The pilot reported that during the approach the airspeed was too high. He decided not to go around as the tall trees surrounding the strip made it look restricted. He flew the aircraft straight and level to wash off airspeed and felt he could still land and stop before the end of the runway.

On touchdown the aircraft ballooned. The pilot recovered to fly the aircraft parallel to the runway but did not add power, to overcome the ballooning effect, as he felt he would run short of runway. On the second touchdown the aircraft bounced and on the third touchdown the nosewheel collapsed. The aircraft skidded to a halt towards the left side of the runway.

The accident sequence was typical of other accidents where the runway perspective appears different to that previously experienced by the pilot. The perspective can be altered by a narrower than usual runway for its length and/or by the surrounding terrain or foliage.

The pilot was landing on the westerly strip at McCaffrey Field with 10 knots of wind from the north (all cross wind). During the round out for landing, the aircraft ballooned, and the pilot pushed the nose down and at the same time retracted the air brakes. The aircraft struck the ground in a nose down attitude and bounced. It then veered left under the influence of the cross wind and bounced again, before running into the boundary fence.

During climb to cruise, passing 7,500 ft, the ground proximity warning system sounded as the aircraft encountered moderate rain and light hail. There were storm cells on either side of track.

Post flight inspection revealed hail damage to all leading edges, right landing light cover, and radome.

The ground proximity warning system often gives a false alarm when it encounters precipitation (heavy rain and/or hail). This is a known deficiency against which there is no technological defence.

The pilot had remained clear of the storm cells by using his airborne radar. It is a known phenomena that hail can fall well outside its associated storm cells.

Sequence of Events

The instructor pilot said that his student had completed four dual circuits with very satisfactory landings off each approach. During the fifth approach, the student flared the aircraft too high and before the instructor could take control, it stalled and struck the ground in a heavy landing.

The left main gear collapsed, and the aircraft came to rest on its bent nose gear and left-wing tip.

Analysis

The instructor was unprepared for the high round out following the student's good landing performance on the previous occasions. He did not take control in time to prevent a heavy landing.

Whilst on descent through about FL240 with C autopilot engaged, the aircraft rolled rapidly to the right but immediately corrected itself. Speed brakes were extended at the time.

Flight Data Recorder information did not reveal any unusual flight control inputs, however individual spoiler positions are not recorded, only the speed brake control handle position is recorded. A ground functional test of the flight control system was normal, but a loose electrical connector at number 6 spoiler (left wing) power control actuator was found. It is considered that the loose connection may have commanded the spoiler to retract, causing a roll to the right which was corrected by the autopilot.

The operator has instigated a fleetwide check of spoiler electrical connections.

The pilot was conducting a landing on a grass strip. During the landing roll the glider overran the strip end and struck a wire perimeter fence.

A report by the Gliding Federation of Australia indicated that the pilot did not compensate for the prevailing wind when executing the approach.

The pilot had initially planned to land to the north on a strip which was about 950 metres long. When he saw that a formation flight was preparing for a take-off to the west on the 400-metre strip, he decided land to the west. The wind was a light north westerly. He reported that his aircraft touched down near the 270 threshold at 60 knots with full flaps and then bounced a couple of times before he attempted a go-around. The local chief flying instructor (CFI) witnessed the accident from one of the formation aircraft and said that the aircraft looked to be faster on touchdown, more like 65 knots.

During the attempted go-around, the pilot selected flaps fully up and full power but almost ran out of strip before becoming airborne. While attempting to avoid a tree near the end of the strip, he stalled the aircraft which then settled onto a fence.

The CFI believed that the go-around would have been successful if the pilot had selected the flaps up in stages rather than going from full flap to zero flap while attempting to become airborne in a short distance.

The pilot reported that the flight departed from an agricultural strip located in a valley surrounded by hills. The aircraft carried a full load of superphosphate to be spread on a property approximately one mile from the strip. The pilot had previously surveyed the property and the flight path. He had selected a route that took him up through a valley between hills and then over a low ridge to the property.

After take-off the pilot set climb power and selected climb flap in order to follow his predetermined route to the property. The pilot advised that as the aircraft flew towards the low ridge it appeared to be descending rather than climbing. He elected to carry out a partial dump and to apply extra flap to clear a clump of trees. The speed deteriorated to 60 knots from the initial climb speed of 70 knots. The pilot did not increase power.

Some 300 metres later another partial dump was carried out to clear another tree. As that tree was cleared the pilot again initiated a partial dump and turned to the right in an endeavour to escape from a rapidly deteriorating situation. Immediately the turn was initiated the right wing dropped and the aircraft stalled, impacting the ground onto the right wing and cartwheeled to a stop some 50 metres from the initial impact.

The company chief pilot examined the accident site and advised that the flight path through the valley was in a classic false horizon situation whereby the surrounding hills caused the pilot to consider that the flight path was over flat terrain whilst in reality the terrain was rising approximately 5 degrees up to the ridge. The chief pilot also advised that the aircraft would not have been able to outclimb the terrain at high gross weight with only cruise power set.

