Summary
A private pilot flying an amateur-built Vans RV-10 encountered a door separation event during cruise flight. The incident occurred at an altitude of 4,500 feet MSL and an estimated speed of 145 knots. The pilot declared an emergency and returned to the departure airport without further incident. The separated door was not recovered.
Preflight Inspection
During preflight, the pilot confirmed that the doors were locked by checking the lock indicator lights on the instrument panel and the lock annunciators on the electronic flight information system. No anomalies were noted at that time.
In-Flight Event
While in cruise flight, the pilot noticed the right door vibrating. He reached over to grip the door handle, at which point the door began to open upward. Shortly thereafter, the door opened completely, separated from the airframe, and struck the right horizontal stabilizer. The pilot then declared an emergency and returned to the departure airport.
Postaccident Examination
A postaccident examination of the airplane was conducted but was inconclusive. The door was never found despite a search.
Survey of Similar Aircraft
As part of the investigation, five other RV-10 airplanes equipped with the same door locking mechanism were surveyed. The survey revealed varying degrees of door lock pin extension lengths among the airplanes.