HISTORY OF FLIGHT On April 22, 2002, at 1725 central daylight time, a Beech 200, N26SJ, operated by Flying Dollar Air Incorporated as a subcontract flight for Max Air, received minor damage when the passenger/crew door departed the airplane during cruise at flight level (FL) 190, near Hillsdale, Wisconsin. The flight crew performed an emergency landing at the Chippewa Valley Regional Airport (EAU), Eau Claire, Wisconsin. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 135 passenger flight was operating on an instrument flight rules flight plan. The two flight crewmembers and seven passengers were uninjured. The flight departed from the St. Paul Downtown Holman Field Airport (STP), St. Paul, Minnesota, at 1715, and was en route to the Outagamie County Regional Airport, Appleton, Wisconsin. The pilot said that the copilot told him that he latched the door, and the door handle was rotated to the over center position. The copilot illuminated the door light to check that the latch pins were in place. The annunciator for the door was not illuminated once the door was closed. He said the airplane was cruising at an indicated airspeed of 195-200 knots and an outside air temperature of -16 degrees Celsius. He also said that the cabin differential pressure indicated 3,200 feet and 6.1 psi. There was no air turbulence. At 1735, the airplane was approximately 35-40 nautical miles (nm) northwest of EAU at FL 190 when the door departed the airplane. The door annunciator light illuminated and remained illuminated for the duration of the flight. The passenger/crew door has two forward latch bolts, two aft latch bolts, and two upper hooks. The upper latch bolts are ramped to draw the door into place as they are extended. When the upper latch bolts are extended, the door frame rollers must rest a minimum of 0.12 inches past the tangent portion of the latch bolts. The structural limitation for the forward and aft latch bolts are 6,000 hours. Beech 200 service difficulty reports (SDRs), from 1974 to April 24, 2002, include 11 records of cabin and cargo door failures. Of the 11 records, 8 involved cabin door separations from the airframe. Additional SDRs relating to the Beech 100, 99, and 90 cabin doors are included in this report. Logbook entries show that on September 25, 2000, at an airplane total time in service of 5,946.2 hours, four cabin door pins (part numbers: 50 430177-5 and 50-430018-4) were replaced. The airplane accumulated 6,352.6 hours at the time of the accident. The passenger/crew door was found in an agricultural field approximately 30 nm northwest of EAU. The door handle and latch bolts were in the locked position. The upper aft latch bolt was broken off and lying within door structure. The fuselage door frame and latch plates were undamaged. The door was sent to the National Transportation Safety Board's Materials Lab. Visual and scanning electron microscope examination of the latch bolt confirmed that fatigue fracture within the threaded portion of latch bolt was the fracture mode.