Light Sport Aircraft
Flight Crew Commercial
Flight Crew Last 90 Days 35; Flight Crew Total 426; Flight Crew Type 87
Distraction; Troubleshooting; Situational Awareness
Aircraft Equipment Problem Critical; Ground Event / Encounter Object; Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Runway
Aircraft Aircraft Damaged
Aircraft
Additional co-pilot brakes had been added to the aircraft by owner/pilot.  Low speed taxi tests went well.  Progressively higher taxi speeds were used to determine if co-pilot side brakes were operating correctly.  During a higher speed taxi test on the main runway the aircraft began to veer to the left.  Pilot was unable to maintain directional control of the airplane and struck one 't-post' (not connected to any fencing) on the side of the runway.  The impact caused minor damage to the underside of the of the fuselage; a small puncture in the Dacron skin.  The minor damage to the aircraft does not fit the definition of 'substantial damage' it was determined that no accident report was required at this time.  After further inspection the co-pilot side left master cylinder was found to be 'sticking' when depressed and appears to have locked the left side brakes causing the loss of control.  Without disassembling the master cylinder was unable to determine the cause of the master cylinder 'sticking'.
Rans S6 Coyote Light Sport Aircraft pilot reported while completing a high-speed taxi to test out new brakes the aircraft veered left and struck a pole on the side of the runway.