Two Rescuers Fell When Hoist Cable Damaged After a Loss of Hover Reference (Australian Helicopters Bell 412 VH‑EMZ)
On 9 November 2009 Australian Helicopters Bell 412 VH‑EMZ was involved in a hosting accident that left two crew members seriously injured.

Severed Hoist Cable of Australian Helicopters Bell 412 VH‑EMZ (Credit: ATSB)
The Australian Transport Safety Bureau (ATSB) issued their safety investigation report on 21 January 2011.
Preparations for the Medevac Flight
The helicopter, call sign ‘Rescue 700’, based at Horn Island Aerodrome, Queensland was tasked to rendezvous with a 281m container ship Maersk Duffield located about 132 km west of Horn Island.

Container Ship MV Maersk Duffield (Credit: Chris Howell, Southern Shipping Services Limited via ATSB)
The flight was to medevac an ill crew member to hospital. On board were to be four crew:
On board the helicopter were the pilot, who was seated in the front right seat; an air crew officer (ACO), who was seated in the front left seat; and a rescue crew officer (RCO) and paramedic, who were seated in the rear cabin.
The ACO “generally occupied the front left seat and relocated into the rear cabin” when required to operate the hoist. The RCO’s role was to accompany the paramedic during hoisting.
The pilot had c 8000 hours of flying experience, 2000 on type in command. The ACO had 7 years of experience with about about 690 hours of operational experience, but just 25 hoist sorties of which only 8 had been involved ships. No experience details were provided for the RCO or paramedic.
Before departure, the crew had been advised that the patient would need to be hoisted from the ship’s forecastle. This area was ahead of the 16.2 m high forward mast with c 8-9 m horizontal clearance. The crew were provided with photos.
The decision to undertake the winch to the forecastle was made by the master. The other options available for consideration were the ship’s bridge wings, the monkey island; or the top of the containers on the deck. The bridge wings and monkey island were considered unsuitable because of the number of aerials and other obstructions present, and the height of the containers above the deck meant that they were not accessible by the ship’s crew.
While awaiting the arrival of the paramedic, the pilots AO and RCO developed a plan. They would…
…request the ship to manoeuvre to provide a relative wind that was about 30° off the starboard side in order to provide the pilot with a visual reference of the ship.

Australian Helicopters Bell 412 VH‑EMZ Intended Hoisting Area on Forecastle of Maersk Duffield View from Foremast (Credit: ATSB)
[In] order to reduce the overall time required to conduct the retrieval, the RCO suggested that he and the paramedic be winched together directly onto the forecastle.
The suitability of the plan was to be confirmed on arrival overhead.
The Accident Flight
The helicopter departed Horn Island at 15:00 local time, arriving on scene at about 15:38.
The pilot conducted a number of orbits of the ship to assess the proposed winching area and the relative wind via smoke from the ship’s funnel.
Following that reconnaissance, the pilot requested that the ship’s master change the ship’s heading and reduce speed in order to obtain the originally planned relative wind. There was no restriction to the manoeuvring of the ship in preparation for the winch.
While the ship altered its heading, the helicopter conducted a final orbit and the crew confirmed they were were ready to commence hoisting.
The ship’s master then advised the pilot that the ship was established on the requested heading, the speed was reducing to the target speed of 10 kts and that he was cleared to commence winching.
At about 1550, the pilot approached the ship and terminated to the hover alongside at a position known as the ‘datum’, from which the crew had a clear view of the winching area.

Approach of Australian Helicopters Bell 412 VH‑EMZ (Credit: ATSB)
While established at the datum with the helicopter facing into the relative wind, the pilot and ACO assessed the obstacles in the proximity of the winching area and confirmed that the helicopter had sufficient power margin…
The pilot reported that although the helicopter airspeed indicator showed about 30 kts while hovering at the datum, there was no associated turbulence.
It was agreed to commence hoisting to RCO and paramedic as the pilot began moving the helicopter towards the forecastle with the helicopter facing into the relative wind. The ship’s master recalled there was “no observable pitching or rolling of the ship” during the hoisting.

