TBM Case Study - Republic Airways: Keeping Aircraft Flying with LeanSigma
TBM Consulting Group, April 22, 2009
A regional air carrier uses lean to decrease planned maintenance cycle times and lower logistics costs associated with overnight maintenance.
Client: Republic Air is a regional carrier, based in the Midwest, that operates flights for companies such as American, Delta, US Airways, Continental, Midwest Airlines and United.
Challenge: Republic Air wanted to improve the scheduled maintenance process by reducing the amount of time an aircraft spent in the maintenance cycle. Reducing the maintenance cycle by five days was the equivalent of adding an aircraft to the fleet.
Solution: Republic Airways teamed up with TBM to implement lean and conduct shop floor and business process kaizen events. Using these lean methodologies, the company was able to maintain safety while improving the efficiency of the C-check maintenance and reduce overall cycle time by creating standard work, establishing workload leveling, and implementing 5S.
Results: The preliminary C-Check kaizen work centered on the “open up and inspect” part of the C-check process, which is all of the work up to the start of actual repairs. With some very basic kaizen work, the airline was able to remove one full day from that process. This included a 66 percent reduction in walk time, an 80 percent reduction in time spent locating parts, a 36 percent reduction in floor space, and a 22 percent reduction in lead times. As the company delves further into its processes with lean, it expects to make even greater improvements.
A Routine Check-up
Airlines are required to regularly take aircraft out of service for scheduled heavy maintenance, a requirement that isn’t taken lightly. Heavy maintenance, known as C-check, can remove an aircraft from service for anywhere from five days to two weeks. Airlines make money when aircraft are flying, so finding approaches to making the maintenance process more efficient while also increasing the quality of that process means that airlines can improve their revenue without sacrificing safety or quality.
A C-check consists of three phases. When an aircraft enters a maintenance hangar for a C-check, it is completely gutted—everything from inside the aircraft is removed, including the cockpit, the galley, the lavatories, the seats, the overhead bins, the floorboards, and the headliners. Once the aircraft has been completely “opened” then it must be cleaned inside and out to prepare it for inspection.
The inspection phase requires two or three people, who use checklists to examine each section of the aircraft. What the checklists require depends on the usage of the aircraft prior to that inspection.
Aircraft arrive at the maintenance hangar with a list of known maintenance items that must be completed, for example, items that have reached their maximum use life and must be replaced. The inspection process generates another list of unplanned maintenance items that must also be addressed.
The third phase of the process is “close up,” where all maintenance and repairs have been completed and everything is put back in the aircraft to ready it for use.
The kaizen process was also approached in phases. The initial part of the work focused on the open up and inspect process, looking at how long it took to open up the aircraft and get it cleaned and inspected and ready to move into the repair phase. This was basic kaizen work that involved a lot of 5S, establishing visual controls, and improved parts management to help drive productivity. In this phase, the company’s goals were to review and map the current-state process, reduce “open up” lead time, and develop a performance management process. The results obtained during this first phase showed the promise of future gains through continued application of lean tools and kaizen.
Additionally, the process had just a 77 percent on time record while at the same time of 350 hours of overtime every two weeks.
Next, the kaizen team prepared a spaghetti diagram of the current-state open up process. They found that the walking time alone during open and close consumed 5 hours. Searching for parts during close ate up another 7.5 hours. The problem was that while parts were stored on shelves and in bins, which were labeled, they weren’t necessarily stored in any sort of logical order so that when it came time to put them back in the aircraft a lot of time was wasted looking for the proper parts.
A Kaizen Prescription
To address this problem, one of the first things the kaizen team did was to create a new set of racks and rolling containers that were identified and stored by aircraft section. Containers were also tailored to accommodate certain items, such as overhead bins. As the interior was torn down, the parts were placed in order in these racks and bins so that when it came time to put them back on the aircraft, all anyone had to do was work in reverse order through the same racks and bins to find the needed parts for the appropriate section of the aircraft. Each cart was labeled and contained a bill of material that stated exactly what was in the cart and where it goes in the aircraft. By tailoring carts for specific parts, the risk of parts damage was also minimized. This example of creating a visual workplace and reducing waste by using 5S made a huge difference in the amount of time that was wasted walking and looking for parts. At the same time, the team looked at ways to improve the flow of parts to and from the aircraft by reworking the floor plan and storage locations for the carts and bins.
