What happened
On 5 May 2014, a BK117 helicopter was performing a hospital patient transfer flight between Ashburton and Christchurch. During the flight, the aircraft experienced a simultaneous loss of power in both engines. The pilot was forced to perform an emergency landing on farmland near Springston. There were five people on board the aircraft at the time of the incident. Despite the loss of power, there were no injuries to the occupants, though the helicopter sustained minor damage.
The investigation
Investigators determined that the engine failure was caused by fuel starvation. Although the main fuel tanks contained a significant amount of fuel, the fuel was unable to reach the engines. The investigation established that the pilot had incorrectly configured the aircraft's fuel supply system. Specifically, the fuel transfer pumps were not activated after the engines were started.
Several contributing factors were identified during the inquiry. The pilot lacked recent experience and formal competency assessments on the BK117 within the previous five years. Furthermore, the pilot did not utilize written checklists during pre-flight or post-start procedures, which would have likely identified the configuration error.
Environmental and design factors also played a role. A cockpit lighting modification intended for night vision use made it difficult to read caution lights during daylight hours when the dimmer switch was active. This prevented the pilot from noticing the warnings regarding the fuel system. Additionally, the aircraft's design allowed both engines to lose power almost simultaneously and lacked an audible warning for critically low fuel levels in the supply tanks.
Findings
- The primary cause of the power loss was the failure to switch on the fuel transfer pumps, leading to fuel starvation.
- The pilot's lack of recent experience and the absence of a recent type-specific competency check increased the risk of error.
- The operator's oversight systems were insufficient to ensure the pilot was sufficiently current on the aircraft type.
- A cockpit lighting modification hindered the visibility of caution lights during the day when the dimmer was engaged.
- The absence of an aural warning for low fuel levels in the supply tanks meant the pilot was not alerted to the impending loss of power.
- The operator did not mandate the use of checklists for pilots lacking recent experience, a practice that could have prevented the incident.