Airworthiness Directives; Bell Helicopter Textron-manufactured Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, and UH-1P Helicopters; and Southwest Florida Aviation SW204, SW204HP, SW205, and SW205A-1 Helicopters

This amendment supersedes an existing airworthiness directive (AD), applicable to Bell Helicopter Textron (Bell)-manufactured Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, and UH- 1P helicopters; and Southwest Florida Aviation SW204, SW204HP, SW205, and SW205A-1 helicopters, that currently requires modification and inspections of the tailboom vertical fin spar (vertical fin spar). This amendment requires the same modification and inspections plus two additional inspections and replacement of the vertical fin spar. This amendment is prompted by 6 accidents, 2 of which involved fatalities, involving fatigue cracks in the vertical fin spar that have occurred since the issuance of AD 97-20-09. The actions specified by this AD are intended to prevent in-flight failure of the vertical fin spar and subsequent loss of control of the helicopter.