Investigation Summary
The accident occurred during a non-routine demonstration flight requested by the Falsterbo Coast Guard base. The Swedish Accident Investigation Board (SHK) found that this demonstration was performed in deviation from internal operational rules and without specific operational instructions. After completing two low-altitude passes along the canal, the crew performed a third approach. As the pilots tipped the wings to salute the observers, the left wing lower skin failed completely. The SHK found that the failure originated from a fatigue crack approximately 84 cm long located where the wing attached to the fuselage. This crack was hidden beneath doublers, making it invisible during standard external inspections. The SHK determined that a major factor was the 'unsuitable design of the attachment of the wings to the aircraft fuselage' because the fairings between the fuselage and wing transmitted vertical loads they were not designed to carry, creating stress concentrations in the lower skin. Furthermore, the manufacturer's maintenance schedule failed to include inspections capable of detecting such cracks, despite this specific aircraft being a high-cycle 'lead' airframe in the Coast Guard fleet.
Final Conclusions
The SHK concluded that the accident was caused by an inadequate maintenance system regarding fatigue crack inspections, compounded by an unsuitable wing-to-fuselage attachment design. The investigation noted that while the Coast Guard's low-level operations subjected the airframe to high loads, these remained within permitted limits. The manufacturer was found to have underestimated material stress in the affected area and overestimated the fatigue strength of the wing. Following the crash, the Swedish Coast Guard grounded its remaining C-212 fleet; subsequent inspections found similar, though less developed, fatigue cracks on the remaining aircraft, leading to their permanent withdrawal from Swedish service.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
First Officer
Systems & Failure Modes
Wing Lower Skin
A primary load-bearing structure of the wing that failed due to Multiple Site Damage (MSD) fatigue cracking.
Wing-to-Fuselage Fairings
Aerodynamic components that the SHK found were inadvertently transmitting vertical loads to the wing skin, contributing to fatigue.
Maintenance Program
The manufacturer-prescribed inspection cycle was found insufficient as it did not require the specific non-destructive testing needed to find cracks hidden by doublers.
Interesting Facts
- 01The left wing lower skin contained a pre-existing 84 cm fatigue crack at the time of the accident.
- 02A similar, less developed fatigue crack was discovered in the right wing during the wreckage analysis.
- 03The fatigue cracks were located under doublers and were not visible from the outside of the wing.
- 04The accident aircraft was the operating time leader for the Swedish Coast Guard's C-212 fleet.
- 05Following the accident, one of the remaining fleet aircraft was used for destructive testing by the manufacturer to study crack growth before the others were transferred to Uruguay.
Safety Actions & Advisories
Fleet Grounding
The Swedish Coast Guard grounded its remaining CASA C-212 fleet immediately following the accident.
Mandatory Inspections
The manufacturer and aviation authorities prescribed special inspections of the wing attachment areas for all C-212 aircraft in service.
Fleet Replacement and Research
After the grounding and discovery of fatigue cracks in the remaining aircraft, one airframe was used for destructive testing by the manufacturer. The remaining operational units were eventually sold to Uruguay and replaced by Bombardier Dash-8 Q300 aircraft.
Known Controversies & Unanswered Questions
Unauthorized Flight Maneuvers
Reference ↗The investigation revealed that the crew performed unauthorized maneuvers, including a 360-degree turn at 500 feet shortly after takeoff and the low-level demonstration fly-bys at Falsterbo. These were conducted in deviation from internal operational rules and without specific instructions. It was reported that the initial maneuver was performed to show the aircraft to a work experience student, a detail that highlighted a lack of operational discipline despite not being the direct cause of the structural failure.