Wednesday, April 1, 2009
Oklahoma City ALC: Military MRO in Transition
At almost 70 years old, the Oklahoma City Air Logistics Center (OC-ALC) at Tinker Air Force Base would seem ripe for retirement. But that’s far from the case for this beehive of airframe and engine maintenance activity.
Despite its aging infrastructure, the ALC is front and center in applying methods such as Lean and critical chain program management to its work processes. Without the benefit of the new USAF approach, known as High Velocity Maintenance (HVM), workers have increased efficiency dramatically in the past decade.
The Oklahoma City ALC has its hands full. A small town, it boasts more than 16,000 military, civilian and contractor employees. The ALC’s largest wing is the 76th Maintenance Wing, which performs programmed depot maintenance (PDM) on the KC-135 tankers, B-1B and B-52 bombers, and E-3 command and control aircraft, as well as depot-level maintenance on the Navy E-6 aircraft, and maintenance, repair and overhaul of F100, F101, F108, F110, F118, F119 and TF33 engines for the Air Force, Air Force Reserve, Air National Guard, Navy and foreign military sales customers. In a recent year the ALC did PDMs on 48 KC-135s, 17 B-52s, 13 B-1s and six E-3s. On the propulsion side, officials expect to overhaul 396 engines this year with 196 of them being completed in the 546th Engine Repair Squadron — 97 of two variants of the F108, 78 of two versions of the F110, and 21 F118s. The other 200 engines will be completed by the 545th Engine Repair Squadron- 79 F101, 12 F100, and 109 TF-33.
The heart of the ALC is Building 3001, which Douglas Aircraft constructed in 1942 to assemble small C-47s. One of the maintenance world’s wonders, Building 3001 covers 62 acres of industrial and administrative space and stretches for seven-tenths of a mile. It’s reportedly big enough to hold a dozen KC-135 air refueling tankers — along with engine work areas and support staff. But it’s an aging wonder, boasting only two hangar doors.
The hangar doors cause delays because they are too small. Before a KC-135 can be brought into the work area, its tail must be removed, explains Walt Spicer, the KC-135 PDM Support Squadron chief.
Even then, the airplane has to be wedged in at an angle. And the two hangar doors service nine docks. That means that airplanes in the middle of the work floor can get "trapped" and find it a challenge to get out again. The aircraft on the perimeter, in various stages of disassembly, have to be moved multiple times in order for the trapped KC-135 to get out. So it’s something of an achievement that maintainers were able to reduce PDM time for the KC-135 from 413 days in fiscal year 2000 to 225 days recently. Officials hope eventually to get that number down to 130 days.
The Air Force plans to cut another entry way, improving the door-to-dock ratio. Some aircraft will still get trapped, but the interior spots will be reserved for cases needing extra attention. There are also plans for a new three-bay hangar to help with the KC-135 workload. And officials have signed a lease on a 3.8-million square foot facility formerly used by GM. The facility was bought by local government, which has leased two-thirds of the space to the Air Force — for activities such as sheet metal work — and will lease the remainder to aerospace companies. After refurbishment, the new tenants are expected to be in place by 2014.
The next step towards productivity increases will be the adoption of the High Velocity Maintenance methodology. Developed at the Warner Robins ALC, HVM is patterned after cycle checks in the commercial airlines. The system involves more frequent, more homogeneous maintenance visits, as opposed to the all-encompassing PDM approach.
The B-1 will be the first to embrace HVM at Tinker, says Kevin O’Connor, deputy director of the 76th Aircraft Maintenance Group. This aircraft was chosen because it is "probably one of our most predictable at this point," he notes. But the ALC plans eventually to roll HVM across all of the weapons systems that it does PDMs for.
The beauty of HVM, O’Connor asserts, is that the airplane will come into the depot a lot more frequently, perhaps in intervals as short as 18 months, although the exact timing will depend on the individual weapon system. Because HVM assumes better knowledge of aircraft condition and the focus of upcoming visits will be known well in advance, "this gives your supply chain the chance to position itself for you to be successful," he explains. And instead of fixing pretty much everything — since the aircraft won’t visit the depot again for a number of years — non-flight-critical maintenance can be deferred to the next cycle, increasing throughput.
With the next-generation tanker program still on hold, the 50-year-old KC-135 remains the workhorse of the USAF air refueling fleet. Oklahoma City performs PDM for about 65 percent of the approximately 420 aircraft. The remainder of the fleet is serviced by the manufacturer, Boeing, and Alabama Aircraft Industries (formerly PEMCO). L-3 handles the small number of specialized 135s.
In the last 10 years the ALC has improved efficiencies in KC-135 heavy maintenance. A key factor has been the ability to conduct three to four major structural repairs in a concurrent fashion, Spicer explains. Thanks to a new fixture developed by ALC engineers, for example, belly skin repairs can now be conducted on both sides of the lower fuselage at the same time.
Although HVM hasn’t arrived yet, the B-1’s depot flow time has already decreased, in part because of Oklahoma City’s embrace of critical chain program management and Lean. The time required for depot maintenance has shrunk from 200 – 205 days in FY 2002 to an average of 155 days in FY 2008. In FY 2009, Oklahoma City recorded a low of 137 days.
