WPR24LA045

The pilot was landing at his destination airport when the airplane veered to the left after touchdown. . The pilot attempted to correct the movement and turn the airplane back to the runway centerline with the addition of power and right rudder inputs, but the airplane then veered to the right and departed the right side of the runway. The pilot did not recall experiencing any mechanical anomalies with the brakes during the accident flight and observed normal resistance during the landing. Postaccident examination of the brake system revealed that the right brake master cylinder failed to release pressure twice during testing and the piston had to be manually lifted before the cylinder would release pressure, which the pilot was unlikely to have been able to do during landing. The seized brake master cylinder was likely due to a deformed return spring that had bowed at some point during its service life. The manufacturer reported that the failure of the cylinder to release pressure would have resulted in a locked brake. Although the pilot could not recall if he applied brakes, both his and the witness’ recollection that the airplane abruptly turned right and departed the runway suggests that he may have applied right brake as the airplane was veering left. During this time the piston likely failed to release pressure due to the faulty return spring, which resulted in a runway excursion.

On November 27, 2023, about 1305 Pacific standard time, a Cessna 170B, N170HT, was substantially damaged when it was involved in an accident near Cameron Park, California. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, he completed four successful full-stop landings at a nearby airport before he returned to his home airport, Cameron Park Airport (O61). During his landing attempt at O61 the airplane touched down normally and immediately veered to the left. The pilot attempted to correct the movement by adding power and rudder input, but the airplane then veered to the right and departed the right side of the runway. He could not recall if he used brakes when he was trying to correct the movement. The airplane sustained substantial damage to the fuselage. A witness reported that he was about midfield and heard the airplane before it came into his field of view. As the airplane came into his field of view, he heard the engine power increase and then saw the main landing gear touch down with the tail wheel still in the air. The airplane then veered right, and the right main landing gear impacted a dirt berm before the airplane came to rest in an upright position. According to the pilot’s operating handbook (POH), the airplane was equipped with conventional toe-type brake pedals at the top of the rudder pedals. Two brake master cylinders were mounted directly to the pilot’s hydraulic brake pedals. The POH states that the brakes are actuated by applying toe pressure to the pilot’s rudder pedals. This movement actuates the master brake cylinders, which results in a braking action on the main landing gear wheels. According to the master brake cylinder section of the illustrated part’s catalogue, the cylinder is comprised of a piston rod and a piston return spring accompanied by securing hardware, O-rings, and sleeves. Examination of the brake system revealed no mechanical anomalies with the right and left main landing gear brake calipers. The left brake master cylinder functioned normally when tested while the right brake master cylinder was tested twice and failed to release pressure. The piston had to be manually raised before the cylinder would release pressure. Disassembly of the right brake master cylinder revealed that the piston return spring was deformed (bowed). According to the manufacturer, the failure of the cylinder to release pressure would have resulted in a locked brake. A review of the airplane maintenance records from 2002 to the date of the accident showed that the airplane was involved in an incident that required a repair of the pilot-side right brake master cylinder attachment area by installing a doubler on June 20, 2015. The endorsement also showed that the shafts of both brake master cylinders were replaced along with O-rings. The pilot-side left brake master cylinder was subsequently replaced on July 13, 2016. Therewas no maintenance requirement for the return spring to be inspected or replaced, nor was there any indication in the maintenance records that the return spring had ever been replaced. Federal Aviation Regulations Part 43 Appendix D lists “brakes – for improper adjustment” as required inspection items for annual and 100-hour inspections. The pilot stated that the brakes felt normal when he tested them before the accident flight. He also noted that he felt resistance on the brakes and that neither were mushy when he activated them upon touchdown and lost directional control of the airplane. He had also completed a full-stop landing at the nearby airport he flew to before to the accident and did not observe any issues with the brakes when he applied them.