The Airbus AS350 B3e helicopter ZK-ITD, popularly known as a Squirrel, was being flown from the operator’s base in Milton on September 16, 2021, to a client’s cherry orchard near Alexandra to conduct frost protection operations.
The flight departed approximately one hour before the beginning of morning civil twilight (when the centre of the rising sun’s disc is 6 degrees below the horizon). It proceeded normally until just before reaching the township of Lawrence.
The helicopter had conducted a series of turns on its way but, while over the Lammerlaw Range, it made a descending right-hand turn through nearly 160 degrees before entering a left-hand spiral dive that ended in a near vertical nose-down impact. The helicopter was destroyed, and the pilot (the sole occupant) did not survive.
The pilot almost certainly encountered cloud in the vicinity of Lawrence and was likely attempting to manoeuvre around it. With increasing cloud cover and little or no terrestrial light in the Lammerlaw Range, it was also likely the pilot had lost sight of clearly defined horizon.
The helicopter continued to climb straight ahead for nearly three minutes before the pilot likely became disorientated. This resulted in a high angle of bank turn, followed by the rapid descent, which was consistent with spatial disorientation and loss of control.
The final flight path over the Lammerlaw Range. Credit: TAIC
The pilot had met the requirements for a restricted night rating. However, it had been about nine years since the pilot had last logged instrument flying practice. It was unlikely the pilot was proficient in flight with sole reference to aircraft instruments at the time of the accident, the report said.
The rules and guidance information for night Visual Flight Rules (VFR) are ambiguous. This could lead to night VFR pilots flying longer distances than permitted and encountering conditions outside their capabilities. The rules do not adequately mitigate the risks of inadvertent flight into conditions where the clearly defined horizon is lost.
The commission made two recommendations on these safety issues to the director of Civil Aviation. It has long been known that instrument flying skills are perishable and need to be regularly refreshed. This equally applies to night flying.
The risk of losing a clearly defined horizon by not remaining clear of cloud and in sight of the surface increases when flying at night. An immediate transition to instrument flight is required to maintain situational awareness and control of the aircraft to re-establish a clearly defined horizon.
Visual night cross-country flying requires additional training and different skills from those required for visual night flying near a lighted aerodrome or heliport. The use of tracking technologies to supplement onboard emergency locator transmitters can significantly reduce the time taken to locate missing aircraft.
Cockpit video recorders, where fitted, can provide valuable information about causes of accidents and help avoid recurrences. All pilots and operators, and those who use the services of helicopters, especially those who are involved in night operations such as frost protection, may benefit from the findings and recommendations in this report.
