War on waste: Maintenance

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Lean processes, which have transformed aircraft production lines, are finding new applications in maintenance, repair and overhaul programmes

Bullet holes hastily patched, cockpit windows dulled by rotor-blown sand that still lurks in airframe crevices, US Army AH-64 Apache attack helicopters returned from a year-long tour of duty in Iraq move tail-first down the line at Boeing's Williams Gateway airport plant in Mesa, Arizona.

The Apaches are just a part of the army's massive "reset" programme, which restores war-worn equipment to pre-deployment condition ready to return to the fight. But the Williams Gateway operation represents a revolution in the reset world, Boeing says, because it uses lean processes more usually seen on production lines.

 
© Boeing   
War-torn Apaches are repaired and rebuilt on a pulsed moving line in Mesa

As the Apache reset illustrates, lean is finding new applications in the maintenance, repair and overhaul (MRO) sector. Pulsed moving lines, point-of-use kitting, pull systems, self-directed work cells - all the buzzwords of lean manufacturing are now being heard across commercial and military maintenance and modification.

Lean lessons learned during the dramatic reconfiguration of Boeing's commercial aircraft production lines are being applied by its Support Systems business to reshape programmes from Apache reset to KC-135 tanker overhaul. And airlines and MRO providers are interested in the results, the company says.

"Lean is easier in a production environment," says Tim Coyle, vice-president and general manager of the Boeing Support Systems Center in San Antonio, Texas, where KC-135s, KC-10s and C-130s are overhauled and upgraded. "In the MRO environment, 50% of what we find is unexpected, so we have to be better."

Accustomed to resetting Apaches at its own maintenance sites, the US Army awarded Boeing a one-year, 15-aircraft contract in 2004 to prove the concept of using the original manufacturer to refurbish its helicopters. Much of the work was conducted in a traditional maintenance environment - aircraft remaining in one station while they were stripped, repaired and rebuilt.

The operation changed from "stationised" to "productionised" with a second, two-year contract for 70 aircraft awarded in 2005. Lean principles were applied, resulting in a pulsed moving line, with the aircraft moving once every six days through four stations. Boeing has committed to reset an Apache in 60 days, from induction to delivery flight tests, compared with the army standard of 89 days.

Self-directed workers

Each station is a self-directed work cell, workers deciding for themselves what tasks are performed where, and each is responsible for ensuring the aircraft is ready to move to the next station when the line is pulsed. A key lean tool, moving or pulsing the line brings a sense of urgency to the work at hand. The Apache line is pulsed every six days, with the move taking 6min. In an adjacent hangar, where US Air Force Northrop T-38 trainers are undergoing an extensive avionics upgrade, the line is pulsed every 28h labour hours, the move taking 4min.

Like Boeing's AH-64 production line elsewhere in Mesa, the Williams Gateway plant has the hallmarks of a lean environment - a factory floor free of clutter, neat point-of-use bins for tools and materials, adjacent feeder lines where components removed from the helicopters are refurbished, and abundant visual cues to the status of each aircraft, clearly showing any behind-schedule work.

Aircraft coming in for reset can have damage from hostile fire, hard landings and sand abrasion, so 30 days before induction a team goes to the base to assess its condition and order parts to mitigate the lead time. Required modifications are rolled in with the reset without adding to cycle time, and Boeing engineers are on hand to design repairs to damage and any "quick fixes" made in the field.

Boeing says the lean approach pioneered at Williams Gateway will be used at other Apache reset sites, as well as the US Army's depot, and could be applied to phased maintenance at the units.

Boeing's San Antonio centre, meanwhile, is two to three years ahead of the Williams Gateway plant on the lean journey, says Coyle. Formerly part of the US Air Force's San Antonio Air Logistics Center, the business was established in 1998 after Kelly AFB was closed. Initially a troubled operation, the site has seen a dramatic turnaround as lean has taken hold, he says.

