Collision with terrain

On arrival overhead Minlaton, at the lowest safe altitude of 1600 feet above mean sea level, the pilot identified the town and airport. A visual descent to 500 feet above ground level was continued as the aircraft joined the circuit for runway 33. The pilot flew a tight circuit and after aligning the aircraft on final looked into the cockpit for a final check of the power settings. When he looked out, he had lost sight of the runway lights and before he could take corrective action the aircraft struck the ground about 800 metres before the runway threshold.

The left outer wing struck the ground and then a fence and was broken off, the landing gear was torn off and the aircraft came to rest after a ground slide of about 75 metres. The pilot was uninjured and vacated the aircraft unaided.

A second aircraft which arrived overhead Minlaton a short time after VH-CRT, advised Adelaide of the accident. The pilot of this aircraft then held in the area for about 20 minutes because of poor visibility and light before a landing could be accomplished.

The pilot was conducting a scheduled passenger service flight from Port Augusta with a stop at Innamincka. A commercial pilot, travelling as a non-paying passenger, occupied the co-pilot's seat to observe the operation. Two additional passengers were on board the aircraft for the entire flight.

After landing at Innamincka, the aircraft was refuelled by the pilot in command and the oil levels of both engines were checked by the observer, who experienced difficulty securing the combination oil filler cap-dipsticks. He asked the pilot for instructions and, although some advice was given, the pilot did not check the security of the dipsticks.

Take-off was commenced towards the north into a 10-15 knot wind with a surface temperature of about 20 degrees C. Shortly after lift-off, at the first power reduction, the observer in the co-pilot's seat advised that there was oil seeping back along the cowl from the right-side oil filler hatch. The pilot reported that he increased power to both engines but believed there was no response from the right. He began an immediate left turn to complete a circuit and attempted to secure the right engine and feather the propeller. The aircraft then began a roll to the right, the nose dropped, and the aircraft impacted the ground. As the aircraft rolled right and the nose dropped, the pilot reported that he had secured the left engine and feathered the propeller. The observer in the co-pilot seat reported hearing a continuous stall warning horn as the right wing began to drop.

All occupants, although injured, were able to vacate the aircraft through the main cabin door. The pilot provided assistance to the passengers and then returned to the airport to summon help.

Examination of the wreckage revealed that the aircraft impacted the ground in a nose down, right wing low attitude while turning right. The landing gear collapsed due to impact forces and the right wing separated. Deceleration and impact forces were severe. The right propeller was found in the fine pitch range with no damage to the uppermost blade and the other two bent backwards. The right engine oil filler cap-dipstick was found to be correctly installed in the oil filler neck. There was a pattern of engine oil over the rear of the engine and inside the cowl originating from the oil filler neck.

The left engine was partially torn from its mountings and displaced about 90 degrees to the right. Its propeller was in the fully feathered position. The oil filler cap-dipstick was on the ground adjacent to the engine. An oil spill pattern similar to that on the right engine was evident.

The pilot in command held a Senior Commercial Pilot Licence, a Command Instrument Rating, and a current Class 1 Medical certificate. He was endorsed on the aircraft type and had last been checked in emergency procedures eight months previously.

The person in the co-pilot's seat had recently qualified as a commercial pilot and had completed some flying training with the operator. He was on board the flight to observe a typical commercial operation to enhance his employment prospects as a pilot. This observer status had been previously granted to other pilots. The company management provided strict guidelines to pilots in command of such flights regarding the non-active role of these observer pilots.

The aircraft maintenance release was valid, and the aircraft had been loaded within the Flight Manual maximum weight and centre of gravity limits at the time of the accident.

The right engine was run on a test stand and assessed as being capable of normal operation. The combination oil cap-dipstick prevented oil loss when correctly inserted and clipped down. When in place but not clipped down, with the engine running above 1800 rpm, an oil leak pattern similar to that seen at the accident site occurred over the rear of the engine.

It is considered likely that the dipstick had been loose prior to impact but was correctly replaced in the filler neck after the accident. The design of the oil filler system tends to restrict oil loss with a loose dipstick. This condition would not require an immediate reaction by the pilot to prevent engine damage.

The right propeller was dismantled for inspection and found in the normal fine pitch range but capable of feathering. The uppermost blade was not damaged and backwards bending of the other two blades indicated that it was stationary or rotating slowly at impact.

Severe impact damage to the left engine precluded a test run. It was bulk stripped with no defects evident that would have prevented normal operation. The left propeller was dismantled and found to have been in the fully feathered position prior to impact. Damage sustained would indicate that it was stationary or rotating slowly at impact.

Based on the physical wreckage and impact examination and on the pilot and passenger comments, it is evident that when the pilot secured the right engine and began the left turn, the airspeed dropped, and the aircraft stalled. When the right wing dropped the aircraft entered an incipient spin. Due to the low altitude at which control was lost, the pilot was unable to effect a recovery.

