Reference number
RA2021-00038
Published date
Mode
Affected operation/industry
Concern subject type
Reporter's deidentified concern

Multiple reporters approached the ATSB with concerns regarding loss of control incidents involving AW139s operated by search and rescue (SAR) operators, crewed with single pilots utilising night vision goggles (NVG).

The reporters collectively state that single pilot SAR and Emergency Medical Service (EMS) NVG operations began in Australia as a way to allow aircraft operators to conduct their existing operations (mainly night out-landings and winching during low-visibility conditions), in a safer manner than under previous Nightsun operations/exemptions.

Conducting single pilot NVG operations for out-landings is in line with other jurisdictions. However, the Australian SAR/EMS NVG single pilot role has expanded to include advanced low-level operations, searching, advanced winching, vessel winching and low visibility operations. These operations are frequently being conducted as emergency situations in poor useable cue environments (UCE) due to the tasking priority and task approval by the contracting agency. The heightened risks of single pilot NVG operations are outlined in multiple research papers, regulator guidance and past incident and accident reports.

The reporters collectively state that the Australian industry’s liberal interpretation of the mandatory second occupant, has allowed aircrew officers (ACO) to operate from the cabin during NVG winching operations. One reporter stated that when the ACO is in the rear cabin, their attention is required on other critical duties and is no longer focused on the cockpit. In the winching phase, the full attention of the ACO is required on exactly that, resulting in the pilot being left with degraded or no cockpit support at the time of highest risk, when they would benefit from it most (ATSB investigation AO-2018-039). Conversely, if the pilot has any expectation of help or crosscheck from the ACO, it may exacerbate a situation when it is not forthcoming, as highlighted in ATSB investigation AO-2016-160.

The reporters believe that Australia continues to base the SAR night winching crewing model from a time when smaller, performance limited helicopters, that could not accommodate multi-crew, were used. This is no longer the case in the era of AW139s, which is an aircraft that is designed for, and mostly operated by multi-crew. Australia’s crewing model and mission profiles are outside global norms, best practice, and beyond the intention of CASA regulations and the rotorcraft manufacturer’s certifications.

All the reporters believe that even non-complex night SAR operations utilising NVGs is at the upper end of pilot cognition, regardless of single pilot experience or training.

The pilot may be required to plan an unscheduled approach at any time throughout the night, to a remote, unfamiliar scene, often with uneven terrain. The pilot must take into account associated winds, groundspeed, vortex ring considerations, turbulence and degraded NVG vision considerations, while alternating their visual scan from inside the cockpit to outside. The pilot is required to manage winching, the person on the cable below the helicopter, the visual reference and the instrument scan at the same time, while considering a departure plan. The pilot is also expected to have the capacity to deal with abnormal events without reaching task saturation.

The Christopher Wickens model recognizes that the human brain has limited processing capacity, and if overloaded with inputs, the attentional resources allocated to the various mental operations needed to effectively perform a task will significantly diminish.

One reporter provided an example of the winch emergency process at night for a winch runaway, approved by many operators, where the single pilot in the hover has to take their eyes off their external reference and instruments, to look inside and locate a switch on the centre console to turn off the winch at the ACO’s command. This process can take up to 45 seconds, during which the pilot’s attention is taken away from already demanding simultaneous visual and instrument scans, to locate the switch, while experiencing no depth perception, no peripheral vision, reduced field of view and a higher cognitive load for the operation overall. The reporter states they have observed this process resulting in loss of altitude and drift on multiple occasions. This is supported by Wickens & McCarley (2008) who stated that while searching outside for cues, changes on instruments can be missed. These missed changes can lead a pilot to believe that their knowledge of their position and trajectory in space is accurate.

Another reporter stated that in some cases, the best cues are on the left side and not able to be seen by the pilot in the right seat. Additionally, wind or obstacles may prevent turning to the better cues resulting in winch activities being conducted with sub-optimum cues. Wiggins et. al (2012) stated that pilots tend to underestimate the likelihood of loss of control and overestimate their ability to continue to control the aircraft if visual references are lost.

While tasking, fatigue, culture, weather, illumination and lighting may be contributing factors to loss of control incidents, the reporters believe that these are secondary to the primary safety issue. That is, the workload is too high and the flight control characteristics and control laws of the AW139 are too demanding for single pilot NVG winch operations. While this is partly the reality of the type of operation, it could be overcome if a pilot was in the left seat to affect the winch.

