Night HEMS BK117 Loss of Control (CHC BK117C2 VH-SYB)
On the evening of 21 October 2016, Helicopter Emergency Medical Service (HEMS) Airbus BK117C2 VH-SYB operated by CHC Australia suffered a serious incident over New South Wales.
The Accident Flight
The Australian Transport Safety Bureau (ATSB) explain in their safety investigation report that:
The crew were returning [from Canberra, ACT] to their home base at Orange, New South Wales, after conducting a [HEMS] task [that saw them depart from base at 1650]. 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 [ITT M949 ANVIS-9] night vision goggles (NVG).
The pilot had arrived early, at 1600, for duty due to commence at 1730 as the night shift pilot. She had 5,065 hours total time, 602 on type. The pilot had c 770 hours of night experience including about 300 hours on NVIS. The pilot had completed an NVIS proficiency check flight on 9 August 2016.
In contrast the ACM was on a 0730-1730 day shift. Remarkably she would not however exceed a 14 hour duty day report ATSB as ACM duty time only commenced when the aircraft was tasked. The ACM had 859 hours total experience, 465 hours on type. She had last completed an NVIS capability check flight on 31 May 2016. As an ACM, she had been trained to provide assistance to pilots in deteriorating visibility conditions and in-flight recovery procedures.
The pilot planned the return flight as an NVIS NVFR flight rather than under instrument flight rules (IFR) “as it provided more diversion options along the planned route” as thunderstorms were forecast.
The helicopter departed Canberra Hospital at 2010 for the return flight to Orange, with both the pilot and ACM wearing NVG.
ATSB note that:
NVGs are not designed to be used for flight under IFR, however, it is possible to ‘see through’ areas of light moisture when using NVGs which increases the risk of inadvertently entering IMC.
They report that:
Approximately 20 NM north-west of Crookwell the pilot determined that the weather conditions were no longer suitable for continuing the flight due to closing gaps between the storms and reduced visibility ahead. After some discussion between the pilot, ACM and paramedic regarding suitable diversion sites, it was decided to divert to the Crookwell Medical helicopter landing site (HLS).
They waited there until 2240 until the storm had passed.
The pilot reported that she had no specific pressure or reason to return to Orange that night. However, she felt a responsibility to complete the mission and to return the helicopter back to home base if possible and safe to do so, thereby allowing further emergency medical service (EMS) or search and rescue (SAR) tasking from the Orange base
The pilot reported that when the helicopter reached the take-off safety speed, she adjusted the helicopter attitude but the searchlight reflecting off the rain limited her forward visibility. She adjusted the searchlight down and to the right so she could see the ground more clearly, but the forward visibility did not improve enough for her to be comfortable with continuing the flight in that configuration. She then adjusted the helicopter’s attitude to slow the helicopter and help maintain visibility with the ground.
From this point, there was a rapid series of events. The pilot recalled that a flash of the anti-collision light reflecting off cloud alerted her to the presence of low cloud above. She immediately assessed that returning to land was no longer an option and called ‘inadvertent IMC’ while initiating the operator’s inadvertent IMC recovery procedure.
She transitioned to flying on instruments, and commenced a rapid, vertical climb at maximum power, announcing that she was climbing to the other occupants. With the next flash of the anti-collision light, they had entered cloud.
In an attempt to reduce the distracting effect of the anti-collision light, the pilot asked the ACM to turn the light off. The ACM removed her NVG, took a few seconds to locate the switch and, not realising the switch had three positions, inadvertently moved the anti-collision/strobe light switch from the ACOL (anti-collision light) position to the ON (anti-collision and strobe light) position. This changed the reflected light from red to bright white, which the pilot subsequently reported had a blinding effect on her vision while wearing NVG. The pilot again asked the ACM to turn the light off, which the ACM then actioned.
The pilot recalled that, during this period, the momentum of the helicopter’s climb was decreasing and the airspeed was reducing, so she lowered the helicopter’s nose to increase the airspeed. She recalled that she intended to lower the pitch angle by 5° but inadvertently overcorrected to about 15° nose-down, as well as inadvertently allowing a slight roll to the left. She also noted that during this period, the flashing of the reflected external lights had been distracting, and her transition to effective instrument scanning had not been ‘tidy’.
Very soon after the helicopter entered the unusual attitude, the enhanced ground proximity warning system (EGPWS) provided an aural ‘caution terrain’ alert. The pilot called ‘climbing, climbing, climbing’ and commenced unusual attitude recovery actions (in accordance with the operator’s procedure) by adjusting the helicopter’s attitude to wings-level and initiating a climb, with the helicopter still at full power. She recalled that the transition from the unusual attitude to the recovery attitude was conducted promptly and smoothly.
The pilot estimated that the unusual attitude event occurred between 200 and 400 ft above ground level (AGL). The ACM estimated that it occurred at about 500 ft AGL, and that she believed the helicopter could not have descended below 200 ft AGL as she did not recall the altitude alerter (normally set at 200 ft AGL during a departure) annunciating.
Due to continuing poor weather the helicopter ultimately diverted to Bathurst, NSW landing after an instrument approach at 2331.
The Safety Investigation
The helicopter was not fitted with a Flight Data Recorder (FDR) nor was one required by regulation.
