Avia Stroitel AC-5M N40233

Summary

On 5 July 2023 at about 18:30 local time, a Avia Stroitel AC-5M registered N40233 was involved in an accident near North Plains, Oregon, United States. One person was on board and one was seriously injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

5 July 2023 at 18:30

Classification

Accident

Location

North Plains, Oregon, United States

Nearest airport

North Plains Glider Port (1OR4)

Coordinates

45.5764, -123.0604

Aircraft

Avia Stroitel AC-5M

Registration

N40233

Category

Glider

Year built

2000

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

North Plains → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR23LA255

1 person was seriously injured.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full 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.

Quoted verbatim from the NTSB record.