The reporters collectively agree that there is no way for a single pilot to cross check flight instrument parameters at a level of best practice for night operations without detracting from their primary scan of the outside environment. The ability to remain stationary and not drift in poor UCE is impossible, without very high order AFCS or alternative provision for drift cues (e.g. helmet mounted head-up displays). But these require significant training, proficiency, cost and procedural discipline. None of this is available on the current AW139 fleet in Australia, nor is it appropriate unless CASA were to pursue a construct of dedicated SAR aircraft with increased configuration requirements and pilot proficiency standards.



Manufacturer’s guidance



The Original Equipment Manufacturer (OEM) determined a two-crewing requirement for NVG operations, specifically, minimum crewing requirements of the AW139 Rotorcraft Flight Manual (RFM) Supplement 60, which states: ‘For single pilot operations (see Supplement 24 or Supplement 32 FAA Only): an additional, trained, crew member must be equipped with and use NVG’s during take-off and landing, on unimproved sites, to assist in obstacle identification and clearance.

One reporter believes that the RFM statement ‘..to assist in obstacle identification and clearance’ fails to highlight the additional protections of pilot monitoring and division of cockpit workload. The second occupant is not only intended for obstacle clearance and workload sharing, but for aircraft attitude monitoring and intervention (e.g. ‘Attitude … Attitude … ATTITUDE ..TAKING OVER’).

The reporter further states that the OEM is aware of the limitations of the AW139 for NVG winching operations, and also many pilots’ lack of understanding of the flight control characteristics. As such, the test report for single pilot NVG approval with an additional trained crew member was for surveyed airport to surveyed airport (including heliport) only.



The test report states that “it is conceivable that more complex operational tasks into unprepared locations would benefit from an ‘extra pair of eyes’ and assistance in operating more complex role equipment. Although arguably this is an issue that should be covered by the Operational Rules, the example given in MG16 of possible Flight Manual Supplement content represents a pragmatic approach to managing the interface between Operational and Airworthiness Rules”.

The reporter states that the lack of any testing by the OEM for single pilot night time winching operations indicates that the OEM did not intend for the aircraft to be used for single pilot NVG winching operations, nor is the OEM prepared to certify the aircraft for that operation and crewing model. Instead, the OEM has passed responsibility of risk controls for NVG winching operations to the relevant regulator.



The reporters believe that Australia, utilising the ACO in the rear cabin for night time winching operations, has been operating beyond the intention of the certification basis applied by the OEM and approved under EASA Part 29.

ATSB Comment

The ATSB made informal enquiries with multiple credible sources within industry, both in Australia and overseas, regarding the reporters concerns. It was evident from these enquiries that there are wide-ranging opinions within industry regarding the appropriateness of NVG winching risk controls and some of the reporters statements.

The ATSB also conducted a review of associated ongoing and closed ATSB investigations and the ATSB occurrence database.

That review, in combination with the industry feedback, provided sufficient reason to progress the reporters concerns through to CASA for comment.

To ensure transparency with industry, gain an understanding of any additional potential safety issues, and importantly, to ascertain if there were existing controls in place by operators to mitigate the risk(s), the full REPCON report was forwarded to the seven Australian operators who currently conduct single-pilot NVG operations in the AW139 for their information and comment. Five operators provided feedback.

The ATSB noted there are varying opinions regarding the technical suitability and intentions of the original equipment manufacturer (OEM) and CASA regulations for the conduct of single-pilot NVG winching operations in the AW139.

A review of the responses from Australian AW139 operators indicates that, while some operators are not opposed to a minimum two pilot requirement, others identified that an amendment to the crewing model had the potential to introduce new risks to these operations, such as:

  • pressure to complete single-pilot tasks prior to last light
  • crew resource management procedures and proficiency issues
  • reduction in performance margins of the aircraft due to increased weight and/or payload limitations.

However, regardless of an operator’s position on the crewing model, all operators stated it is not the only risk control that should be considered for NVG winching operations.



All operators agreed that the patient risk assessments and subsequent tasking of aerial assets by the state based rescue coordination centres needs to be addressed. This concern has also been raised in several active ATSB investigations, and is being progressed separately through the ATSB REPCON process (RA2021-00074).



