Fracture mechanics

December 3, 2013 - 1:05am

The Jan. 4, 2014 implementation date for new Part 117 regulations on fatigue applies only to scheduled air carriers, but many observers believe elements of the new law will eventually work their way to business aviation.

April 4, 2013 - 1:35pm

Eurocopter says it has made significant progress in solving the main gearbox issue that has blighted the EC225 medium twin since last May, reporting that a third test campaign at its headquarters in Marignane, France “is establishing” the cause of crack initiation.

Eurocopter attributes the issue to “a combination of factors” leading to a degradation of the vertical shaft’s fatigue resistance. The helicopter manufacturer has excluded any “abnormal dynamic overload.” Failure of the bevel gear shaft causes a loss of lubrication.

January 26, 2011 - 5:00am

U.S. and European civil aviation authorities have issued new airworthiness directives (ADs) for the inspection and possible repair or replacement of the Sikorsky S-92A’s main gearbox. The updated ADs build on 2009 directives and mandate action on a new gearbox design that was supposed to solve the problem, at least temporarily.

July 8, 2008 - 11:29am

There were many times during my years as a mechanic when I was working totally exhausted, but for a number of reasons I continued past the point that I was in danger of causing damage to an aircraft or to myself. For years many of my coworkers and I believed that we were OK to work and not impaired by a lack of rest.

October 3, 2007 - 12:17pm

How much would it be worth to be able to reliably predict the structural failure of any part or component of an aircraft long before any flaw becomes visible? To be able to discover that there would be a structural failure in the top of a fuselage, in a vertical stabilizer or even in a landing gear before there was any visible indication such as a crack?

September 15, 2006 - 11:19am

MD Helicopters MD 900, Mesa, Ariz., Sept. 8, 2004–The NTSB attributes the accident during the test flight to the fracture of a tension-torsion strap in the fan because of progressive fiber failure of the composite material from compression and/or transverse shear stresses with repeated manipulation of the antitorque control pedals without the fan operating at full rpm.