King Air C90 E90
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 95; Flight Crew Total 25000; Flight Crew Type 2500
Situational Awareness; Workload
Aircraft Equipment Problem Less Severe; Ground Excursion Runway; Inflight Event / Encounter Loss Of Aircraft Control
Aircraft Aircraft Damaged; Aircraft Automation Overrode Flight Crew; General Maintenance Action
Aircraft; Procedure
Upon landing; BETA was used to slow the aircraft. The aircraft suddenly yawed to the left very hard due to overspeed of the left engine in beta. The aircraft became uncontrollable and ran off the left side of the runway. The left propeller impacted a runway sign; damaging the sign and the left propeller and engine. Additionally; when the sign came apart; it damaged the leading edge of the left wing; scrapped the underside of the left wing and damaged the outboard left flap. No injuries or other known damage. There was a company employee in the copilot seat and a passenger in the cabin of the aircraft.The right engine had an apparently unauthorized repair to an oil access cap when one of the 4 studs had partially broken. The Mechanic had modified the cap by drilling down one of the stud holes in order for the nut to thread onto the remaining portion of the stud. Although this was not a contributing factor to the accident described; the cap should not have been modified to keep the aircraft flying. No leaks were observed from the cap; but the repair was unauthorized as was the ensuing flight. Contributing factors were the need to keep the aircraft and revenue going in a tight economy. New parts were ordered and obtained to make the proper repair.
During landing a BE-9L pilot selected BETA to help slow the aircraft but the left engine oversped causing the aircraft to exit the runway and strike a runway sign which damaged the left propeller; engine; leading edge and flap. No injuries resulted. Additionally; an unauthorized oil access cap repair had been made which did not contribute to the overspeed.