HISTORY OF FLIGHTOn January 18, 2015, about 1235 mountain standard time, a Beech A36TC, N3685W, experienced a nose gear collapse during landing at Flagstaff Pulliam Airport, Flagstaff, Arizona. The airplane was registered to, and operated by, the pilot under the provisions of 14 Code of Federal Regulations Part 91. The commercial pilot and passenger were not injured, and the airplane sustained substantial damage. The cross-country personal flight departed Brackett Field Airport, La Verne, California, at 0934 Pacific standard time. Visual meteorological conditions prevailed, and no flight plan had been filed.
The pilot reported that the airplane was travelling at 90 knots as they passed over the runway threshold, and that they touched down just past the displaced threshold. The airplane then bounced, and in response, he applied back pressure to the elevator control in an effort to deplete the excess energy. They touched down a second time on the main landing gear, and he held the airplane in a nose high attitude. The pilot surmised that at this point the nose landing gear scissor link (upper torque knee) failed, causing the nose wheel to over extend and release from the airplane. As the airspeed decreased, the airplane came to rest on its nose.
Two air traffic controllers witnessed the accident from the airport's control tower. The tower controller stated that he observed the airplane bounce two or three times after landing and then the nose landing gear collapsed. The ground controller reported that he observed the airplane land hard on the nose wheel first, then porpoise up and down two more times, each time landing on the nose wheel first, before it collapsed.
The airplane sustained substantial damage to the lower fuselage during the accident sequence, and the lower landing gear assembly, which was composed of the nosewheel, fork, and lower torque knee had become detached. TESTS AND RESEARCHThe airplane was equipped with retractable landing gear, driven by an electrical actuator connected to a series of link rods. The nose landing gear extended forwards, and was held in the locked and down position by a wishbone-shaped aft brace and a single forward brace. In the extended mode, both braces were held in position by a series of control arms connected to the landing gear link rods.
Sections of the lower nose gear assembly were recovered from the airplane and examined by the NTSB investigator-in-charge.
Examination revealed that the nose wheel fork and piston assembly had separated from the barrel. The nose wheel fork casting had bent about 3 degrees aft relative to the piston. The lower torque knee remained attached to the fork by its pin. Its connecting bolt for the upper torque knee was bent about 10 degrees, and remained in place with its bushings, washers and nut.
The upper torque knee remained attached to the barrel assembly. The upper knee's attachment lugs had been ground down to their bearing surfaces, with the score marks in a longitudinal direction consistent with runway surface contact. The lug connecting the lower knee was twisted about 5 degrees, and the forward section of the lug was not located. The lug exhibited similar grinding damage, and the radius of its attachment hole was elongated.
The forward landing gear brace had separated into three sections. Reassembly of the fragments revealed that the brace had bent 30 degrees midspan in a downwards direction prior to failure. The forward section remained attached to the barrel and brace assembly of the landing gear; the lug at the aft end of the brace had broken away.
The nosewheel tire remained attached to its axle. The tire exhibited a half inch deep gouge to a six inch portion of its center tread.
The separation surfaces of all the components exhibited varying combinations of rough grainy texture, jagged edges, ductile dimpling, and 45-degree sheer lip features. No ratchet marks, striations, or "beachmarks" were observed.