Fatigue Cracking Tore the Left Wing From a Training Piper

The flight was a training exercise

On 4 April 2018, an airline transport pilot and a private pilot were conducting commercial-pilot checkride maneuvers in Piper PA-28R-201 Arrow III N106ER. The flight included a touch-and-go landing at Daytona Beach International Airport. During the climb after that landing, the left wing separated near the wing root and the aircraft collided with terrain.

The radar track did not show an extreme maneuver

Radar-derived data showed the aircraft's climb and heading after the touch-and-go. The recorded profile was not consistent with maneuvering that would reasonably be expected to create airframe loads sufficient to cause an in-flight structural failure. The aircraft was also within its maximum allowable gross weight and center-of-gravity limits.

The wing separated near the root

Witnesses close to the accident site reported that the airplane climbed normally on a westerly heading before the left wing separated from the fuselage. The aircraft's final recorded radar point was about 900 feet mean sea level at a groundspeed of roughly 80 knots. Both occupants died in the resulting impact.

The fracture was fatigue, not an overload maneuver

Examination identified extensive fatigue cracking in the lower cap and doublers of the left-wing main spar. The cracks had grown to a critical size. The investigation linked their initiation and growth to the repeated loads associated with flight training, including frequent low-altitude operations and landing cycles.

Inspection criteria were part of the finding

The official conclusion also addressed the inspection system. Previously established inspection criteria were insufficient to detect the fatigue crack before it became critical. The result was a structural failure that occurred during a normal-looking portion of the flight rather than during a maneuver that exceeded the aircraft's known limits.

The accident also demonstrates why the aircraft's operating limits and its actual flight path must be distinguished. Being within gross-weight and center-of-gravity limits does not eliminate the possibility of fatigue damage, and the investigation specifically identified the crack as a pre-existing structural condition that developed over time. The wing separation was therefore not presented as a sudden unexplained failure with no physical evidence.

Fatigue Cracking Explained the Wing Separation

The NTSB probable-cause finding states: ‘Extensive fatigue cracking in the left-wing main spar lower cap and doublers, which resulted in the in-flight separation of the left wing.’

Accident Facts

Sources

• NTSB investigation ERA18FA120: https://www.ntsb.gov/investigations/Pages/era18fa120.aspx