STAR-X Collaboration: Wire Strikes in Agricultural Operations
Vol.9 Issue 3

Through the STAR-X Program, Dr. Hannah Baumgartner and Wayne Fry joined efforts to create a focus group to study wire strikes in agricultural aviation operations.

Hannah Baumgartner, Engineering Research Psychologist in the Flight Deck Human Factors Research Lab at the Civil Aerospace Medical Institute.

Power lines in rural areas can be hazardous unless proper safety measures are taken. The goal is to keep people and property safe, while protecting the reliability of power. Wire Strikes are a common accident occurrence in Part 137 Agricultural Operations, with many pilots reporting previous awareness of the wires before the collision. The presentation covered results from focus groups with pilots who have previously experienced wire strikes in agricultural operations, providing insight into the conditions and events that lead to said accidents.

Dr. Hannah Baumgartner is an engineering research psychologist with the Flight Deck Human Factors Research Laboratory (AAM-510) of the Aerospace Human Factors Division at the Civil Aerospace Medical Institute. Dr. Baumgartner has a broad range of research interests including, fatigue across aviation operations, evaluating decision making in agricultural aviation operations, and human factor risks and mitigations within helicopter air ambulance operations.

Wayne Fry, Division Manager in General Aviation (Division E) for the Flight Standards Service.

Wayne Fry oversees nine General Aviation offices, including many agricultural aviation operators. He is a 25-year veteran of the Federal Aviation Administration, holding management positions in the Flight Standards Regional offices in Seattle and Fort Worth, in the Flight Standards District Offices of Oklahoma City, Houston and Baton Rouge, and the Aircraft Maintenance Division in Washington, D.C.

Data shows that many agricultural accidents have happened over the years. Fry felt that they were not looking at the root causes of these accidents and wanted to see if human factors were involved. Noticing that most fatalities have to do with wire strikes, it was then established that wire-strikes and in-air collisions with obstacles are the leading cause of accidents in the aerial application industry (NTBS, 2014). Another important finding was that many pilots reported being previously aware of the obstacles that they collided with. Pilots statistically know the wires are there, having avoided them on multiple previous passes, indicating that there are other issues at play.

The focus groups in this study consisted of 22 total participants, with each group having anywhere from 6 to 10 participants. At the National Agricultural Aviation Association (NAAA) annual Ag Expo, the group of attendees who have experienced at least one wire-strike event were brought together and given a conventional qualitative content analysis. All of the groups and content within this study were taken directly from content at the NAAA Ag Expo.

Participants of these focus groups were asked four questions. Here are the results of their answers.

What conditions or events contributed to the in-air collision?

The conditions and events that contributed to these in-air collisions were situational factors and cognitive factors.

One of the situational factors was "technically difficult operations," (wires in the middle of the field, a field full of wires, and difficult parts of the field to reach) and this was reported by 55% of pilots.

"It was an area that I could only get two passes into the side of a busy road."

"…it’s [the field] just a wiry mess"

Another situational factor was flight stages, (trim pass, entering field, or exiting field) reported by 55% of pilots.

"One of them [wire-strikes] was obviously exiting the field, and the other two entering the field."

The third situational factor brought to attention was internal risk factors, (fatigue, heightened emotional states, lack of experience, or lack of familiarity with the aircraft) reported by 50% of pilots.

"It was at the end of the day too, so you know, probably a little bit tired."

"The reason that I hit it is because I was flying a 402 and I hadn’t flown a 402 for 12 years or something, and then I got the 502, so I didn’t know, I didn’t have all my amenities in it…"

The final situational factor from this focus group was environmental factors (night flying, poor visual conditions, weather conditions) reported by 23% of pilots.

"The rain hit the windshield and I looked off to see where the rain was, because it was kind of in the distance coming."

In regard to the cognitive factors, one was splitting attention, or distraction, (distracted by other obstacles in the field, avoiding owner property, distracted by future work, radio calls, etc.) reported by 59% of pilots.

