The National Transportation Safety Board did not travel to the scene of this accident.
Additional Participating Entity:
Federal Aviation Administration / Flight Standards District Office; Spokane, Washington
Aviation Accident Final Report - National Transportation Safety Board: https://app.ntsb.gov/pdf
Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms
Aviation Accident Data Summary - National Transportation Safety Board: https://app.ntsb.gov/pdf
http://registry.faa.gov/N810GL
NTSB Identification: WPR15LA218
14 CFR Part 91: General Aviation
Accident occurred Tuesday, July 14, 2015 in Cascade, ID
Probable Cause Approval Date: 04/04/2016
Aircraft: DAFOE GERALD W TCOW SMITH CUB, registration: N810GL
Injuries: 1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The private pilot/owner of the ultralight airplane was conducting a personal flight. He stated that, after landing, he applied the brakes to slow the airplane. He did not feel any right brake resistance, and the airplane swerved left due to left brake application. He attempted to correct with rudder inputs, but the airplane ground looped to the left, which resulted in the right landing gear collapsing and damage to the right wing. The pilot stated that the he had recently been having ongoing difficulty with the airplane’s right brake function.
Examination and disassembly of the right brake master cylinder revealed that the master cylinder piston O-ring had a gouge in it. The gouge likely allowed brake fluid to bypass the seal, which resulted in a loss of brake pressure and, therefore, reduced effectiveness after landing.
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
A gouge in the right brake master cylinder piston O-ring, which resulted in a loss of brake pressure and reduced effectiveness after landing. Contributing to the accident was the pilot’s decision to operate the airplane with an ongoing brake issue.
On July 14, 2015, at 1030 mountain daylight time, a Dafoe TCOW Smith Cub, N810GL, ground looped after landing, collapsing the right landing gear and substantially damaging the right wing. The private pilot was not injured. The airplane was registered to the pilot, and was operated as a personal flight under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the flight, and no flight plan had been filed.
The pilot stated to the NTSB investigator that after landing he applied brakes to slow the airplane. He did not feel any right brake resistance, and the airplane swerved left due to left brake application. He attempted to correct with rudder but the airplane ground looped to the left, collapsing the right landing gear, and damaging the right wing.
An FAA inspector examined the airplane and the brake system. He did not note any unusual wear on the pins or brake pads. He did note that the owner had installed an additional brake fluid reservoir to the right brake master cylinder. There was no indication of brake fluid leak. The pilot/owner did state to the inspector that he had been having on-going issues with the right brake.
The NTSB investigator authorized the pilot to disassemble and examine the right brake system. The pilot reported back that he found a gouge in the master cylinder piston o-ring that would allow brake fluid to bypass the seal.
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