Emergency AD Issued for Great Lakes Aircraft Built in 1970s, 1980s
Great Lakes biplane (From EAA Archives)
June 6, 2012 - The FAA issued an emergency airworthiness directive (AD) that addresses a safety problem with Great Lakes aircraft produced in the 1970s and 1980s (models 2T-1A, 2T-1A-1, and 2T-1A-2, aircraft serial numbers 501 through 1012). The problem, according to a special notification by current Great Lakes type certificate holder Waco Classic Aircraft, involves the potential failure of the right horizontal stabilizer on a Great Lakes 2T-1A-2 in March 2011.
According to the FAA, the stabilizer separated from the aircraft on final approach after the plane had completed some aerobatic maneuvers. Examination revealed a pre-existing crack in the front spar at the rivets securing the steel attach fitting tube that caused the spar to move outward and disengage from the fitting. At least one maintenance facility has also reported similar cracks in stabilizer front spars during routine maintenance.
Waco Classic Aircraft did not produce the planes subject to this AD, nor does the AD apply to new Waco-produced aircraft. The company says it has redesigned the affected area to prevent this condition from recurring.
The FAA requires inspection of the front and rear horizontal stabilizer spar assemblies and replacing parts as necessary. The AD also requires sending the initial inspection results to the Chicago Aircraft Certification Office. As the FAA considers this AD an interim action, it may take further AD action after evaluating the inspection results.
Waco Classic Aircraft adds that in addition to inspecting the spars, owners should ensure that both the front and rear center beams turn freely and are well lubricated.