"I remembered from the year before that there was a very small GPS tower in the corner of that field…I glanced out to see if it was in the field, so my attention was drawn from where it should have been, a little too far ahead."

"It was the last field for this customer, and we were going to be moving on. I might have been thinking about where we were going from there."

Another cognitive factor studied was judgement call errors, (forgetting the wire was there, misjudging proximity to the wire, etc.) reported by 27% of pilots.

"I just flat out forgot about it."

"I basically went one pass too long and I thought I could sneak under it, and [I] hit it."

The other two cognitive factors brought up were performance pressure, (doing highest quality work or internal pressure to hurry) reported by 27% of pilots, and breaking their own rules, (explicit reference to breaking personal rules) reported by 9% of pilots.

"I was trying to do a good job and had been under a lot of pressure to do good work… Doing a quality job, trimming the field, and getting too close to the poles, getting all the way to the edge of the field."

"It was an area that I could only get two passes into the side of a busy road, and I broke my own rules. Normally, first pass is a power and height to make sure I clear everything."

What immediate recovery steps did you take after the collision occurred?

Assessment of the situation (e.g., gain situational awareness, environmental awareness)

"I just didn’t know what to do. Where do I go? What do I do? You know there’s so many things going on, and it probably took me thirty seconds before I realized what even happened on my end… It takes a long time for your brain to catch up with you when something like that happens, and you’ve got a lot to process."

Assessment of damage during the flight (e.g., double check, circle back)

"Everything was still going. I thought, what was that? It took me a little bit, then I realized I’m holding real hard left aileron to keep this airplane flying straight. I looked out to my left wing, and on the aileron, I had about a four-inch hole in the aileron."

Maneuver the aircraft; maintain airspeed (e.g., change altitude to avoid other obstacles, keep the aircraft straight/level, add power)

"Immediately after, like I said, I thought I missed it and as I was slowing down, I realized I didn’t. At that point, you don’t really have much control other than you do what you’ve always been taught, fly the aircraft. So, I kept flying until the wire broke."

Observe/maintain/monitor gauges

"You start scanning everything and looking. Everything’s good. Everything’s green."


"What do I have underneath the airplane? I couldn’t get ahold of anybody at home, on the radio, so I just started calling on the phone…Then they looked, they said I had my landing gear, everything looked good, but unsure if there was air in the tires."

Head to the airport

"Everything was good, so I went back to my primary airport where my mechanic was and landed there."

Assess damage after flight (i.e., after landing)

"Fly back to base, land, shut down and do an assessment and go from there."

To what degree were you aware of this wire or obstacle before the collision occurred?

From the 31 total wire strike events described by the 22 pilots, 20 were previously aware of the wire, while 11 were previously unaware.

What could you have done differently that would have prevented the collision?

When asked what could have been done differently to prevent the collision, study group pilots stated three options:

Check conditions/situational awareness

"…what I should have done differently was paid attention the whole time and just knew where I was at."

"Not sprayed the field. I’ve sprayed around it several times knowing there was wires all around it, and it was close to a power plant, it was wired up as we say. I circled and circled and circled trying to pick out all the wires and probably at some point, I should have said there’s too much and I need to leave."

View of power lines in fields

Avoid deviating from the plan

"Right at the last minute when I was leaving, I thought I got a little bit in the hopper, might not have gotten that end good enough. I slid back in there to throw a pass in, and I probably should have done another reconnaissance and thought it through."

Don’t break your own rules

"…broke a rule that I told my guys not to do, I trimmed the field first."

This focus group study had an incredible outcome, and research is not over yet. Researchers now know pre-flight and in-flight risk factors. They know that most pilots are already aware of the wire before collision, and recovery includes immediate reactions and next steps. They are also aware of potential prevention steps, largely focused on situational awareness, and limitations.

Wayne Fry concluded by saying, "It was moving listening to them… these were a large part of their lives." Fry also stated, "Next steps are to brief NAAA and gather what they are doing with what we are going to get more information on in the reporting process."

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