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INVESTIGATION REPORT

The BEA investigations are conducted with the sole objective of improving aviation safety and are not intended to apportion blame or liabilities.

BEA2019-0632.en/November 2020

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Accident to the McDonnell Douglas 369Dregistered F-GJLXon 16 October 2019at Blancey (Côte-d'Or)Time 15:50(1)

Operator Jet Systems Hélicoptères Services (JSHS)Type of flight Aerial surveyPersons on board Pilot, system operator, technical observerConsequences and damage Helicopter severely damagedThis is a courtesy translation by the BEA of the Final Report on the Safety Investigation published in September 2020. As accurate as the translation may be, the original text in French is the work of reference.

(1)Except where otherwise indicated,

times in this report are local.

1 - HISTORY OF THE FLIGHT

Note: the following information is principally based on statements and GNSS data from the aircraft’s equipment.

The crew(2) of the MD 369D registered F-GJLX were inspecting several sections of medium voltage(3) powerlines in the Blancey region (Côte-d'Or), on behalf of Enedis.

The crew were performing their third rotation and had already logged more than one flight hour since they had last taken off. Shortly before 16:00, they were carrying out an inspection of a last powerline section before returning to Pouilly - Maconge aerodrome (Côte-d'Or) to refuel for the final time of the day.

While the pilot was maintaining a safety distance with the line to be checked, the helicopter’s airframe struck a high voltage(4) powerline cable perpendicular to the one being inspected(5) and the main rotor cut through another cable of this line (see point of Figure 1 below).

The pilot maintained control of the helicopter and decided to carry out a precautionary landing in a field close to a country road.

(2) See §2.2.2.

(3)The medium voltage (MV) category

concerns electrical installations in

which the voltage is between 1,000 V and

50,000 V AC or 1,500 V and

75,000 V DC.

(4) The high voltage (HV) category

concerns electrical installation in which the voltage exceeds

50,000 V AC or 75,000 V DC.

(5) During the mission, powerlines from neighbouring grids were crossed

several times.

Collision with powerline during a powerline inspection flight, precautionary landing

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Source: BEA

Figure 1: path of F-GJLX

2 - ADDITIONAL INFORMATION

2.1 Aircraft information

The F-GJLX is a McDonnell Douglas MD 369 D helicopter, also called the Hughes 500.

The F-GJLX is not equipped with an upper or lower cable cutter unlike the second Hughes 500 operated by JSHS(6).

In light of the operational aspect of the accident, the BEA did not go to the site. JSHS indicated that the helicopter had suffered the following damage:

� dents linked to the electric arcs created when the cable was cut, on the rotor head, blades and airframe;

� damaged canopy.

(6) Jet Systems Hélicoptères Services is an aircraft operator

based at Valence Chabeuil, founded in 1987 and holds

an Aircraft Operator Certificate. JSHS is specialized in

passenger transport and aerial work.

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2.2 Mission and flight preparation

2.2.1 Mission

The flight was operated by JSHS on behalf of Enedis (EDF group). The day’s mission was a combined inspection which consisted of visually detecting the anomalies on the Enedis MV powerline grid in the Blancey region of Côte d’Or and of analysing the vegetation bordering the powerlines using technical equipment (camera and LIDAR(7)).

According to JSHS’ operations manual, part C, section 3.2.2.1.B, concerning combined inspections (analysis of vegetation and line check), the helicopter should travel at a height of 5 to 15 m above (generally to the left of ) the powerline being inspected, at a speed of between 20 km/h and 60 km/h.

The operations manual also highlights the risk of collision with surrounding obstacles such as tall trees, powerlines from neighbouring grids, antennas, etc.

2.2.2 Role of crew members

According to the operations manual, part C, section 3.2, powerline inspections, the crew must be composed of the following personnel for this type of mission:

� A pilot-in-command in the left seat. � A system operator (also called navigator) in the right seat(8) responsible for the operation

of the camera and LIDAR system, and who analyses the vegetation as well as providing help with navigation. He informs the pilot-in-command of any corrections to be made to the position of the helicopter with respect to the powerline being inspected and of any other intersecting powerlines.

� A technical observer, in the rear right seat (JSHS personnel) who visually identifies the anomalies on the powerlines and records them in the appropriate software.

2.2.3 Briefing

The operations manual indicates that the crew must carry out a pre-flight briefing in order to determine the route to be taken to inspect the power grid according to the latest weather information. The dangerous areas are also to be covered in this briefing: terrain, presence of cables, ski lifts, intersections with HV cables and neighbouring grids for example. Based on the aforementioned points, the crew determine a strategy to optimize the route as best as possible. The navigator has the predominant choice with respect to the route to be followed. When the mission lasts several days, this briefing is also repeated at the end of the day for the following day.

