RV-8
Flight Crew Instrument; Flight Crew Private
Flight Crew Last 90 Days 75; Flight Crew Total 2500; Flight Crew Type 75
Communication Breakdown; Confusion; Situational Awareness
Aircraft Equipment Problem Critical; Ground Event / Encounter Ground Strike - Aircraft; Inflight Event / Encounter Loss Of Aircraft Control
Aircraft Aircraft Damaged; General Maintenance Action; General Flight Cancelled / Delayed
Aircraft; Human Factors
At the completion of an otherwise normal local flight in my RV-8 aircraft; approximately early afternoon; I had a landing incident on Runway XX at ZZZ airport. After a normal touchdown for a wheel landing; the aircraft slowed and the tail wheel came down normally. With the landing assured; I began to brake the aircraft and as soon as pressure was applied; the left brake completely locked. Due to the left brake locking; the airplane came around to the left. I applied opposite (right) rudder and brakes to try and stop the rotation; but the right brake then locked causing the airplane to nose over and come to rest on the spinner. I subsequently determined the cause of the locked brakes to be activation of the aircraft Parking Brake Valve. This activation was caused by the sheath of the Parking Brake Actuator cable slipping in a clamp allowing the valve to actuate on its own. To prevent this in the future; I plan to remove the Parking Brake System; which is rarely; if ever; needed on this class of aircraft. Otherwise; careful inspection and maintenance of the actuator for any parking brake. [Recommend] a positive locking system or other visual means of identifying that a parking brake is actuated prior to landing could have prevented this situation. Damage to the aircraft includes: prop blades and spinner destroyed. Engine requires Prop Strike Inspection. Damaged wheel pants. Minor structural deformation of the left gear tower and skins.
Reporter stated the Parking Brake Valve was not part of the Van's RV-8 Build Kit. The Parking Brake Valve and cable were purchased from a parts supplier. No Supplemental Type Certificate (STC) required since the aircraft is considered an Experimental. Installation is the responsibility of the Owner. The valve has two chambers; two check valves; and two paths for the brake fluid with a common shaft and arm that is positioned by the push-pull Parking Brake cable 'T' handle. The independent left/right solid tubing brake lines are attached to the separate chambers on the valve.Reporter stated when the 'T' handle is pulled; the cable moves a lever (arm) on the Parking Brake valve that is attached to a common shaft for the two chambers and positions the valve to allow brake fluid to only go one-way.  That is the purpose of the check valve inside each chamber. The clamp holding the cable was similar to an ADEL metal clamp without the cushion material around the clamp. The clamp had loosened; allowing the entire cable to shift and move the position lever at the Parking Brake valve to the 'Park' position; without any indication at the 'T' handle in the cockpit. Although he had reported he would remove the Parking Brake System; he may instead add a micro-switch that illuminates whenever the Parking Brake valve arm is moved (actuated).  He was recently informed no damage was found on the Engine after the Prop Strike Teardown Inspection was completed.
Pilot reports the left brake completely locked on his Van's RV-8 aircraft during landing rollout; followed by the right brake locking when he applied right rudder and brakes. The aircraft nosed over and came to rest on the spinner. Parking Brake Valve had actuated; caused by the sheath of the Parking Brake Actuator cable slipping in a clamp; allowing the valve to actuate on its own.