Findings

1. The aircraft had a valid maintenance release and was within maximum weight and centre of gravity limitations at the time of the accident.
2. The pilot-in-command was correctly licensed and endorsed for the aircraft type.
3. Oil levels had been checked and oil added to the right engine by a non-crew member.
4. The combination oil cap-dipsticks had not been checked for correct installation by the pilot-in-command and were probably loose at take-off.
5. The oil filler design of the engine will restrict oil loss when a dipstick is not correctly secured.
6. The left propeller was feathered, and the right propeller was in the fine pitch range; both were stationary or rotating slowly at impact.
7. The right engine was capable of normal operation and was successfully run on a test stand after the accident.
8. Impact damage to the left engine precluded a test run but a strip inspection indicated that it was capable of normal operation.
9. The aircraft stalled and entered an incipient spin to the right prior to ground impact.

Significant Factors

1. The pilot-in-command reacted inappropriately to a perceived engine problem shortly after take-off.
2. Control of the aircraft was lost at a height insufficient to effect a recovery.

While taking off from a forestry strip the aircraft performance achieved was less than expected. Concerned about terrain proximity after liftoff the pilot operated the dump lever. This did not prevent the landing gear from striking a log beyond the end of the strip. The aircraft continued to fly, and the pilot diverted to Albury Airport. During the subsequent landing roll, the right main landing gear leg collapsed.

Soft sand had been put on portions of the centre of the forestry strip, and it appeared this had adversely affected the take-off performance. A spreader was fitted to the aircraft to assist in distribution of the hopper load. When the dump was attempted, the spreader severely reduced the effectiveness of the dump and only about 20 per cent of the load was jettisoned.

Significant Factors

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

1. The presence of soft sand on the strip surface.

2. The pilot did not anticipate the effect the sand would have on the take-off performance.

3. Fitment of the spreader resulted in a severe reduction in the performance of the dump system.

The pilot was taking his passenger for a flight to demonstrate the aircraft. Following preflight and pre-take-off checks the take-off was commenced from runway 28. The aircraft accelerated normally until 60 knots when the aircraft was established in a 400 feet per minute climb. As the aircraft crossed the upwind threshold it began to sink. The pilot checked the performance and found that the airspeed was 60 knots, and the engine was developing full power. He lowered the nose of the aircraft to the straight and level attitude and the aircraft maintained level flight. However, as the nose was raised again to outclimb trees ahead, the aircraft again began to sink. The pilot turned the aircraft to the right towards a clear area but was unable to avoid the trees.

The aircraft came to rest upright in an area covered by 15 foot high regrowth. The pilot was able to extricate himself from the wreckage but because of his injuries could not free the passenger.

The pilot had not operated from Mareeba prior to this flight and was unaware that local pilots do not normally use runway 28 for take-off because of downdraughts near the upwind threshold.

At the time of the accident the weather was fine and clear with a temperature of 22 degrees Celsius and no wind.

The aircraft was flying over the Grampians Mountain ranges, the highest peak of which is nearly 4000 feet. The pilot reported that he had diverted slightly to the north of track to avoid the higher peaks of the first range but also to keep clear of a storm to the south and to keep below cloud. As the flight proceeded, the pilot realised that the aircraft was not going to clear the rising ground. He attempted to turn away from the rising ground but realised that the aircraft was going to sink into the trees in the heavily timbered terrain. The pilot lowered flap and stalled the aircraft into the tops of the trees, estimated to be between 20 and 30 metres high.

The aircraft was destroyed as it fell through the trees to the ground. The two occupants spent the night at the site. Early the next morning, when there was no longer any sign or smell of fuel, they turned the radio on and made a call to Melbourne, after which search and rescue procedures were commenced.

The pilot initially believed that the engine had suffered some form of power loss. The wreckage was inspected by an aircraft engineer who reported that damage to the propeller was consistent with the engine delivering significant power at the time of propeller impact. The Bureau of Meteorology advised that there were active thunderstorms in the area at the time with the possibility of severe downdrafts. In addition, conditions were conducive to the formation of carburettor ice. However, an eyewitness reported that the wind was calm, and the sky was clear at the time of the accident.

The accident was not formally investigated by the Bureau, and it was therefore not possible to determine significant factors that could be supported by sound evidence.

Shortly after lift-off, at about 50 feet, the right engine surged and lost power. The pilot was unable to control the yawing effect and attempted a landing beyond the departure end of the airstrip. During this attempt the engine surged to power once but as this exacerbated his control difficulties the pilot closed both throttles. The aircraft cartwheeled after striking the ground with the left wingtip. The aircraft came to rest in a paddock beyond the 1,000 metre airstrip.

