[The FAA is] adopting a new airworthiness directive (AD) for certain CFM International, S. A. (CFM) model CFM56-5 and CFM56-5B series turbofan engines.
This AD was prompted by corrosion of the delta-P valve in the hydro-mechanical unit (HMU) fuel control caused by exposure to type TS-1 fuel. This AD requires cleaning, inspection, and repair of affected HMUs.
We are issuing this AD to prevent seizure of the HMU, leading to failure of one or more engines and damage to the airplane.
This AD is effective September 3, 2013.