of the adjacent ranges and there were showers and associated low cloud in the accident area. The aircraft struck the ground at 2140 feet amsl, while flying level, banked 20 degrees right, under control and on a heading 80 degrees to the right of the flight planned track. Shortly before the accident occurred the aircraft entered an extensive area of hill fog whilst being flown at low level and at cruising speed. The pilot was probably attempting to turn back when the aircraft collided with trees on higher ground than a valley he had just overflown.

Circumstances:

The daily flying program authorised the instructor to fly with the student for a period of general flying revision in the training area. Prior to boarding VH-BUO the instructor discussed with the instructor from another Cessna aircraft, VH-HCE, his intention to proceed on a scenic flight to Lake Burragorang. The specific intention was to view an old telephone box located on an island of Kerswell Point. As the instructor from VH-HCE had not flown in this area it was agreed that both aircraft would proceed in company, with VH-BUO leading. Approaching Lake Burragorang, both instructors established radio communications on a VHF discrete frequency. When in the vicinity of the western extremity of the lake both aircraft descended and turned to take up a generally easterly track over the water. It was reported the aircraft levelled at a height of approximately 500 feet above water level. Approaching Kerswell Point from the west, VH-HCE gradually closed on VH-BUO. When the aircraft were about one kilometre east of Kerswell Point, VH-HCE passed to the right of VH-BUO with a lateral separation of 100 to 200 metres. The crew then lost sight of VH-BUO which appeared to be in a shallow climb and about 100 feet higher than VH-HCE. The instructor in VH-HCE attempted to call VH-BUO on the discrete frequency, but there was no response. There was no further contact with VH-BUO. Concerned by the sudden loss of contact, the instructor of VH-HCE turned back towards Kerswell Point. When there were no sighting of the Cessna and no radio contact, he set heading for Camden. However, about 10 kilometres from Camden, he again returned to the Kerswell Point area for another unsuccessful search. Upon returing to Camden the instructor reported that VH-BUO was overdue. A search was begun later in the afternoon but it was not until the following day that wreckage from the Cessna was found on the shoreline south of Kerswell Point. The aircraft was eventually located on the lake bed by sonar in 47 metres of water, approximately 3 kilometres east of Kerswell Point. The wreckage was subsequently recovered and an examination revealed the aircraft had collided with the water at a speed of about 100 knots, consistent with the aircraft being in a shallow descent and moderately banked to the left at the time of impact. No evidence was found to indicate the aircraft was other than airworthy immediately prior to the accident. Weather conditions over Lake Burragorang at the time of the accident were reported to be fine and clear with an easterly breeze of 5 to 10 knots, and scattered cloud at 3500 feet. The events which occurred immediately before the collision with the water, were not positively determined. However, the circumstances of the accident are consistent with the aircraft being operated at a very low height. During the course of the investigation, evidence was obtained concerning the conduct of operations by the training organisation which reflected adversely upon the level of supervision. These matters were bought to the attention of the appropriate authorities for separate investigation.

Significant Factors:

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

1. Unauthorised low flying in an environment conducive to visual illusions.

2. Inadequate level of supervision exercised over the conduct of flying training operations.

Circumstances:

The aircraft had flown from Bendigo to Mudgee where it was refuelled. After leaving Mudgee the pilot diverted from his planned route due to weather and tracked via Muswellbrook, Maitland, Gloucester, and Taree. At 1626 hours the pilot reported at Port Macquarie at 5 000 ft and requested airways clearance. The aircraft was cleared to track coastal to Coffs Harbour and to enter the control area at 4 500 ft. The pilot's acknowledgement of this clearance was the last recorded transmission from the aircraft. The estimated entry time for the control area (at 25 nm from Coffs Harbour) was 1642 hours. At 1645 Coffs Harbour Flight Information Service attempted to contact the aircraft for traffic purposes, but there was no reply. At 1807 hours a search aircraft reported an Emergency Locator Beacon signal on 121.5 MHz in the South West Rocks area. However, due to the inaccessible nature of the terrain, and mist after dark, the wreckage was not found until 0330 on the following morning. The accident site was in the Hat Head National Park, about 38 nm from Coffs Harbour, and about 4 nm east of the direct Port Macquarie to Coffs Harbour track. The aircraft had struck trees, in a wings level attitude, at a descent angle of 16 degrees to the horizontal, on a track of 021 degrees. Although subsequently destroyed, the aircraft had been intact at initial impact. Witnesses reported that a severe electrical storm with hail had passed through the area between Kempsey and South West Rocks between 1630 and 1700 hours. Based on estimated time intervals and known groundspeeds, it was considered that the accident occurred at about 1638-1640 hours. A Bureau of Meteorology analysis indicated that at this time the severe thunderstorm would have been almost over the accident site. Severe updraughts and downdraughts are known to occur in the vicinity of such large storms and the magnitude of such downdraughts could exceed the climb capability of a light aircraft.

