Incident Overview
On October 26, 2008, at approximately 1000 eastern daylight time, two experimental amateur-built aircraft, a Vans RV-8A (N88FG) and a Vans RV-6A (N914ES), were involved in a ground collision at Cambridge-Dorchester Airport (CGE) in Cambridge, Maryland. The RV-8A was parked, and the RV-6A was taxiing to park. Both aircraft sustained substantial damage, but no injuries were reported among the pilots.
Sequence of Events
Both pilots provided statements that described similar events. After landing at CGE, both airplanes taxied to the parking area. The RV-8A parked first, and the RV-6A pilot intended to park immediately to the right of the RV-8A. As the RV-6A approached the stationary RV-8A from the right and perpendicular to it, the pilot applied the right brake to turn the airplane into the intended parking spot. The right brake "failed totally." The pilot pumped the brake several times without response. The pilot then applied the left brake to avoid striking the RV-8A, but the right wing of the RV-6A struck the right wing of the other airplane. The RV-6A turned to the right, and its propeller struck the right horizontal stabilizer of the RV-8A, substantially damaging it.
Examination and Findings
A Federal Aviation Administration (FAA) inspector examined both airplanes and noted brake fluid on the exterior of the right brake and on the ground around the right wheel of the RV-6A. The inspector found damage to the right wing tips of both aircraft and the horizontal stabilizer of the parked airplane.
According to the pilot/builder of the RV-6A, a post-accident disassembly of the right brake revealed that the o-ring between the main brake housing and the piston had "deteriorated." The RV-6A's most recent conditional inspection was completed on September 23, 2008, and the airplane had accumulated 718 total hours of operation on that date.
The National Transportation Safety Board (NTSB) retained the o-ring and sent it to the brake assembly manufacturer for testing. An acceptance test using a new brake assembly with the accident o-ring installed showed immediate hydraulic fluid leakage from the piston area. When the accident o-ring was replaced with a new o-ring, no leaks were observed.
The manufacturer performed material analysis on the o-ring. A Fourier Transform Infrared Spectroscope (FTIR) analysis indicated that both the accident o-ring and a new control o-ring were made of nitrile rubber, conforming to the manufacturer's engineering drawing. However, the accident o-ring's FTIR spectrum showed an unknown substance on its outside diameter surfaces. Dimensional measurements revealed the accident o-ring was smaller than the control o-ring, with a compression set of about 8 percent on contacting radial surfaces. Hardness testing showed the accident o-ring was harder than the control o-ring. The testing concluded that the abnormalities were consistent with the accident o-ring having experienced excessive heat.
Weather and Flight Details
Visual meteorological conditions prevailed at the time of the accident. Neither airplane was operating on a flight plan. Both personal flights had departed from Eastern West Virginia Regional Airport (MRB) in Martinsburg, West Virginia, and were conducted under 14 CFR Part 91.