FAA AD on original design prompts airframer and airline to evaluate improvements
Boeing is evaluating the results of recently completed flight tests conducted with American Airlines that tested an improved fuel pump for the 767, following performance issues with the current pump design.
The new Hamilton Sundstrand-developed unit, dubbed the "G" pump, was tested after problems developed with both of its predecessors, the "D" and "F" designs.
Boeing says that the original configuration "D" centre fuel override fuel pumps became subject to a US Federal Aviation Administration airworthiness directive (AD), and that performance issues then subsequently cropped up with the "F" version designed to replace it.
The original AD on the D pump was issued when several operators reported loose screws in the pump assembly that "could have resulted in some loose steel parts in the pump", says Boeing.
"In response, the FAA issued an AD requiring periodic pump inspections, and that the pumps be turned off when the fuel level in the centre tank reaches 454kg (1,000lb). As a result, the "F" pump was installed as a replacement," it adds. Although there was no similar restriction for the F pump, that is an integrated part that is cast in place, operators began to experience output pressure problems which resulted in a fuel imbalance.
Again Boeing reiterates that, although an operational issue, this was not "creating a safety issue". Not all operators experienced the issues, but American Airlines had one 767 in particular that encountered the fuel imbalance problem several times.
This aircraft was instrumented and fitted with the new pump at the airline's Tulsa, Oklahoma site before a Boeing/American test team deployed to Kona, Hawaii for a test flight effort in October. Boeing says "the testing involved 10 flights in five days. We are now analysing the test data regarding the performance of the 'G' pump."
It adds that the introduction into service of the new pump design will not occur until "the very end of 2007, or more likely early 2008".
Source: Flight International
