Collision with terrain

Circumstances:

At approximately 1809, (23 minutes before last light) during final approach to landing at Carnarvon, the pilot noticed that the landing gear had not extended correctly. The aircraft remained in the circuit area whilst the pilot attempted to lower the landing gear using both manual and emergency methods. He also sought assistance from the company's, Perth based, duty pilot and Carnarvon based engineers. After exhausting all possible methods of lowering the gear the pilot decided to land with the landing gear and flaps retracted. The pilot rejected a landing on the sealed runways because he was apprehensive that it would cause unnecessary damage to the aircraft and could result in a fire. He considered landing in a riverbed (rejected by the Senior Operational Controller), alongside one of the sealed runways (the surface was unsuitable) and on one of the dirt strips. The pilot was offered a flare path on dirt runway 27 however, he declined and indicated that he would try to land using the available light. At 1856 (last light was at 1832) the pilot attempted a landing on runway 27. On late final approach the aircraft collided with a one and a half metre high levy bank, 270 metres short and 115 metres to the right of the threshold. The pilot was trapped in the wreckage for some time after the aircraft came to a stop. The landing gear problem arose when the left main landing gear would not lower. Examination of the aircraft revealed that both hinges fitted to the inboard landing gear door had fractured. The forward hinge had fractured as a result of fatigue and the rear hinge as a result of overload. The fatigue crack initiation had occurred at a sharp edged, prominent forging flash on the inner radius of the hinge and had grown over approximately 4000 load cycles. A similar fatigue problem had been identified on an earlier version of the hinge (part number 46653-00), however, regular inspections for fatigue cracking were discontinued when hinges with part number 47529-32 (as fitted to VH-DEG) were introduced in 1980. Similar fatigue cracking was found in the forward door hinge of another PA31 during the investigation. The fractured hinges jammed the left main landing gear mechanism and neither the normal or emergency extension systems could extend the gear. The pilot was apprehensive about wheels up landings. Much of his decision making was aimed at reducing the risk of fire and minimising the damage the aircraft would sustain during the landing. e.g. Selection of a dirt runway instead of the sealed strip, landing with flaps retracted etc. During the pilot's attempts to rectify the landing gear problem, and up until the time of his touchdown, he was subjected to considerable radio transmission traffic involving questions, directions and suggestions which distracted him from his primary tasks. The pilot indicated on at least two occasions that he was ready to land, however, each time advice and questions from the ground personnel involved overrode his intentions. When the pilot was asked if he wanted a flare path on runway 27 there was still some natural light available and he was intending to land. However, by the time he was able to make his final approach it was dark and he was unable to see the ground. Studies have shown that aircrew subjected to high levels of stress can suffer skill fatigue and cognitive task saturation, which in turn can lead to a breakdown in the decision-making process. It was apparent from the pilot's radio transmissions and the quality of the decisions made in the latter part of the flight that his information processing and decision-making abilities had been degraded by the stress of continuous radio transmissions and continuous, and sometimes conflicting, instructions. As a result, what should have been a relatively simple wheels up landing in daylight was turned into an extremely difficult wheels up landing at night. With the landing gear retracted the aircraft's taxi and landing lights were not available to the pilot.

Significant Factors:

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

1. Manufacturing defect. A forging flash created a stress concentration which led to fatigue cracking.

2. Inadequate inspection procedures. Previous inspection procedures introduced to disclose similar cracking were withdrawn on the introduction of later part numbered hinges.

3. Apprehension of the pilot. The pilot was apprehensive about apparently significant dangers of landing an aircraft, wheels up, on a sealed runway.

4. Inordinate interference in aircraft operations by ground-based advisors. The ground advisors input overrode the pilot's decision on a number of occasions with the result that a simple exercise became very complicated.

5. Cognitive task saturation and skill fatigue. The amount of information, advice and suggestions being passed via the radio communications system overloaded the pilot decision making abilities.

6. Improper in-flight decisions. As a result of task saturation, the final decision made by the pilot to attempt a night landing on an unlighted strip was incorrect.

7. The pilot did not see and therefore was unable to avoid the levy bank.

Recommendations:

That the Civil Aviation Authority give consideration to amending AD/PA-31/93, to include the later part number hinges (P/N 47529-32 and 46653-00 (steel) which were introduced by SB 682) for a repetitive inspection in addition to the inspection called up for Pre SB 682 hinges.

The pilot was attempting to bring the helicopter to a hover in the lee of a hill, but found that there was insufficient power to arrest the rate of descent. The aircraft struck the ground and rolled over. The pilot reported that the conditions were very windy. The helicopter was reported to have been operating normally prior to the accident. The pilot stated that in attempting to arrest the rate of descent he had inadvertently overpitched the rotors at an altitude from which recovery was not possible. This accident was not the subject of an on-site investigation.

