Air France A330 Incident Spotlights Problematic Fuel

Jul 28, 2023

Airbus plans to recommend that affected A330 operators upgrade fuel hose-attachment assemblies to minimize the risk of leaks that have led to at least two inflight occurrences.

In the text of a planned service bulletin, revealed in a recent Bureau d’Enquetes et d’Analyses (BEA) report on an Air France A330 diversion in December 2020, operators are urged to swap original fuel-hose mounting flanges with a new design released in 2015. The work can wait until a scheduled maintenance visit, the bulletin will say.

In the 2020 Air France incident, the crew noted a fuel load anomaly early into a scheduled trip from Brazzaville, Congo, to Paris. The issue—later diagnosed as a significant fuel leak from where the main fuel hose connects to the left engine—led the pilots to divert to Chad.

While the BEA probe and its recommendations focused largely on the flight crew's actions, it also spotlighted safety risks with the fuel hose assembly.

The flange used on A330s with General Electric (GE) CF6-series engines is similar to one on CF6-powered Boeing 747s flagged in fuel-leak incidents, the BEA says. GE and flange vendor Collins Aerospace discovered that design issues with the part contributed to the flange being misaligned during maintenance. The part's location makes it difficult for technicians to verify correct installation, and post-maintenance leak tests were not reliable because a well-tightened but misaligned assembly might not leak right away.

Collins redesigned the A330 flange in 2015 and stopped selling older versions in 2017. But a related bulletin informing operators of the new part's availability did not say why the part was redesigned, but noted using the older flanges was permissible so long as new torque values were used. Neither Airbus nor GE informed operators of the new part's existence or the old one's risk, the BEA says.

Meanwhile, at least four in-service instances of A330 mounting-flange leaks occurred from 2014 to 2017. Each one involved the old design and three took place "shortly after reassembly of the flange," the agency says. One case led to a commanded inflight shutdown.

One of the instances occurred on an aircraft that heavy maintenance specialist Haeco worked on in December 2015. After this, the organization put a one-time training in place "to draw the attention of the maintenance personnel to the specific difficulty of mounting flange assembly," the BEA says.

The A330 involved in the 2020 incident, F-GZCJ, was on its seventh flight following a post-storage maintenance visit at Haeco. The visit included removing both of the A330's engines.

"During the reassembly, the primary fuel hose (PFH) shoulder was incorrectly positioned on the left engine, probably due to poor visibility and the difficulties with carrying out the assembly operations," the agency report says. The engine passed a post-maintenance fuel system pressurization check, and no issues were detected during six subsequent flights.

"During the occurrence flight, probably as a result of vibrations on the ground and in flight, the PFH shoulder moved in the bore of the mounting flange, which loosened the whole assembly and caused a fuel leak," the BEA says.

The technicians that performed the work took the flange-specific training class in 2016, the BEA notes.

"The lack of a clear methodology for checking for correct alignment, the lack of information about the possible consequences of a mounting flange misalignment and the lack of clarity in the explanatory diagram referenced in the maintenance task probably limited the maintenance technicians’ awareness of the risk of an assembling error and the risk of leakage," the report says.

Collins told the BEA that in its first four years the old flange was taken off the market—through the end of 2021—and only 51 versions of the new one were sold.

"As this part is not often replaced during an airplane's life, the proportion of old and new mounting flanges in operator inventories is not well known," the BEA says. "As a result, it is possible the old design will continue to be installed for several years."

In response to the Air France incident and the apparent low number of flange replacements, Airbus and Collins developed an All Operator Letter (AOL) "warning of the possibility of incorrectly installing the former design and its consequences, and explaining the benefits of the new design," the BEA says. The AOL went out in October 2021.

Airbus plans to have its service bulletin out in "late 2022," the BEA says.

Air France is proactively upgrading the flanges, the agency says. The airline also has introduced recurrent training for technicians on flange assembly for both its employees and vendors.

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