A Civil Aviation Authority safety advisor says a handling error led to a gyrocopter plunging nose-first to the ground and killing two people in 2009.
An inquest is being held in New Plymouth into the deaths of Neville Ronald Adlam and Stephen John Chubb. Their gyrocopter crashed into a paddock at Normanby, in South Taranaki.
At the time, Mr Chubb was an instructor giving tuition to Mr Adlam in his gyrocopter.
A farmer said he saw the aircraft climbing, turning left, and then nose-diving with the engine going until it hit the ground.
CAA principal safety advisor Alan Moselin believes the pilot pushed the control stick forward too rapidly, causing the aircraft to lose stability, and nose dive.
He said once the gyrocopter was weighted too far forward, the situation became irretrievable.