Summary
We propose to adopt a new airworthiness directive (AD) for certain CFM International, S. A. (CFM) model CFM56-5 and CFM56-5B series turbofan engines. This proposed AD was prompted by corrosion of the delta P valve in the hydromechanical unit (HMU) caused by contaminants in type TS-1 fuel. This proposed AD would require cleaning, inspection and repair of affected HMUs. We are proposing this AD to prevent seizure of the HMU, leading to failure of one or more engines and damage to the airplane.