The pilot of a Bell Long Ranger 206L-1 was returning to base following an agricultural crop-spraying task. While transiting a ridgeline of the Connors Mountain Range, the helicopter collided with wires and impacted the ground in a densely wooded area about 200 metres beyond the wires.
The pilot received fatal injuries and the helicopter was destroyed in a post-crash fire. Witnesses had observed a helicopter approaching the ridgeline at a very low height, and reported that, shortly afterwards, a pall of black smoke was visible.
The helicopter had struck two three-strand lightweight high-tensile steel wires of a powerline supplying a repeater site. A wire strike protection system (WSPS) had not been fitted to the helicopter. The wires were aligned on 060 degrees magnetic, with a maximum height of 31.5 metres for the upper wire and 30.1 metres for the lower wire. The position of the wires was not annotated on the relevant Visual Terminal Charts and they did not have high visibility devices attached. Company employees said that it was usual for the pilot to fly at a low height when transiting to and from the work location.
Examination of the wreckage indicated that the helicopter had struck the ground with a vertical downward force and at a low forward speed on a heading of 030 degrees magnetic. The main rotor blades were severely fractured by contact with the surrounding trees. The tail boom was severed just forward of the horizontal stabiliser and the tail rotor gearbox and blades were intact. Fire destroyed the helicopter cabin and heavily damaged the engine compartment and upper transmission deck. Examination of the engine to determine pre-impact airworthiness was limited due to fire damage.
The white-colour coded main rotor pitch control rod, broken sections of the windscreen, and the top section of the main transmission cowling were found along the flight path about 75 metres before the main wreckage. One main rotor blade severed the upper wire. The lower wire contacted the fuselage in the area of the forward canopy, progressed up to the fibreglass transmission cowl, and separated the top lip of the cowl. That wire, together with the separated section of cowl, then contacted the flight controls above the main rotor swashplate, causing static overload and separation of the white colour-coded main rotor pitch change rod. Directional control of the helicopter was lost following the separation of the control rod.
The investigation found no evidence to suggest that the helicopter was not fully serviceable at the time of the accident. It is likely that the oblique angle of approach to the wires limited the pilot's ability to detect them, and "contour flying" offered minimal reaction time for the pilot to avoid the wires had they been detected.
A review of the Australian Transport Safety Bureau (ATSB) database for the period January 1, 1995, to March 3, 2001, revealed six fatal agricultural helicopter accidents in Australia. These accidents represented seven fatalities and 42% of all fatal helicopter wire-strike accidents during the period.
Previous safety action
The Australian Transport Safety Bureau (then known as the Bureau of Air Safety Investigation) made a recommendation in 1995 to the Civil Aviation Safety Authority (then known as the Civil Aviation Authority) following a similar fatal accident related to a wire strike of a helicopter. The recommendation, R19950120, stated:
The Bureau of Air Safety Investigation (BASI) recommends that the Civil Aviation Authority (CAA):
(1) Require the fitment of approved WSPS kits for all helicopters engaged in low flying activities for which a kit exists; and
(2) That only agricultural spray kits compatible with WSPS be approved for fitment to these helicopters.
The CAA response to the recommendation was as follows:
While WSPS may have been of benefit in this and similar accidents, the Authority believes that the fitment of WSPS should not be mandatory. However, the CAA is of the view that it should be strongly encouraged when suitable equipment is available.
The CAA in conjunction with BASI, is prepared to undertake an industry education program highlighting the hazards associated with low level helicopter operations as well as the advantages provided by the fitment of WSPS to appropriate helicopters.
On 15 May 1996, BASI classified the recommendation CLOSED- No further action, however, continued to monitor the number of wire strike accidents.
Although the Civil Aviation Safety Authority (CASA) implemented training programs to educate the industry on the hazards associated with low level helicopter operations, it is believed that WSPS kits may yet prove beneficial in mitigating helicopter wire strike accidents.
As a result of this investigation, and after a review of the ATSB accident database statistics relating to agricultural helicopter wire strike fatal accidents, the ATSB is concerned that fatalities are continuing to occur in agricultural helicopter operations despite the earlier recommendation (R19950120). The ATSB therefore issues the following recommendation.
The ATSB recommends that CASA:
(i) Require the fitment of approved Wire Strike Protection System kits for all helicopters engaged in low flying activities for which a kit exists; and
(ii) That only agricultural spray kits compatible with Wire Strike Protection Systems be approved for fitment to these helicopters.
|Date:||29 January 2001||Investigation status:||Completed|
|Time:||1800 hours EST|
|Location:||8 km SSW Sarina|
|Release date:||30 April 2001||Occurrence class:||Operational|
|Report status:||Final||Occurrence category:||Accident|
|Highest injury level:||Fatal|
|Aircraft manufacturer||Bell Helicopter Co|
|Type of operation||Aerial Work|
|Damage to aircraft||Destroyed|
|Departure point||Inneston, QLD|
|Departure time||1745 EST|
|Role||Class of licence||Hours on type||Hours total|