AD 2022-07-13 Prompted By An In-Flight Shutdown (IFSD) Of An Engine Due To An Air/Oil Heat Exchanger Leak

The FAA is adopting a new airworthiness directive (AD) for all Pratt & Whitney Division (PW) PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 model turbofan engines.

This AD was prompted by 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. This AD requires an inspection of the air/oil heat exchanger and, depending on the results of the inspection, replacement of the air/oil heat exchanger. This AD also provides instructions for storing an air/oil heat exchanger after inspection. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective May 2, 2022.

Supplementary Information: 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 this event, on December 19, 2021, the manufacturer was made aware of another oil leak related to the air/oil heat exchanger that was discovered during a post-flight inspection after the first flight out of storage. Subsequent investigation revealed 19 air/oil heat exchanger leaks occurred on the affected engines during the past year, which is significantly higher than the three to four air/oil heat exchanger leaks typically occurring each year. After further investigation, the manufacturer determined that the air/oil heat exchanger leak was due to corrosion. The manufacturer published Pratt & Whitney Special Instruction No. 255F-21A, dated February 15, 2022, which provides instructions 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 provides instructions for storing an air/oil heat exchanger after the inspection. 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. The FAA is issuing this AD to address the unsafe condition on these products.

FMI: www.regulations.gov