Airworthiness Directive · Amendment 39-21975 · Turbine engine compressor section
Pratt & Whitney Division Turbofan Engines
This AD applies to Pratt & Whitney Division (PW) PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 model turbofan engines, with a 1st-stage low-pressure compressor (LPC) blade, with part number 52A241, 55A801, 55A801-001, 55A901, 55A901-001, 56A201, 56A201-001, or 56A221, installed.
The FAA is superseding Airworthiness Directive (AD) 2019-03-01 and AD 2021-05-51 for certain Pratt & Whitney Division (PW) PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 model turbofan engines. AD 2019-03-01 required performing initial and repetitive thermal acoustic image (TAI) inspections for cracks in certain 1st- stage low-pressure compressor (LPC) blades and removal of those blades that fail inspection. AD 2021-05-51 required performing a one-time TAI inspection for cracks in certain 1st-stage LPC blades and removal of those blades that fail inspection. This AD was prompted by three in- flight failures of a 1st-stage LPC blade, with one failure resulting in an engine fire during flight, and subsequent manufacturer publication of service information specifying improved inspections for three critical locations on the 1st-stage LPC blade. This AD requires initial and repetitive ultrasonic (UT) inspections and TAI inspections for cracks in certain 1st-stage LPC blades and removal of those blades that fail inspection. The FAA is issuing this AD to address the unsafe condition on these products.
(i) For 1st-stage LPC blades that have accumulated any number of cycles since new (CSN) greater than zero, before further flight after the effective date of this AD, perform a flow path and a mid span ultrasonic testing (UT) inspection of the 1st-stage LPC blades in accordance with the Accomplishment Instructions, Part A—Initial Inspection of All LPC Fan Blades Prior to Their Return to Service, paragraph 1.A. through C., of Pratt & Whitney Alert Service Bulletin (ASB) PW4G-112-A72-361, dated October 15, 2021 (PW4G-112-A72-361). New 1st-stage LPC blades that have zero CSN do not need to undergo the initial 1st-stage LPC blade flow path and mid span UT inspection required by paragraph (g)(1)(i) of this AD, but must undergo the repetitive inspections of paragraph (g)(2) of this AD.
(ii) Within the following compliance times after the effective date of this AD, perform a thermal acoustic image (TAI) inspection of the 1st-stage LPC blades for cracks using a method approved by the FAA:
(A) For 1st-stage LPC blades with 1,000 CSN or more, with no prior TAI inspection, inspect before further flight.
(B) For 1st-stage LPC blades with 1,000 flight cycles (FCs) or more since the last TAI inspection, inspect before further flight.
(C) For 1st-stage LPC blades with fewer than 1,000 CSN, with no prior TAI inspection, inspect before accumulating 1,000 CSN.
(D) For 1st-stage LPC blades with fewer than 1,000 FCs since the last TAI inspection, inspect before accumulating 1,000 FCs since the last TAI inspection.
Note 1 to paragraph (g)(1)(ii): The FAA-approved TAI inspection method and the vendors that can perform the FAA-approved TAI inspection are specified in the Accomplishment Instructions section and the Vendor Services section of PW4G-112-A72-361, respectively.
(i) Before exceeding 275 FCs since the last flow path UT inspection, and thereafter at intervals not exceeding 275 FCs since the last flow path UT inspection, perform a flow path UT inspection of the 1st-stage LPC blades in accordance with the Accomplishment Instructions, Part B—Repetitive Inspection of All LPC Fan Blades After Their Return to Service, paragraph 1.A., of PW4G-112-A72-361.
(ii) Before exceeding 550 FCs since the last mid span UT inspection, and thereafter at intervals not exceeding 550 FCs since the last mid span UT inspection, perform a mid span UT inspection of the 1st-stage LPC blades in accordance with the Accomplishment Instructions, Part B—Repetitive Inspection of All LPC Fan Blades After Their Return to Service, paragraphs 1.B. and C., of PW4G-112-A72-361.
(iii) Before exceeding 1,000 FCs since the last TAI inspection, and thereafter at intervals not exceeding 1,000 FCs since the last TAI inspection, perform repetitive TAI inspections of the 1st-stage LPC blades using a method approved by the FAA.
Note 2 to paragraph (g)(2)(iii): The FAA-approved TAI inspection method and the vendors that can perform the FAA-approved TAI inspection are specified in the Accomplishment Instructions section and the Vendor Services section of PW4G-112-A72-361, respectively.
If any 1st-stage LPC blade fails any inspection required by paragraphs (g)(1) or (2) of this AD, before further flight, remove the 1st-stage LPC blade from service and replace with a part eligible for installation.
For the purpose of this AD, a “part eligible for installation” is a new, zero CSN 1st-stage LPC blade or a 1st-stage LPC blade that has passed the inspections required by paragraphs (g)(1) and (2) of this AD, as applicable.
