What happened
On April 1, 2011, a Dornier 228-212 aircraft, registration PH-CGC, was conducting an operational Coast Guard flight over the North Sea. While cruising at 1,000 feet, the crew heard a sound similar to a snapping cable, followed immediately by a sharp, powerful downward movement of the aircraft's nose and intense vibrations in the control wheel.
The crew promptly reduced speed to 150 knots and consulted the manufacturer's flight operations bulletin regarding elevator skin detachment. The pilot successfully stabilized the aircraft and returned to Schip and Schiphol Airport, where the aircraft landed safely. Upon inspection, it was discovered that the plastic covering on the right elevator had largely detached, remaining attached only at the underside of the trailing edge.
The investigation
The Dutch Safety Board (OVV) investigated the structural failure and the subsequent reporting process. The investigation focused on the maintenance history of the aircraft, specifically a repair performed on the elevator in 2004. Investigators also examined the reporting procedures used by the Ministry of Defence and the Coast Guard regarding the incident.
Findings
- The primary cause of the detachment was that maintenance work to reattach the plastic covering was not performed strictly according to the manufacturer's Structural Repair Manual.
- Specifically, methyl ethyl ketone was used as a thinner for the adhesive instead of the required toluene.
- The repair lacked the use of specific tools, such as a spatula, which are necessary for ensuring proper adhesion, though the manual's instructions for this specific task were noted as being somewhat general.
- The investigation also revealed significant deficiencies in the reporting systems within the Ministry of Defence, noting that procedures for reporting incidents involving civil-registered aircraft were insufficiently clear.
Safety action
Following the incident, the manufacturer updated the aircraft's abnormal and emergency procedures to include the specific flight procedures for elevator skin detachment. Additionally, the manufacturer now provides 'on the job' training for maintenance organizations performing repairs or replacements of elevator coverings.