Piper L 21B N99031 accident near Big Timber, Montana

Probable cause

The pilot's decision to fly at low altitude in the vicinity of power lines, which resulted in a wire strike.

NTSB analysis

The private pilot reported that, after departure, he followed the course of a river at an altitude about level with the treetops. Although the pilot was aware of powerlines in the area, he did not see them before the airplane collided with the powerlines about 90 ft above ground level. The airplane subsequently nosed down and impacted the river, resulting in substantial damage.

According to the manager of the airport from which the airplane departed, it is not uncommon for pilots to fly at low altitudes in that area to avoid turbulent air in the summertime. He further reported that the power lines were not equipped with aerial marker balls. Following the accident, the airport manager agreed to install signage in the fixed base operator at the airport to caution pilots of the presence of power lines in that area.

Text from the NTSB. Open the NTSB docket for WPR17LA145 for the full record.