Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor
Flight Crew Last 90 Days 111; Flight Crew Total 3546; Flight Crew Type 1.5
Time Pressure; Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Ground Strike - Aircraft; Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Taxiway
Aircraft Aircraft Damaged; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
During the flight portion of a flight review/IPC; we experienced a taxiway excursion due to a total loss of brake pressure.After landing and taxing back to runway XX; in ZZZ; the brakes lost pressure while entering the runway. We decided not to takeoff. I checked my brakes and they did not work either.Exiting on taxiway; the aircraft seemed under control and we were discussing shutting down the engine once we made it to the ramp area.The aircraft started veering to the left. I joined on the pedals; full right rudder and full brake; no change; still veering. I told pilot to shut it down. He pulled the mixture to cutoff. The aircraft then went off the side of the taxiway; the propeller struck two taxiway lights and the right main ran over one light before the plane came to a stop. The engine seemed slow to shut down while at mixture cutoff. Pilot said that the boost pump was on and that was most likely the reason for the delayed shutdown. The engine was shut down; however; the propeller continued to windmill.Two of the propeller blades were damaged and there was a scratch on the side of the wheel fairing. No other damage to the aircraft. Neither of us were injured.
Lancair ESP Flight Instructor reported a taxiway excursion due to a total loss of brake system.