Airworthiness Directive · Amendment 39-22167 · Turbine engine combustion section
General Electric Company Turboshaft Engines
This AD applies to General Electric Company (GE) CT7-8A model turboshaft engines.
The FAA is adopting a new airworthiness directive (AD) for all General Electric Company (GE) CT7-8A model turboshaft engines. This AD was prompted by the manufacturer revising the airworthiness limitations section (ALS) of the existing engine maintenance manual (EMM) to incorporate reduced life limits for certain stage 1 turbine aft cooling plates, stage 2 turbine forward cooling plates, turbine interstage seals, and stage 4 turbine disks. This AD requires revising the ALS of the existing EMM and the operator's existing approved maintenance or inspection program, as applicable, to incorporate reduced life limits for these parts. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Within 90 days after the effective date of this AD, revise the ALS of the existing GE CT7-8 Turboshaft EMM and the operator's existing approved maintenance or inspection program, as applicable, by incorporating the following reduced life limits:
(i) For stage 1 turbine aft cooling plate, part number (P/N) 6064T09P02, change the life limit cycles from 6,600 cycles since new (CSN) to 4,900 CSN;
(ii) For stage 2 turbine forward cooling plate, P/N 4106T80P01, change the life limit cycles from 8,000 CSN to 7,200 CSN;
(iii) For turbine interstage seal, P/N 4111T86P03, change the life limit cycles from 29,200 CSN to 19,000 CSN; and
(iv) For stage 4 turbine disk, P/N 6068T32P04, change the life limit cycles from 24,100 CSN to 12,100 CSN.
(2) After performing the actions required by paragraph (g)(1) of this AD, except as provided in paragraph (h) of this AD, no alternative life limits may be approved.