The pilot was engaged in a muster of cattle for a brucellosis test. He was chasing a calf that had broken away from the main herd. When the animal turned towards the helicopter, the pilot attempted to take evasive action. He felt the aircraft rock, and believing that it had been struck by the animal, pulled it up to about 40 feet above the ground. The aircraft began to yaw. During the subsequent landing, while still yawing, the landing skids collapsed. The investigation revealed that the animal had not contacted the aircraft. During the evasive action taken by the pilot the tail rotor had contacted the ground which resulted in the loss of directional control. This accident was not the subject of an on-site investigation.

The aircraft was the first of a group of four aircraft being used to return staff to an alluvial gold mine after a weekend break. The weather in the area of the destination was not suitable for a visual arrival and the aircraft was initially held for several minutes in an area five kilometres to the south of the strip, awaiting an improvement in the weather. The aircraft was then flown towards the strip and the pilot reported to a following aircraft that there had been a lot of rain and that the strip looked wet. He also advised that he intended to carry out a precautionary circuit and check if it was safe to land. No further transmissions were received from VH-TLQ. The wreckage of the aircraft was subsequently found burning in a river valley, 300 metres west of the threshold of runway 34. Surviving passengers stated that the aircraft struck trees shortly before impact. There were no ground witnesses. The aircraft had impacted the ground in a steep nose down left wing low attitude, at a low forward speed, then cartwheeled up rising ground before coming to rest inverted, 42 metres from the point of impact. The cabin area was destroyed by an ensuing fire. An inspection of wreckage did not reveal any mechanical defect or failure that could have contributed to the accident. The reasons for the apparent loss of control of the aircraft could not be determined.

The pilot was attempting to take-off at night from an unlit runway, using the headlights of a car positioned at the upwind threshold for guidance. After becoming airborne the aircraft failed to climb away normally and collided with the car, killing one of the occupants. Although the aircraft had sustained substantial damage it remained airborne, and a safe landing was carried out at the planned destination. It was calculated that the aircraft was travelling at an approximate airspeed of 105 kt when it struck the car. No fault was found with the aircraft that would have prevented it from climbing normally after lift off. The reason the aircraft failed to climb could not be determined.

The aircraft was engaged in the aerial spotting of sheep and relaying the information by radio to ground mustering parties. When the muster was completed in that area, the aircraft was abserved to climb away, but the pilot's intentions were unknown. The aircraft was not seen again that day and when it had not returned by night a search was commenced. The wreckage was located the following morning near the site where the aircraft had last been observed. The aircraft had struck the ground in a nose low, right wing low attitude with no apparent forward speed. No fault was found with the aircraft that could have contributed to the accident. It is probable that while operating at a low altitude the aircraft had stalled and that the pilot had been unable to effect a recovery in the height available.

The pilot reported that while cattle-spotting at about 200 feet above ground level the engine lost power. He commenced a forced landing into a large clearing when, at about 30 feet, the engine regained power. He reported that he attempted to fly away but the aircraft sank, nose-down and left wing low, to the ground. Examination of the engine found no explanation for the reported loss of power. The left wingtip had scraped the ground for a distance of 28 metres, with the aircraft banked at an angle of approximately 45 degrees. The aircraft had then yawed left and cartwheeled for 65 metres before coming to rest. Damage to the propeller was consistent with the engine producing high power.

On the evening preceding the accident the pilot indicated his intention to commence mustering early the next morning. The pilot arose at about 0530 hours and it is believed that the aircraft took off at about 0600. The aircraft was seen at about 0620 by the stockmen. It was flying at about 100 ft agl and when the engine noise ceased and the aircraft was not seen again one stockman rode to a nearby bore and found the inverted aircraft wreckage. The aircraft had impacted the ground in a near vertical attitude. No contributory fault could be found with the aircraft or the associated systems. The pilot did not hold a mustering approval and no evidence of him having undergone such training could be found. It is probable that the aircraft stalled at low level and that the pilot was unable to regain control before ground impact.

Circumstances:

A weather front was approaching Rottnest Island from the north-west. The pilot departed before the weather arrived, climbing to 1500 feet whilst intercepting the south easterly track to Jandakot. Shortly after reaching 1500 feet, the weather closed in, and the pilot was unable to avoid entering cloud. The pilot did not request assistance from Perth Air Traffic Services. Instead, he turned towards the island and commenced an instrument descent expecting to descend clear of the cloud and land at Rottnest without difficulty. The aircraft exited the cloud at a low height above the sea, to be suddenly confronted with boats and land. During the sharp left hand avoidance turn, the left wing struck the water. The aileron was torn off and the wing and fuselage were damaged by the impact. The pilot retained control and carried out an emergency landing at Rottnest Island airport.

The weather was fine when the pilot departed Bankstown, however, deteriorating conditions were encountered enroute. Communication was lost with the aircraft after the pilot reported he was holding at a point some 15 kilometres from his destination. Searchers subsequently discovered the wreckage of the aircraft in water, 900 metres from the intended landing strip. No fault was found with the aircraft that would have been likely to contribute to the accident. Thunderstorms, low cloud and extremely heavy rain were present in the area. It is probable that the pilot was manoeuvring the aircraft for a landing when it struck the water.