Loss of control

Circumstances:

The pilot was landing at a property prior to conducting crop spraying. During the landing roll, the aircraft veered off the strip and overturned in a wheat crop. A subsequent investigation established the left mainwheel hub had failed due to a fatigue crack, allowing the wheel to travel up the landing gear leg. A partial collapse of the left leg then resulted when the axle dug into the ground. The crack had originated from corrosion pitting on the inner wheel half interior surface, which was not visible with the wheel in situ.

The pilot was landing on a property strip in gusty crosswind conditions. Directional control was lost during the landing roll and the pilot was unable to prevent the aircraft from running off the side of the strip. As he attempted to taxi the aircraft back onto the strip the nosewheel entered an area of soft sand and subsequently collapsed. The particular strip in use was only 20 metres wide, and consequently did not meet the requirements for an Authorised Landing Area. The strength of the crosswind component could not be determined.

Circumstances:

The aircraft was landing downwind on an agricultural strip. During the landing roll the aircraft departed the left side of the strip following the failure of the right brake coming to rest inverted in a rice paddy. The investigation found the right brake master cylinder had buckled in the reservoir area. The buckling and resultant misalignment of the piston rod caused a bending failure of the rod and liberation of the piston with a subsequent loss of hydraulic pressure to the right brake. The reason for the failure of the master cylinder was not determined. There are no other recorded accidents involving master cylinder failures in this type of aircraft. The failure is therefore considered an isolated case.

Significant Factors:

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

1. Material failure of the right brake master cylinder piston rod.

2. Loss of hydraulic pressure to the right brake.

3. The pilot was unable to maintain directional control on the landing roll.

This aircraft was intended to be the production version of the "Stratos" aircraft. The prototype version had successfully flown some 340 hours. The production model incorporated significant changes made by the designer/pilot. These changes included the removal of the dihedral from the main wing and the use of full span elevators on the canard wing and full span ailerons on the main wing. The engine mounting was lowered such that the ducted propeller was totally below the main wing and the lower part of the propeller duct was extended well forward to form a "channel or strake". The main purpose of the "channel wing" was an attempt by the designer to lower the stall speed of the aircraft to 30 knots and to reduce both landing and takeoff speeds and distances. As far as the investigation could determine, the effect of these modifications had not been checked by wind tunnel or other methods prior to this flight. On the day of the accident the pilot and his assistants had worked at the factory preparing the aircraft for testing. The preparation included a determination of the centre of gravity, although no record was kept of these calculations. Following these preparations the aircraft was loaded onto a trailer and taken to Penfield. The weather conditions at the time were fine, with light winds. The pilot subsequently carried out a series of taxying tests, to establish the optimum position for the control column. He then conducted a take-off, and operated in the local area for about 17 minutes. Witnesses reported that the aircraft then carried out a very slow pass over the aerodrome at a height of between 400 and 500 feet above ground level. About one minute later it was seen to turn back towards the strip. However, shortly after the turn was completed, control of the aircraft was evidently lost. It is uncertain whether the aircraft suddenly pitched nose up or nose down, but all witnesses agreed that it then fell vertically while the nose swung in a pendulous motion. The aircraft struck the ground in an inverted attitude with little or no horizontal speed. An inspection of the aircraft found that all airframe components were essentially intact and there was no indication of any airframe or control failure prior to ground impact. The engine was test run and strip inspected and no fault could be found. No aerodynamic testing was carried out on the airframe to determine the likely effect on performance of the various modifications made to this aircraft. However, given that the prototype appeared to suffer no adverse flying characteristics, it is possible that the modifications incorporated in the new aircraft had an adverse effect on the stall characteristics. Analysis of the modifications indicates that the most significant effect on the stall characteristics would have resulted from use of full span elevators on the canard wing. The use of full span elevators results in a relatively uniform loading of the canard as the elevator is deflected approaching the stall. The result is that the canard would be developing more lift, compared to the same wing without full span elevators, before the wing stalled and the stall would be sharper. Because the main wing is still producing lift at this stage the nose down pitch following the stall of the canard would be aggravated. It is considered likely that the accident sequence was initiated by a full canard stall followed by a rapid nose down pitch. Also, the altitude at which the flight was conducted would not have allowed the pilot time to make the necessary corrective control imputs following the stall before the aircraft impacted the ground.

Circumstances:

The student was authorised to conduct solo circuit practice in generally light easterly wind conditions. During the session, the wind began to swing through more than 90 degrees, with associated strong gusts. In the landing flare on the circuit prior to the accident, a wind gust lifted the left wing and rolled the aircraft to the right. Experiencing considerable difficulty, the student regained control and climbed the aircraft for another circuit. Being unsettled, the student forgot that he could seek advice from his instructor through Perth Flight Service. He elected to terminate the session with his next landing. Again, as the student flared the aircraft for landing, a strong gust lifted the left wing, rolling the aircraft to the right. Before he could correct the roll, a second gust struck the aircraft. Despite recovery efforts the student realised he was losing control and attempted to go-around. The aircraft with a bank angle of 50 degrees, stalled and contacted the ground right wing tip first, coming to rest 95 metres from the runway centre line.

