On February 23, 1973, a Douglas DC-3 (registration ZK-AOI) operated by Southern Air Super was involved in an aviation accident near Seddon, New Zealand in flight. One person was killed. Investigators recorded the probable cause as: In-flight separation of the starboard wing due to loss of structural strength from extensive fatigue cracks in the lower centre wing wraparound and internal doublers inboard of station 142, with crack initiation and propagation to failure resulting from… This summary draws on records from the Bureau of Aircraft Accidents Archives (B3A).
While conducting a crop spraying flight, the aircraft's right wing detached in flight, causing the pilot to lose control. The airplane crashed in an open field and was destroyed; the sole occupant pilot was killed. Investigation attributed the wing separation to fatigue cracks from overstress.
The Accident
During a crop spraying operation, the pilot lost control of the airplane after the right wing separated from the aircraft in flight. The airplane subsequently crashed into an open field and was destroyed. The pilot, the sole occupant, was killed.
Investigation Findings
The official investigation determined that the accident was caused by the in-flight separation of the starboard wing. This separation resulted from a loss of structural strength due to extensive fatigue cracks in the lower centre wing wraparound and internal doublers inboard of station 142. The initiation and propagation of the cracks in the right wing to the point of failure were attributed to consistent overstress.
Structural Details
The fatigue cracks were located in the lower centre wing wraparound and internal doublers, components critical to the wing's structural integrity. The consistent overstress conditions over time led to the initiation and growth of these cracks until the wing could no longer sustain flight loads, resulting in its detachment.
Probable cause
In-flight separation of the starboard wing due to loss of structural strength from extensive fatigue cracks in the lower centre wing wraparound and internal doublers inboard of station 142, with crack initiation and propagation to failure resulting from consistent overstress.