Bell Helicopter Co 47G-4A, VH-AHL

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.

¹
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.