FlarePath

What happened

NTSB summary, verbatim

The purpose of the flight was to perform low-level aerial surveillance of power transmission lines using an external gimbal-mounted infrared camera to detect problems with the patrolled power lines. While patrolling above a power line that passed through a valley, the helicopter struck another power line that crossed perpendicular to the helicopter's flightpath and was at a higher elevation than the patrolled power line and ran from poles mounted atop higher terrain. The struck power line was not marked with high-visibility balls nor was it required to be. The sun was directly in front of the helicopter and 30 degrees above the horizon at the time of the accident, which likely made it difficult for the pilot to see the crossing wire. Postaccident examination of the helicopter did not reveal any preimpact anomalies. Given that this was a low-level surveillance flight of power transmission lines, the pilot should have familiarized himself with the power lines he was going to patrol and any other wires or obstructions in the area before the flight. It is likely that he did not adequately plan for the flight and that, if he had, he might have been aware of the power line and been able to avoid it.

Photographs

11the aircraft, and what the investigators found

Wreckage and site documentation · 11 photographs from the docket

Photographs are NTSB docket attachments — works of the US government, in the public domain. Captions are the Board’s own.

Probable cause

the Board's determination

The pilot’s inadequate preflight planning for a low-level aerial surveillance flight of power transmission lines, which led to his being unaware of the crossing power line while flying toward the sun and his subsequent failure to maintain sufficient clearance from the wire.

Occurrence sequence

2 stepsNTSB coding · CICTT taxonomy

1 · Maneuvering-low-alt flying
Collision with terr/obj (non-CFIT)
2 · Maneuvering-low-alt flying
Low altitude operation/event
defining event

Findings

5 causal · 1 contributing

CAUSE
Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Altitude — Not attained/maintained
CAUSE
Personnel issues › Task performance › Planning/preparation › Flight planning/navigation — Pilot
CAUSE
Personnel issues › Psychological › Attention/monitoring › Monitoring environment — Pilot
CAUSE
Environmental issues › Physical environment › Object/animal/substance › Wire — Awareness of condition
CAUSE
Personnel issues › Action/decision › Info processing/decision › Identification/recognition — Pilot
FACTOR
Environmental issues › Conditions/weather/phenomena › Light condition › Glare — Effect on personnel

NTSB analysis

from the final report

The purpose of the flight was to perform low-level aerial surveillance of power transmission lines using an external gimbal-mounted infrared camera to detect problems with the patrolled power lines. While patrolling above a power line that passed through a valley, the helicopter struck another power line that crossed perpendicular to the helicopter's flightpath and was at a higher elevation than the patrolled power line and ran from poles mounted atop higher terrain. The struck power line was not marked with high-visibility balls nor was it required to be. The sun was directly in front of the helicopter and 30 degrees above the horizon at the time of the accident, which likely made it difficult for the pilot to see the crossing wire. Postaccident examination of the helicopter did not reveal any preimpact anomalies. Given that this was a low-level surveillance flight of power transmission lines, the pilot should have familiarized himself with the power lines he was going to patrol and any other wires or obstructions in the area before the flight. It is likely that he did not adequately plan for the flight and that, if he had, he might have been aware of the power line and been able to avoid it.

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