AD 98-19-13 Amendment 39-10990

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 98-19-13, which was sent previously to all known U.S. owners and operators of BHTC Model 407 helicopters by individual letters. This AD requires, on or before the accumulation of 50 hours total time-in-service (TIS) on the engine-to- transmission driveshaft (driveshaft), replacing the driveshaft with an airworthy driveshaft. This amendment is prompted by analysis and test data which revealed that the life limit of the driveshaft is less than that which is stated in the applicable maintenance manual. The actions specified by this AD are intended to prevent failure of the driveshaft, loss of engine drive to the rotor system, damage to critical structural components, and subsequent loss of control of the helicopter.