Loss of control

The pilot requested taxi clearance for departure from runway 11, but as this runway was not available due to maintenance being carried out on the arrestor cable, he was instructed by air traffic control to taxi for runway 18 and advised of a 9-knot crosswind component.

During take-off the pilot lost directional control, and the aircraft ground looped to the left, collapsing the right landing gear leg. The aircraft came to a stop at the intersection of runways 36/18 and 29/11.

The flight was planned from Maroochydore to Griffith with a refuelling stop at Nyngan. On arrival at Nyngan the refuelling agent could not be contacted so the pilot diverted to Dubbo to refuel. Prior to departure from Dubbo, the pilot estimated that he would arrive at Griffith at last light. He was not night VFR rated. The aircraft ultimately arrived at Griffith at about last light. Conditions were dark and runway lights were required for landing. The pilot made several circuits of the aerodrome while he attempted to turn on the pilot activated aerodrome lighting (PAL) system.

The pilot reported that he made two attempts to turn on the PAL but without success. He then made an attempt to land without the aid of runway lighting. After touchdown he realised he had landed well beyond the threshold and would not be able to stop by the end of the runway. He applied power and attempted to go around but the aircraft stalled and hit the ground in a left wing low attitude after which it cartwheeled to a stop. Although the aircraft was substantially damaged and there was still a significant amount of fuel in the tanks, there was no post impact fire.

During a practice touch and go landing, the aircraft ballooned during the flare. The pilot applied some power to prevent a subsequent heavy touchdown/bounce and persisted with the landing attempt. She said that she was then distracted by the proximity of a runway strip marker on the left side of the aircraft. The pilot lost directional control of the aircraft, and a ground loop ensued.

FACTUAL INFORMATION

Sequence of events

The pilot was conducting a visual flight rules scenic flight. These flights were done on a regular basis by the operator and the pilot had flown the DH-82 type on many of these. Commonly, the route flown was from Jandakot to the Fremantle area, north to about Mullaloo Point, then Observation City, Perth City and back to Jandakot. The pilot occupied the rear cockpit seat and the passenger the front cockpit seat. Shortly after passing the Fremantle Golf Course, at an altitude of 1,000 ft, the engine misfired and commenced to vibrate badly. The pilot transmitted a Mayday call to the Perth Radar Advisory Service (RAS). At this stage, the indicated altitude was 900 feet.

The pilot told the RAS controller that he had a partial power failure and said he was going to put the aircraft down in an area near Leeuwin Barracks, on the bank of the Swan River. The pilot was aware of the general details and location of the selected area. He tracked for a left base, while losing altitude, intending to land towards the west. The aircraft was halfway through the turn onto final, at a height of about 300 feet and with everything proceeding as planned, when the pilot suddenly saw a set of high-voltage power lines across his track. A large transmission-line tower for these lines was also now directly in front of him.

The pilot decided to complete a 270-300 degree right turn over the water to avoid the tower and pass under the wires and still land in the selected area. It was a tight, gliding turn and when passing through a heading of about east, at a height of about 150 feet, the aircraft stalled and started to spiral right. The pilot applied left rudder but was unable to prevent the aircraft from diving into the river at a steep angle. After impact, the aircraft floated vertically with the tail out of the water and both cockpits under water. The pilot found himself out of his cockpit swimming on the surface, but the passenger was still in the front cockpit.

Shortly afterwards, assistance arrived, and the passenger was released from his seat by a water-police diver. Both pilot and passenger were then conveyed to hospital.

Wreckage examination

Inspection of the engine showed that the number one connecting rod had failed. Approximately half the rod, including the big end attachment to the crankshaft, was missing. Inspection of the remaining fracture surfaces showed that the fracture was caused by fatigue crack growth. The crack had propagated along the centre of the connecting rod 'I' beam from the region of the connecting rod/crankshaft bearing housing. The reason for the initiation of the fatigue cracking could not be determined, due to the absence of pieces crucial to the investigation. The other three connecting rods were inspected but no cracks were found in any of these. The investigation was unable to trace the history of the failed connecting rod.

Each shoulder harness was attached to a transverse cable which in turn was attached, via a bracket at each end, to the aircraft structure. One of the attachment brackets for the rear seat shoulder harness had failed, with the bolt pulling out of (tearing) the bracket. The rear seat lap strap also failed. This probably happened because the seat moved during the impact sequence and the strap was cut by the metal edge of the seat. Even with the failures the rear seat harness absorbed considerable impact energy before failing although, the pilot did receive some facial injuries. One of the front seat shoulder harness attachment brackets, which was attached by three bolts, sustained a partial failure when two of the bolt heads separated. The harness however, remained intact.

