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Hawker Mandatory Service Bulletin: Hydrogen Embrittlement Alert

September 2009

Hydrogen Embrittlement is defined as the process by which various metals become brittle and crack following exposure to hydrogen. During the manufacture of landing gear parts, hydrogen is introduced into the metal, mostly steel, during the plating process. The parts then undergo a baking period at a certain temperature for a certain period of time, which releases the hydrogen gasses trapped in the metal. If this baking period does not occur or is not done precisely as described, then hydrogen embrittlement will occur.

This is the reasoning behind Hawker-Beechcraft’s latest Service Bulletin 32-3962 and pending Airworthiness Directive. If your gear was overhauled, exchanged or had maintenance performed on it during the period of April 1, 2005, and March 31, 2009, there is a chance that it contains parts that have not been through the proper procedure for releasing the hydrogen gases and are susceptible to hydrogen embrittlement.


If your landing gear was overhauled by Duncan Aviation, we have kept records and can determine which landing gear have had these OEM parts installed. If you provide us with the part number and serial number of your landing gear assembly that Duncan Aviation has performed maintenance on, we can provide you with information pertaining to whether these OEM parts in question have been installed on your landing gear assembly.  

If your landing gear has had maintenance performed by another facility you should contact that facility concerning whether these parts were replaced during that maintenance action. If determination cannot be made as to the origin or date of manufacture of the suspected parts, then they must be replaced.