When the pilot was on the ground in Canberra planning the flight from Canberra to Orange, there had been a significant meteorological information (SIGMET) issued, indicating thunderstorms in a squall line with hail. In addition, the current area forecast (ARFOR), valid from 1925, stated there were frequent thunderstorms in a squall line, as well as isolated thunderstorms with hail. The pilot reported that she checked the weather information using the operator’s tablet computer, but did not see the SIGMET or a statement in the ARFOR about frequent thunderstorms in a squall line. Instead, she recalled that the information in the ARFOR was the same as she had seen prior to departing Orange (which was issued at 1600 and included isolated thunderstorms). The reason why the pilot did not notice the SIGMET or the updated ARFOR while on the ground at Canberra (or subsequently at Crookwell) could not be determined.
Prior to departing Canberra, the ACM and paramedic had significant reservations about the approaching line of thunderstorms, and they stated their concerns to the pilot. The pilot briefed the ACM and medical team about the weather conditions, advised she had uploaded sufficient fuel for en route diversions and holding, and that they had multiple diversion options on the route. The pilot had experience flying operations in thunderstorm conditions. It is likely that her confidence flying in similar weather conditions moderated the ACM’s and paramedic’s reservations, and led to them agreeing to conduct the flight even though they both still had concerns.
Again…
Prior to departing from Crookwell, the paramedic initially stated to the pilot that he was not comfortable with departing as he was not confident the storms had passed, and the departure was delayed until all the parties were comfortable that the storms had passed.
The ACM subsequently reported that, in hindsight she was fatigued prior to the flight from Crookwell and should have stated to the pilot that she was fatigued.
ATSB comment that:
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 operator noted that its policy was for IFR to be used wherever practical for such flights. It also advised that, following the occurrence, it identified that this policy had not been applied consistently across all of its EMS/SAR bases.
ATSB notes that:
Crookwell Medical HLS was not equipped with a published instrument flight rules (IFR) departure procedure and there were no recorded weather observations available.
Furthermore:
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.
While the pilot asked the ACM to switch the light off, the ACM was not familiar (or required to be familiar) with the operation of the light switch, and inadvertently switched on the strobe light.
Exactly when the strobe light was switched on, and whether it contributed to the unusual attitude, could not be determined.
Safety Actions
ATSB report that:
On 25 November 2016 [CHC] issued a Flying Staff Instruction (FSI) to all EMS/SAR pilots and aircrew to standardise IFR flight planning policy and clarify the conditions under which NVIS operations below lowest safe altitude (LSALT) could be planned and conducted.
Fourteen months later:
On 31 January 2018, the operator incorporated the text of that FSI into the Operations Manual Part F (OMF).
They also stated the operator was assessing “the potential fitment of flight data monitoring equipment to all of its fleet”.
ATSB 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.
Historical Context
This serious incident occurred less than six months after a fatal CHC accident in Norway and the CHC Group filing for Chapter 11 bankruptcy protection in the US. It occurred less than 5 months before a CHC Ireland fatal night SAR helicopter accident positioning to a refuelling site.
Safety Resources
The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn. You may also find these Aerossurance articles of interest:
- Air Ambulance Helicopter Struck Ground During Go-Around after NVIS Inadvertent IMC Entry
- A HEMS Helicopter Had a Lucky Escape During a NVIS Approach to its Home Base
- NVIS Autorotation Training Hard Landing: Changed Albedo
- SAR Helicopter Loss of Control at Night: ATSB Report
- HEMS A109S Night Loss of Control Inflight (N91NM)
- Air Ambulance A109S Spatial Disorientation in Night IMC (N11NM)
- Deadly Dusk Air Ambulance Bird Strike
- HEMS Black Hole Accident: “Organisational, Regulatory and Oversight Deficiencies”
- HEMS S-76C Night Approach LOC-I Incident
- Drift into Danger: AW109SP Night HLS Accident
- ‘Procedural Drift’: Lynx CFIT in Afghanistan
- US Fatal Night HEMS Accident: Self-Induced Pressure & Inadequate Oversight
- HEMS Black Hole Accident: “Organisational, Regulatory and Oversight Deficiencies”
- Taiwan NASC UH-60M Night Medevac Helicopter Take Off Accident
- Italian HEMS AW139 Inadvertent IMC Accident
- Dim, Negative Transfer Double Flameout
- BK117B2 Air Ambulance Flameout: Fuel Transfer Pumps OFF, Caution Lights Invisible in NVG Modified Cockpit
- HEMS Black Hole Accident: “Organisational, Regulatory and Oversight Deficiencies”
- EC135P2 Spatial Disorientation Accident
- EC135P2+ Loss of NR Control During N2 Adjustment Flight
- Austrian Police EC135P2+ Impacted Glassy Lake
- That Others May Live – Inadvertent IMC & The Value of Flight Data Monitoring
- Crashworthiness and a Fiery Frisco US HEMS Accident
- HEMS S-76C Night Approach LOC-I Incident
- FOD and an AS350B3 Accident Landing on a Yacht in Bergen
- Air Methods AS350B3 Air Ambulance Tucson Tail Strike
- Air Ambulance B407 Hospital Helipad Deck Edge Tail Strike During Shallow Approach
- South Korean Fire-Fighting Helicopter Tail Rotor Strike on Fuel Bowser
- NTSB on LA A109S Rooftop Hospital Helipad Landing Accident
- HEMS Downwash Injuries: Two More Case Studies
And:
- The Tender Trap: SAR and Medevac Contract Design Aerossurance’s Andy Evans discusses how to set up clear and robust contracts for effective contracted HEMS operations.
On error management:
- Professor James Reason’s 12 Principles of Error Management
- Back to the Future: Error Management: revisiting James Reason’s 1997 classic Managing the Risks of Organizational Accidents
…and our review of The Field Guide to Understanding Human Error by Sidney Dekker presented to the Royal Aeronautical Society (RAeS): The Field Guide to Understanding Human Error – A Review
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