Unexpected Load: AS350B3 Under Slung Load (USL) / External Cargo Accident in Norway
The - the Statens Havarikommisjon for Transport [SHT] in Norwegian) has issued its final report on a helicopter accident that occurred near Toms, in Norway on 20 July 2016. It involved Airbus Helicopters AS350B3 LN-OSN of HeliScan that was supporting powerline construction by Consorzio Italia 2000 for power utility Statnett. The AIBN report that:
During a landing to load off [three] personnel, an external load was attached to the helicopter by longline without the commander being aware of it.
At lift off, the long line tightened, and the commander experienced a jerk in the helicopter that made him decide to make an emergency landing in terrain with birch trees. The rotor blades and the landing gear sustained damage.
The pilot, the sole occupant, was uninjured.
It emerged during the investigation that it was given an unclear message from the [construction company] principal who gave room for the commander and task specialist to have different understanding of the task to be performed.
The commander had the notion that it should be transport of [all] personnel from a mast point along the power line [as he had just move three of the five personnel from that site].
[The] task specialist, who believed that stringing of pilot lines was the next task [and that only the key personnel needed to be moved], attached longline to the load hook.
This caused the helicopter to take off in such a way that [4 seconds into the flight] there was a strong pull due to the weight that hung in longline when it was tightened.
The report [only available in Norwegian] focuses on cooperation and communication between the commander and task specialist, and the equipment used for communication.
The AIBN note that:
EASA OPS Annex VIII Part-SPO (Special Operations) Subpart E HESLO (Helicopter Sling Load Operations) which was introduced in Norway 1 January 2016 has in its AMC / GM (Acceptable Means of Compliance / Guidance Material) defined minimum standards for communication equipment to be used in this type of assignment:
AMC 1 SPO.SPEC.HESLO.100 Standard operating procedures, Party C Equipment (4) Adequate radio communication equipment (eg VHF, UHF, VHF) should be installed and serviceable in the helicopter for co-ordination with the task specialists Involved in the operation. (5) Task specialists Involved in the operation should be equipped with hand-held communication equipment, protective helmets with integrated earphones and microphones.
In this case the task specialist / loadmaster did not use his more basic hand-held VHF radio because of the noise. The helicopter was fitted with mirrors that would have given the pilot a view of the belly hook but as the pilot was not expecting a load to be added, the action of the task specialist went unnoticed.
In 2009 the Norwegian Civil Aviation Authority (the NCAA or Luftfartstilsynet) established an air safety forum for operators of inland helicopters, which commissioned a safety study:
The reason for this study was a concern for the development of aviation safety in this part of the Norwegian helicopter operations. In particular the accident rate for aerial work and passenger flights [is] unsettling.
The study was released in December 2013 and included 41 recommendations. Two of these were linked to this accident by the AIBN:
- Recommendation T04 Training between pilot and load master. “This measure will help strengthen crew members total skill level with regard to counteract operational errors”.
- Recommendation T22 Personal equipment for pilots and loadmasters. “The measure is expected to increase crew members safety. In addition, measure contribute to signal opposite crew members that safety is a priority in company”.
The AIBN note that that study also showed a perception that passenger flights were much lower risk than other aerial work tasks and postulate that perception may have contributed to a lower level of attention when expecting a passenger flight compared to the aerial work tasks that were subject to the completion of a specific Job Analysis and Risk Assessment Form.
The AIBN note the communication failure between load master and commander when a change in plan occurred.
Responsibility for a common understanding of what should be carried out on a mission rests with the helicopter company working personnel. One must inform each other’s intentions and changes, and confirm that the information is received.
No safety recommendations are made by the AIBN in connection with this investigation.
Also see our articles:
- What the HEC?! – Human External Cargo
- Helicopter Underslung Load: TV Transmitter
- French Skyscraper: Helicopter Underslung Load
- Keep Your Eyes on the Hook! Underslung External Load Safety
- The Tender Trap - the design of aviation service tenders and contracts
- UPDATE 5 February 2017: Our new article Fatal Low Altitude Hover Power Loss: Power Line Maintenance Project looks at how an engine compressor failure while installing power line markers resulted in an unsurvivable impact and fire.
The Flight Safety Foundation (FSF) run Helicopter External Load Operations for Ground Personnel training.