Investigation Summary
Flight 4374 was a non-scheduled flight returning engineers to Auckland after they had serviced another aircraft in Gisborne. As the aircraft approached Auckland, the region was experiencing its heaviest rainfall in over four decades, resulting in restricted visibility. At 14:28, the aircraft was at 3,000 feet and being vectored for an ILS approach, but the crew transitioned to a visual approach upon encountering visual conditions. During the descent, the aircraft's speed increased to 211 knots, which was 11 knots above the company's stipulated Vno. As the crew performed the base turn, a heavy rain shower obscured the runway threshold and the First Officer reported being unable to see the approach or runway lights. The investigation concluded that a visual illusion, common in such low-visibility and high-moisture conditions, misled the pilots into believing they were maintaining a safe approach path. Consequently, they did not sufficiently monitor their altimeters or rate of descent. The aircraft struck the water in a relatively flat attitude. Rescue efforts were significantly hampered by the fact that Auckland Airport's primary rescue hovercraft was undergoing an overhaul and was unserviceable, and one of the available inflatable rescue boats suffered an engine failure.
Final Conclusions
The official investigation (Aircraft Accident Report No. 79-034) concluded that the probable cause was a visual illusion in conditions of reduced visibility. This illusion misled the crew into believing they were at a safe height, which resulted in a failure to monitor flight instruments effectively to confirm a safe approach path. The report also highlighted deficiencies in the airport's rescue and firefighting capabilities, specifically the unserviceability of the rescue hovercraft and backup inflatable boats.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Flight Instruments
The crew failed to effectively monitor the altimeter and vertical speed indicators, relying instead on external visual cues that were distorted by rain.
Airport Rescue and Firefighting Services (ARFF)
The rescue response was compromised by the unserviceability of the airport's hovercraft and mechanical failure of an inflatable boat's outboard motor.
Interesting Facts
- 01The aircraft was 8 years old and had previously been operated by the New Zealand National Airways Corporation (NAC).
- 02Auckland was experiencing its heaviest rainfall in 43 years at the time of the accident.
- 03The airport's rescue hovercraft had been inoperable for a year at the time of the crash.
- 04A Boeing 737 departing shortly after the crash attempted to alert the tower, but controllers denied that they were alerted by the departing aircraft.
- 05The two survivors were rescued by navy divers using inflatable Zodiac boats while clinging to the tip of the fuselage.
Safety Actions & Advisories
Rescue and Fire Services Commission of Inquiry
A commission was appointed to investigate deficiencies in airport rescue services, leading to increased fire rescue staff and facility upgrades at Auckland, Wellington, and Christchurch.
Meteorological Equipment Upgrade
A wind-measuring system was installed at the end of the runway at Auckland Airport shortly after the accident.
Hovercraft Maintenance Program
A more effective maintenance program was instituted for the Auckland Airport rescue hovercraft to ensure its availability for water-based emergencies.