WPR17LA145 · Piper L 21B B
Piper L 21B B · Accident: loss of control in flight while maneuvering
From Big Timber Airport (6S0) to Big Timber Airport (6S0)
Event
- NTSB case
- WPR17LA145
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Piper L 21B B
- Aircraft type
- Piper L-21
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N99031
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Big Timber Airport (6S0), Big Timber, MTTo Big Timber Airport (6S0), Big Timber, MT
- Aircraft age
- About 63 years (built 1954)
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Maneuvering · low-altitude flying
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Loss of control in flight
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Aircraft › Aircraft oper/perf/capability
- Personnel issues › Action/decision
- Personnel issues › Psychological
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
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.
Probable cause
The pilot's decision to fly at low altitude in the vicinity of power lines, which resulted in a wire strike.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR17LA145
- Event ID
- 20170708X13311
- Case number
- WPR17LA145
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: c1428c119b6bd814f6540d755b61c63d22343aeee8e86b8d3262cef858b17a11; retrieved 2026-09-16T05:31:10.970Z.