The fuel selector for the right engine was found in the auxiliary position. The pilot later commented that he probably missed the fuel selection out of his pre-take-off checklist. He said that he had been in the habit of using a memorised checklist for the operation of the aircraft and at times he had forgotten to switch the tank selection from auxiliary to main tank prior to landing, as required by the operating instructions in the aircraft flight manual. The pilot also commented that he felt uncurrent in asymmetric operations.

Examination of the right engine did not reveal any defects which could cause a power loss.

Significant Factors

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

1. The pilot did not follow flight manual operating instructions for the operation of the aircraft fuel system.

2. The pilot relied on a memorised checklist.

3. The pilot was uncurrent in asymmetric operations.

The pilot advised that at the time of the incident he was carrying out a last +fly around; of his property which had recently been sold. The pilot's three year old son was the only other passenger on board. While manoeuvring at low level the pilot's attention was diverted into the cockpit for a period of time, assisting his son who had become ill. During this period of distraction the pilot had inadvertently allowed the aircraft to descend. He recalls looking outside the aircraft again just as it impacted the ground. The pilot confirmed that the aircraft's engine and flight controls were operating normally at the time. The pilot received serious injuries to both ankles in the accident. The passenger received only minor cuts and bruising. The aircraft was damaged beyond economical repair.

The pilot was taking off from the 020 degree grass strip but was using only the last 700 feet of the available 2200 feet. Partial engine failure occurred when the take-off roll was well established. The engine surged. The pilot applied carburettor heat, full rich fuel mixture and full throttle without regaining full power. The pilot continued the take-off and became airborne. He advised that he had to turn to avoid trees. The aircraft stalled from somewhere between 50 and 100 feet. The wings were damaged. The engine was pushed back into the firewall and the undercarriage collapsed.

The owner subsequently advised that no fault has been found with the airframe, engine or fuel system. He believes that the likely cause of the loss of engine power was carburettor icing.

Significant Factors

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

1. The engine suffered a partial engine failure probably because of carburettor icing.

2. The pilot did not reject the take-off.

The club was carrying out joy flights in VH-WVQ and earlier in the day another pilot had flown these. A second pilot then took over this task. He flew his first flight with an adult passenger and no operating anomalies were noted. For his second flight a 12 year old boy was carried in the front seat, along with 13.5 kilograms of ballast.

On aero tow take off the pilot noted the stick had to be pushed fully forward to lift the tail. He said the handling felt a little "strange" in the air, but he elected to continue. Release was at 2800 feet, and he commenced circling in the Gap area to try and obtain lift. Positive two stages of flap was set, with a speed of 42 knots and 30 degrees of bank.

Lift conditions were poor; they were just maintaining height. At about 300 feet above a ridge the glider stalled with the left wing going down and the tail also dropping slightly. Recovery seemed slow even though the stick was pushed completely forward. It became impossible to avoid trees and on contact these pulled the wings backward. The glider came to rest in the trees with the canopy dislodged and the nose pointing down at the ground some 30 feet below.

The pilot was unable to prevent the passenger from undoing his belt and attempting to get out onto a branch. In the process the passenger slipped, then managed to briefly hold on to the branch with a hand before falling to the ground. He was injured but managed to walk to a nearby road where a motorist picked him up. The pilot got out of the aircraft onto a branch but could not get down to the ground which was still some 25 feet below. He remained there until rescued about 1.5 hours later.

It was a fine day with virtually no surface wind. Other glider pilots who flew either before or at about the time of the accident said that lift conditions were poor and intermittent. One of those who flew in the Gap area commented that he had to circle close to the mountain to get lift. As his turn took him out from the side of the mountain he lost the lift, with the variometer indicating -1. Post accident calculations indicated that the position of the centre of gravity was at 38.7 per cent Mean Aerodynamic Chord (MAC). The approved range was 22-40.6 per cent MAC.

Significant Factors

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

1. The conditions were unfavourable for obtaining adequate lift for prolonged flight.

2. The pilot continued the flight in marginal lift conditions.

3. The pilot allowed a severe stall to develop at a low height above the terrain.

The pilot reported that he was making an aerial inspection of the Benambra airstrip prior to landing. He overflew the strip at about 150 feet above the ground and then commenced a left turn at a bank angle of about 45 degrees. While turning, the pilot said he was looking at obstructions in the vicinity of the airstrip and neglected to monitor the airspeed. He felt the aircraft shudder and then it stalled. He managed to level the wings but was unable to arrest the descent. The aircraft struck the ground in a flat attitude in swampland immediately to the north of the strip.

The pilot said that the day was hot and the aircraft was heavier than usual, in that there were three persons on board. Usually he is the sole occupant. The elevation of the airstrip is 2250 feet.

Significant Factors

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

1. The pilot became distracted while manoeuvring in the circuit area and as a result the airspeed decayed and the aircraft stalled.

2. The pilot was operating the aircraft in a circuit area at a higher density altitude and higher weight than what he normally operated at.