The aircraft was equipped with leading edge slats on the upper wing. These devices have the facility to be locked closed. When unlocked, they open up when the aircraft approaches stalling speed. The slats have the effect of slightly reducing the stall speed and also provide a warning to the pilot that the aircraft is close to the stall. The flight manual for the aircraft included a statement that slat extension provides acceptable visual warning of approaching stall.

There were two placards in the cockpit that stated that the slats were unserviceable and not to be operated. Also, the operator's handling notes for the type included instructions that the slats were not to be used for take-off or landing. The slats were locked closed.

Weather data

The surface wind at Jandakot on departure was from the south-west at about 12 knots.

Forced Landing Options

The power loss occurred over a built-up area. There were very few forced landing areas available within gliding range. The Fremantle Golf Course, which was behind the aircraft when the engine malfunction occurred, was probably one option. Another was the area, near Leeuwin Barracks selected by the pilot. This latter area was aligned approximately east-west and had a set of high-tension power lines across the eastern end, aligned approximately north-south. The pilot was not previously aware of the power lines. The power lines and associated tower were not particularly obvious when looking down on them from above, and the restricted visibility from the rear cockpit of the DH-82A was another inhibiting factor.

ANALYSIS

The major reason for the accident was the engine malfunction which forced the pilot to attempt an emergency landing in a built-up area. The location of the engine malfunction meant that the pilot's options were limited. His choices were the golf course, which by then was behind the aircraft and out of sight, or the Leeuwin Barracks area.

To use the golf course the pilot had to execute a 180-degree turn. To reach the Leeuwin Barracks area the pilot only had to make a right turn of about 90 degrees. As a result, he opted for the site near the Leeuwin Barracks.

The pilot was satisfied all was going well until late in the approach when he suddenly saw the power lines and tower. This late sighting caused him to rapidly change his plans and attempt to avoid them. The aircraft was in a poor position, at a height of about 300 feet, for the pilot to attempt a large turn. However, this appeared his only option. During this attempted turn through 270-300 degrees, the pilot allowed the airspeed to reduce to stalling speed and he lost control of the aircraft. There was insufficient altitude to recover control before impact.

The fact that the slats were unserviceable and locked closed possibly deprived the pilot of an important stall warning indication. Had they been available and unlocked, they may have assisted in preventing the loss of control.

SIGNIFICANT FACTORS

The following factors were considered relevant to the accident:

1. Fatigue cracking of the engine's number one connecting rod caused it to fail. The factors which led to the fatigue crack could not be determined.
2. The failure of the connecting rod caused significant vibration and loss of power. These led to a forced landing.
3. There was a lack of suitable landing areas.
4. The pilot did not detect a power line and its associated tower until very late in the approach.
5. The pilot's attempt to avoid the power line led to a significant loss of airspeed.
6. The loss of airspeed led to a stall followed by loss of control at a height that was too low to effect recovery before impact.
7. The unserviceable slats may have been a factor in the pilot's failure to recognise the impending stall in time to prevent loss of control.

After landing on runway 34R in light rain, the aircraft vacated to the right, via taxiway 'T', continuing to decelerate, with the flaps still in the landing configuration. As the aircraft turned left onto taxiway 'J', the aircraft ran off the paved surface to the right of the taxiway and became bogged in soft wet ground. The crew reported they felt minor slipping during the turn but were unable to regain directional control by braking action or the application of reverse thrust. The wind was reported as 050/10-15 and there were patches of standing water on the taxiway. A subsequent engineering investigation found no fault with the aircraft or its steering system.

The taxiways were constructed with a slight camber, designed to assist water runoff. Photographic evidence indicated that the aircraft had commenced the left turn whilst on the right side of the centreline. A replay of the recorded surface movement radar indicated that the aircraft entered the turn faster than preceding aircraft, at about the maximum design speed for the taxiway.

It is considered likely that the north-easterly wind, acting upon the vertical surfaces of the aircraft, reduced the steering effectiveness of the nose gear in the slippery wet conditions as the aircraft turned from a northerly to a westerly heading on the right side of the cambered taxiway. Corrective action by the crew could not prevent the aircraft leaving pavement.

The pilot stated that he was spreading "Urea" on a cotton crop. Prior to commencing a procedure turn the aircraft overflew a stand of trees. When the aircraft was about three quarters of the way through the turn, the pilot felt the aircraft begin to stall. He lowered the nose and increased power, but the aircraft descended into the trees. It continued to fall between the trees and slid for 70 metres before coming to rest. The pilot stated that during a previous landing he had experienced a willy-willy which had originated from the stand of trees. He was conscious of downdrafts near the trees. During previous turns he had flown well past the trees before commencing a turn. On this occasion he feels that the aircraft was affected by a downdraft.

The pilot was tasked to fly parachutists to altitude where they would exit for a display at the Melbourne Masters Games.

