Summary
We propose to adopt a new airworthiness directive (AD) for certain Airbus Model A330-300, A340-200, and A340-300 series airplanes. This proposed AD was prompted by a determination that ballscrew rupture could occur on certain trimmable horizontal stabilizer actuators (THSAs). This proposed AD would require repetitive THSA ballscrew shaft integrity tests, and replacement if necessary. We are proposing this AD to detect and correct ballscrew rupture, which, along with corrosion on the ballscrew lower splines, may lead to loss of transmission of THSA torque loads from the ballscrew to the tie-bar and consequent THSA blowback, which could result in loss of control of the airplane.