Airworthiness Directives; Hiller Aircraft Corporation Model UH- 12, UH-12A, UH-12B, UH-12C, UH-12D, UH-12E, CH-112, H23A, H-23B, H-23C, H-23D, H-23F, HTE-1, HTE-2, and OH-23G Helicopters

Résumé

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Hiller Aircraft Corporation Model UH-12, UH-12A, UH-12B, UH-12C, UH-12D, UH-12E, CH-112, H-23A, H- 23B, H-23C, H-23D, H-23F, HTE-1, HTE-2, and OH-23G helicopters, and Model UH-12D and UH-12E helicopters, converted to turbine engine power in accordance with Supplemental Type Certificate (STC) No.'s SH177WE and SH178WE, that currently requires inspections of the control rotor blade spar tube (blade spar tube) and cuff for cracks, and repair or replacement as necessary. This action would require inspections of the blade spar tube and cuff for corrosion or cracks, or elongation, corrosion, burrs, pitting or fretting of the bolt holes, and repair as necessary, and would define specific intervals in which the inspections must be performed. This proposal is prompted by analyses that showed that the amount of calendar time that elapses between the current repetitive inspections may allow corrosion to develop. The actions specified by the proposed AD are intended to prevent separation of the control rotor blade assembly and subsequent loss of control of the helicopter.