Recommendation R19970177

Recommendation issued to: Australian Airports Association

Recommendation details
Output No: R19970177
Date issued: 13 February 1998
Safety action status:


Powerline markings and aerodrome information.


The aircraft, a PA 38-112 Tomahawk, was on final approach for a landing at Torquay (Vic.) ALA when it struck powerlines. The aircraft suffered significant damage from the powerlines and further damage from the impact with the ground. The pilot and his passenger (also a pilot) were not harmed.


THE POWERLINES: The aircraft collided with two strands of 3 X 12 gauge (2.75-mm) galvanised steel powerlines, grey in colour. The pole height was 12 m and the line dropped to 6.55 m above ground level at its lowest point. The line ran perpendicular to the runway direction, a short distance outside the fence marking the end of the runway surface. The line was marked by orange marine buoys of 200-mm diameter that had faded on the upper surface to a dull white. This combination of grey powerlines and faded markers made the lines virtually indistinguishable from the dry, light brown surface, especially in the prevailing bright but overcast conditions. The electricity company had conducted a ground inspection of the markers every 3 years but had no requirement to check the upper surface for fading. At the time of the accident the markers had been installed for approximately 8 years.

Many aerodromes and landing areas around Australia are situated near buildings or homesteads, and many of these have power supplied to them by overhead powerlines. Many of these lines have been marked prior to the publishing of the relevant standard in 1991, hence a wide variety of markings have been used, many of which are not effective in ensuring clear visibility from the air.

Australian Standard 3891.1 recommends that any powerlines which infringe the transitional slope or the approach and take-off slope of an aerodrome shall be marked by a minimum of three spherical markers of at least 600-mm diameter placed less than 30 m apart. One of the markers should be off- white and the other colours should be chosen to provide maximum contrast with the ground. The other recommended colours are canary yellow and signal red, with international orange available for circumstances requiring an unusual contrast. The markers should also be made of a material that is resistant to deterioration caused by ultraviolet light. The document containing the full details of this standard is available from Standards Australia. Comparing the installed markers with the Australian standard, the marine buoys installed were a third of the diameter required and they had lost their colour on the upper surface.

There is a good chance that this accident would not have occurred had the powerlines been marked to meet the Australian standard. If the standard had been followed there would have been at least three markers on the line, each of which presented over eight times more visible surface than the installed markers. In addition, the brightly coloured material would have provided a strong contrast with the background.

AERODROME MARKINGS: The Torquay airport operator had placed displaced landing threshold markers some way into the runway 18 strip to establish a safe approach gradient over the powerlines. These markers were painted white, as were the runway edge markers, which extended the full length of the runway surface. The colouring of the airfield surface, at the end of a hot dry summer, did not provide adequate contrast to allow the pilot to see the white landing threshold markers against the dry grassed surface of the runway. The aerodrome was marked correctly, however, the local dry conditions contributed to the accident by preventing easy identification of the displaced threshold.

AERODROME INFORMATION: The Aircraft Owners and Pilots Association (AOPA) Airfield Directory contains information supplied by the aerodrome operator on a survey form supplied by AOPA. That survey form does not follow the example on page 55 of the Airservices Australia publication, the Enroute Supplement Australia, in that it does not list any examples of hazards that need to be considered. An airport owner may not consider relevant or cover all the hazards associated with the aerodrome unless there was a list for reference. The information published for Torquay did not mention powerlines or any displaced landing thresholds.

Before departing for Torquay the pilot had studied the AOPA airfield directory and phoned the operator for approval to land. He also asked about local conditions and was informed of parachute operations that day. The pilot did not ask, nor was he told about any powerlines or displaced thresholds. The pilot and his passenger were familiar with the runway layout having flown over the aerodrome previously, however neither had landed at the aerodrome. Approaching Torquay they had heard another aircraft broadcast that it was landing on runway 18 so they joined crosswind for that runway, noting as they flew overhead the worn take-off threshold area adjacent to the fence.

The pilot followed the correct procedure by telephoning the airport prior to departure, however when questioned later by the investigator, the operator advised that he had not brought the powerline or the displaced threshold to the attention of the pilot. Also, the operator later advised that the correct details and a diagram could be found in the other private airfield directory, the Country Airstrips Guide. He did not check which guide the pilot was using.


- Power lines in the vicinity of some aerodromes and landing areas are not adequately marked.
- Under some conditions, aerodrome colouring can make runway markers difficult to distinguish, particularly if the pilot is unaware of any displaced thresholds.

Output text

That the Australian Airport Owners Association bring to the attention of its members the information concerning powerlines, aerodrome markings and published aerodrome information detailed above and recommend to them that they contact their local electricity supplier if they believe any powerlines affecting their airfields are not marked in accordance with the Australian standard.

Initial response
Date issued: 09 March 1998
Response from: Australian Airports Association
Action status: Closed - Accepted
Response text:

Thank you for your letter BS/970063 dated 13 February in which you sought advice of AAA action concerning the above recommendation.

The AAA Board has been advised of the problem and after its meeting on 19th March 1998, will publish the information that you have provided in its newsletter to members.

You are probably aware that the AAA does not represent all aerodromes in Australia, and Torquay is not a member. Further, whilst CASA regulates licensed aerodromes, unlicensed aerodromes are not regulated and owners are not obliged to adhere to the rules, practices and standards that apply to licensed aerodromes. This includes aerodrome markings.

As you point out in you report, the pilot followed correct procedures in telephoning the aerodrome operator, but the operator failed to mention the power lines. As far as I am aware, neither the AOPA Airfield Directory nor the Country Airstrip Guide is an official publication and pilots should not rely on either of them to provide accurate aerodrome information.

If a flight safety issue exists with powerlines near airports, then CASA should legislate for aerodrome operators to liaise with power companies to have powerlines marked in accordance with Australian standards. This legislation may have to extend to unlicensed aerodrome operators.

Finally, AAA will make its members aware of information concerning powerlines and Australian standards, remind them about aerodrome markings, remind licensed aerodrome operators to check that hazards involving powerlines are included in ERSA and remind unlicensed aerodrome operators to observe the unlicensed aerodrome check list in ERSA.

Last update 01 April 2011