What happened
On the evening of 3 May 2007, an Air New Zealand Boeing 737-319, registration ZK-NGK, was climbing through 20,000 feet near Paraparaumu when multiple cockpit warning lights suddenly illuminated. The alerts included indicators for engine overheat, hydraulic system failure, and pressurization issues. While the pilots initially believed the signals were spurious, the situation escalated when a strong smell of electrical burning and a visible haze appeared in the flight deck.
In response to the fumes, the captain declared a state of urgency and diverted the aircraft to RNZAF Base Ohakea. During the approach, the crew encountered a secondary issue when the landing gear indicators failed to show the gear was locked down. After a go-around and a subsequent attempt, the aircraft landed safely at Ohakea. No injuries were reported among the 121 passengers or the 5 crew members on board.
The investigation
Investigators determined that the electrical malfunction originated from a coffee spill that had occurred in the cockpit approximately four hours prior to the flight. Although the spill had been cleaned up by a previous crew, some liquid had seeped into the avionics control pedestal. Over the course of several flight sectors, the heat from the cockpit electronics evaporated the water in the coffee, leaving behind a concentrated, conductive residue of sugar.
This sugary residue facilitated a slow electrical breakdown within a light switch assembly, eventually leading to the melting of components and a short circuit. The investigation also noted that while the crew managed the emergency effectively, they did not use the external viewing ports to verify the landing gear status during the final approach, relying instead on cockpit indications and physical sensations.