Keeping helicopters and wires apart, despite the education and awareness, is a never-ending effort. In aerial firefighting, the threat of wires is ever-present, and any lesson is worthwhile learning.

Aerial firefighting is a risk operation at the best of times. When things go well, people get pats on the back if they are lucky; there is an expectation that the job will get done. That desire to get the job done, for some reason, is ingrained into many helicopter pilots. Is it a form of egotism or is just the type of person drawn to helicopter operations is very task focused? Maybe a bit of combination of both. Firefighting pilots see mayhem, destruction and peoples’ livelihoods going up in flames so there’s a strong desire to achieve good results.

Aerial firefighting is also a risky environment where helicopters, and fixed wing for that matter, are operating; not along air routes, not with significant infrastructure support and not in set scenarios where extensive planning can happen. Aerial firefighting happens close to the ground, in a dynamic and uncomfortable environment, and one where high risk abounds. It also happens where the wires are.

The only real defenses against wire strikes in the firefighting environment are awareness, procedure and if all else fails, protection.

The scenario below happened. It has been de-identified because we need to focus on the lessons and understand how this happened. It happened to a crew who were doing a survey of powerlines as floods were abating and the lessons here are the same lessons any aerial firefighter needs to remember.

What happened?

The helicopter was being used to conduct a powerline survey before power could be restored to an area impacted by floods. The area had and was still experiencing significant flooding at the time of the inspection.

The helicopter was equipped, in accordance with the client’s specification, with a Wire Strike Protection System (WSPS). The weather at the time of the occurrence included a cloud overcast at about 4,500ft. The sun was low on the horizon due to the time of day and the season. At the time of the occurrence, the crew were actively looking for a set of wires that were marked on a map but were almost impossible to see with the crew looking towards the sun in a low contrast environment.

The crew convened at the operator’s hangar early in the morning and undertook a pre-flight briefing. The crew, a pilot, an observer (front left seat), and inspector (rear right seat facing forward) had flown together previously and reported that they were comfortable operating as a team.

The Observer reported that he received information about the lines to be inspected early in the morning and was due to fly an hour later from a local airport. Other things were happening that distracted them so the time that they had to study maps and plan the flight was condensed.

About 25 minutes after the helicopter departed for the inspection area, it descended to commence the inspection flight. The client and operator procedures required that a high reconnaissance be conducted before the helicopter descended low level. The purpose of the high reconnaissance procedure was to provide the crew with an opportunity to identify known and any potential unknown obstructions. This procedure was not conducted before the helicopter was flown to low level because, well, no-one (client of operator crew) had followed the procedure in years because, after all, crews felt that they ‘knew’ the area. This failure to follow this procedure had become entrenched and so, had become a ‘normalized deviation’; something that will be discussed later.

A short time later, as the crew were following a line, the Observer turned the page of the map and advised the pilot that they would soon come upon a set of powerlines crossing the river roughly perpendicular to their flight path. The crew looked and looked hard for these wires. The conditions of the day made these wires almost impossible to see. The pilot was getting uneasy and slowed the helicopter when the crew then saw the wires, just before impact. The helicopter hit three unenergized powerlines. The Wire Strike Protection System cut the wires. The height of the helicopter above the ground when it stuck the wires was about 30 metres (nearly a hundred feet).

The pilot retained control of the helicopter and picked a safe place to land; landing safely just a few minutes after the impact.

The wires spanned from a pole on a hill, located to the right of the helicopter’s flightpath following down the hill slope and across the river to a pole on the other side of the river to the helicopter path’s left.

After the impact, the helicopter landed safely with minor damage and the crew suffering no injuries.

So, what were the factors in this occurrence? Causal factors included the environment (ambient lighting which made the wires difficult to see), the lack of warnings on wires or supporting structures, and the map scale (resulting in a delayed notice to look for the wires). Consequently, did that mean the accident was inevitable? The wires were almost impossible to see after all.

The wires were marked on maps, the crew were aware of approaching the wires; so, the question has to be why did the helicopter hit them?

Fundamentally, the occurrence causation could be attributed to two primary root causes:

A lack of in-depth planning (shortage of time and a familiarity with the task) and the introduction of other requests diverting the crew’s attention from the primary task during planning; and

Not conforming with the published procedure in not conducting a high-level reconnaissance, at the very least, of a high-risk area such as the area they were operating. Not doing the high reconnaissance had apparently become the process within the client’s workforce and the operator essentially because they felt they were familiar with the areas in which they were working. This was a classic normalization of deviance.

Normalized Deviation

Normalization of deviance is a term used by the American sociologist Diane Vaughan (in her analysis of the Challenger space shuttle disaster) to describe a process, in which deviation from correct or proper behaviour or rule becomes normalized in the organization.

It is a process where a clearly unsafe practice comes to be considered normal if it does not immediately cause a catastrophe - often with a long incubation period [before a final disaster] with early warning signs that were either misinterpreted, ignored, or missed completely.

Although everyone involved was accustomed to mission-completion pressure as a factor in decisions regarding the Challenger launch, the fact that 24 previous launches had been successful with known leaks in seals (called O-rings) between rocket stages may have been the most important human factor. The term normalization of deviance — the gradual process by which the unacceptable becomes acceptable in the absence of adverse consequences — can be applied as legitimately to the human factors risks in any operation as to the Challenger accident. The shortcut, slowly but surely, over time, becomes the norm.

In this helicopter wirestrike case, the high reconnaissance procedure had been put in place years before to ensure crews had an opportunity to check for known and unknown obstacles including wires and towers, but the procedure had not been followed for some time, probably through familiarity.

So, what are the lessons?

Whether engaged in powerline work, emergency medical service operations or aerial firefighting, wires are a constant threat. Any pilot who operates within a low-level environment and forgets wires is exponentially increasing the risk of not coming home. The factors involved in avoiding wires has been mulled over, published and highlighted for decades and yet, wirestrikes continue happening.

In a 2006 report produced by the Australian Transport Safety Bureau (ATSB), it noted that the rate of wire-strike accidents reported per 100,000 hours flown ranged from around 0.9 in 1997 and 1998 to 0.1 in 2003. The figures suggested a downward trend beginning in 1998, but with a return to previous accident rates in 2004. In another report, the ATSB noted, “between 1 January 2010 and 31 December 2020 there were 350 reports of aircraft collisions with powerlines. Of these 12 resulted in fatal accidents, with an additional 25 accidents resulting in serious injuries.” – this was in Australia alone. According to the ATSB, some 63% of pilots involved in wirestrike accidents reported that they were aware of the powerlines they hit but had forgotten about them before the wires were struck. Interestingly, the Bureau also found that, based on data from electricity distribution and transmission companies, at least 40% of wirestrike occurrences in Australia between July 2003 and June 2011 were not reported to the ATSB. Also of interest is that it tends to be experienced rather than newly trained pilots who hit wires – this could be due to familiarity, or it is only experienced pilots employed to particular work.

It is a given that wires are generally hard to see for a variety of reasons including sun direction, background, wire aging (reduced or no reflectivity), and contrast (‘flat’ seeing conditions). There are also a variety of wires, from high voltage strung on high lattice work towers to Single Wire Earth Returns (SWER), ski lifts, and flying foxes (lines strung across areas (usually rivers) to get material from one end to the other. How do we combat the problem of the invisible.

Wirestrikes are not inevitable

Wirestrikes have been an ongoing issue for aircraft operating at low heights. Poor light and visual conditions including smoke can make wires practically invisible so pilots should plan and fly in such a way to minimise the risk of wire contact.