The team also created a “Safety, Quality, Cost, and Delivery” (SQCD) board on which they recorded both planned and unplanned work hours, how many “squawks” (rejects) were found on a particular aircraft, and what the maintenance cycle time was, and they were able to see some significant reductions in turnaround time. These may seem like relatively small changes, but the result was to reduce the time the aircraft spent in the maintenance hangar by a day. In revenue terms, one day is a big step closer to the goal of reducing maintenance time by five days. Five days is the equivalent of one whole aircraft, worth $1 million, that was then available to fly and generate revenue.
Here a Part, There a Part
Although not truly a part of the C-check process, the airline also used kaizen to address some overnight maintenance issues. In the normal course of events, aircraft will arrive at a final destination at the end of that day—the overnight base. There is standard maintenance that is performed on aircraft during the brief overnight “rest” period, but due to faulty business processes often the airline found that the needed parts weren’t in the right locations. This meant having to courier parts from one overnight base to another in order to have the aircraft ready to fly on schedule. Obviously the cost of couriering parts around the country can quickly add up.
In this case, Republic Air used a business process kaizen (BPK) to address parts movement and replenishment at overnight bases. One very successful BPK event centered on the large backlog of purchase orders and the lack of daily turnover for parts ordering. By taking a segmentation approach and assigning different parts ordering to different people or groups, the company was able to start turning purchase orders daily. This was a huge step toward solving the courier challenge because one reason overnight bases were running out of needed parts was a lack of timely ordering of those parts
Some small but significant changes in the process around parts ordering enabled the airline to realize a tremendous savings in the logistics costs involved with parts couriering.
Onward and Upward
The next big efficiency push planned for the C-check process is managing planned and unplanned repairs. This is not straightforward and will require concentration on routing standardization and creating flow in the actual repair process. Given the age of this particular fleet of aircraft, total required repair hours are divided about evenly between planned and unplanned repairs. This means that if an aircraft requires 1,000 hours of total work, only half of that is known about when the aircraft arrives in the maintenance hangar. An additional 500 hours worth of work will be generated from the inspections. This creates an additional level of complexity because fully half the work cannot be anticipated before the aircraft arrives, so the challenge will be to create better flow in spite of that huge unknown factor.
One strategy being considered is to look at the types of unplanned repairs that are being repeated from aircraft to aircraft. If certain unplanned repairs are required in a majority of the aircraft, then it makes sense to automatically plan for those repairs, even if they aren’t part of the standard checklist. This will involve revisiting some of the assumptions and parameters on which the planning system is based and then working out a process for sequencing those repairs. This is the next big piece to be worked on.
Another area that will be tackled in future events is managing for daily improvement (MDI). The challenge in the aircraft repair process is that cycle, or takt times for aircraft repairs must be measured in hours or days. For example, removal and replacement of an engine requires something like 25 hours. Thus we have to take a different approach to MDI so that line leaders and supervisors understand how to know whether at the end of the shift, or midway through the shift, they are on schedule. The concept of an hour-by-hour chart changes to something more like a shift-by-shift chart in this type of business, so the company will need to take a more creative approach to some of these problems. But kaizen and continuous improvement embrace creativity, so it’s entirely possible for even organizations with unique situations to make the power of kaizen work for them.
Taking Off
Clearly Republic Air is just in the earliest stages of its lean journey, but already it has found ways to improve quality and safety, save time, and reduce costs. Savings in walking time, parts location, and lead time mean that maintenance crews need to put in less overtime, while also getting aircraft through the repair process more quickly and efficiently. This means that more aircraft can be serviced in one location and that the aircraft are in the air longer, which means greater revenue for the airline. If Republic Air can gain this much from those first small steps on a lean journey, imagine how high it can fly once lean becomes a way of life.
Physical Fitness Report
The first step for addressing C-check efficiency was to map the current state and identify problems and wasteful practices. Among the issues that caused increased costs and reduced efficiency were the following:
- Excess walking during “open up and close” process
- Parts storage (including risk of damage to parts and time spent finding parts)
- Time spent locating tools
- Cannibalization of parts
- Time spent cleaning the aircraft—varying definitions of “clean”
- Time required to label parts—a necessary non-value added process
- Poorly defined standard work
- Missed defects (i.e., defects that were found at close)
- Lack of metrics
- Mechanic turnover and new mechanic training
- Lack of workload balance
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