Accident Overview
On March 28, 2021, at about 1200 Pacific daylight time, a Maule MX-7-235, registration N235X, was substantially damaged in a ground loop accident near Ontario, Oregon. The private pilot and a passenger were not injured. The flight was conducted as a personal flight under Title 14 Code of Federal Regulations Part 91.
Pilot Report
According to the pilot, during the landing roll after an uneventful touchdown, he applied left and right toe brakes to decelerate. The left brake operated normally, but the right brake pedal provided no resistance and depressed fully to the floor. The airplane veered left immediately, the right wing contacted the ground, and the airplane ground looped. After exiting the airplane, the pilot observed hydraulic fluid on the right main landing gear wheel.
The ground loop was not reported to the National Transportation Safety Board until approximately six months after the accident. Photographs taken by the pilot showed substantial damage to the right aileron and elevator.
Background
The pilot was ferrying the airplane from Utah to his home after purchasing it. One month before the accident, he informed the previous owner that the right brake pedal on the pilot's side was not functioning, with pedal movement similar to that experienced during the accident. The owner stated he would have his mechanic examine the issue, but the problem was not resolved when the pilot arrived the day before the accident. The owner's mechanic then bled the brake, which temporarily appeared to fix the issue. The pilot flew for two hours that day and landed without any brake anomalies. The following day, before the accident flight, the pilot taxied the airplane the length of the runway twice and performed full stops to test both brakes, noting equal pedal pressure.
Brake System and Examination
The airplane's brake system included master and slave cylinders at the pilot and front passenger rudder pedal positions, connected by brake lines to a hydraulic inlet port at the brake. Braking was achieved via hydraulic pressure extending a piston against a disc on the wheel. The last annual inspection had been completed eight months before the accident.
An examination of the retained brake system components did not reveal any preimpact mechanical anomalies. However, the original inlet fitting and hydraulic brake lines had been discarded by the mechanic before the accident was reported and were not available for examination. The original master and slave cylinders were not replaced and were successfully tested by the mechanic after new brake components were installed.