What happened
On 21 November 2005, the pilot of a Fletcher FU24-950, registration ZK-DZG, completed aerial topdressing operations. During the previous evening, the pilot had identified that the airspeed indicator was stuck at 80 knots and arranged for an engineer at Whangarei Aerodrome to clear the pitot-static system. On the morning of the accident, the pilot and a loader-driver departed an airstrip approximately 50 km northwest of Whangarei to continue fertilizing a farm property.
As the morning progressed, weather conditions deteriorated due to strong, squally winds from the south. Around 1131, the aircraft departed the airstrip for Whangary. Witnesses observed the aircraft flying at an altitude of approximately 500 feet, appearing to drift sideways due to the wind. Shortly thereafter, the aircraft was seen entering a steep, tightening descending turn before disappearing behind trees. The wreckage of ZK-DZG was located the following morning in Pukenui Forest, roughly 50 metres below a ridge. The crash resulted in two fatalities.
Findings
Investigations revealed that the aircraft was being operated with an unserviceable airspeed indicator, which prevented the pilot from accurately monitoring speed and potentially allowed the aircraft to exceed structural limits during turbulence. However, the primary cause of the accident was a structural failure of the vertical fin caused by undetected fatigue cracks in its leading edge. These cracks were obscured by a black rubber anti-abrasion strip, making them impossible to see during routine inspections. The investigation also noted that maintenance programs had not been sufficiently updated to account for the increased inspection needs of the vertical fin following the installation of a more powerful turbine engine.