Accident Summary
On a flight near Bella Bella, British Columbia, a Canadian Coast Guard Messerschmitt-Bolkow-Blohm (MBB) BO 105 helicopter (registration C-GCHX, serial number S695), operated by Transport Canada as flight CTG357, was conducting external load operations. Having completed 27 external loads, the helicopter was returning to the Canadian Coast Guard ship (CCGS) Bartlett from Dryad Point Lighthouse Station with an empty cargo bonnet.
While en route over water at an altitude of about 200 feet, the bonnet rose above and behind the tail rotor, causing the longline to become hung up on the back of the helicopter. The helicopter subsequently slowed, began to descend, turned right, and crashed into the water, sinking immediately. The pilot managed to exit the sunken helicopter but remained face down in the water, wearing an uninflated lifejacket. He was rescued within three minutes and revived, but remained in critical condition for several days. The helicopter wreckage was later found at a depth of 26 metres on an ocean floor slope.
Weather conditions at the time included scattered cloud at 2000 feet, visibility of about 15 miles, calm winds, and rippled seas.
External Load Configuration
The sling equipment consisted of a 33-metre synthetic rope longline attached to the helicopter's belly hook, terminated with a swivel hook. Attached to that hook was a bonnet containing some rope gear and slings, lashed closed with a polypropylene rope. The bonnet weighed less than 10 kg, and the total external load weight was less than 40 kg. The surface area of the external load was approximately 2.6 square metres.
Findings
The investigation determined that the polypropylene rope used to snug the top of the bonnet most likely slid up the beckets, allowing the bonnet to open in flight. The pilot observed the starboard front area of the bonnet folded inward, likely due to a separated becket creating an asymmetric shape. The resulting shape, combined with the bonnet's light weight and high drag, caused the bonnet to fly up into the flight path of the helicopter, carrying the longline with it. The longline then contacted the tail rotor, disabling it and rendering the helicopter uncontrollable.
At impact, the pilot's upper body likely moved around the cabin due to the lack of an upper-body restraint device, as evidenced by his fractured helmet. The helmet protected his head from severe injury, enabling him to extricate himself from the sunken wreckage. However, in this type of helicopter, even properly secured front-seat occupants risk hitting their heads on the fixture normally used to secure the liferaft.
The colour of the pilot's helmet and flight suit (grey and navy blue, respectively) made him difficult to see in the ocean, increasing the risk of delayed rescue.
Safety Actions
Transport Canada issued a safety notice on 9 May 2005 restricting operations with empty or light external sling loads. On 25 May 2005, it produced draft Standard Operating Procedures for helicopter external load operations, which restricted the use of bonnets and cautioned about light and unstable loads.
The Transportation Safety Board (TSB) sent a Safety Information Letter to Transport Canada on 31 May 2005 highlighting that, despite regulations, helicopter slinging operations without upper-body restraint continued. Transport Canada responded by noting that if restraint equipment is used properly in accordance with regulations, it provides intended protection, and that operators are responsible for compliance. It also initiated research on crew restraint in vertical reference external load operations.
Additionally, the TSB sent a safety advisory on 31 May 2005 regarding the hazard of front-seat occupants hitting their heads on the liferaft fixture, recommending modification or use of helmets. Transport Canada reviewed the applicable certification data and considered adding padding and requiring helmets.
On 1 June 2005, the TSB sent another safety information letter highlighting continued operational practices with empty or light slings, referencing a 1993 recommendation. Transport Canada acknowledged the certification framework and ongoing safety promotion efforts.
This report concludes the TSB investigation, authorized for release on 5 October 2005.