McDonnell Douglas (MDC) MD-90s will have to be checked for airframe fatigue cracking earlier than originally estimated, results from the fatigue-test airframe and other structural analysis have revealed.
It will be years before the lead airframe in service reaches the newly designated 16,000-cycle point, when the first checks are due, but the US Federal Aviation Administration has issued an airworthiness directive (AD) on the subject.
The 16,000-cycle checks will apply to several principal structural elements (PSE) in the wing, fuselage and tail. The AD requires changes to inspection requirements in a document known as the MD-90 Airworthiness Limitations Instructions. "This is similar to a supplemental inspection document, which [traditionally] comes late in the life of an aircraft, whereas this is a document compiled at entry-into-service," says MDC, which produced the original structural inspection report based on its own fatigue analysis.
"It changes some of the time-fences for particular inspections, though none of them comes down dramatically and, in fact, some are extended." The FAA says: "The actions specified by this AD are intended to ensure that fatigue cracking of various PSEs are detected and corrected. Such fatigue cracking could adversely affect the structural integrity of these aircraft."
Source: Flight International
