What happened
On the evening of 6 June 2003, an Air Adventures New Zealand Limited Piper PA 31-350 Navajo Chieftain, registered ZK-NCA, was conducting a scheduled charter flight from Palmerston North to Christchurch. The aircraft was carrying one pilot and nine passengers.
As the flight approached Christchurch Aerodrome under instrument meteorological conditions at night, the aircraft was performing an ILS approach to runway 20. During the descent, the aircraft dropped below the minimum allowable altitude. Due to significantly reduced visibility, the pilot was unable to identify the runway or approach lights. The aircraft subsequently struck trees and terrain approximately 1.2 nm short of the runway threshold. The impact destroyed the aircraft and resulted in 8 fatalities (the pilot and seven passengers) and 2 serious injuries.
The investigation
The investigation focused on the descent profile and the pilot's monitoring of the aircraft's altitude. Investigators examined the aircraft's maintenance records, the meteorological conditions at the time of the accident, and the cockpit environment.
Key elements reviewed included the use of electronic devices in the cabin, the status of the aircraft's avionics, and the pilot's flight technique during the high-speed approach. The investigation also looked into whether the pilot's use of a cellphone or potential electronic interference could have impacted the glide slope indication, though it was determined that the aircraft's altimeter was functioning correctly and the descent was not caused by mechanical failure.
Findings
- The aircraft descended below the minimum altitude because the pilot failed to monitor the altimeter during a critical phase of the approach.
- The pilot was likely experiencing high workload or distraction, potentially due to transitioning to hand-flying the aircraft and the use of a cellphone during the flight.
- The approach was unstabilized and high-speed, which contributed to the difficulty in maintaining the correct descent path.
- Reduced visibility prevented the pilot from visually identifying the terrain or runway lights once the aircraft descended below safe limits.
- The lack of a Terrain Awareness and Warning System (TAWS) meant there was no automated alert to warn the pilot of the impending collision.
Safety action
Following the investigation, several safety recommendations were directed to the Director of Civil Aviation:
- Monitoring the implementation of TAWS equipment for smaller IFR air transport aircraft.
- Developing educational materials regarding the prohibition of cellphone use during IFR operations.
- Using the accident details to train single-pilot IFR operators on managing instrument approaches and workload.