Fixes For PW4000-Powered 777s Edge Closer

Damage to the wing and the body fairing of the United Airlines flight 328 Boeing 777-200 following an engine failure Feb. 20, 2021.
Credit: NTSB

Pratt & Whitney and the FAA are close to approving revised inspection protocols for PW4000s that power grounded Boeing 777s, but Boeing-led work on nacelle modifications will likely push the fleet’s return-to-service approval into 2022.

The global fleet of 128 777s with PW4000s has been grounded since late February following a failure onboard a United 777 near Denver, Colorado—the third PW4000-powered 777 in-service event in three years linked to a cracked fan blade. The FAA is working with Pratt on revised inspection protocols, and an agreement is close, An FAA mandate outlining the new inspections is expected out by year-end, sources familiar with the matter told Aviation Week.
The revised protocols are expected to combine new ultrasonic inspections with Pratt’s proprietary thermal acoustic imaging (TAI) inspections that have been in place for the life of the program, the sources said. The NTSB cited inadequate TAI inspection procedures and intervals as contributors to a 2018 in-flight engine failure of a United 777-200 en route to Honolulu, Hawaii, that started with a fractured blade—the first of the three incidents that led to the grounding.
In two of the events, both involving United aircraft, investigators confirmed damage from the blade failure caused parts of the nacelles to break away and strike the airframe. Little information has been released about the third event, onboard a JAL 777-200 last December.

The new fan-blade inspection protocol is one of two related issues keeping the PW4000-powered 777s on the ground. The other is nacelle modifications.

Boeing has been working on nacelle changes since before the most recent in-flight failure. But the sources with knowledge of the situation confirm that the work is not likely to be done and approved before 2022. The FAA is not expected to approve any of the aircraft for revenue service until both issues are solved, the sources added.

Boeing declined to comment on a time frame for the fixes.

"Boeing is working closely with the FAA, our customers and Pratt & Whitney to safely return PW4000-112-powered 777 airplanes to service," the company said. "We have identified design changes and are working to finalize them, including a robust certification effort.”

Inquiries to the FAA and Pratt were not immediately returned.

United Airlines, which has 52 of the grounded aircraft in its fleet, is optimistic that work being done to get the aircraft back is bearing fruit.

"We've gone through an extensive set of analysis and testing of the engines in conjunction with our partners at Pratt & Whitney, Boeing and the FAA and are in the process of returning those aircraft to service,” United chief commercial officer Andrew Nocella said during a Cowen-hosted investor conference Sept. 9. "We'd like to see those aircraft to go back up in the air sometime late this year, early next year and be ready for full flying by the spring of next year.”

Sean Broderick

Senior Air Transport & Safety Editor Sean Broderick covers aviation safety, MRO, and the airline business from Aviation Week Network's Washington, D.C. office.


1 Comment
High expectations for an even greater fuel efficient aircraft engine has let the airline industry to this today. On going issues abound with the ducted fan gear driven also a split spool way to power these large fans. Looking back this may have been problematic at the start of the race who would be the out front to produce the largest fan.