AD 2003-13-11 Airworthiness Directives; Pratt & Whitney PW4074, PW4074D, PW4077, PW4077D, PW4090, and PW4090-3 Turbofan Engines

This AD is applicable to Pratt & Whitney (PW) PW4074, PW4074D, PW4077, PW4077D, PW4090, and PW4090-3 turbofan engines with high pressure compressor (HPC) rear cases, part numbers (P/Ns) 55H425-01, 55H385-01, and 56H396-01 installed. These engines are installed on, but not limited to, Boeing 777 series airplanes.

Compliance with this AD is required as indicated, unless already done. Initial Inspection (f) Perform an initial visual or fluorescent penetrant inspection (FPI) of the HPC rear case J flange for cracks at bolt hole location numbers 22, 67, 68, and 69, in accordance with Accomplishment Instructions of PW Service Bulletin (SB) No. PW4G-112-72-256, dated April 2, 2003, using the compliance times specified in the following Table 1: Table 1.—Initial Inspection Schedule HPC rear case P/N For cycles accumulated of: Then: (1) 55H425-01 modified by PW SB No. PW4G-112-72-150, dated April 16, 1998 (i) 4,000 or more cycles-since SB modification (CSM) Inspect within 50 cycles-in-service (CIS) after the effective date of this AD.   (ii) 2,500 CSM or more, but fewer than 4,000 CSM Inspect within 75 CIS after the effective date of this AD.   (iii) 1,850 CSM or more, but fewer than 2,500 CSM Inspect within 150 CIS after the effective date of this AD.   (iv) More than 1,700 CSM, but fewer than 1,850 CSM Inspect within 300 CIS after the effective date of this AD.   (v) 1,700 CSM, or fewer Inspect before accumulating 2,000 CSM (2) 55H385-01, 55H396-01, and 55H425-01 incorporating a scalloped J (i) 7,200 or more CSN Inspect within 300 CIS after the effective date of this AD.   (ii) Fewer than 7,200 CSN Inspect before accumulating 7,500 CSN. Previous Credit (g) Previous credit is allowed for initial inspections for cracks at bolt hole location numbers 22, 67, and 68 that were done in accordance with PW SB PW4G-112-72-256, dated April 2, 2003, before the effective date of this AD. Previous credit is also allowed for initial inspection of bolt hole location number 69 if bolt hole location number 68 was previously inspected before the effective date of this AD. (h) Disposition the HPC rear cases using the criteria in the following Table 2: Table 2.—HPC Rear Case Disposition Criteria If HPC rear case has: Then: (1) One or more inboard cracks that have penetrated beyond the pedestal and into the shell wall Remove HPC rear case before further flight. (2) One or more inboard cracks that have penetrated into the pedestal but not into the shell wall Remove HPC rear case within 25 cycles-since-last inspection (CSLI). (3) One or more inboard cracks that have not penetrated into the pedestal Remove HPC rear case within 250 CSLI. (4) One or more outboard cracks Perform repetitive inspections as specified in paragraph (i) of this AD. (5) No cracks Perform repetitive inspections as specified in paragraph (i) of this AD. Repetitive Inspections (i) Perform repetitive inspections of the HPC rear case J flange for cracks at bolt hole location numbers 22, 67, 68, and 69 in accordance with the Accomplishment Instructions of PW SB No. PW4G-112-72-256, dated April 2, 2003, and the following: (1) If last inspection of HPC rear case was a visual inspection, then visually inspect or FPI within: (i) 600 CSLI if no cracks are found. (ii) 300 CSLI if one or more outboard cracks are found. (2) If last inspection of HPC rear case was an FPI, then visually inspect or FPI within: (i) 1,000 CSLI if no cracks are found. (ii) 600 CSLI if one or more outboard cracks are found. (3) Remove HPC rear cases from service or re-inspect rear cases using Table 2 of this AD. Alternative Methods of

This AD is prompted by 32 reports of cracks propagating from bolt holes in the HPC rear case J flange, two of which were reports of high-cycle HPC rear cases with cracks propagating into the shell wall, which required immediate removal before further flight. The actions specified in this AD are intended to prevent fracturing and rupturing of the HPC rear case, resulting in uncontained engine failure.