Summary
This supplemental NPRM revises an earlier proposed airworthiness directive (AD), for Honeywell International LTS101-600A series and LTS101-700D-2 turboshaft engines, and LTP101-600A-1A and LTP101-700A-1A turboprop engines with power turbine blades, part number (P/N) 4-141-084-06, installed. That proposed AD would have required removing power turbine blades, P/N 4-141-084-06 from service, using a drawdown schedule specified in that proposed AD. That proposal was prompted by reports of fatigue cracks in the airfoil of the power turbine blade. This action revises the proposed rule by expanding and clarifying the applicability to include more engine models and power turbine blade P/Ns that could have the unsafe condition, and by clarifying the applicability by specifying power turbine rotor P/Ns instead of the blade P/Ns. The actions specified by this proposed AD are intended to prevent fracture of the power turbine blade airfoil, which could result in sudden loss of engine powerand prevent continued safe flight or safe landing.