AS350 B3e course · Astar hazards
Wire strikes
The hazard LowOps was built for
The essentials
Wire strikes kill helicopter crews every year, mostly in low-level work: patrol, construction, agriculture, filming, EMS landings and low flight in valleys.
Pilots rarely see the wire that hits them. They see — or miss — the structures: poles, towers and cleared corridors.
Defences, in order: know where the wires are (planning, reconnaissance, databases), fly where they aren't (height, crossing at structures), and wire-strike protection as the last resort.
What the numbers say
A Flight Safety Foundation study of US helicopter accidents from 1996 to 2000 found 50 wire strikes among 934 accidents — about 5 %. Every one destroyed or substantially damaged the aircraft; 15 were fatal and 9 caused serious injuries.
More than half — 26 — happened while manoeuvring, and aerial application had the most of any purpose (13). The data are old, but the pattern holds: low, busy, and close to the job.
Source 1
Why wires are hard to see
A wire is thin, often against a busy background, and has no depth cue. In flat light, against the sun, against trees or terrain, it can be effectively invisible even when you are looking for it.
That's why the advice is always to look for the things that carry wires — not the wires.
Reading the structures
Every wire has a support at each end. Useful cues:
- a line of poles or towers, and the direction it runs
- a cleared corridor through trees
- a pole on one bank of a river or side of a road — expect its partner, and the wire between
- buildings, pumps and gates in open country — power often reaches them
- towers on ridges — the span may cross the valley you're about to fly up
Source 3
Reconnaissance from above
Before descending into an area, fly a pass high enough to be above any wires and look for structures, cleared lines through trees, and wires between buildings. Plan the approach and departure to avoid them, and to cross any you can't avoid at a structure.
A new site is a reconnaissance site, every time.
Source 3
Crossing a line
Cross at a structure. The wires are at their highest there, and you can see exactly where they are. Mid-span, they sag lower and you're guessing.
Climb early, cross with margin, and don't descend again until you're sure the span is behind you — and that there isn't a second line beyond the first. Roads, rivers and valleys often carry several.
Source 3
When the wires aren't the job
Wire work at least has wires in the briefing. Many strikes happen when the wires are incidental: a low transit along a valley, an off-airport landing site, a photo pass, a search.
The common thread is low flight below the height the wires live at, in places the pilot hasn't looked at from above. Any time you're down there, the reconnaissance rules apply.
Saturation
Wire strikes often happen while the pilot's attention is fully on something else — a load, a target, a camera position, a patient on the ground. The wire was in the area all along; the attention wasn't.
Brief known wires before the task starts, when there's spare capacity. Set a height you won't go below in transit. Use a second set of eyes when you have one, and give them the job of watching for wires.
What protection does and doesn't do
A wire-strike protection system — a windshield deflector plus upper and lower cutters — is designed for horizontally strung wires met by the nose, cutting them before they catch the mast, controls or skids. It doesn't protect the rotors or the tail, or help with a wire met some other way.
It has saved crews. It is worth having and not worth relying on.
Source 1
Woomera, 2019
In 2019 an AS350 stringing a new power line near Woomera, South Australia, struck one of the line's poles with its main rotor, about 17 m up. The pilot, very experienced, had modified the method taught; it put the aircraft low near the poles, raised dust, and with the sun and a nose-high attitude likely hid the pole. The pilot was killed.
In wire work the method is the safety margin. Changing it changes the margin.
What LowOps's data can and can't tell you
LowOps combines several recorded datasets — official obstacle data, utility data where it's available, and mapped lines — and removes duplicates. Coverage differs from region to region.
Gaps to expect: distribution lines to farms and houses, temporary and new construction, and lines nobody has mapped. A recorded wire may have no height — unknown is not low. Positions are as good as the source that recorded them.
Use it to plan and to cue your eyes. The reconnaissance still decides.
What should you look for to find wires?
The structures that carry wires are far easier to see than the wires.
Wire-strike cutters are fitted. Does that make low flight near wires safer?
Cutters are a last resort with real limits. Your height and your eyes are the defence.
You see a single pole on one bank of a river. What should you assume?
Every wire has a support at each end. Find the partner before you fly the river.
When is the best time to brief the wires on a job?
Attention is used up during the task. Brief the wires when you can still think about them.
LowOps shows a wire with no recorded height. What does that mean?
Unknown is not low. Plan as if it could be at any height you'd fly.
Sources
- Data show 50 U.S.-registered helicopters involved in wire-strike accidents from 1996 through 2000 · Flight Safety Foundation, Helicopter Safety Vol. 28 No. 4 · July–August 2002
- Investigation AO-2019-015, AS350 VH-SZS, near Woomera · ATSB · Final report, 9 March 2021
- Helicopter Flying Handbook (FAA-H-8083-21B) · FAA · Chapter 10, Advanced Flight Maneuvers
- Poor supervision led to powerline crash: ATSB · Australian Flying · 10 March 2021 (reporting ATSB AO-2019-015)
Educational only. Not approved training material, and never a substitute for the Rotorcraft Flight Manual, an instructor, or your operator's procedures. Figures marked as manufacturer data or test results are not limitations. This content is a draft and has not yet been reviewed by an instructor.