Lawrence La Beau

From the Federal Register: With FAA assistance, the National Institute for Aviation Research (NIAR) investigated and concluded the root cause of the stabilator horn cracking was stress corrosion. (also)There is no service history of this unsafe condition on the Models PA-24-400, PA-30, and PA-39 airplanes, including inspections from the ICS operator survey. Also, these models have a thicker torque tube, which reduces clamp-up forces; clamp-up forces are a key factor of the stress corrosion cracking. Therefore, we are not including the..... From the above comments it would seem the torque values of the stabilator horn need to be reviewed and reduced. Also the torque tube needs to be replaced with a thicker tube reducing clamp-up forces reducing cracking of the horn.