The FAA and EASA recently issued emergency airworthiness directives (EAD) for Eurocopter’s popular twin-engine helicopter – the EC 135. There are some differences between FAA’s EAD 2012-10-51 and EASA’s AD 2012-0085-E, but both were implemented because cracks have been found in the hub-shaft flange of a main rotor hub. These cracks could result in the failure of the main rotor hub, which subsequently would make the helicopter uncontrollable.
The emergency ADs resulted from a previous AD issued by EASA in March, which required inspection of the same area. Since that AD, two additional cases of cracks were found, causing the agencies to issue the recent EADs.
U.S. EC 135 operators are required to immediately inspect the “lower hub-shaft flange for a crack and each blade attachment bolt for a deformed safety pin.” This inspection is required for each subsequent preflight and can be done by the pilot. In addition, within five hours of flight time a thorough inspection must be completed by a mechanic.
The FAA EAD applies to select EC 135 models, which according to the EAD includes 244 helicopters in the United States. In addition to the select EC 135 models, EASA’s AD also applies to some EC 635s.
The cause of the cracks has yet to be determined and further instructions can be expected once the cause has been found.