We are adopting a new airworthiness directive (AD) for certain Hartzell Propeller, Inc. propeller models HC-(1,D)2(X,V,MV)20-7, HC-(1,D)2(X,V,MV)20-8, and HC-(1,D)3(X,V,MV)20-8. This AD was prompted by failures of the propeller hydraulic bladder diaphragm and resulting engine oil leak. This AD requires replacement of the propeller hydraulic bladder diaphragm. We are issuing this AD to prevent propeller hydraulic bladder diaphragm rupture, loss of engine oil, damage to the engine, and loss of the airplane.
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