Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Bell Helicopter Textron, Inc. (BHTI) Model 206A and 206B helicopters, that currently requires an inspection of the main transmission input driveshaft assembly (driveshaft) at intervals of 300 hours time-in-service (TIS); the application of a zinc chromate primer inspection visual aid; and, daily visual checks of the driveshaft. This action would require inspections of the driveshaft at intervals of 300 hours TIS; the application of a self-adhesive temperature indicator visual inspection aid; and, preflight visual owner/operator (pilot) checks of the driveshaft. This proposal is prompted by recent studies that indicate that self-adhesive temperature indicators are a more reliable means of detecting overheat conditions on grease-lubricated couplings than the zinc chromate primers that are currently in use. The actions specified by the proposed AD are intended to prevent failure of the driveshaft due to coupling wear or overheating, which could result in loss of power to the main rotor and a subsequent forced emergency landing.