The accident helicopter
Airbus Helicopters AS350 B3e, ZK-ITD, loss of control in flight, Lammerlaw Range, 40 km northwest of Dunedin Aerodrome, 16 September 2021
Status
Closed
Occurrence Date
Report Publication Date
Jurisdiction
NZ
What happened
On Thursday 16 September 2021, an Airbus AS350 B3e helicopter ZK-ITD was being flown from the operator’s base in Milton 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 conducted a series of turns immediately before, and after, reaching the township of Lawrence. Soon after passing Lawrence, while over the Lammerlaw Range, the helicopter 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 with the ground.
The helicopter was destroyed on impact and the pilot (the sole occupant) did not survive.
Why it happened
The helicopter had departed the operator’s base one hour after the moon had set and one hour before the beginning of morning civil twilight. It was close to the darkest part of the night.
The pilot almost certainly encountered cloud in the vicinity of Lawrence and was very likely attempting to manoeuvre around it. With increasing cloud cover and little or no terrestrial light in the Lammerlaw Range area it was very likely that the pilot lost their clearly defined horizon soon after passing Lawrence.
The helicopter continued to climb straight ahead for nearly three minutes before the pilot very likely became disorientated. The pilot’s disorientation very likely resulted in a high angle of bank turn, followed by the rapid descent of the helicopter, which was consistent with spatial disorientation and loss of control of the helicopter.
The pilot had met the currency requirements for their restricted night rating. However, it had been about nine years since the pilot had last logged instrument flying practice. It was very unlikely that the pilot was proficient in flight with sole reference to aircraft instruments at the time of the accident.
Two safety issues were identified:
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 at night and encountering night flying conditions outside their capabilities.
The current rules for and guidance on instrument currency for night VFR do not adequately mitigate the risks of inadvertent flight into conditions where the clearly defined horizon is lost.
The Transport Accident Investigation Commission made two recommendations to the Director of Civil Aviation to address these safety issues.
What we can learn
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 in order 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.
Who may benefit
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.
On Thursday 16 September 2021, an Airbus AS350 B3e helicopter ZK-ITD was being flown from the operator’s base in Milton 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 conducted a series of turns immediately before, and after, reaching the township of Lawrence. Soon after passing Lawrence, while over the Lammerlaw Range, the helicopter 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 with the ground.
The helicopter was destroyed on impact and the pilot (the sole occupant) did not survive.
Why it happened
The helicopter had departed the operator’s base one hour after the moon had set and one hour before the beginning of morning civil twilight. It was close to the darkest part of the night.
The pilot almost certainly encountered cloud in the vicinity of Lawrence and was very likely attempting to manoeuvre around it. With increasing cloud cover and little or no terrestrial light in the Lammerlaw Range area it was very likely that the pilot lost their clearly defined horizon soon after passing Lawrence.
The helicopter continued to climb straight ahead for nearly three minutes before the pilot very likely became disorientated. The pilot’s disorientation very likely resulted in a high angle of bank turn, followed by the rapid descent of the helicopter, which was consistent with spatial disorientation and loss of control of the helicopter.
The pilot had met the currency requirements for their restricted night rating. However, it had been about nine years since the pilot had last logged instrument flying practice. It was very unlikely that the pilot was proficient in flight with sole reference to aircraft instruments at the time of the accident.
Two safety issues were identified:
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 at night and encountering night flying conditions outside their capabilities.
The current rules for and guidance on instrument currency for night VFR do not adequately mitigate the risks of inadvertent flight into conditions where the clearly defined horizon is lost.
The Transport Accident Investigation Commission made two recommendations to the Director of Civil Aviation to address these safety issues.
What we can learn
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 in order 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.
Who may benefit
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.