On May 8, 2004, approximately 1100 mountain daylight time, a Dornier DO27A4, N276MK, was substantially damaged following a hard landing at the Cabin Creek Landing Airport (97MT), Marion, Montana. The commercial pilot and her two passengers were not injured. Visual meteorological conditions prevailed for the personal flight, which was conducted in accordance with 14 CFR Part 91, and a flight plan was not filed. The flight had departed the Ferndale Airfield (53U), Big Fork, Montana, approximately 30 minutes prior to the accident. According to the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2), the pilot reported that as she approached the destination airfield she observed the weather deteriorating, with a shower present where she would normally glide in, and more showing up. The pilot stated, "I decided to slip the Dornier in. I had pulled 90 percent out of the slip when I touched down, hitting the left landing gear, but not enough to prevent a 'perfect attitude and directionally controlled landing' after the initial touchdown." The pilot further stated that the landing gear was solid and she didn't notice any discernible difference during taxi. The pilot reported that after breakfast, "...I asked all there to watch as I did a 360 degree taxi on the tarmac to see if there was any weakness observed. I felt none [and] the 5 or 6 pilots present said it was solid. I [then] flew it to home (53U)." The pilot stated that the damage to the airplane was not discovered until it was examined and repaired two months later. In written reports submitted to the Federal Aviation Administration (FAA), several witnesses reported that the left main landing gear was bent/splayed out further than the right main landing gear, and that the left cabin door would not operate properly. Witnesses also stated that prior to her departure the pilot secured the door with some borrowed rope. The FAA was notified on November 4, 2004 that N276MK was involved in an accident on May 8, 2004. On January 5, 2005, the NTSB investigator-in-charge (IIC) was made aware of the event by the FAA. On January 31, 2005, based on information provided by an airframe and powerplant mechanic to the IIC, it was concluded that the aircraft had sustained substantial damage during the hard landing and that he had repaired it in accordance with Advisory Circular (AC) 43.13-1A.