Volume 04, Issue 10
|Integrated Defense Systems|
Plug a leak, save big bucks
KC-135 maintenance improvements put a stop to wing fuel leaks, slashing rework costs
BY ED MEMI
The old adage that "nobody is perfect" applies to every product and process. So when workers get together and look at their processes, major savings can result.
In the case of KC-135 tanker aircraft undergoing Programmed Depot Maintenance at Boeing Support Systems, San Antonio, it took workers only about a week to fix a problem with fuel leaks in the wing. That fix is saving about 300 to 400 hours of rework on each plane.
Before these improvements, virtually every aircraft undergoing PDM at this site was experiencing production-break fuel leaks on the flight ramp. The production break is a joint where wing segments attach. This not only added significant cost to the program, but also increased PDM flow days, delaying the return of the asset to
Workers were pulled together in an accelerated improvement workshop (AIW) last May and asked to examine their procedures for cleaning, aligning, sealing and installing production breaks during the extensive depot maintenance program. On each wing, there are three inboard production breaks and three on the outboard wing. These breaks were created to make it easier to transport portions of the aircraft for final assembly.
Today, the incidence of production-break fuel leaks has been greatly reduced on the KC-135s, and the lessons learned by the San Antonio team are being shared with the workers at Tinker Air Force Base, Okla., where the customer also performs KC-135 PDM.
"The customer spends a large amount of hours fixing fuel leaks. Our goal is to be as helpful as we can," said Eddie Huff, a Boeing industrial engineer who led the AIW to look at problems.
What was the problem? Huff said it was too many defects during the production-break fitting inspection, removal and reinstallation process. Most of the fuel leaks occur because of bad seals, usually at a joint or fastener. The solution, using Lean management concepts, was improved cleaning of all parts and common structure, better application of sealant, better sealants, better training for mechanics, and pressure testing the wing tip, which has an integral fuel tank, before final installation.
"We formed a team where we brought in maintenance experts from every area," Huff said. Pemco Aeroplex Inc. in Birmingham, Ala., which also performs KC-135 PDM work under subcontract to Boeing, participated. "They were better at fixing their leaks, so they shared their best practices during the workshop," he said.
Write their own procedures
Pablo Fernandez, a Boeing industrial engineer lead and co-facilitator on the team, said a key finding of the working group was the need to write its own procedures to do the work right the first time. Now, for every task there is a process data sheet that tells workers how to perform each task.
"Everybody was doing it their own way in the past," said Guillermo Martinez, a Boeing aircraft mechanic who works on the production breaks. "We standardized the work to where everybody is doing it the same way."
"The time to perform the work on these production breaks stayed about the same," said Ernest Vasquez, lead mechanic for the KC-135 production-break crew, "but we now have a lot more attention to detail and we take a lot more time to make sure everything is clean; and by doing that, our processes are improving."
Vasquez said about 400 square inches in the production-break area have to be sealed. "We found that improper cleaning affected how the sealant adhered to the metal," added Huff, "so we started using bead blasting or a 12,000 psi power washer to clean it better."
Workers like the detailed procedures, Vasquez said, because they don't like to go out on the flight line to fix a leak after fuel has had to be drained. Vasquez said the fuels section now comes in and does a leak check before the wingtips are reinstalled on the aircraft. "If there are any leaks, we fix them on the ground prior to (the wingtips) being hung," he said, but added they find very few leaks during this check.
Huff said fixing leaks was a huge problem. Because of the rework, the team had to stop the line in the flight ops section to defuel the airplane after filling it, and had to fix 30 to 50 leaking points in the wings. They had to remove fasteners, especially around the vent box area; many of these areas were hard to access and smelled of fresh fuel. "All of that rework now has been saved because we have reduced the incidence of production-break fuel leaks on the flight line," he said.
In addition, the team now uses sealant caps, which are formed to fit over fasteners. Team members said it's much easier to apply sealant over a fastener because of these caps.
"We just put it on the fastener and turn it and we're done," Vasquez said. The new caps also save time. There are 250 to 300 fasteners that have to be sealed on a production break.
Among the other improvements:
Huff is proud of the AIW efforts. "We drilled down to the top defects, set up a plan to attack those defects and got them out of the process," Huff said.
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