Significant Factors:

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

1. The pilot continued VFR flight into adverse conditions.

2. Weather conditions were extreme with a severe thunderstorm.

3. The pilot encountered circumstances beyond his control and was unable to prevent the aircraft descending into the ground.

The pilot had completed a number of take-offs and landings from the one-way agricultural strip prior to the final flight. On each of the previous flights the pilot had turned right after take-off, climbed out and and carried out spreading operations over ground that fell away from the strip. On the final flight the pilot was to carry out spreading on a paddock to the left and uphill from the strip. The pilot inspected the rising ground and assessed that the aircraft's performance was sufficient to outclimb the rising ground with safety. The final take-off was normal until the pilot had reduced power, raised the flaps and commenced a slight left hand turn. At that point the pilot observed that the aircraft appeared to lose height, relative to the ground, and he considered dumping the load and landing the aircraft on the up slope. He rejected both of these options as he considered that obstructions caused by a fence and a powerline would make the situation worse. Before the pilot could take any further action the aircraft's mainwheels touched down, the aircraft bounced back into the air, collided with the fence and came to a stop in a recently ploughed and planted paddock, just short of the powerline. At the time of take-off, wind conditions may have created slight downdrafts. The gradient of the rising ground was about 7 percent. With optimum conditions (airspeed control, engine performance, etc.), at the prevailing density altitude and aircraft weight, the aircraft could have been expected to outclimb the rising ground. In this case the conditions were not optimum and the aircraft flew into the ground and fence.

The pilot conducted a daily inspection of the helicopter prior to meeting another company pilot to fly two helicopters to a mustering camp. After start he reported by radio to the pilot of the lead aircraft that he was ready to depart. Ground witnesses saw the two helicopters depart in company. The lead pilot proceeded to Hell's Gate and landed but the second aircraft did not arrive. The second helicopter was found one day later about 7 km from Doomadgee and on the extended centre-line of the runway. Examination of the wreckage indicates that the helicopter struck the ground inverted and with a high rate of descent. No pre-existing defects were found in the helicopter. No evidence to indicate that the pilot was other than healthy or suffered from any incapacitation was found during a post-mortem examination. While the factors associated with the cause of this accident were not determined, one possibility is that the pilot suffered a flicker induced seizure. This phenomenon can be caused by the passage of sunlight through the main rotor creating a strobe effect in the cockpit. It may have resulted in control inputs, by the pilot, which could have caused the helicopter to become inverted and crash.

Circumstances:

The aircraft had been refuelled from drums at a refuelling point located at one end of the lagoon. The refuelling point was surrounded by tall trees, so the pilot decided to hover taxi out over the lagoon and to execute a take-off from a more open area. The take-off had to be initiated with a slight tailwind, and the pilot intended to turn and to depart upwind after the aircraft had obtained translational lift. As the pilot initiated the take-off, the aircraft experienced a tailwind gust and began to lose height. In an attempt to check the descent, the pilot overpitched the main rotor. The right skid contacted the water surface and the aircraft simultaneously pitched forward and rolled to the right before coming to rest on the lagoon bed. The two occupants evacuated the aircraft without injury.

Significant Factors:

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

1. The aircraft experienced a tailwind gust as the pilot initiated the take-off.

2. The pilot overpitched the main rotor while attempting to counter height loss from the gust.

3. Loss of lift resulted in the right skid contacting the lagoon surface. This accident was not the subject of an on-scene investigation.

