A92W0177-Trans North Turbo Air Ltd. McDonnell Douglas 369D (Helicopter) C-FBVG Exeter Lake, Northwest Territories 15 mi E 24 August 1992
Safety Action Required
(as indicated in the TSB Report)
Helicopter Slinging Equipment
Since 1976, there have been 15 reported helicopter accidents resulting from tail rotor damage caused by contact with slings. These accidents resulted in five fatalities, four serious injuries, and in most cases, substantial aircraft damage. Seven of the accidents involved flights with an intentionally empty, unweighted sling, even though the helicopter community recognizes this to be a hazardous practice. Eight accidents resulted when loads separated from the sling during transit, causing the now-empty sling to stream aft into the tail rotor.
Over the years, there have been several initiatives to reduce the incidence of helicopter rotor/sling strikes. Transport Canada (TC) has produced an educational video on slinging, has published numerous articles in its "Vortex" newsletter on unsafe equipment and practices in helicopter operations, and is currently working on regulations to cover the operational requirements for slinging. As recently as May 1992, Bell Helicopter Textron re-issued an Operations Safety Notice to caution owners and operators of helicopters that "flights with unloaded cables extending from helicopters must not be performed." Notwithstanding these measures, the use of unsafe slinging equipment in an unsafe manner continues.
Supplemental equipment in the aviation industry is normally designed and tested in accordance with Technical Standard Orders (TSO), or is type-approved under a Supplemental Type Certificate (STC). At present, helicopter slinging equipment is considered to be part of the load rather than the aircraft; therefore, it has not been subjected to a TSO or STC approval process.
Discussions with suppliers of helicopter slinging equipment revealed that most slings and associated hardware have been designed to the same standards used for the construction industry. Airworthiness requirements, such as behavioral characteristics in flight, have not necessarily been a consideration in the design or intended use of this slinging equipment.
In view of the continuing incidence of helicopter accidents resulting from empty slinging equipment coming into contact with helicopter rotors, the Board recommends that:
The Department of Transport coordinate the development and implementation of airworthiness standards and operational limitations for helicopter slinging equipment. A93-12
Transport Canada's Response:
Transport Canada Aviation (TCA) recognizes that the consequences of any mistake in slinging operations can be very serious, and therefore supports the Boards efforts in finding the best possible solution to reduce these types of occurrences.
The TSB accident analysis implies that the publication of a TSO standard and the issue of airworthiness approvals and operational limitations for sling equipment could eliminate the cause or reduce the number of accidents that occur during external load operations. However, the TSB report has not taken into account the many variables (such as the number of rotorcraft types, the variety of sling equipment, types of loads and operations), which could make the solution of the problem complex, time consuming and very costly (extensive flight testing could be required). It is felt that better results can be obtained by requiring through the new Order dealing with external load operations, that company Operations Manuals contain instructions about the type of equipment to be used for a specific operation, i.e. sling length, material, size, storage instructions, inspection schedules and procedures, etc.
One of the task of the Transport Canada Regulatory Renewal Project is to develop Aerial Work Regulations which will include operational standards and procedures related to rotorcraft external (sling) load operations. It is intended that the regulations will include a requirement for a company Operations Manual to include the information mentioned in the foregoing and an outline of crew training.
TCA participants in the Rotorcraft Subcommittee of the U.S. Federal Aviation Administration’s (FAA) Aviation Rulemaking Advisory Committee (ARAC), which has prepared draft rulemaking and advisory material for helicopter external load carriage. TCA will comment on the draft Advisory Circular with a view to adopting its contents.
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