Cracks found on the horizontal stabiliser centre section ribs of several Boeing MD-80 and MD-90 aircraft have prompted the US Federal Aviation Administration to propose an airworthiness directive on the Boeing 717 due to the similarity of the designs in the affected area.
The agency issued an airworthiness directive (AD) for the MD-90 in January 2011, calling for repetitive high frequency eddy current (HFEC) inspections on hinge bearing lugs on the centre ribs. Nine cracks had been found on aircraft with flights ranging from 9,051h and 26,053h and total flight cycles between 8,939 and 25,260 cycles.
A similar mandate for the MD-80 series aircraft was proposed in August, following cracks found in two MD-80 series aircraft having accumulated between 23,300 and 35,294 cycles.
The Boeing 717 proposed AD, to be published on 19 January, calls for operators of the entire fleet of 717s (129 aircraft, according to the FAA) to perform HFEC inspections on the hinge bearing lugs before an aircraft accumulates 35,000 total flight cycles, or within 8,275 flight cycles after the AD becomes final. If no crack is found, operators must perform the inspection again within 10,500 flight cycles.
The FAA said inspections should cost $510 per aircraft and take six hours to complete.
According to Flightglobal Pro, US operators of the 717 are AirTran, with 88 717-200s, and Hawaiian Airlines with 15 717-200s. AirTran was acquired by Southwest Airlines in May of last year.