Based on the theory of constraints, critical chain program management is a way to handle execution on a day-by-day basis, O’Connor says. In business terms, that means that "you manage to your constraints and you remain flexible throughout your execution," he explains.
The system focuses on constraints such as skill imbalances and part shortages and tries to compensate for them in order to increase velocity. The approach started with the B-1s but has since been extended to the E-3 and B-52 lines.
The ALC also has begun to apply critical chain methodology, in addition to Lean, to the KC-135 line. This systematic approach to day-to-day execution, backed up by software such as the Concerto program, helps in the management decisions.
At the macro level, managers want to "move all of our inspections to the left, to get as much inspected on that aircraft as early as possible in the flow so that we will recognize any extended repairs, structural repairs, that we may have to accommodate," Spicer says. This helps the supply chain and workforce to be better prepared, he explains.
Maintainers want to be able to assess the condition of an incoming KC-135 within the first 30 days, so that "the rest of the flow can be supportable," Spicer says. An initial, five-day assessment window proved to be too short, he conceded.
"We’ve doubled that time now to 10 days — doubled the shift, doubled the personnel." So now the goal is to find "90 percent of an aircraft’s problems early in the flow — still within the first 30 days — as opposed to finding a much smaller percentage and finding more ‘stumble-ons’ as we go."
Closely allied to the critical chain efforts is the ALC’s "5 S+1" program. (These letters stand for sort, straighten, shine, standardize, and sustain, plus safety.) 5 S+1 involved seemingly simple changes to the working environment, such as improving the lighting, painting the floor and organizing where everything is located. When an aircraft is torn down, for example, a lot of equipment and other items build up around the plane, eventually restricting efficiency. Addressing such mundane areas, however, has helped to increase productivity.
The depot also does more kitting. "We like to say we make the mechanic the center of gravity," O’Connor says. "We try to feed him the tools he needs on a daily basis, the technical data and parts, to make sure we have good velocity, good flow on the aircraft," something his group has done on the B-1 and E-3 PDM lines. Work is also carefully orchestrated, or sequenced, on a day-to-day basis.
Maintainers also have been able to work concurrently on the E-3. The process of removing the aircraft’s huge rotodome, for example, used to be done sequentially and in a different facility from PDM because of lifting requirements and building constraints, O’Connor says. However, two to three years ago, the E-3 PDM workspace was upgraded, so the dome can now be removed during PDM, a development which increases concurrency and reduces flow days. E-3 flow days have been slashed from about 268 in FY 2001 to 170 in FY 2008. The record this year is 154 days.
The ALC also has increased the efficiency of its engine maintenance, repair and overhaul operations. To meet war readiness level challenges with the Pratt & Whitney F100 engine, which powers the F-15 and F-16 fighters, the ALC hired Battelle, under an up-to-$500-million contract, to apply Lean and cellular principles to F100 MRO operations, among others. The GE engine side of the house, meanwhile, has improved performance through internal efforts at much less cost.
The ALC recently completed its F100 business unit transformation, said Jeff Bradley, director of the 544th Squadron. "Our real focus is the mechanics — making sure they have the parts, tools and equipment to be able to do their jobs, to be as efficient as possible," he explained.
Bradley emphasized that his squadron wanted to take "90 percent ownership of all our parts." Before, his unit simply disassembled and then reassembled engine modules, while specialized back shops repaired piece parts. Under the new approach, which started in 2005, people and equipment in back shops associated with the F100 have been physically moved to his squadron.
Work is divided into 28 cells. Progress is closely monitored by means of status boards positioned at every cell. The chits on the boards represent all the parts being worked on at a given time and indicate where every part is in the process. Everyone knows when a part needs to be "produced" and where it goes next.
If there should be a glitch, the support staff of engineers, planners and schedulers are right there on the shop floor, Bradley says. These people used to have offices some distance away, at the back of Building 3001.
Performance numbers have improved. The time required to tear down, repair and reassemble F100 inlet fans, for example, has decreased from 65 to 34 days, while the time for the same procedures with F100 fan drives has fallen from 129 to 60 days.
Oklahoma City also handles GE F108, F110 and F118 engines for the KC-135, F-16 and B-2, respectively. This side of the house has applied Lean from within. A major achievement has been the reorganization of the rotor shop to reduce the travel time of parts through the shop during the repair and overhaul process, according to Tom Leinneweber, production flight chief with the 546th Propulsion Maintenance Squadron. The six-month-long effort reduced monthly component travel within the shop by about one-third — from 7.49 miles to 5 miles — and freed up 450 square feet. During the process, tool inventory also was reduced by $97,000.
The number of "mission impaired capability, awaiting parts," or MICAP, items also decreased dramatically, from 859 at the end of FY 2003 to three at the end of the second quarter of FY 2004. All for an upfront investment of $300,000, he said.
The massive renewal project of their F100 neighbors even yielded a dividend for the F110 and F108 engine business units. They were moved to "redesigned" areas with new flooring, lighting and overhead steel.