The pre-flight briefing the day of the occurrence (and for all of the mission) had been in English as the navigator was Polish. No member of the crew expressed comprehension problems. The crew also planned the mission taking into account the Enedis recommendation not to exceed six flight hours per day.

(7) Light detection and ranging.

(8) In the scope of the occurrence

flight, the operator was employed by

the subcontractor, Visimind.

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The briefing was carried out with a map in order to decide on the itinerary and to visualize the various obstacles. The navigator proposed a route, which the pilot-in-charge requested to fly in the opposite direction to better take into account the weather situation on all of the route (sunlight, cloud cover, wind). The navigator specified that he was more concentrated on the powerlines as a whole and recognizing the zones, than on the precise location of the powerline intersections or other obstacles on the path.

2.3 Crew information and statements

2.3.1 Pilot

The French, 35-year-old pilot held a Commercial Pilot License - Helicopter (CPL(H)) issued in December 2017.

He had logged a total of 2,862 flight hours of which 168 flight hours on the Hughes 500. He had started carrying out inspection missions in April 2019 and had logged 300 flight hours in this field.

The following information is based on his statement:

The pilot did not see the powerline before striking it due to the small amount of contrast between the HV powerline and the surrounding area making it difficult to detect the cables, and due to the absence of a metal support in his field of vision. The section of line being inspected at the time of the collision was slightly orientated into the sun but the sun was not dazzling.

He indicated that he had not felt particularly tired during the flight. They had debriefed on the ground with the rest of the crew. The pilot indicated that the navigator had zoomed in on the screen display too much and that consequently he had not detected the HV line even though it was in the software. The navigator indicated that this was his first inspection of MV lines and that he was more used to the long straight lines of HV powerlines which, unlike the MV powerlines, were made up of numerous sections which do not require such a large zoom in. They had not worked together before this mission.

The pilot explained that communication between the pilot and navigator is important for this type of mission and he considered that the navigator did not necessarily advise of the relevant dangers or did so a little late (they are usually indicated 300 m or three “supports” beforehand). He considered that it was the navigator’s job to warn of dangers and notably, of an upcoming intersection with another powerline. He specified, however, that the navigator had numerous tasks to carry out.

2.3.2 System operator (navigator)

The Polish, 28-year-old navigator was employed by Visimind. He had started his navigator training in October 2018 when he was recruited. He had also followed a five-day training course at JSHS in January 2019 which had led to a practical examination and a certificate awarded by ENEDIS.

The day of the accident, he had logged 150 flight hours of high-risk operations on the Hughes 500 and the Robinson 44 which permitted him to work in France as system operator.

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He indicated that while flying in a straight line along the last section of the powerline and before the collision, he was checking, with the data acquisition software (see Figure 2), that they had not missed a powerline section, before landing. Consequently, he had zoomed in on the map, had not detected the HV powerline (in red in Figure 2) on the helicopter’s path and had not been able to warn the pilot.

Source: Visimind

Figure 2: second screen available to navigator, MV powerline being inspected in blue

2.3.3 Technical observer

The French, 42-year-old observer had held this position at JSHS since 12 February 2019.

On the day of the accident, he had logged a total of 1,200 flight hours of which 800 flight hours on the Hughes 500 as observer.

He indicated that, contrary to normal practices, there was very little dialogue between the navigator and the pilot and concluded that, in his opinion, this was not the norm. He also added that he had not felt that any of the crew were particularly tired.

3 - CONCLUSIONS

The conclusions are solely based on the information which came to the knowledge of the BEA during the investigation. They are not intended to apportion blame or liability.

Scenario

During the third rotation of the day to inspect powerlines of a MV grid, the crew of the Hughes 500 struck and cut through two cables of a HV powerline running perpendicular to their path. The navigation software used by the system operator contained the HV line but the operator had not set the screen zoom parameters to allow him to see it and give the pilot prior warning. In addition, given the environment and layout of the HV powerline poles, it was difficult for the pilot to detect the powerline.

The pilot managed to maintain control of the helicopter and carried out a precautionary landing in a field situated 200 m straight ahead, close to a country road.

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Contributing factors

The following factors may have contributed to the collision with the HV line while inspecting the MV grid:

� Inappropriate management of the tools made available to inspect the powerline and monitor the neighbouring grids.

� A pre-flight briefing which insufficiently reviewed the obstacles which would be present during the flight.

� The difficulty of detecting powerlines when flying into the sun in an environment where there is little contrast and the poles do not reflect the light. Moreover, the poles were not in the pilot’s field of vision and were spaced at intervals of more than 600 m.