SA-227 AC Metro III
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Aircraft Equipment Problem Critical; Ground Event / Encounter Loss Of Aircraft Control; Ground Event / Encounter Object; Ground Excursion Runway
Aircraft Aircraft Damaged
Aircraft
At ZZZ a normal approach and landing was conducted on Runway XX for Aircraft X. The winds were 240 [degrees] at 3 kts. After touchdown; around the 2;000 ft. marker; the brakes were applied and immediately the left brake locked up. This resulted in an un-commanded yaw to the left. To counteract the left yaw; full right reverse and right braking was applied. This was not enough to keep the aircraft on the pavement. The engines were shut down immediately after the aircraft came to a stop. The aircraft came to rest at about a 45 degree angle to the runway; with the tail just off the pavement and the nose wheel approximately 30 ft. off the pavement and into the grass. After inspecting the aircraft and runway with the airport personnel; it was discovered that one of the right propeller blades hit and damaged a taxi light. Both the taxi light and a small piece of the propeller blade were found on the runway. During the inspection; we found that there was a completely solid tire skid mark from the left main tires that started at about the 2;000 ft. marker all the way to resting place of the aircraft. No skid marks were found from the right main tires. Once maintenance was able to replace the tires and brakes on the left main; the aircraft was towed backward onto the runway; then back to the parking spot at the FBO. Both tires were found with bald spots and the brakes were welded together due to the high temperature experience. During take-off and landing; we steer the metro's using differential braking and differential thrust. I used as much reverse and braking in the opposite direction than the yawing motion. I don't believe that I could have saved the plane from going off the pavement; but after reflecting on the incident; I could have thought to use some nose wheel steering to try and help.
SA-227 Captain reported left main landing gear brakes locked up during landing.