CHI99LA241

The wheel separated from the aircraft. The pilot said that in the roll out, the aircraft decelerated to 10-15 mph and the aircraft veered to the left. The pilot applied the brakes and the aircraft moved to the left of the runway. The aircraft began to skip and tipped to the right. The airplane came to rest off the left side of the runway. The right wing dragged on the runway. The landing gear gouged the asphalt. The prop struck the dirt alongside the runway. The wheel was found lying on the runway. The right spring on the tail wheel was found detached. The accident airplane's annual inspection was completed on May 25, 1999 and accumulated nine hours of flight time since the annual. The axle was sent to the National Transportation Safety Board's Materials Laboratory for examination. An excerpt from the laboratory's report states, 'The circumferential portion of the fracture surface was located on the inboard side of the circular plate at the top of the axle and had a dark brown and rubbed appearance, indicative of a crack that has been in existence for an extended time. This portion of the fracture was directly adjacent to the circular plate, through either the weld of heat affected zone adjacent to the weld between the upper struts and the circular plate. The circumferential portion of the fracture contained what appeared to be a wide but shallow crack arrest position, suggestive of crack initiation from a wide area approximately in the center of this portion of the fracture.' The pilot's safety recommendation states, 'The crack in the axle was tucked within the brake cylinder. The only way to inspect it would be removal of the wheel & brake assembly.'

On July 13, 1999, at 1215 central daylight time, a Taylorcraft BC12-D, N96884, sustained substantial damage during a landing on runway 16 (4,018 feet X 75 feet, dry/asphalt) at Aitkin Municipal-Steve Kurtz Field, Aitkin, Minnesota. The commercial rated instructor pilot and dual student reported no injuries. Visual meteorological conditions prevailed during the 14 CFR Part 91 instructional flight. The airplane was not on a flight plan. The local flight originated from Aitkin Municipal-Steve Kurtz Field Airport at 1200 and was practicing touch and goes at the time of the accident.

At 1157, the Aitkin Municipal-Steve Kurtz Field observation was: Wind calm; visibility 10 statute miles; sky condition clear; temperature 24 degrees C; dew point 22 degrees C; altimeter 29.81 inches of mercury.

In his written statement the student pilot said, "We completed one [touch and go] and had landed on the second and were in the roll out. The aircraft had decellerated to 10-15 mph. The handling of the aircraft became ineffective and attempts to control the aircraft were to no avail. The aircraft was veering to the left." The pilot stated that the instructor said "... to use the rudder." The student stated, "I replied I had and he said to use the brakes. I firmly applied the heel brakes and the aircraft suddenly careened to the left of the runway." The student said, "Near the edge of the runway the aircraft began to skip and tipped to the right. It came to rest off the left side of the runway, right wing down with the tail still on the runway. The right wing had dragged the last 6-8 foot on the runway. The landing gears and the wheel had gouged the asphalt in a scored pattern as it skipped across it. The prop had struck twice in the dirt alongside the runway. I don't recall where the wheel was other than that it was separted from the aircraft and lying on the runway." The student said that the right spring on the tail wheel was found detached.

An annual inspection of the accident airplane was completed on May 25, 1999. See appended inspection checklist. The airplane accumulated nine hours of flight time since the annual inspection.

The axle was sent to the National Transportation Safety Board's Materials Laboratory for examination. The axle's surfaces were examined with an optical microscope. An excerpt from the laboratory's report states, "The circumferential portion of the fracture surface was located on the inboard side of the circular plate at the top of the axle and had a dark brown and rubbed appearance, indicative of a crack that has been in existence for an extended time. This portion of the fracture was directly adjacent to the circular plate, through either the weld of heat affected zone adjacent to the weld between the upper struts and the circular plate. The circumferential portion of the fracture contained what appeared to be a wide but shallow crack arrest position, suggestive of crack initiation from a wide area approximately in the center of this portion of the fracture." See appended Materials Laboratory Factual Report No. 00-016.

The student pilot's safety recommendation states, "The crack in the axle was tucked within the brake cylinder. The only way to inspect it would be removal of the wheel & brake assembly."