Loss of control

Circumstances:

A ground witness heard the aircraft's engine power increase and observed the aircraft pull up, roll over and enter a spin to the right. He estimated the aircraft was about 3000 feet above the ground. The aircraft spun six to eight turns to the right and at about 600 feet above ground level the right spin ceased before the aircraft entered a spin to the left. The left spin stopped after about one turn and the aircraft appeared to be recovering from the dive when it hit the ground in a wings level, 45 degrees nose down attitude. The pilot-in-command, who occupied the rear seat, held a low-level aerobatic approval to operate down to 1000 feet above ground level. He had often spun the aircraft but is reported to have normally recovered after two turns. The other pilot who occupied the front seat, held an aerobatic endorsement but this was his first flight in a Zlin. It is not known which of the pilots was at the controls when the aircraft entered the right spin, however, the aircraft was normally commanded from the front cockpit. Injuries sustained by the pilot-in-command indicate that he was at the controls at the moment of ground impact. The normal technique prior to the entry of an intentional spin in the Zlin is to reduce power to idle. Considering the report that engine power was increased prior to the spin, it is possible that the spin entry was unintentional. It is the recommended practice in the Zlin to recover from a spin after two to three turns. Why the pilot(s) failed to recover from the right spin after two to three turns could not be determined. An examination of the wreckage and associated aircraft documentation did not reveal any fault that may have contributed to the accident. The prevailing weather was not considered a factor.

Significant Factors:

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

1. Entry to the right spin was possibly unintentional.

2. The pilot at the controls probably experienced some difficulty recovering from the initial spin to the right.

3. Recovery from the right spin was inadequately executed and the aircraft entered a spin to the left.

4. There was insufficient height for the aircraft to recover from the left spin.

The Private Pilot Licence holder was undergoing type endorsement training. During the third landing, on runway 29 Left, the aircraft commenced to swing to the right. The pilot in command reported that after checking that there were no obstructions he allowed the swing to continue. The student pilot was unable to stop the swing and as the aircraft turned through 40 degrees it began to skid, with the result that the landing gear folded. The aircraft is fitted with a tailskid but no brakes, and was unable to use the normal unsealed landing area as that area was wet and out of service. At the time of the landing the wind conditions resulted in a quartering tailwind from the right at five knots.

The pilot had purchased the aircraft some 12 months previously but had carried out only limited and infrequent training. This training had not progressed to the stage where turns were performed, and was limited to straight and level hops along the strip. On the morning of the accident the pilot had performed several hops, taking off and landing into a light easterly breeze. On about the fifth flight the aircraft climbed to a height of about 85 feet, levelled off momentarily and then descended with reduced power as if for a normal landing. When the aircraft was about 50 feet above the ground and close to the end of the landing area, power was applied, a climb was made to about 200 feet and turns were made to position the aircraft on a downwind leg. Witnesses noted that the aircraft was under control until it suddenly adopted a nose-high attitude, followed by a rapid pitch-down which continued into a tumbling motion. Two in-flight impact noises were heard above the sound of the engine and shortly afterwards the aircraft struck the ground in a steep nose-down attitude while cartwheeling to the left. Wreckage examination showed that there had been two strikes on the tail fin and rudder by the rotor blades, causing the rudder to become detached from the aircraft in flight. It was considered that the pilot endeavoured to carry out a circuit of the strip after he perceived that there was insufficient distance remaining to safely land the aircraft. The reason for the sharp change of attitude on the downwind leg could not be positively established, but was probably due either to turbulence or an incorrect control input by the pilot. When the nose pitched down, the airflow through the rotor disc would have been significantly reduced. This would have led to a loss of rotor RPM and a consequent loss of performance of the rotor to the stage where control of the aircraft could not be regained.

According to his log book, the pilot had flown the aircraft on two previous occasions of about 15 minutes duration each. The pilot was briefed by the owner of the aircraft on power settings and speeds. He then took-off into the south from the strip which is aligned approximately north-south. There was a light southerly breeze blowing at the time. The aircraft was seen to make one right-hand circuit, but it could not be determined if the aircraft actually made a landing from that circuit. When the aircraft was on final approach from a second right-hand circuit at an estimated altitude of about 200-300 feet, it entered a turn to the right. As the turn progressed onto a northerly (downwind) heading, the angle of bank became progressively steeper until it was about 90 degrees. The nose then dropped and the aircraft dived to the ground. The first persons on the accident scene experienced difficulty in removing the pilot's motor cycle type safety helmet (with full face enclosure) before resuscitation could be applied. The investigation did not reveal any pre-existing defects that may have caused the accident. Other pilots reported some turbulence and windshear in the area where the accident occurred. The area was inspected by an officer from the Bureau of Meteorology who specialised in micro-meteorology. His opinion was that turbulence or windshear effects at the time of the accident would have been minimal. The pilot had been receiving dual flight instruction from an ultralight flying school. After a dual instructional flight on the morning of the accident, he had been strongly advised by his instructor not to fly solo until he had completed more dual instruction as the instructor believed that the pilot was not sufficiently competent to fly solo. The pilot lost control of the aircraft for reasons which were not determined.

