The Australian Transport Safety Bureau did not conduct an on scene investigation of this occurrence. The report presented below was derived from information supplied to the Bureau.
Sequence of events
At about 0900 Eastern Summer Time on 1 November 2004, the pilot of a Bell Helicopter Company 47G-4A, registered VH-AHL, repositioned the helicopter for loading prior to departing from his property airstrip for a locust spraying operation. That involved the pilot air taxiing1 the helicopter around and behind another helicopter that had already been loaded, and was about to depart the designated loading area.
The pilot reported that, as he air taxied abeam the other helicopter, he noted a power pole about 300 m from the helicopter, but had forgotten about the power cables that passed about 50 m from the airstrip. Those power cables were estimated to be at tree top height, which was less than 90 m above the ground. During the repositioning, the helicopter struck the power cables, and the pilot reported 'fighting' the helicopter to the ground. The helicopter was destroyed by the ground impact and post-impact fire. The pilot suffered minor injuries.
The pilot was appropriately qualified for the flight, and reported being medically fit and feeling well. There were no reported environmental or helicopter maintenance factors relevant to the circumstances of the occurrence.
In the pilot's opinion, had the power cables been marked,2 he would have seen and been able to avoid them. The pilot commented that land owners were expected to pay the cost of installing power cable markers, and that the installation costs could be prohibitive.
The requirements for the mapping and marking of power cables and their supporting structures are published in the following Australian Standards:3
- AS 3891.1 - 1991 Part 1: Permanent marking of overhead cables and their supporting structures. This standard was approved on 18 February 1991 and published on 15 April 1991, and '...specifies the requirements for aircraft warning markers for use on overhead cables and their supporting structures'. In general, there is no requirement for the marking of cables with a height above terrain or obstacles of less than 90 m.
- AS 3891.2 - 1992 Part 2: Marking of overhead cables for low level flying. This standard was approved on 1 September 1992 and published on 14 December 1992, and '...specifies requirements for permanent and temporary marking of overhead cables and their supporting structures for visual warnings to pilots of aircraft involved in low-level flying operations'. The Standard assumes pilot familiarity with the hazards in the low-level operating area, and that a visual reminder only is required of the exact location of the cables. Pilots are required to '...be satisfied as to the need for and effectiveness of markers prior to commencing low-level operations'. The installation of above ground markers requires the approval of the cable owner.
The responsible power company indicated that the land owner contacted the company after the occurrence regarding the possibility of marking the repaired power cables.
Airborne movement of the helicopter at low speed and generally when
in ground effect.
2 Identifiable by a marker or markers installed on the power cables or their supporting structures or poles.
3 Prepared by the Standards Australia Committee on Geographic Information Systems in response to growing concern expressed by certain pilot and private and commercial aviation interest groups, the Civil Aviation Safety Authority, Government instrumentalities about the increase in incidents involving aircraft and overhead power cables.
The responsible power company has:
- installed overhead markers to the repaired power cables. Those markers approximate 'truck mudflap size', are bright in colour and include a reflector in the centre of the marker
- nominated to be included in the Standards Australia committee responsible for the development of the standards affecting the mapping and marking of power cables and their supporting structures
- indicated its intention to propose the overhead markers used to mark the repaired power cable for inclusion within the relevant Australian Standard.
The Australian Transport Safety Bureau has commenced a research project that will examine the potential influence of contractual structure and organisational interaction on the safety of aviation campaign operations such as invertebrate pest management and airborne fire-fighting activities. That examination will include the responsibilities for the management of the unique risks inherent to those types of campaign, and seek to highlight risk mitigation options for consideration by future aviation campaign participants.
|Date:||01 November 2004||Investigation status:||Completed|
|Time:||1015 hours ESuT|
|State:||New South Wales||Occurrence type:||Wirestrike|
|Release date:||23 December 2004||Occurrence class:||Operational|
|Report status:||Final||Occurrence category:||Accident|
|Highest injury level:||Minor|
|Aircraft manufacturer||Bell Helicopter Co|
|Type of operation||Aerial Work|
|Damage to aircraft||Destroyed|
|Departure point||Binomea Homestead, NSW|
|Departure time||0900 hours ESuT|
|Role||Class of licence||Hours on type||Hours total|