WPR23LA255 · Avia Stroitel AC-5M
Avia Stroitel AC-5M · Accident: loss of control in flight while maneuvering
From North Plains Gliderport (1OR4) to an unrecorded destination
Event
- NTSB case
- WPR23LA255
- 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
- Event fatalities
- Unknown
- 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
Avia Stroitel AC-5M
- Aircraft type
- Avia Stroitel AC-5
- Category
- Glider
- 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
- N40233
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From North Plains Gliderport (1OR4), North Plains, ORTo not recorded
- Aircraft age
- About 23 years (built 2000)
- 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
- 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
- Aircraft › Aircraft structures
- Organizational issues › Development
- Personnel issues › Experience/knowledge
- 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
The pilot stated the airspeed may have been too slow when he initiated a 30° - 45° right turn during his first flight in the foreign-manufactured experimental motor glider. The glider immediately entered a clockwise, tight spiraling dive. After several revolutions, he was able to arrest the rotation, but the motor glider’s high airspeed produced significant vibrations. He applied gentle aft pressure on the control stick to regain control, but an inflight separation of the right wing ensued. The pilot released the canopy, egressed about 500 ft above ground level (agl), and deployed his parachute. The motor glider impacted the ground, and the pilot’s parachute landing resulted in serious injury. Postaccident examination of the motor glider’s wing structure revealed that the right wing’s main spar fractured due to overstress from upward bending loads. No evidence of fatigue was observed with the fracture. However, the wing spar was likely weaker than expected due to wrinkles in the composite fiber reinforcement layers in the upper and lower caps at the critical location where the spar intersected the reinforced closeout rib at the inboard section of the wing. Since the overstress fractures showed no evidence of damage before separation from a progressive failure mechanism or impact, the loads on the right wing during the accident flight were likely higher than any previously applied loads. However, the extent and angle of the wrinkles in the reinforcement layers at the fracture location indicated that the load that produced the right wing failure in this accident was considerably less than the expected failure load for the design and was possibly lower than the expected maximum design operating load. However, without knowing the actual ratio between the design ultimate failure load and the maximum design operating load of the wing for this experimental foreign-made aircraft, it is uncertain whether the design maximum operating load was exceeded based solely on analysis of the lab findings.
Probable cause
The pilot’s failure to maintain control of the motor glider, which resulted in an inflight overstress separation of the right wing during a high-speed, high-wing-load spiral dive recovery. Contributing to the accident was the inadequately manufactured wing structure.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR23LA255
- Event ID
- 20230705192533
- Case number
- WPR23LA255
- 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: be5032b4d3371a0a41e41e590ad0e89f5a0531a54c36c61c8bfc5eb6d1eafb05; retrieved 2026-09-16T17:48:41.429Z.