The pilot was performing a take-off in crosswind conditions of about 15 knots. When the aircraft had reached a speed of about 40 knots it suddenly veered to the left, and despite corrective action the pilot was unable to maintain directional control. With full power still applied, the aircraft ran off the side of the strip. It then passed over an embankment, and travelled a further 200 metres before colliding with trees which were some 60 metres from the edge of the strip. The initial loss of directional control was associated with a wind gust in excess of the maximum for the capabilities of the aircraft. The pilot had persisted with the take-off attempt after the aircraft ran off the strip, because he considered that to have reduced power would have caused the aircraft to ground loop. He had endeavoured to dump the load, but had initially inadvertently applied the spray handle. As a result, only about 10 of the load had been dumped before the collision with the trees.

Towards the end of a 4 hour competition flight, the pilot realised that the aircraft would not reach the finishing line and that an outlanding would be necessary. After establishing the aircraft on final approach to the selected paddock, the pilot noticed a pile of stones obstructing the target touchdown area. While manoeuvring to avoid this obstruction, the left wing of the aircraft struck the ground and a ground loop ensued. The pilot had been suffering the effects of a head cold and sinus infection, and had probably become fatigued during the flight in demanding conditions. He had persisted in his efforts to reach the finish until the glider was too low to allow a more suitable paddock to be selected for the outlanding. This accident was not the subject of an on-site investigation.

The pilot stated that a characteristic of the strip in use was that there existed off the north-eastern end an area of downdraught caused by prevailing wind blowing over the adjacent terrain and trees. To counteract this downdraught it was necessary to climb to at least 150 feet above the ground level prior to overflying the end of the strip. On this occasion, the pilot believed sufficient altitude had been gained after takeoff, and turned to the left to take advantage of the upgoing air. However, the aircraft encountered a downdraught and the pilot reported that he allowed the airspeed to get too low and the aircraft enetered a spin to the left. During the recovery attempt the aircraft entered a spin to the right and complete recovery was not achieved before ground impact.

The aircraft had been refurbished during the preceding months, and at the completion of this work the pilot intended to carry out a short test flight. He subsequently reported that as soon as the aircraft became airborne after a normal take-off roll, it veered sharply and the right wing dropped. Corrective control inputs had no effect, the wing and propeller struck the ground and the aircraft overturned, coming to rest about 200 metres from the start of the take-off roll. The surface wind was reported to be varying up to 30 degrees off the runway direction, and gusting up to 15 knots. Because of the degree of damage sustained however, it was not possible to determine whether the wind conditions or the rigging of the aircraft was the major factor contributing to the accident.

Arrangements had been made for three Tiger Moth aircraft to carry out a fly-past at Walcha as part of celebrations to commemorate the first Australian superphosphate spreading operation by air. Earlier in the day VH-BII was flown from Williamtown to Maitland and Scone, where all three aircraft were refuelled in readiness for the flight. The pilots briefly discussed the flight procedures to be used enroute to Walcha and agreed that the pilot of the aircraft planned to take-off last would be responsible for navigation for the group. There was little or no discussion about how the aircraft would form up after take-off prior to departing on track. The aircraft were positioned for take-off with VH-BII planned to be the second of the group to become airborne. The first aircraft took off normally and commenced a left turn when at a height of about 500 feet. VH-BII was observed to follow a similar pattern, however the third aircraft commenced a right turn after take-off to intercept the track to Walcha. Shortly afterwards VH-BII, which had made a gradual turn to the left through about 45 degrees was observed to rapidly enter a steeply banked turn to the right. The angle of bank increased and the aircraft entered a spin. Any recovery action attempted by the pilot was unsuccessful and the aircraft struck the ground in a steep nose-down attitude after passing through a set of power lines. Fire broke out immediately and engulfed the wreckage. Subsequent investigation did not disclose any defect or malfunction of the airframe, engine or systems of the aircraft which might have affected the pilot's ability to safely control the aircraft.

This flight was to be the pilot's first flight in a minimum aircraft. He was briefed to carry out a take-off and landing along the beach. When the aircraft became airborne a left bank was adopted and right rudder was used to attempt to regain directional control. As speed was increased directional control was achieved but oncoming obstructions made further manoeuvring necessary. After starting to climb, directional control was lost. The aircraft crashed into trees and caught fire. The pilot mentioned to his rescuers that the ailerons had been inoperative. The pilot later succumbed to his injuries in hospital. Investigation of the apparent aileron failure was hampered by the degree of fire damage to the aircraft. This damage was a result of the inability of the plastic fuel tank to withstand the impact with the ground. The precise cause of the accident remains undetermined.