Approach of Australian Helicopters Bell 412 VH‑EMZ (Credit: Crew of Maersk Duffield via ATSB)
A short time later, the pilot called ‘losing sight’ [of the winching area; inevitable as the helicopter came overhead] and the ACO commenced providing verbal guidance to allow the pilot to manoeuvre… The pilot recalled that this guidance included instructions to descend as the helicopter approached the forecastle. The ACO reported that the crew had agreed to maintain about 20 ft vertical clearance from the foremast.
The pilot was using the ship’s structure as a hover reference. He glanced inside the cockpit to check the instruments.
On looking back outside he could no longer see the ship. In response, the pilot changed hover reference to the view of the horizon directly to the front of the helicopter and announced to the ACO that he had ‘lost reference’.
The pilot reported that although he had not considered the possibility of losing sight of the ship, he believed that any unintended movement of the helicopter due to the inferior hover reference would be compensated for by guidance from the ACO.
At that moment the RCO and paramedic were about 6 m above the deck and nearing the centre of the hoisting area.
A short time later, the ACO observed the helicopter begin to drift rearwards towards the ship’s foremast. The ACO immediately announced the drift to the pilot and requested that he move the helicopter forward.
In response, the pilot applied a forward correction that he assessed would be sufficient to arrest the movement. However, the helicopter continued to drift towards the foremast.
The ACO again requested that the helicopter move forward and in response, the pilot applied a second, larger correction.
Despite this, the helicopter continued to drift towards the foremast and the RCO and paramedic contacted the radar scanner platform railing on the foremast.
The ACO started lowering the winch cable at full rate to reduce tension on the cable and informed the pilot that the cable was fouled on the foremast. The helicopter continued to drift backwards over the ship and to the left of the foremast.
The ACO observed that the winch cable was perversely caught on the helicopter’s ‘skid guard’, which begs questions on the suitability of the guard (which seems to be designed to protect the float bags).

Australian Helicopters Bell 412 VH‑EMZ: Approximate Cable Angle At Failure With Snag (Credit: ATSB)
The cable was…
…running at an angle down towards the foremast, and that despite [the ACO] continuing to pay out on the cable, it remained under tension.
The pilot…felt a slight movement of the helicopter and the ACO informed him that the winch cable had separated and the RCO and paramedic had fallen [c 10 m] to the ship’s deck.
Both we seriously injured. One was recovered by another helicopter c 2 hours later and the other transferred ashore by boat.
The ATSB Safety Investigation
Technical Examination
The hoist cable separated about 14 cm from the hook.

Hoist Hook & Bump Stop from Australian Helicopters Bell 412 VH‑EMZ (Credit: ATSB)
There was also evidence of white paint on the bump stop striker plate, which was consistent with contact between the winch cable and the ship’s white-coloured foremast structure.

White Paint Transferred to Bump Stop Striker Plate of Australian Helicopters Bell 412 VH‑EMZ (Credit: ATSB)

Abrasions on MV Maersk Duffield’s Foremast (Credit: ATSB)

Abrasions on MV Maersk Duffield’s Foremast Handrail (Credit: ATSB)
Additionally, marks on the helicopter’s main and tail rotor blades, right horizontal stabiliser and cabin roof were consistent with the cable having recoiled following the separation and contacting the helicopter.
MRB Cable Abrasions: Australian Helicopters Bell 412 VH‑EMZ (Credit: ATSB)

TRB Damage: Australian Helicopters Bell 412 VH‑EMZ (Credit: ATSB)

Horizontal Stabiliser Damage: Australian Helicopters Bell 412 VH‑EMZ (Credit: ATSB)
Workshop strip examination of the hoist showed it was in good condition with no defects that would have affected its operation.
The 3/16th inch diameter winch cable comprised an independent wire core that was surrounded by a layer of central strands.
Hoist Cable (Credit: Wire Rope Technical Board via ATSB)
The 19 strands each consisted of seven smaller diameter individual wires.
To determine its breaking strength, six samples of the cable were subjected to tensile strength testing. These exceeded the minimum specification of the cable. The cable material was also found to comply with the cable’s specification.
Examination…via visual and scanning electron microscopy techniques identified that about 17% of the cable had been severed through abrasive contact with the foremast structure.

