NTSB Recommends Stricter Inspection Intervals for Military Helicopter Tail Rotor Gears

The National Transportation Safety Board has issued a new recommendation directed at the Federal Aviation Administration regarding military surplus Bell Helicopter Textron UH-1 and TH-1 series helicopters. The board advises that an Airworthiness Directive be issued to address safety concerns related to repeated heavy lift operations. Specifically, the directive would require periodic magnetic particle or equivalent inspections of the gear teeth in the input spiral bevel gear located within the tail rotor drive shaft intermediate gearbox, identified by part number two zero four dash zero four zero dash zero zero three dash thirty seven. The board notes that historical failure data indicates the current inspection intervals are insufficient. Consequently, the recommended interval between these mandatory inspections should be substantially less than two hundred hours to ensure continued airworthiness and operational safety for these aircraft.