Examination of the wreckage did not disclose any pre-impact factors that may have contributed to the accident. Weather and pilot workload were not considered to be factors in this accident.

The pilot had flown approximately 1200 hours on agricultural operations and 244 hours on the type. His loss of situational awareness could be due in part to his relatively low experience.

Significant factors

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

(1) At high weight, and with climb power applied, the pilot flew the aircraft on an inappropriate flight path into rising terrain.

(2) The pilot did not take appropriate remedial actions when the aircraft could not outclimb the terrain and the aircraft speed deteriorated.

(3) The pilot lost control of the aircraft while attempting a turn at low speed.

The pilot was positioning the helicopter for the first spray run.  As he lowered the collective lever and commenced a turn, he noticed that the rate of descent was higher than usual and that the dual tachometer needles had split. Realising that the engine had lost power, he performed an autorotative descent from less than 100 ft above ground level (agl).  During the touchdown on slightly sloping terrain, the right front skid tube broke, and the helicopter rolled on to its right side.

During the helicopter retrieval, the engineer estimated that he drained 4 to 5 litres of AVGAS from the helicopter's undamaged fuel tank.  The drained fuel was not accurately measured. The pilot's estimate of drained fuel was 6 to 8 litres.  No evidence was found of fuel having leaked onto the ground prior to or during the retrieval.  The engineer found no evidence of fuel leaks, blockages, water or significant foreign matter in the helicopter's fuel system.  His opinion was that the engine lost power due to fuel starvation.

The pilot cannot remember the fuel gauge reading immediately before the accident.  The failure occurred about 1.5 minutes after take-off from the loading base and 34 minutes flight time since the last refuel.

The pilot had refuelled approximately every 30 minutes of flight time during the previous four hours of spraying. 

After refuelling, he did not dip the tank to measure the fuel accurately. He advised that the last refuel consisted of 60 turns of a rotary hand pump.  He believed that every turn of the handle had pumped 0.8 litre into the fuel tank. In his opinion, the fuel gauge reading compared with the estimated amount of fuel pumped into the tank at each refuel.

A warning in the Hiller 12E flight manual states: - "Operating with fuel indicator in the yellow arc during sideward or rearward flight may result in loss of power", because the fuel tank pickup pipe may be exposed and cause the fuel pump to momentarily suck air in lieu of fuel.  The helicopter was not flying sideways or rearwards when engine power was lost.  The unusable fuel listed in the flight manual was only 1 litre for normal level flight.

The pilot thought that the engine did not stop completely during the descent but ran down to idle and that it idled very briefly after touchdown because he saw a small post-crash fire caused by the drift marker oil, a very light oil, dribbling into the exhaust.  Engineers were doubtful that the engine could have run on the ground with the helicopter steeply on its right side with the two carburettor float bowls side uppermost.

The pilot did not dispute that the helicopter appeared to have experienced fuel starvation.  However, he believed 48 litres of fuel were added at the last refuel before the accident. Since the helicopter had consistently used 60 to 62 litres per hour in recent times and because its tank was not empty at the commencement of the last refuel, in excess of 13 litres of AVGAS should have been in the fuel tank when the power loss occurred.

Several litres of AVGAS have not been accounted for.  No evidence was found to indicate that the drum refuelling pump was unserviceable.

It has not been possible to resolve discrepancies in fuel since the accident; nor has any fault been found with the aircraft which may have contributed to the accident.

The pneumatic system on this aircraft type operates the landing gear, flaps and brakes. The aircraft is equipped with a castering nosewheel and steering is achieved by differential braking. The pneumatic system normal operating pressure is 450 to 600 psi. The minimum pressure for engine start is 90 psi. Prior to engine start, the pilot noted that the pneumatic pressure was about 250 psi. He anticipated the pressure would increase to normal operating pressure after engine start.

The engines were started and the aircraft commenced taxiing. Shortly afterwards the pilot noted that pneumatic pressure had not increased to normal operating pressure as anticipated. At about this time he recalled that he had activated the pneumatic system drain valves during a ground inspection of the aircraft. He suspected that he may not have tightened the valves and that this could be the reason for lack of pneumatic pressure. He therefore decided to return to the parking area and investigate.

As there was still over 100 psi pressure, he considered it safe to taxy back to the hangar (bearing in mind that 90 psi is the minimum for start which infers that the brakes should work at that pressure). Approaching the hangar which involved taxiing on a downhill slope, he applied differential braking but there was no response. Realising that he would be unable to turn the aircraft he quickly shut the engines down. The aircraft rolled slowly towards a hangar where it collided with a scaffolding fence, incurring minor damage to the nose gear doors and skin areas of the nose and one wing.

During a post incident inspection, the pilot noted that the pneumatic system drain valves had not been properly tightened. This explained the reason for the lack of normal system pressure build up after engine start. However, the pilot said he believed there should still have been enough pressure for differential braking/steering. Accordingly, he would have a complete check made of the pneumatic system after the damage sustained in the incident had been repaired.