On March 18, 2021, about 1427 mountain standard time, an experimental, amateur-built Lancair Evolution, N469KS, was substantially damaged when it was involved in an accident near Phoenix, Arizona. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, he began a climb after he departed on an instrument flight rules flight plan from Falcon Field Airport (FFZ), Mesa, Arizona. As the airplane climbed through 22,000 ft mean sea level, about 30 nm west of the departure airport, the cabin door departed the airplane and impacted both the horizontal and vertical stabilizers. The pilot diverted and landed uneventfully. Photos of the airplane taken by the accident pilot showed substantial damage to the left horizontal stabilizer. The cabin door was not recovered. The airplane was equipped with one 42-lb main cabin door located on the left side of the cockpit that opened and closed by two hinges at the top of the door frame. When closed, the door locked the pressurized cabin through eight latches: three at the lower frame, two on the front door post, and three on the rear door post. Each latch mechanism comprised a steel latch arm and ball attached to an aluminum latch body, which was bolted to the door. The door was closed and locked when each latch arm and ball aligned and connected with its respective socket at the steel latch anchor, which is connected to the door frame. The locking mechanism was operated by a single handle rotated clockwise to lock the door, which latched the anchors through a series of sprockets and chains. Moving the handle in the opposite direction would unlatch the latches. (see figure 1)

Figure 1: Lancair Evolution Door Latch and Anchor Alignment According to the kit manufacturer, two potential main door failures had been reported to the company. The first failure occurred in 2010 on another airplane that resulted when a latch was not aligned over center and failed to secure to the latch body. This forced the adjacent latch mechanisms to carry the load, which caused one of the adjacent latches to fail at the aluminum latch body. Another failure occurred in November 2020 and resulted in an explosive decompression during cruise flight as the lower rear latches were not secured. According to the manufacturer, the cause was likely attributed to a failure of the lower rear latch to secure before takeoff. Once the load overstressed the forward latches, they failed in a domino effect that resulted in an explosive decompression. This prompted the manufacturer to issue an inspection advisory that required an inspection of the main door latches for cracks or other physical damage within the next 10 hours of flight. The advisory was issued to all maintenance facilities that regularly serviced their airplanes about three months before the accident airplane received its most recent service. The airplane’s maintenance logbooks did not indicate that the airplane had been inspected in accordance with the advisory and the maintenance facility that regularly serviced the airplane reported that they were not aware of the advisory.   An examination of the accident airplane fuselage frame by a Federal Aviation Administration inspector revealed no damage to the hinges or latch anchors.   Although the main door was not recovered, the airplane manufacturer issued a service bulletin on April 20, 2021, that required the latch mechanism to be inspected to ensure that the eight latch balls seated properly within their sockets without any clearance between the ball and socket. The service bulletin also required an inspection of the hinges at the next condition inspection and for the aluminum latch bodies to be replaced with structural stainless steel alloy bases.