Airworthiness Directive · Amendment 39-16742 · Pratt & Whitney (PW) Models PW4074 and PW4077 Turbofan Engines
Pratt & Whitney (PW) Models PW4074 and PW4077 Turbofan Engines
Superseded. A later AD replaced this one: AD 2012-13-02. Comply with the one in force.
This AD applies to Pratt & Whitney (PW) PW4074 and PW4077 turbofan engines with 15th stage high-pressure compressor (HPC) disks, part number (P/N) 55H615, installed.
We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires removing the 15th stage HPC disk within 12,000 cycles since new (CSN) or, for any disks that exceed 12,000 CSN after the effective date of this AD using a drawdown plan that includes a borescope inspection (BSI) or eddy current inspection (ECI) of the rim for cracks. This AD was prompted by multiple shop findings of cracked 15th stage HPC disks. We are issuing this AD to prevent cracks from propagating into the disk bolt holes, which could result in a failure of the 15th stage HPC disk, uncontained engine failure, and damage to the airplane.
You are responsible for having the actions required by this AD performed within the compliance times specified unless the actions have already been done.
(f) For 15th stage HPC disks that have 9,865 or fewer cycles since new (CSN) on the effective date of this AD, remove the disk from service before accumulating 12,000 CSN.
(g) For 15th stage HPC disks that have accumulated more than 9,865 CSN on the effective date of this AD, do the following:
(1) Remove the disk from service at the next piece-part exposure above 12,000 CSN, not to exceed 2,135 cycles-in-service (CIS) after the effective date of this AD.
(2) For 15th stage HPC disks that are installed in the engine and exceed 12,000 CSN on the effective date of this AD, perform a borescope inspection (BSI) or eddy current inspection (ECI) of the disk rim according to the following schedule:
(i) Within 2,400 cycles-since-last fluorescent penetrant inspection or ECI, or
(ii) Within 1,200 cycles-since-last BSI, or
(iii) Within 55 CIS after the effective date of this AD, whichever occurs later.
(3) If the BSI from paragraph (g)(2) of this AD indicates the presence of a crack in the disk rim, but you can't visually confirm a crack, perform an ECI within 5 CIS after the BSI.
(4) If you confirm a crack in the disk rim using any inspection method, remove the disk from service before further flight.
(h) Use paragraph 1.A. or 1.B. of the Accomplishment Instructions “For Engines Installed on the Aircraft” or 1.A. or 1.B. of the Accomplishment Instructions “For Engines Removed from the Aircraft,” of PW Service Bulletin PW4G-112-72-309, Revision 1, dated July 1, 2010 to perform the inspections.