Most operators indicated that a poor UCE is an overarching factor in the serious incidents that have occurred during single-pilot NVG winching operations. Considerations for potential safety actions to mitigate the risks of operating in a reduced UCE included:

  • Increased currency/recency requirements for operational crew.
  • Review of procedures relating to restrictions due to location, weather and illumination.
  • Enhanced training/procedures regarding multi-stage task assessments and decision-making.
  • Use of the auto hover. Noting that one operator prohibits the use of the flight director hover (HOV) mode during over land winch operations, as their assessment is that the HOV mode may be used inappropriately to allow a pilot to hover when there are insufficient visual references to hover the aircraft manually; while another operator recognises that the auto-flight control system does not provide an adequate hover position in all conditions over land, but crews are well trained in the auto-hover and hover page Horizontal Stabiliser Indicator.
  • All operators agree that additional high intensity searchlights need to be implemented to improve the UCE. However, some operators are concerned that unless this is a regulatory requirement, the cost of implementation would result in difficulties meeting contractual obligations.

All operators are supportive of an industry forum to further discuss the concerns raised above and contribute to the identification of appropriate risk controls associated with NVG winching operations.

Additionally, some operators have highlighted that a number of the incidents and broader concerns referred to in the REPCON are not isolated to the AW139. The REPCON reporters experience and knowledge is limited to the AW139 and the reporters intentions were to highlight what they consider safety issues in that rotorcraft, with a view that any safety outcomes would apply to the majority of single-pilot NVG operations. Their view, that would then set a precedent to review other aircraft types conducting the same operations. 

The ATSB concurs that these concerns are not necessarily limited to the AW139, and noting the number of occurrences involving rotorcraft conducting a SAR/HEMS function that have had a deviation from safe flight in recent years, the ATSB suggests that the focus of the REPCON should be to identify risk controls in all helicopter types conducting single-pilot NVG winching operations. 

In addition, industry could consider whether other (non-winching) single-pilot NVG operations in confined areas around complex terrain present similar risk profiles and would likely benefit from any safety actions that may result from this report. The following ATSB investigations and occurrences are relevant to this REPCON:

AO-2021-022

  • AO-2021-018
  • AO-2021-010
  • AO-2020-038
  • AO-2020-031
  • AO-2018-039
  • AO-2016-160
  • AO-2011-166
  • ATSB Occurrence – 201906474
  • ATSB Occurrence - 201808484
  • ATSB Occurrence - 201704374
  • ATSB Occurrence – 201604008

The REPCON was referred to the regulator for information and comment.  Specifically, the ATSB requested CASA clarifies its interpretation of the AW139 RFM and the intentions of the current regulations relating to single-pilot NVG winching approval.

Regulator's response

CASA advised that they had previously sought clarification from Leonardo on the minimum crewing requirements for NVIS operations in the AW139. Leonardo provided a “No Technical Objection” to a NVG trained crew member in the aircraft cabin in order to satisfy the flight manual requirements. A copy of this correspondence was provided to the ATSB.  Noting the “No Technical Objection” does not specifically address the context of single pilot NVIS winching, and neither does the flight manual. In summary, while not specifically stated, the AW139 RFM does permit for single pilot NVG winching operations.



Providing that the RFM permits single pilot NVIS operations, CAO 82.6 does not prevent a single NVIS pilot and a NVIS aircrew member (winch operator) conducting NVIS winch operations or landing to a HLS NVIS basic. CASA’s intention is to transition the existing legislation into the Civil Aviation Safety Regulations and associated Manual of Standards. This will be achieved under CASA project OS13/19 which involves the transition of the existing NVIS legislation from CAO 82.6 to Part 91, Part 133 and Part 138 MOS’s.

In summary, while not specifically stated, the CASA regulations do allow for single pilot NVG winching operations. However, CASA considers the matters contained with the Repcon to be a valid safety concern and intends to discuss the Repcon at the earliest opportunity with Industry NVIS representatives.



The intended points for discussion at the NVIS TWG are as follows:



• Industry viewpoint on the spike in NVIS incidents

• Suitability of simulation for NVIS manipulative operations (confined areas and winch operations)

• Suitability of current NVIS recency requirements

• NVIS flight iterations for specialist skills i.e. winch, fast roping, fire operations etc

• Use of white light such as nitesun/trakka for winch operations

• Suitability of the AW139 for single pilot winch operations

• Suitability of other similar aircraft for NVIS winch operations

• NVIS winch techniques including – higher hover height for flyaway potential vs lower hover height for better hover reference

The intent is for CASA to seek feedback from industry NVIS operators relevant to the points raised within the Repcon and on other operational safety concerns.



CASA will then assess whether changes are necessary for NVIS minimum crewing requirements or whether requirements for NVIS training, ICUS, recency or in-flight activities are modified with the MOS and NVIS AC.



At time of publishing (August 2022), CASA has agreed to update the NVIS multi-part AC to include detailed information on the UCE and use of white light for situational awareness. Due to competing priorities, it is expected the amendment to the AC will be complete by late September 2022.