Circumstances:

The flight from Orchid Beach was to transport three passengers to Hervey Bay where they were booked on a scheduled flight departing at 1215 hours. The aircraft arrived at Orchid Beach at about 1200 hours, and the pilot hastily loaded the aircraft and departed. The take-off appeared to be normal. The aircraft was seen to make a right turn at about 250 feet above the ground, level with a ridge to the southwest of the aerodrome. The turn was made abruptly, with about 45 degrees of bank. Witnesses then saw the bank angle reduce, and at the same time the aircraft began to lose height. The aircraft was last seen when it was diving in a 45 degree nose down attitude. The aircraft impacted the ground near the base of the ridge. The impact angle was 58 degrees below the horizontal, with a bank angle of 118 degrees and an aircraft speed at impact of approximately 80 knots. No defects were found with the aircraft that may have contributed to the development of the accident. The wind at the time was easterly at about 35 knots, and this would have generated considerable mechanical turbulence in the vicinity of the aerodrome due to the local topography. The behaviour of the aircraft during the moments preceding impact was consistent with a stall leading to loss of control. The wind conditions, excessive bank angle, and control manipulation may have all been contributory.

Significant Factors:

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

1. The pilot was in a hurry to depart and did not climb to a safe height before making a turn downwind in turbulent wind conditions.

2. The pilot apparently did not maintain sufficient airspeed for continued flight under the prevailing circumstances.

Circumstances:

The student pilot was carrying out a touch-and-go landing on his first solo flight. He stated that soon after touchdown the aircraft swerved to the left of the runway centreline and did not respond to his efforts to correct the situation. The aircraft left the runway and travelled for some distance across the grass verge before demolishing a fibreglass boundary marker. The nose gear then separated as the aircraft came to a halt against the bank of a drainage ditch, approximately a hundred metres from the runway. The pilot stated that the aircraft speed was between 70 and 75 knots at touchdown. He said that as soon as the aircraft had settled onto the runway, he retracted the flaps and was in the process of advancing the throttle for take-off when the aircraft veered to the left. Examination of the tyre marks showed that the aircraft was wheelbarrowing and skidding sideways when it left the runway. The elevator trim was found positioned approximately midway between the neutral and the nose down position.

Significant Factors:

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

1. The pilot was inexperienced.

2. The pilot mishandled the flying controls and caused the aircraft to wheelbarrow.

3. The pilot lost directional control of the aircraft.

Circumstances:

The pilot, who was relatively inexperienced, was engaged in pasture spraying, operating from an airstrip located on the property being sprayed. He had been on duty approximately seven hours when commencing his nineteenth flight. After take-off, the pilot initiated a shallow climbing turn onto a southerly heading, affording himself little time in which to review his flight pattern before gaining alignment for the spray run. He began spraying at tree height until the area became sufficiently open to permit descent to about one metre above ground level. Approaching the fence which formed the southern boundary of the treatment area, the pilot initiated a climbing turn to the right, to follow a "racetrack" pattern. Soon after commencing the turn the pilot realised that the aircraft could not climb fast enough to maintain clearance from the hill beginning on the southern side of the treatment area. The pilot dumped the hopper load, and with full throttle attempted to turn across the face of the hill. The aircraft mushed onto the hillside, coming to rest 41 metres from the initial impact and 150 metres from the fence pull-up point. A left turn following pull-up would have taken the aircraft over lower terrain.

Significant Factors:

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

1. The pilot turned toward terrain, the gradient of which exceeded the performance capability of the aircraft.

2. The pilot gave himself insufficient time for adequate flight review.

3. The pilot may have been subject to some skill fatigue.

Circumstances:

The aircraft was being flown for a visual night circuit to runway 11 after completing an instrument approach. The wind was reported as 5 to 10 knots from the south-west. The pilot reported that after touchdown the aircraft commenced to veer to the right. Although left braking and steering was applied, the aircraft continued to veer until it lurched to the right and stopped, as though the right wheel had become bogged. After vacating the aircraft, the pilot found the right main gear oleo had broken away and the aircraft was resting on the right main gear mount, which had dug into the runway surface. A metallurgical examination of the landing gear showed that the inner oleo strut tube had failed as a result of the propagation of a fatigue crack to a critical length. No manufacturing fault was detected; however, the landing gear had a high total time in service history. No other failures of this type are contained in Civil Aviation Authority records, and it is considered that it may have been a "one-off" event.

Significant Factors:

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

1. The landing gear had a high total time in service.

2. Tensile failure of bronze filler in a fatigue and/or large loading environment.

3. Fatigue fracture of inner oleo strut tube.

The pilot was spraying a bean crop in a valley. During a procedure turn the aircraft began to sink towards trees on the side of the valley. The pilot immediately applied full power and dumped the load, but the sink could not be arrested and the aircraft struck the trees. When the sink was encountered the pilot was committed to continue the turn to avoid terrain. The surface wind in the valley was a light southerly breeze, but there was a strong south-easterly at 2000 feet. The pilot had sprayed the field on previous occasions, and was familiar with the local area. The sink experienced on this occasion was considered to be the result of the strong wind at height combined with the local topography. This type of situation is documented in the Agricultural Pilots Manual. No faults were found with the aircraft that may have contributed to the occurrence. It was evident that when the sink occurred the performance available from the aircraft was insufficient to enable the pilot to avoid collision with the trees.