The Civil Aviation Authority (CAA) has released its final report after investigating the cause of the Taylor Monoplane crash near Pukaki Aerodrome that killed the pilot on July 25 in 2020.
Trevor Shadbolt (60) had left the aerodrome to practise stalling in his home-built wooden plane, but then entered a flat spin where the aircraft falls belly first while spinning horizontally like a disk.
The report found that was most likely following a wing-drop stall - where one wing stalls before the other - which the CAA said it could not tell whether the pilot had used the correct recovery actions without success, or if there were other factors that prevented recovery.
"Once the aircraft entered the fully developed flat spin, recovery may not have been possible, regardless of pilot control inputs," the report stated.
It found no evidence of any mechanical or flight control system failure, but could not rule out aircraft factors or a pilot handling error.
Mr Shadbolt was well regarded and received an excellent rating on his most recent microlight instructor renewal less than a year before.
The report noted he faced a challenging situation as he was not up to speed with wing-drop stalling and spinning, with likely a significant level of disorientation.
CAA aviation safety deputy chief executive David Harrison said the accident served as a reminder to all pilots to obtain flight time with an instructor if they were not current in specific exercises or on an aircraft type.
"This accident also highlights the risks of operating aircraft for which the spin characteristics are unknown."
Following the crash, the Recreational Aircraft Association of New Zealand made changes to the pilot currency and renewal requirements.
"Where privileges within a particular group have not been exercised for a period of more than 24 months then practical competence is required to be demonstrated to an instructor before use of the group is continued," the association said.
All new orders for Taylor Monoplane plans would include a covering letter to ensure they stick to the dimension stated following concerns they were being built and operated well above the original design weight.
