History of Flight
On April 5, 2009, about 1130 Pacific daylight time, a Liberty Aerospace Liberty XL-2 (N519XL) lost the majority of its left side cockpit door during cruise flight approximately 3 miles east of Camarillo Airport, Camarillo, California. Separated door components struck and dented the airplane's left stabilator. The airplane, operated by the Armed Forces Aero Club, Inc., San Diego, California, sustained minor damage. Visual meteorological conditions prevailed, and an instrument flight rules flight plan had been filed. Neither the certified flight instructor (CFI), who held an airline transport pilot certificate, nor the private pilot receiving instruction was injured. The flight was conducted under 14 Code of Federal Regulations Part 91 and originated from San Diego about 1000.
The CFI reported that the pre-takeoff checklist was followed and that the student properly and securely closed the left cockpit door before takeoff. No discrepancies were noted with the door's operation. During the instrument training flight, the student did not open or attempt to open the door. According to the CFI, the student was tracking inbound on the localizer to Oxnard Airport while cruising level at about 4,000 feet mean sea level. Minutes after the airplane entered an area of moderate clear air turbulence, the door "popped open" and subsequently separated from the airplane. The CFI took control and diverted to Camarillo Airport. Despite full engine power, level flight could not be maintained, but the airplane landed without further incident. After taxiing, the local air traffic controller reported that an airframe component had fallen onto the tarmac. The lower portion of the separated door, including the latching mechanism, was recovered.
Aircraft Information
The airplane, serial number 14, received a standard FAA airworthiness certificate on April 18, 2006. By the incident date, total time was about 253 hours. The last annual inspection was in July 2008 at 178 hours. The airplane has two doors hinged on their upper surfaces, secured by two locking pins (forward and aft) that extend into fuselage receptacles when the door handle is rotated forward.
Examination Findings
Examination of the right door revealed a functional latching mechanism, but the fuselage near the forward and aft pin receptacles showed abrasion and chipped paint, consistent with impact damage from partial closing with the pins extended. Similar marks were found on the left side fuselage. The left door was broken into several pieces. The composite door frame is not rigid when open and can be torsionally twisted by applied force.
Manufacturer Review
Liberty Aerospace reviewed other inadvertent door openings and identified about six instances where a door pin likely was not seated. Liberty's evaluation indicated that with both pins properly engaged, the door and airframe cannot flex to disengage a pin; however, if one pin is not in its receptacle, the door can flex and open. The airplane's FAA-approved flight manual contained a "BEFORE TAKEOFF" checklist stating "Canopy Doors...CLOSED AND SECURE." In response, the manufacturer revised the checklist to require verification of each individual door pin engagement. Additionally, a tapered door pin for the aft portion was introduced via Service Bulletin SB-09-003 (December 15, 2009) to aid proper engagement.