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The Australian Transport Safety Bureau (ATSB) is reminding helicopter operators about the importance of considering skill consolidation processes when transitioning pilots to a new and technically different helicopter type, and to build safety margins into their operations to give pilots the best opportunity to succeed.
The reminders come following the ATSB’s completion of a systemic investigation into an accident involving a Eurocopter (Airbus Helicopters) EC120B helicopter which collided with the water after the pilot experienced a significant loss of directional (yaw) control during a go-around. The EC120B, registered VH-WII and operated by Whitsunday Air Services, had departed Hamilton Island Airport, Queensland on 21 March 2018 on a charter flight to a pontoon at Hardy Reef, on the Great Barrier Reef, with a pilot and four passengers onboard.
While on a slow approach—to allow several birds to disperse—the pilot yawed the helicopter to the left with the intent to land on one of two positions on the pontoon. This subjected the helicopter to about a 20-knot crosswind from the right. When approximately 7 feet above the pontoon, the pilot noticed a message illuminate on the helicopter’s vehicle engine multifunction display (VEMD) and elected to conduct a go-around.
During the go-around and when about 30–40 feet above the water, the helicopter suddenly and rapidly yawed to the left. After unsuccessful control inputs to recover from the rapid left yaw, and with limited time, the pilot was unable to conduct a controlled ditching and the helicopter collided with water. The helicopter’s emergency pop-out floats were not deployed, and the helicopter almost immediately rolled inverted and rapidly filled with water.
The pilot and two of the three rear-seat passengers evacuated from the helicopter with minor injuries. Although the impact forces were survivable, the other two passengers (seated in the front left and middle rear seats) were unconscious following the impact and did not survive the accident. The helicopter later sank and was unable to be recovered.
“The ATSB’s investigation determined it was likely the pilot experienced a high workload during the final approach to the pontoon and a very high workload during the subsequent go-around,” said ATSB Director Transport Safety Dr Mike Walker.
The investigation found that although none of the possible VEMD messages required immediate action, the pilot considered a go-around to be the best option given the circumstances at the time. During the go-around, after the helicopter started rapidly yawing to the left, it is very likely the pilot did not immediately apply full and sustained right pedal input to counter the rapid left yaw.
In the two weeks prior to the accident, the pilot (with a total of about 1,300 flying hours) had obtained a new type rating to fly the EC120B. While accumulating 11 hours experience in command on the EC120B, the pilot had also flown about 16 hours in another and technically different helicopter type (a Bell 206L3).
“The operator had complied with the regulatory requirements for training and experience for pilots on new helicopter types but had limited processes in place to ensure pilots with minimal time and experience on a new and technically different helicopter type had the opportunity to effectively consolidate their skills required for conducting operations to pontoons,” Dr Walker said.
The EC120B has a clockwise-rotating main rotor and a ‘Fenestron’ shrouded tail rotor system. In 2005, the helicopter’s manufacturer released a service letter to remind pilots that Fenestron tail rotors require significantly more pedal travel than conventional tail rotors when transitioning from forward flight to a hover. A section of that letter stated that pilots needed to be prepared for a significant forward movement of the right foot and that insufficient application of [right] pedal would result in a leftward rotation of the helicopter during the transition to hover.
The ATSB found that the safety margin associated with landing on the pontoon at Hardy Reef was reduced due to a combination of factors, each of which individually was within relevant requirements or limits. These factors included the helicopter being close to the maximum all-up weight; the helicopter’s engine power output being close to the lowest allowable limit; the need to use high power to make a slow approach in order to disperse birds from the pontoon; and the routine approach and landing position on the pontoon requiring the pilot to yaw left into a right crosswind (in a helicopter with a clockwise-rotating main rotor system).
In addition, the investigation also identified safety factors associated with the operator’s use of passenger-volunteered weights for weight and balance calculations, the operator’s system for identifying and briefing passengers with reduced mobility, bird hazard management at the pontoons, and passenger control at pontoons.
“Since this accident, the operator has implemented several additional processes for pilots transferring to new helicopter types and for operations at pontoons,” Dr Walker said.
“This includes pilots conducting only into-wind operations at pontoons until they have obtained 20 hours on type. The operator has also introduced a safety management system, and revised processes for obtaining accurate passenger weights, in addition to several other proactive safety enhancements to its operations.”
In the year following the accident, the helicopter manufacturer released a safety information notice about unanticipated left yaw in helicopters with a clockwise-rotating main rotor system. The notice provided detailed advice regarding the circumstances where unanticipated yaw can occur and the importance of applying full opposite right pedal if it occurs.
The notice also stated that for helicopters with a clockwise-rotating main rotor system, that pilots prefer (as much as possible) yaw manoeuvres to the right, especially in performance-limited conditions.
Dr Walker said this accident, along with many other previous accidents, demonstrates the importance of pilots having helicopter type experience when faced with unfamiliar situations in performance-limited conditions, and to follow the immediate actions specified by the helicopter manufacturer, which typically includes immediately applying full opposite pedal input in the event of a loss of yaw control at low height and airspeed.
“Operators, as part of their safety management processes, should consider skill consolidation during and following the in command under supervision phase and provide as much consolidation as possible to reduce the risk of transitioning to a new aircraft type,” he said.
“This is particularly relevant for types with significant differences to those a pilot has previously flown and for operations with reduced safety margins. Pilots and operators should identify and avoid situations that present potential for loss of yaw control in their helicopter type.
“This could include planning approaches that can be rejected by turning with the torque of the helicopter. For example, if crosswind turns are required when landing, conduct turns to the right in a helicopter with a clockwise-rotating main rotor system.”
The investigation also identified that the passengers were not provided with sufficient instructions on how to operate the emergency exits. The passenger seated next to the rear left sliding door was unable to locate the exit operating handle during the emergency, and as a result the evacuation of passengers was delayed until another passenger was able to open the exit. The nature of the door handle’s design was such that its purpose was not readily apparent, and the placard providing instructions for opening the sliding door did not specify all the actions required to successfully open the door.
“Our investigation emphasises that for helicopter flights over water, given the risk of inversion, capsize and disorientation following a ditching, it is imperative that passenger safety briefings include how to operate the passenger’s seatbelt and the location and operation of the emergency exits,” Dr Walker said.
“Operators and pilots of EC120Bs should ensure that passengers in the rear of the helicopter are specifically briefed about the location of the operating handle and the three actions required to open the rear left sliding exit—which is to pull the handle up, push the door out, and slide the door back.”