Introduction of lean processes began three years ago, Coyle says, after successful efforts to solve the culture problems at San Antonio left the ground "ploughed and ripe" for employee involvement. He refers to the "flywheel" concept: "It was hard to get to started, but once we got the employees involved the flywheel really took off."

Boeing spent the first year and a half "lifting the foundations of the site", Coyle says, focusing in on the programmes over the past year and a half. First to go to a pulsed line was the KC-135 global air traffic management upgrade. Although the line was rearranged, point-of-use tools and materials put in place and support cells set up almost overnight, "it took about a year to get humming", he says.

 
© Boeing   
Boeing has managed to cut KC-135 depot overhaul time to 153 days, from 200

KC-135 programmed depot maintenance (PDM) came next. "That was a little harder. There is a lot more unknown work and a lot of supply-chain involvement," says Coyle. The goal was to halve the cycle time to 100 days but, just as the benefits were beginning to show, the USAF cut the number of aircraft inducted and Boeing had to slow the line to avoid lay-offs.

Boeing has been able to "pulse" an aircraft though all eight lean cells in 153 days, including structural repairs - well below the 200 days previously required for KC-135 PDM, and beating the USAF's future requirement of 175 days. "We could get to 100 days if input was in the 20- to 25-aircraft range," says Coyle.

Expanding the concept

The centre began implementing lean on the KC-10 tanker line late last year, with the goal of reducing a C check from 18 days to 10-12. "The C-17 is right behind, but is a little trickier because every aircraft has different modifications and cycle time is all over the place," says Coyle. TheC-130 avionics modernisation programme is also planned to go to a pulsed line.

San Antonio is a non-union operation, giving Boeing the flexibility to cross-train and move people around, but Coyle says the workforce was "excited about involvement". He believes the centre's experience has value to the commercial MRO industry, and says airlines are showing interest, particularly in its use of kitting for repairs. "We do the kitting, but our vision is to get a third party to do it," he says.

Airlines are showing great interest in the US aircraft manufacturer's lean experience, says Lou Mancini, vice-president and general manager of Boeing Commercial Aviation Services. "Boeing took lean very seriously and shocked the world with moving aircraft production lines, which synchronise the whole supply chain. Now lots of customers ask about lean."

Having created a "huge" lean office to transform its own manufacturing operations, Mancini says, the company is offering its experience to airlines. "Demand is high," he says, "and it is amazing how much transferability there is [between production and maintenance environments] for lean concepts such as standard work and the visualisation of status."

The sense of urgency that lean principles have brought to production is now being used by Boeing Commercial Aviation Services to accelerate the response time in its operations control centre, which opened in December 2005. By tapping into Boeing's engineering resources, the Seattle-based support centre is able to develop approved repairs for customers within hours. "The average is 10h," says Mancini.

Suppliers are also feeling the pull of lean. Honeywell's Consumables Solutions (CS) group, which supplies commodities such as fasteners, bearings and seals to manufacturers, airlines and MRO providers, is seeing the trend. "MROs are going lean, more so than airlines," says Jeff Smith, vice-president, consumables solutions. The group, which stocks more than 750,000 different part numbers, is looking at the kitting of parts for repairs of Honeywell systems as a way to expand its business.

Wide variation

Combining the proprietary and consumable parts needed to repair, for example, an auxiliary power unit (APU), these point-of-use kits would include parts not held as standard. But the wide variation in work practices across the maintenance industry poses a challenge for kitting. "From MRO to MRO to airline the kits would be unique, so we can't just develop a kit and take it to market," says Smith. "We have to get out there and understand the kits that are needed. There might be half a dozen kits to service one APU."

Honeywell's CS group is also working with manufacturers and operators to tackle the bottlenecks that come when busy production lines and maintenance shops draw on the same lean supply chain. Smith says the company is working with Airbus to qualify small, agile "fast shops" than can offload the major suppliers and produce nuts and bolts in smaller lots, with quicker turnarounds.

The wartime pressures that pulse Boeing's Apache reset line on its six-day heartbeat may be unique, but the effects of the lean revolution are being felt across the military and commercial maintenance, repair and overhaul sector.