The release of the ATSB’s report into the terrain awareness warning system alert involving Eurocopter BK-117C-2, VH-SYB, is reminder for pilots of the limitations of night vision imaging systems (NVIS) and night vision goggles (NVGs).
On 26 October, the helicopter took off under night visual flight rules (NVFR) from the Crookwell Medical Helicopter Landing Site with the pilot and aircrew member both wearing NVGs. Shortly after take-off, the helicopter entered unexpected low cloud and the pilot initiated the procedure for an inadvertent entry into instrument meteorological conditions.
As the helicopter’s climb reduced, the pilot lowered the helicopter’s nose to regain airspeed but inadvertently over corrected the pitch angle, triggering a terrain caution alert.
The ATSB found the pilot was likely distracted, during a period of high workload, by the reflection of the helicopter’s anti-collision light against cloud, which was compounded by the use of NVGs.
Clearer guidance may have led to the conduct of a less risker IFR operation
NVGs can increase a pilot’s ability to see the horizon, terrain and objects, but it is important to remember there are also risks and limitations associated with their use. Ambient light, reflections and even the position of the moon, can reduce their effectiveness. NVG use needs to be supported by clear and robust processes from the operator.
During the investigation, the ATSB found there were also some ambiguities in the operator’s manuals about when to conduct NVFR operations with NVIS versus the use of instrument flight rules. Clearer guidance may have led to the conduct of a less risker instrument flight rules operation.
Information on the proper implementation and use of NVIS with NVGs and their benefits and limitations is available in the ATSB aviation research report Night Vision Goggles in Civil Helicopter Operations.
Read the report: Terrain awareness warning system alert involving Eurocopter BK 117C-2, VH-SYB, near Crookwell, New South Wales, on 21 October 2016