FAA issues Airworthiness Directive : The FAA is adopting a new airworthiness directive (AD) 2022-07-13 for all Pratt & Whitney Division (PW) PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 model turbofan engines.
An in-flight shutdown (IFSD) of an engine due to an air/oil heat exchanger leak caused by corrosion and subsequent investigation by the manufacturer that revealed additional air/oil heat exchanger leaks.
On November 9, 2021, a Boeing Model 777 airplane, powered by PW PW4077 engines, on a ferry flight from San Francisco, CA to Honolulu, HI, experienced an oil leak on the number 1 engine that resulted in an IFSD and air turnback to San Francisco , CA.
A post-flight inspection revealed that the oil leak was from the air/oil heat exchanger. After further investigation, the manufacturer determined that the air/oil heat exchanger leak was due to corrosion.
This condition , if not addressed , could result in low oil pressure , failure of one or more engines , IFSD, loss of engine thrust control, reduced control of the airplane, and loss of the airplane.
► Within 30 days prior to the first flight after the effective date of this AD, perform an inspection for leaks of the air/oil heat exchanger in accordance with the Accomplishment Instructions, paragraph 3., of Pratt & Whitney Special Instruction No. 255F-21A , dated February 15, 2022.
► If any air/oil heat exchanger fails the inspection required by above paragraph, before further flight, remove the air/oil heat exchanger and replace with a part eligible for installation.
► A new air/oil heat exchanger with zero CSN , or
► An overhauled air/oil heat exchanger with zero cycles since last overhaul, or
► An air/oil heat exchanger that has passed the inspection required by the Actions segment of this AD.
► According to the manufacturer, the lack of operation may have exacerbated corrosion on the air/oil heat exchanger. Pratt & Whitney Special Instruction No. 255F-21A, dated February 15, 2022.
► This special instruction specifies procedures for performing an inspection of the air/oil heat exchanger and, depending on the results of the inspection, replacement of the air/oil heat exchanger.
► This special instruction also specifies procedures for storing an air/oil heat exchanger after the inspection.
This airworthiness directive (AD) becomes effective on May 2, 2022.
Source - FAA / Picture for representation.
