Eighty percent of Amtrak's Acela Express trains are available for service following completed repairs of trainsets. The railcars were withdrawn from service in August due to cracks in yaw damper brackets identified during a routine inspection.

The repair work, which is continuing daily, is a combined effort made in cooperation with Amtrak, Bombardier, the Federal Railroad Administration and others.

The cracks were found at the connection of the yaw damper bracket mounting plate and the side sill of the power cars, with none of the Acela passenger coaches affected.

Following the appearance of the cracks, analysis revealed that the actual loads measured in operation on the yaw damper bracket substantially exceeded the design loads provided during the design phase, according to a statement by Bombardier.

Repairs related to the yaw damper connection issue and inspections of repaired trains continue. A dye-penetration process is used to check for hairline cracks. Any newly discovered cracks are repaired, re-inspected and approved before the railcars are returned for operation.

Significant progress has been made on the permanent redesign of the yaw damper bracket assembly, said Bombardier. Engineers from Bombardier and Amtrak have discussed alternative design approaches, for which Bombardier has mobilized nearly 100 of its staff.