Bombardier CL600-2B19 CRJ, Lake Michigan, Mich., April 7, 2007–The NTSB determined the probable cause of the in-flight separation of the left engine translating cowling was due to intermittent binding and jamming of the reverser on the accident flight and on previous flights. Inadequate maintenance action due to the operator’s failure to properly resolve the prior reverser malfunctions, the failure of pilots of previous flights to refer earlier failures for maintenance action and incomplete company/manufacturer’s procedures, which did not address anomalous reverser indications during ground operations, were factors.
The Mesa Airlines pilot had noticed a left thrust reverser unlock indication while holding for takeoff at Capital City Airport in Lansing. He cycled the reverser and the messages cleared. On climb-out, there was a small vibration, then he heard a “loud bang” and the CRJ “pitched and yawed/rolled to left.” The flight continued to the intended destination, Chicago O’Hare International Airport, and landed without further incident. The inboard leading edge of the left horizontal stabilizer was dented and crushed and the left side of the vertical stabilizer punctured forward of the center spar, consistent with damage from the cowling hitting the stabilizers. There were no injuries among the three crewmembers and one passenger.