Circumstances:

The aircraft was loaded close to its maximum all-up weight and departed from runway 24. The take-off was normal, and the aircraft was airborne within 500 metres. After take-off, a right turn was commenced which is normal procedure to avoid the rising terrain. The aircraft was apparently performing normally and climbing at about 65 to 70 knots. However, approaching a row of pine trees, it began to lose height. Despite the pilot maintaining the aircraft in the climb attitude, and using full engine power, the aircraft continued to lose height until ground impact. Although fire rapidly developed after impact the pilot successfully assisted the passengers to evacuate. No pre accident defects were found with the aircraft which could have contributed to the accident. At the time of the accident, a low pressure of 995 hPa was situated over the area. This combined with the surface temperature of about 28 to 30 degrees Celsius to produce a density altitude of 4650 feet at the airfield which is 1850 feet above sea level. The weather pattern was also producing gusty winds and mechanical turbulence over the surrounding hills. A combination of high-density altitude and high aircraft all-up weight resulted in a best achievable rate of climb of about 400 feet per minute. This was reduced by the effects of downdrafts, turbulence, and the turn, with the result that the aircraft could not outclimb the terrain.

Significant Factors:

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

1. High density altitude.

2. High aircraft all-up weight.

3. Turbulence and downdrafts over the surrounding hills.

4. Pilot's low aeronautical experience level.

Circumstances:

The purpose of the flight was to revalidate the Night VFR rating of the pilot under check. The pilots intended to conduct several circuits and then carry out a short navigation flight. The flight apparently proceeded without incident during the startup, taxi, and take-off from runway 12. The tower controller reported that he then saw the aircraft initiate a turn as if to fly a right circuit, contrary to previously acknowledged directions for left circuits. When this was queried by the tower, the crew confirmed that they intended to carry out a left circuit, and the aircraft was then seen to turn left. This was the last sighting of the aircraft by the controller as he then transferred his attention to other aircraft. When the aircraft later failed to reply to calls from the tower, a SAR phase was declared and this later developed into a full scale search for the aircraft.

The wreckage was discovered some hours later. The direction of take-off had been to the south-east, away from any ground lights, and on a moonless night. This resulted in no natural horizon being available to the pilots. A partial electrical power failure in the city and surrounds of Alice Springs occurred prior to the aircraft taking off and a total blackout occurred after the time established for the crash. While the reduced area of the ground lights pattern was judged not to have contributed to pilot disorientation by a reduction in visual cues, this unusual phenomenon may have caused the diversion of attention of one or both pilots. However, no positive conclusions could be drawn. The subsequent investigation revealed that the aircraft had crashed with the pilot-under-check at the controls. It had passed through the top of a tree before striking the ground at high speed, in a left wing low configuration. The landing gear and flaps were retracted.

Ground impact had almost totally destroyed the forward fuselage and cockpit, and the aircraft came to rest inverted some 100 metres after ground contact. The engine had been dislodged and was found about 200 metres beyond the fuselage. Detailed airworthiness inspection failed to detect any fault or anomaly in the aircraft which could be considered to have contributed to the accident. The total night flying experience of the check pilot was some 37 hours, of which six hours had been flown in the last 90 days. However, he had successfully completed a Night VFR revalidation flight for another pilot twelve days prior to the accident and flown some two hours at night three days before the accident. The pilot-under-check had only 14 hours total night flying experience and had not flown at night for 25 months. The conclusion was drawn that loss of control of the aircraft occurred for undetermined reasons at an altitude that was insufficient to effect a recovery.

Significant Factors:

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

1. Both pilots had low levels of night flying experience.
2. There was no natural horizon available to the pilots.
3. For reasons undetermined, there was a loss of control of the aircraft at an altitude insufficient for recovery.

Circumstances:

The aircraft was returning to Bankstown at the completion of a cargo charter flight. Take-off from runway 35 proceeded normally until the aircraft reached a height of about 90 feet when severe wind shear was encountered, resulting in a high rate of sink. The pilot was unable to prevent the aircraft from settling back onto the runway with the landing gear retracted. The prevailing conditions were conducive to the formation of mechanical turbulence in the lee of nearby mountains. At the time of the accident, it was reported there were large fluctuations in the wind velocity at Wollongong aerodrome.

Significant Factors:

The following factor was considered relevant to the development of the accident:

1. The aircraft encountered severe wind shear at a critical stage of the take off and lacked the performance to prevent a collision with ground.