Volume 03, Issue 2
Rather switch than fight
Team effort cuts first-year component removals on 777
BY RICK ROFF
The current dispatch reliability rate for the Boeing 777 is 99.31 percent-the highest in the world for twin-aisle airplanes.
As outstanding an achievement as that may be, certain components have sometimes failed in the 777 factory, on the flight line and early in service. To improve the airplane's reliability, the 777 program undertook a team effort to not only boost the airplane's dispatch reliability rate but also significantly cut down component removals during the first year of service.
Boeing initiated a team led by Airplane Programs, Supply Management & Procurement and others to address early component removals that eventually will cover all models built at the Everett and Renton, Wash., factories.
The team presented "stoplight chart" data during a standing meeting attended by all relevant organizations, including selected suppliers, and performed a "deep dive" into the Root Cause Corrective Action of early component removals.
One recent situation involved cockpit indications of possible malfunction in 777 antiskid and parking brake systems. The solution was not easy. Boeing manuals instructed the airlines involved to remove and replace the park brake valve, since the component appeared to be unresponsive.
Several valves had been removed and returned to the supplier for evaluation and retest-but no problems were found.
The data showed multiple parking brake valve units had been returned for various modifications. However, only three were in the category related to the observed problem. Again, testing resulted in no problems found in these units.
"The park brake valve status chart was reporting 'red,'" noted SM&P procurement agent Linda Jameson, "with the root cause unknown and therefore no plan in place to incorporate a fix."
The team investigated deeper into the park brake system itself. Other airlines had noted problems on another part of the system-the park brake lever switch. Repeated testing and close scrutiny of the switch finally revealed something: deterioration on the switch contacts, indicating an over-current condition that could trigger the warnings.
"Until this point, it had been pretty challenging trying to find out what the heck was going on," said Neil Rapues, landing gear systems engineer. "But when we discovered the weakened condition of the switch contacts, we knew we were onto something. It really energized the team."
Because new switches are subjected to a six-month in-service test, replacement switches were not a viable solution. At the same time, in a test conducted at Boeing, it was found that the switches, rated at three amps, were receiving inrush currents greater than four amps when installed on the airplane.
"That's when we looked at the 767, which has the same park brake valve with a different park brake lever switch assembly," said Tom McMillan, flight controls engineer. "It turned out to be a great solution for several reasons."
For one thing, the assembly used a switch that had a higher rating of 10 amps. Plus, the 767 switches were available on a long-term contract and could be purchased at a very competitive price. A third bonus: The rigging machinist confirmed a savings of as much as two hours for installation and setting the switch correctly.
"In order to set the previous microswitch, we had to listen carefully (in a noise-filled factory) for the switch to click (activate) and then with the other hand tighten the switch," said Jeff Davis, assembler and flight control rigger. "It could be real hard to hear the click because it was so much smaller. This new switch is easier to set, and the new assembly only requires a quick, two-minute installation."
The new switch assembly was installed in March on the next 777 airplane to be delivered, which makes this a story where everyone-customers, suppliers and manufacturers-walks away happy.
George Maffeo of the SM&P management team called the outcome a "triple win," saying the experience "is a perfect example of how relentless pursuit of customer satisfaction can drive positive results in areas you don't anticipate."
- Richard Roff firstname.lastname@example.org
- Linda Jameson contributed to this story
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