Ramona, CA, USA
N611JB
BENNETT MIDJET MUSTANG I
The pilot reported that while conducting a series of touch-and-go takeoffs and landings in a tailwheel-equipped airplane, he heard a loud snap sound during his third takeoff followed by the upper left rudder pedal collapsing. The pilot verified that he had rudder control and noticed that the upper left rudder pedal seemed displaced forward of its normal position. He further noticed that the left rudder pedal was binding at various times, but overall was operational, and thus suspected that the left brake master cylinder had disconnected from the rudder pedal. The pilot said that every time he applied left rudder during the landing the airplane veered to the left as if left brake was being applied. Despite his control inputs, the airplane exited the left side of the runway and nosed over within the soft muddy terrain, which resulted in substantial damage to the fuselage and both wings. Postaccident examination of the airplane revealed that the left brake master cylinder was separated from the left rudder pedal at the rudder attach point. Examination of the left rudder pedal and master cylinder revealed that the left rudder pedal was fractured at the lug where it attached to the upper end of the brake master cylinder. The fracture surface was consistent with an overstress fracture. The fracture surface was examined by an NTSB metallurgist using a scanning electron microscope and no evidence of fatigue or other progressive crack growth was observed. The lower surface of the brake master cylinder attachment lug on the left rudder pedal had an impression corresponding to contact with the lower end of the clevis of the left master brake cylinder attachment fitting. A similar impression was observed on the lower surface of the brake master cylinder attachment lug on the right rudder pedal. Deformation consistent with contacting the lower surface of the rudder pedal lugs was observed at the base of the clevis in the upper attachment fittings of both the left and right brake master cylinders.
On April 10, 2011, about 0828 Pacific daylight time, a tail wheel equipped amateur built experimental Bennett Midjet Mustang 1, N611JB, sustained substantial damage while landing at the Ramona Airport (RNM), Ramona, California. The airline transport pilot, sole occupant of the airplane, sustained minor injuries. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight. The local flight originated from RNM about 0810. In a written statement, the pilot reported to the Safety Board investigator-in-charge (IIC) that he was conducting a series of touch-and-go landings on runway 27, a 5,001-foot long and 150-foot wide asphalt runway. The pilot said that his first two takeoffs and landings were very smooth and uneventful. During his third takeoff, as the airplane ascended through about 30 feet, he heard a loud "snap" followed by the upper left rudder pedal collapsing. The pilot confirmed rudder continuity and noted that the "upper portion of the left rudder pedal seemed displaced well forward of its normal position, and at times binding but functional." The pilot stated that he noticed no degradation of the flight controls and suspected that the left brake master cylinder had possibly separated from the rudder pedal. The pilot further reported that he conducted a normal tail-low wheel landing on runway 27, favoring the right side of the runway. As the tail wheel settled onto the runway, the airplane slightly moved to the right. The pilot stated that he inputted left rudder to correct the change in heading and the airplane "lurched hard to the left" as if he had "deliberately applied left brake along with the corrective rudder." Despite the pilot's control inputs, the airplane continued to the left and exited the runway surface. Subsequently, the airplane nosed over in soft muddy terrain, which resulted in substantial damage to the fuselage and both wings. Postaccident examination of the airplane by the pilot revealed that the left brake master cylinder was separated from the left rudder pedal at the rudder attach point. The left rudder pedal and separated portion of the master cylinder attach point clevis were sent to the National Transportation Safety Board Materials Laboratory, Washington, DC, for further examination. Examination of the components by a Senior Materials Engineer revealed that the left rudder pedal was fractured at the lug where it attached to the upper end of the brake master cylinder. The fracture surface was relatively rough and matte gray, features consistent with overstress fracture. The fracture surface was examined using a scanning electron microscope, and no evidence of fatigue or other progressive crack growth was observed. The lower surface of the brake master cylinder attachment lug on the left rudder pedal had an impression corresponding to contact with the lower end of the clevis of the left master brake cylinder attachment fitting. A similar impression was observed on the lower surface of the brake master cylinder attachment lug on the right rudder pedal. Deformation consistent with contacting the lower surface of the rudder pedal lugs was observed at the base of the clevis in the upper attachment fittings of both the left and right brake master cylinders.
The pilot's inability to maintain directional control during the landing roll due to the overload separation of the left brake master cylinder from the left rudder pedal assembly.
Source: NTSB Aviation Accident Database
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