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Back Page: Fighting Fatigue

Sheila Gibson Stoodley

Robb Report has written about vintage planes and the people who collect, restore, maintain, and fly them on a number of occasions. We do so again in this issue with the story on collectors of Grumman amphibians (“Sea and Be Seen”). But questions concerning the maintenance and airworthiness of vintage aircraft in general and seaplanes in particular came to the fore last December when a 58-year-old Grumman Mallard G-73 crashed off the coast of Miami and killed all 20 people aboard.

An old plane is not by definition an unsafe plane, but metal fatigue can afflict planes that are more than 30 years old. The phenomenon’s cumulative effects often appear on the surface of or within the wings in the form of fatigue cracks. It can be difficult or impossible to detect these cracks by sight alone, and the repair costs can exceed the value of the plane itself, but the consequences of failing to find and fix this damage can be devastating: A wing could fall off in flight.

As noted in this issue’s Grumman story, fatigue cracks appear to have played a role in the Miami Mallard crash. Wing losses traced to fatigue cracks caused three separate fatal accidents—in 1999, 2003, and 2004—in the Beechcraft T-34, a popular World War II–era military training aircraft. Since the first accident, the T-34 community and the FAA have sought a solution that addresses the problems without forcing owners to choose between making expensive, and possibly unnecessary, repairs or grounding their planes.

Another vintage training plane, the T6, shed a wing in a May 2005 accident that killed two pilots; this, too, was blamed on fatigue cracks. Also, in 2003, the FAA required wing inspections for several models of 400-series twin Cessnas because of potential cracks. In addition, a pair of 2002 fatal crashes involving elderly ex-military aircraft that had been adapted for fighting wildfires were attributed to cracks worsened by inadequate maintenance. Several news stations broadcast video of one of those crashes, which showed the wings dropping in tandem from the plane before it struck the ground.

Despite these accidents, age-related structural failures are rare, and according to an internal FAA survey of accidents involving general aviation planes that was cited by the Experimental Aircraft Association (EAA), metal fatigue does not rank among the top five causes of crashes.

The fact remains, however, that the average age of a general aviation plane—one that weighs less than 12,500 pounds—exceeds 30 years, and it is unlikely that the people who built Grummans and other aircraft in the early to mid-20th century expected that these planes still would be flying. Warplane makers, in particular, rightly worried more about building machines that could withstand a hit from a 20 mm bullet than the slow-acting scourge of corrosion.

The FAA, EAA, and other leading aviation groups have endorsed a set of maintenance guidelines released in September 2003 and titled Best Practices Guide for Maintaining Aging General Aviation Airplanes. The publication’s 17-strong team of authors draws an analogy between an aging plane and an aging person: Growing older does not necessarily mean becoming unfit, but it does demand greater attention to bodily maintenance. “Health professionals recommend increasingly more intrusive ‘inspections’ as people age,” the guide states. “People accept these recommendations and generally request more thorough physicals as they get older.”

H.G. Frautschy, editor of Vintage Airplane magazine and executive director of the EAA’s Vintage Aircraft Association, agrees with that assessment. “These planes can be operated safely,” he says “but you have to put the work in.”

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