Probe into DA42 Door Separation Prompts Recommendations for More User-friendly Locking Mechanism and Warning System

The Safety In­ves­ti­ga­tion Au­thor­ity of Fin­land (SIAF) has com­pleted an in­ves­ti­ga­tion into a se­ri­ous in­ci­dent in which the pas­sen­ger door of a Di­a­mond DA42 air­plane be­came un­locked and sub­se­quently sep­a­rated af­ter take­off on an in­struc­tional flight from Pori aero­drome in Au­gust 2022. The air­plane re­mained con­trol­lable and re­turned to land with­out fur­ther in­ci­dent. The four-seat air­plane car­ried a flight in­struc­tor and two stu­dents.

“Accidents and Incidents are often a sum of several factors. We accident investigators like to use Swiss cheese as an analogy. In what we call the Swiss cheese model, slices of cheese are piled up together, and when holes in these slices align, all safety barriers are removed. Because the students had logged only a few flights on the airplane type they had not developed a routine in door locking, and since the locking mechanism was operated simultaneously from the cabin and outside the airplane, task-sharing, or “who-does-what” was unclear. Since door opening was noticed by the rear seat occupant and not from warning system activation, the crew members omitted to action the relevant checklist and responded promptly and instinctively in an attempt to lock the door. Furthermore, it is easy to leave the door only partially locked in this airplane type,” explains investigator-in-charge Janne Kotiranta, and continues that even though several in-flight door opening events on the DA40 and DA42 have been reported worldwide, airplane operators and flight crew members have remained unaware of locking-related issues.

The European Union Aviation Safety Agency (EASA) responded to the issue in 2010, but modifications and checklist updates have failed to solve the problem. The monitoring of the effectiveness of corrective actions has also been inadequate.

The SIAF issued safety recommendations both to the type certificate holder and EASA. The recommendations focus on the door locking mechanism and the monitoring of the effectiveness of corrective actions that have already been implemented.