Aviation safety investigations & reports

Terrain awareness warning system alert involving Eurocopter BK 117C-2, VH-SYB, near Crookwell, NSW, on 21 October 2016

Investigation number:
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase

Final Report

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What happened

On the evening of 21 October 2016, a Eurocopter BK 117 C-2 helicopter, registered VH-SYB, departed Crookwell Medical helicopter landing site, New South Wales. The crew were returning to their home base at Orange, New South Wales, after conducting an emergency medical service (EMS) task. The flight was conducted as a night visual imaging system (NVIS) operation under night visual flight rules (NVFR), with the pilot and aircrew member (ACM) both wearing night vision goggles (NVG).

Shortly after take-off, the helicopter unexpectedly encountered low cloud, and the pilot initiated the operator’s inadvertent entry into instrument meteorological conditions (IMC) procedure. As the momentum of the helicopter’s climb reduced, the pilot lowered the helicopter’s nose to regain airspeed, but she inadvertently over corrected the pitch angle to 15° nose-down, as well as allowing a slight roll to the left. The resulting unusual attitude triggered a caution alert from the helicopter’s enhanced ground proximity warning system.

What the ATSB found

The ATSB found that the pilot had undertaken relevant recent training in inadvertent IMC recovery, and the pitch over correction was probably (at least in part) associated with the surprising nature of the event. In addition, during a high workload situation, the pilot was probably distracted by the reflection of the helicopter’s red anti-collision light reflecting off nearby cloud while wearing NVG.

In response to the distraction, the pilot asked the ACM to switch the light off. However, the ACM was not familiar (or required to be familiar) with the operation of the light switch, and inadvertently switched on the strobe light, which exposed the pilot to bright white light reflecting off cloud while wearing NVG. Exactly when the strobe light was switched on, and whether it contributed to the unusual attitude, could not be determined.

Earlier that evening, the pilot had diverted to Crookwell during a flight from Canberra to Orange due to the presence of thunderstorms and reduced visibility en route. The flight from Canberra to Orange was conducted under NVFR with NVIS, when the use of instrument flight rules (IFR) was practical and involved less risk. The ATSB identified that although the operator’s policies stated that EMS flights should be conducted under IFR where practical, this policy was not reinforced in the manual that covered NVIS operations. An IFR departure was not available for the take-off from Crookwell.

What’s been done as a result

As a result of this occurrence, the helicopter operator undertook several proactive safety actions, including clarifying its flight planning policy on IFR and NVIS operations and enhancing its training and advisory materials. The operator is also assessing the potential fitment of flight data monitoring equipment to all of its fleet.

Safety message

Although NVIS/NVG can significantly improve the quality and quantity of visual information available to pilots at night, the use of such devices also involves risk in some situations. This occurrence highlights the importance of ensuring that operators and pilots have robust processes for deciding when to conduct NVIS operations. It also serves as an example of the limitations and risks of NVIS operations when there are external light sources or reflections, and highlights the benefit of having a predetermined strategy for responding to degraded visibility conditions.

Download final report
[Download  PDF: 1.35MB]
Alternate: [Download  DOCX: 627KB]

The occurrence


Safety analysis


Safety issues and actions

Sources and submissions

Safety Issue

Go to AO-2016-160-SI-01 -

Policies and procedures for planning IFR and NVIS flights

Although CHC Helicopter Australia’s operations manual stated that emergency medical service flights should be conducted under instrument flight rules (IFR) ‘where practical’, its procedures for night visual flight rules (NVFR) operations using night vision goggles did not clearly state when IFR rather than NVFR should be used.


Safety issue details
Issue number: AO-2016-160-SI-01
Who it affects: Operating crew and other occupants on emergency medical service flights
Status: Adequately addressed
General details
Date: 21 October 2016   Investigation status: Completed  
Time: 2240 AEST   Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): Crookwell Medical (HLS)   Investigation phase: Final report: Dissemination  
State: New South Wales   Occurrence type: E/GPWS warning  
Release date: 06 November 2018   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Eurocopter  
Aircraft model BK 117 C-2  
Aircraft registration VH-SYB  
Serial number 9203  
Operator Lloyd Helicopters trading as CHC Helicopter Australia  
Type of operation Medical Transport  
Sector Helicopter  
Damage to aircraft Nil  
Departure point Crookwell, NSW  
Destination Orange, NSW  
Last update 14 November 2018