Hawker Beechcraft King Air 200, Leonardtown, Md., Oct. 12, 2006–On approach to Runway 29 at St. Mary’s County Regional Airport, the King Air’s landing gear showed “three green lights.” After a “firm but normal” landing, and immediately after touchdown, the landing gear warning horn sounded intermittently and the right wing began to “drop.” The right gear collapsed and the airplane then veered to the right, and the right propeller struck the runway. Most of the right wing and the majority of the right side of the fuselage were “consumed” by the resulting fire. No one was injured.
Both landing-gear assembly down-lock plates had been installed with their beveled surfaces facing aft, although they should have been installed facing forward. As installed, the down-lock plates and down-lock hook had a mutual contact area of less than 0.05 inch. When correctly installed, the contact area increased to 0.25 inch.
On Dec. 16, 2006, the repair station that had sold the plates notified its customers that the down-lock plates might have been installed incorrectly. The manufacturer’s component maintenance manual had no guidance regarding down-lock plate orientation. In November 2007, the manual was revised to “ensure that the lock plate is installed with the beveled edge down” and that “the end of the lock plate makes contact with the back of the down-lock hook.”