Recommendation R19970179

Recommendation issued to: Aircraft Owners & Pilots Association of Australia

Recommendation details
Output No: R19970179
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 lines 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.

The 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 required diameter 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 landing strip of runway 18 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) Airports 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.

The Enroute Supplement (ERSA) lists items to be considered by pilots before a safe operation can be conducted into an unfamiliar aerodrome. Listed below are the specific obstacles, hazards and special procedures used as examples in ERSA, along with further items that may need to be considered (this list is by no means meant to be comprehensive).

Obstacles: - Power lines, trees, buildings, terrain, roads, railways, fences, windmills, towers and masts etc.
Hazards:- Turbulence, updraughts, downdraughts, livestock, birds, wildlife, long dry/wet grass, effect of recent rain (e.g. washouts or soft spots), ditches, drains, earth mounds, tree stumps, vehicles, anthills, animal burrows, non-standard markings, rough areas and obstacles hidden by long grass etc.
Special Procedures:- Circuit direction, noise sensitive areas (eg cattle yards or homes), sport aviation and displaced thresholds etc.

- Powerlines 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.
- A pilot that does not have access to detailed information regarding local conditions may not be able to conduct safe operations into an unfamiliar aerodrome.

Output text

That AOPA bring to the attention of its members the above information and amend the Airports Directory survey form to include, as examples, specific mention of the obstacles, hazards and special procedures detailed earlier.

Initial response
Date issued: 26 March 1998
Response from: Aircraft Owners & Pilots Association of Australia
Action status: Closed - Accepted
Response text:

Thank you for the opportunity to indicate AOPA's action in accordance with your recommendation.

Firstly, AOPA no longer publish an Airfield Directory. New Directories will be published by AOPA Foundation with the first Issue going to print shortly. AOPA Foundation have changed the Directory Information Survey Form from that previously used by AOPA to include a section relating to special procedures and obstacles etc.

Not withstanding the above it should be brought to your attention that the Survey Form, as with the previous AOPA Survey Form, also solicits information on availability of toilets, telephones, rental cars, accommodation and local attractions.

My advice from the Directors of AOPA Foundation is that this is not an operational document. It is, in fact, a guide to planning. However, the Foundation has suggested that it will provide numerous disclaimers and instructions to that effect throughout the document.

The Foundation is also acutely aware that with the smaller amount of information now able to be accessed from official documents such as ERSA, that there may be a tendency for Pilots to use Airfield Directories in a manner for which they were not intended. 1 have personally raised this matter with Airservices at a recent RAPAC meeting in South Australia.

The Foundation have asked whether BASI would be prepared to supply AOPA Foundation with all information BASI have regarding Airfields and any unusual problems that exist. If so, we would be pleased to receive such data as a matter of urgency. If not, we respectfully request a reason, as to why.

With regard to the recommendation that AOPA brings to the attention of its members, the information contained in the body of the report on Occurrence No 9700822, AOPA agrees with the recommendation and will publish the report in due course.

Last update 01 April 2011