Cross-section of the hoist cable with abrasion-damaged strands highlighted in red: Australian Helicopters Bell 412 VH‑EMZ (Credit: ATSB)
The separation of the remainder of the cable was consistent with the effects of a combination of shear and tensile overstress. There was no evidence of fatigue failure within any of the cable strands. …aside from the damage close to the separation point, there were no other forms of degradation such as corrosion, broken wires or kinks.
Of note is the ATSB observation that:
This occurrence highlights the importance of preventing contact between the winch cable and any metal surface, including the helicopter’s skid landing gear at all times when conducting winching operations. In the event that the cable does become fouled, it is vital that the movement of the helicopter relative to the target area is minimised to prevent the application of dynamic or ‘shock’ loading to the potentially weakened winch cable.
Examination of Hoisting Procedures
ATSB noted that:
There was no requirement for the crew to confirm the existence of adequate reference prior to lowering personnel…
A discussion with the chief pilots of five other comparable organisations identified two operators that similarly left the decision of the need to assess the adequacy of the available hover reference prior to placing personnel on the rescue winch up to the pilot.
The other three chief pilots advised that their procedures required confirmation that adequate hover reference existed prior to deploying personnel on the rescue winch.
The helicopter operator had conducted task risk assessments for a number of regular activities, including hoisting. Among the hazards identified was:
Insufficient hover reference causes excessive drift leading to hoistee impact with obstacles.
The associated risk mitigations included:
- the calculation of out-of-wind helicopter performance to facilitate improved hover reference
- the use of the ACO to assist the pilot by providing a continual commentary of height, position and obstacle clearance in a hover position with no hover reference.
However, this does not seem to have feed through to procedures as:
There was no reference in the operations manual to the procedure to be followed in the event of a loss of hover reference.
In this case:
The pilot stated that there was no discussion among the crew of the procedure to be followed in the event of a loss of hover reference, as it was assumed that adequate reference would exist during the conduct of the winch.
Such an assumption was not unique to this case:
During the course of this investigation, the ATSB was notified of another event involving a different helicopter operator that occurred during a winching sortie to a small vessel. In that instance, the pilot lost visual reference with the vessel and while manoeuvring to regain reference, a crewman was injured. The involved pilot reported that there was no discussion among the crew of the potential for the loss of visual reference, and that no assessment of the hover reference was conducted prior to commencing winching.
In the Horn Island accident the ACO did provide a commentary to guide the pilot but ATSB note that it “was ineffective in arresting the drift and the subsequent fouling of the winch cable”.
ATSB comment that:
A requirement to confirm that adequate hover references existed, prior to the deployment of personnel on the rescue winch, would have identified that visual reference with the ship would be lost as the helicopter approached the forecastle.
This would have highlighted to the crew that a modification to the plan, such as the use of a Hi-line transfer or different relative wind, was required to ensure that the helicopter and flight crew were not exposed to any significant hazard. The lack of any restriction on the ability of the ship’s master to manoeuvre would suggest that an alternate relative wind may have been possible.
Safety Actions
Shortly after this occurrence, the operator issued a flying staff instruction [that] detailed the importance of adequate power margins and hover reference and that, where practical, they should be assessed over the intended winch area at the intended hover height.
The instruction also stated that where it was expected that the hover reference may be inadequate, the reference was to be assessed overhead the intended winch location prior to lowering personnel below the level of any obstructions or recovering personnel.
Paradoxically while it is stated that “an initial review shortly after the occurrence concluded that the content” of the Operations Manual “was appropriate and contained sufficient guidance”, a subsequent “more detailed review” considering “established best practice procedures within the industry” was initiated.
This ongoing review, including the development of an appendix detailing the procedures for application when winching to ships, will emphasise the need to ensure that adequate hover reference exists during those operations.
Also:
Although no safety issue was identified concerning the equipment that was carried by the paramedic and rescue crew officer, the operator intends to limit the equipment carried on the rescue winch hook to reduce the potential for fouling or injury.
The operator is also developing a policy on the carriage and availability of medical equipment during the conduct of actual winching operations, or the training for such operations. This policy is proposed to be included in the operations manual.
The operator also updated their risk assessments and ensured they were available at each base.
Our Safety Observations
Having imagery of the hoisting area in advance is helpful. However, the opportunity to examine photos of the vessel’s forecastle before departure may have resulted in a degree of confirmation bias that the hover reference would remain adequate; something the pilot effectively admitted above.
The ATSB mention the potential use of a hi-lines, which would have allowed a greater offset between the helicopter and vessel. It is surprising this wasn’t emphasised more by ATSB or in the safety actions.
This accident is a good reminder on the risks of hoist cable abrasion. We have previously discussed damage on unguarded aircraft structure: HH-60L Hoist Cable Damage Highlights Need for Cable Guards and snagging on aircraft structure SAR Hoist Cable Snag and Facture, Followed By Release of an Unserviceable Aircraft
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:
- SAR Hoist Cable Snag and Facture, Followed By Release of an Unserviceable Aircraft
- HH-60L Hoist Cable Damage Highlights Need for Cable
- Guarding Against a Hoist Cable Cut
- Fatal Fall From B429 During Helicopter Hoist Training
- TCM’s Fall from SAR AW139 Doorway While Commencing Night Hoist Training
- SAR AW139 Dropped Object: Attachment of New Hook Weight
- Military SAR H225M Caracal Double Hoist Fatality Accident
- Fatal Taiwanese Night SAR Hoist Mission (NASC AS365N3 NA-106)
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