Prior to any jumps, the pilot had held a safety briefing for about 50 parachutists involved in the event. According to the Safety Support Officer of the Australian Parachuting Safety Council, the safety briefing stipulated that every jumper would climb out onto the helicopter's landing gear skids and then leave one at a time at five second intervals without pushing off.

On about the eighth jump run, four parachutists climbed out onto the skids of VH-JGE. This placed two parachutists on the left skid and two on the right. The pilot flew from the right front seat, which is normal practice in a Bell 206.

When the helicopter was at 3,500 ft and 50 kts over Olympic Park, the target area, one parachutist from the left rear position departed the skid, immediately followed by the second parachutist from the left side. With the two remaining parachutists still standing on the right skid, plus the pilot in the right front, the helicopter's lateral centre of gravity limits were exceeded. According to the pilot, he was unable to prevent the helicopter from rolling to the right. At some point during the roll, the two parachutists standing on the right skid also departed. In the opinion of the pilot, the right side parachutists pushed off rather than stepping off and that the push aggravated the rate of roll. The roll continued through 360 degrees. The helicopter recovered at 70 kts after a height loss of six or seven hundred feet. The pilot advised that torque and rotor RPM limits were not exceeded during the incident.

After the incident the pilot landed and inspected the aircraft. He discovered evidence of a slight mast bump. He then flew the helicopter to Essendon where further inspections were performed by engineers. The main rotor mast was removed and checked for ovality and runout. The manufacturer was consulted during the inspections. When no fault was found with the helicopter, it was returned to service.

Just prior to the incident there had been some reorganisation of jump loads due to a six place helicopter arriving. The parachutists involved in the incident had, in rapid succession, been assigned to a four place load, then a six place load and finally to a different four place load. The Safety Support Officer subsequently determined that the two parachutists on the left side thought that all four parachutists were going to exit simultaneously on an exit count of `ready set go' given by the parachutist on the front left. The parachutists on the right side had previously briefed with a different group which had planned to exit alternatively left and right at five second intervals; they believed this was the standard briefing and had not discussed it with the left side jumpers after being reassigned to the Bell 206.

Since the incident, the Australian Parachute Federation, via a News Sheet and News Letter, has reinforced the importance of the pre-jump safety briefings, and the exit practice. Also, parachutists have been reminded of the need for extra care at special events where normal exit procedures may be varied due to operational requirements.

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

1. The pre-jump safety briefing was probably inadequate.

The pilot was tasked with spreading urea on dry rice crops.

He took off to the south in calm conditions. At an altitude of about 30 ft in the initial climb, he commenced a left procedural turn while continuing to climb at 70 kts to approximately 100 to 150 ft. The pilot then noticed that the airspeed had decayed to about 60 kts so he lowered the nose. Airspeed continued to decay so he stopped the turn while heading northwest and lowered the nose to increase airspeed. The aircraft continued to sink and touched down in a ploughed paddock. The pilot maintained climb power during the ground roll, hoping that the aircraft would take-off again. After a ground roll of 300 to 400 metres through the ploughed paddock, the aircraft collided with a low earthen embankment and overturned.

No fault with the engine or airframe has been reported to have contributed to the accident. The pilot admitted that the inflight turns were somewhat tight. It is probable that the aircraft stalled causing it to mush to the ground. It is also probable that the drag effects of the ploughed soil prevented the aircraft from accelerating enough to become airborne.

Significant Factors

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

1. The pilot probably allowed the airspeed to decay during a tight procedural turn.

2. The pilot did not attempt to stop the aircraft in the ploughed paddock.

3. The pilot did not select full power for the attempted take-off from the ploughed paddock.

The pilot reported that, prior to take-off, the windsock indicated nil wind. He advised that the take-off roll appeared normal and that the aircraft had became airborne at approximately 50 kts. After lifting off, at a height "well above" the windsock, the aircraft suddenly appeared to lose airspeed. The aircraft then descended to contact the ground nose first and bounced again before coming to rest on the western side of the runway. The total distance from commencement of the take-off roll to where the aircraft came to rest was approximately 900 metres.

Both the pilot and passenger were able to exit the aircraft safely.

Witnesses working near the runway advise the aircraft may have been effected by a gust of wind that passed through at the time.

The pilot reported that he had completed two touch-and-go landings on runway 22 left and had been cleared for a touch-and-go on runway 22 right which had a displaced threshold. The approach, which was being flown with 20 degrees flap and about 1500 rpm engine power, was shallower than the earlier approaches. The pilot said that, about two metres above the ground, as he was about to increase power slightly to ensure that the aircraft did not touch down before the displaced threshold, the nose dropped. The nosewheel struck the ground firmly and the aircraft nosed over. The pilot could not recall hearing the stall warning sound during the approach, although it had tested serviceable before the flight.