Airworthiness Directive · Amendment 39-22586 · Turbine engine combustion section
Pratt & Whitney Division Engines
This AD applies to Pratt & Whitney Division (PW) Model PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 engines.
The FAA is superseding Airworthiness Directive (AD) 2018-02- 10, which applied to certain Pratt & Whitney Division (PW) Model PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 engines. AD 2018-02-10 required performing repetitive fluorescent penetrant inspections (FPIs) to detect cracks in the outer diffuser case (ODC), removal of any ODC that fails inspection, and updating the mandatory inspections in the Airworthiness Limitations Section (ALS) of the Instructions for Continued Airworthiness (ICA). Since the FAA issued AD 2018-02-10, PW developed a modification to reduce the susceptibility of ODC cracking. This AD retains the ALS update requirement from AD 2018-02-10, requires replacing certain ODC part numbers with parts eligible for installation, expands the applicability to all ODC part numbers, and adjusts the compliance threshold of the FPIs of the ODC. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Within the compliance times specified in paragraphs (g)(1)(i) though (iii) of this AD, perform an initial high sensitivity fluorescent penetrant inspection (FPI) of the ODC T3 thermocouple probe boss (Tt3 boss) for crack indications in accordance with the Accomplishment Instructions, paragraph 1.F. of Part A or paragraph 1.B. of Part B, as applicable, of PW Alert Service Bulletin PW4G-112-A72-347, Revision 4, dated September 1, 2022 (ASB PW4G-112-A72-347, Rev 4).
(i) For an ODC that has accumulated less than 12,000 cycles since new (CSN) with no prior high sensitivity FPI of the ODC Tt3 boss, perform the high sensitivity FPI before accumulating 9,200 CSN or within 1,000 flight cycles (FCs), after the effective date of this AD, whichever occurs later.
(ii) For an ODC with unknown CSN or an ODC that has accumulated 12,000 CSN or more with no prior high sensitivity FPI of the ODC Tt3 boss, perform the high sensitivity FPI before accumulating 13,000 CSN or within 1,000 FCs, after February 26, 2018 (the effective date of AD 2018-02-10), whichever occurs later.
(iii) For an ODC that has undergone a high sensitivity FPI of the ODC Tt3 boss prior to the effective date of this AD that resulted in no crack indication, perform the high sensitivity FPI before accumulating 2,000 FCs since performance of the last FPI or during the next engine shop visit, whichever occurs first.
(iv) For an ODC that has undergone a high sensitivity FPI of the ODC Tt3 boss prior to the effective date of this AD that resulted in an indication of a crack, perform the actions required by paragraphs (g)(3)(i) through (iii) of this AD, as applicable.
(2) Thereafter, repeat the high sensitivity FPI of the ODC Tt3 boss at each engine shop visit or before exceeding 2,000 FCs from the last high sensitivity FPI of the ODC Tt3 boss, whichever occurs first, in accordance with the Accomplishment Instructions, paragraphs 1.F. of Part A or paragraph 1.B. of Part B, as applicable, of ASB PW4G-112-A72-347, Rev 4.
(3) If, during any inspection required by paragraphs (g)(1) or (2) of this AD, there is any crack indication, perform the actions specified in paragraphs (g)(3)(i) through (iii) of this AD.
(i) For engines installed on an aircraft, repeat the high sensitivity FPI or remove the ODC from service in accordance with the actions and compliance times specified in the Accomplishment Instructions, Part A, paragraphs 1.G. and 1.H., of ASB PW4G-112-A72-347, Rev 4.
(ii) For engines not installed on an aircraft, repeat the high sensitivity FPI or remove the ODC from service in accordance with the actions and compliance times specified in the Accomplishment Instructions, Part B, paragraphs 1.C. and 1.D., of PW ASB PW4G-112-A72-347, Rev 4.
(iii) For engines at an engine shop visit, before further flight, remove the ODC from service.
(4) Within 30 days after the effective date of this AD, revise the Airworthiness Limitations Section (ALS) of the existing engine maintenance manual or Instructions for Continued Airworthiness and the existing approved maintenance program, as applicable, to include the piece-part inspections of the ODC as defined in Table 1 to paragraph (g)(4) of this AD.
| Description | Part No. | Cleaning, inspection and repair (CIR) manual section | CIR manual inspection | CIR manual |
|---|---|---|---|---|
| Case, Diffuser, Outer | All | 72-41-13 | Inspection/Check (I/C-02) | P/N 51A750 |
(5) For engines with ODC part number (P/N) 50J775 or 50J930 installed, at the next piece-part exposure after the effective date of this AD, replace the ODC with a part eligible for installation.
(1) For the purpose of this AD, an “engine shop visit” is any time the “M” flange is separated.
(2) For the purpose of this AD, a “piece-part exposure” is when the ODC is removed from the engine and fully disassembled.
(3) For the purpose of this AD, a “part eligible for installation” is an ODC with P/N 50J775-001, 50J775-002, 50J930-001, or 50J930-002.
