Schweizer 269D Configuration A (Schweizer 333), G-TAMA
After landing on a post-maintenance flight, the helicopter suffered a seizure of the main rotor gearbox pinion outer bearing due to oil starvation. The main rotor gearbox had been replaced during the recent maintenance. It was determined that maintenance personnel had inadvertently caused metallic debris to enter the bearing oil supply gallery during their attempts to remove a blanking plug from the gearbox low oil pressure switch port, which had been overtightened.
Date of occurrence: 4 February 2008