CEN21FA150 · Aviat A-1B
Aviat A-1B · Accident: loss of visual reference en route
From Mason City, NE (private airstrip) to Holyoke Airport (HEQ)
Event
- NTSB case
- CEN21FA150
- 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
- 1 · 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
Aviat A-1B
- Aircraft type
- Aviat A-1
- 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
- N166WW
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Mason City, NE (private airstrip)To Holyoke Airport (HEQ), Holyoke, CO
- Aircraft age
- About 15 years (built 2006)
- 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
- En route · cruise
- 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 visual reference
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Destroyed
Cause areas
- Environmental issues › Conditions/weather/phenomena
- Personnel issues › Psychological
- Personnel issues › Task performance
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
Primary radar first picked up the airplane about 0555, 1/2 mile south of the private runway. The airplane track proceeded generally west-southwest for about 11 miles when it made a left turn toward the south at a speed of about 88 knots. The track then made right 360-degree turn; during which, the speed of the airplane increased to about 114 knots. Followed by a tighter 360-degree turn at 49 knots and decreasing. The track then zig zagged at an average of 30 knots until 0609 when the track terminated about 1,000 ft from the accident site.
The airplane impacted a field perpendicular to a gully in a very rural area; the debris field was about 300 ft long. The first identified point of impact was a long narrow area of disturbed dirt with the right wingtip nearby. Next were two slash marks consistent with propeller blade slices; followed by a large area of disturbed dirt with propeller blade fragments. The main wreckage came to rest at the bottom of the gully; the last major piece of debris was the engine. Postaccident examination of the airframe and engine did not reveal any anomalies that would have precluded normal operations.
The pilot flew the accident airplane regularly over his land and pastures. It was not abnormal for him to takeoff before sunrise despite not holding an instrument rating. At the time of the accident the moon was 22.97 degrees above the horizon at third quarter phase. Its illumination was 45.1% of the moon’s full potential. There were no high-altitude cloud layers to block the moonlight. Therefore, it was dark with the exception of any ground lights and moon illumination.
The flight track immediately before the accident was consistent with a pilot experiencing spatial disorientation and subsequently losing airplane control. Several factors support this conclusion, which include the low moonlight; few ground lights in a rural area; the pilot’s lack of instrument rating; and the airplane’s abrupt roll, heading, and speed changes leading up to the accident site.
Probable cause
A loss of control and subsequent impact with terrain as a result of spatial disorientation during cruise in dark night conditions.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CEN21FA150
- Event ID
- 20210307102722
- Case number
- CEN21FA150
- 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, coordinates, cause areas. 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: f5fe99c278792241d78fa76e1f95d11f220932db6223634ab04f1089278f9710; retrieved 2026-09-15T07:26:11.722Z.