Airworthiness Directives; Piper Aircraft, Inc. Airplanes

We are adopting a new airworthiness directive (AD) for certain Piper Aircraft, Inc. Models PA-31, PA-31-300, PA-31-325, and PA-31-350 airplanes. This AD was prompted by fatigue cracking in the fuselage station (FS) 332.00 bulkhead common to the horizontal stabilizer front spar attachment. This AD requires repetitive inspections to detect cracks in the bulkhead and any necessary repairs. This AD also provides an optional modification if no cracks are found that will greatly reduce the likelihood of the specified cracks. We are issuing this AD to correct the unsafe condition on these products.