The Red Queen effect on fighter jets

Looking through the glass of a solid execution model improves maintenance activities

Chakravorty cover

By Satya S. Chakravorty

The Red Queen effect refers to the conversation between the Red Queen and Alice in Lewis Carroll’s Through the Looking Glass, the sequel to Alice in Wonderland. In Through the Looking Glass, Alice realizes that she is running as fast as she can, but she is not getting anywhere relative to her surroundings. The Red Queen responds: “Here, you see, it takes all the running you can do to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!”

Simplistically, the underlying message is that continuous evolution is necessary to keep up with changing conditions. Initially, biologists applied this analogy to describe the evolution of species needed to increase the chances of survival in the dynamic environment. Specifically, the Red Queen effect provided logic for understanding how pathogens may maintain sexual reproduction in hosts to avoid extinction.

Subsequently, many theorists have used the notion of the Red Queen effect to explain behavior in various adaptive systems, ranging from organizational competitiveness to the sustainability of societies. In the process improvement context, the Red Queen effect is the ability of an organization to continuously evolve and sustain improvements in performance.

The Warner Robins Air Logistics Complex in Georgia adopted the concept of the Red Queen effect to evolve continuously and sustain improvements in its performance. The air logistics complex maintains or modifies operations on the C-5, C-17 and C-130 cargo aircraft and the F-15 fighter aircraft.

Typically, significant maintenance activities follow similar steps: disassembly (and inspection), repair (or modification), buildup and functional test. We will examine the Red Queen effect on F-15 maintenance and how, over time, the trends show a significant increase in speed (or reduction in flow days), a decrease in work-in-process (WIP) inventory, an increase in quality of finished products and a decrease in cost.

The execution model

The Red Queen logic is implemented by the Air Force Sustainment Center execution model, which is the practice of using science to move an organization. The execution model detailed in Figure 1 promotes achieving world-class status by improving the speed of aircraft maintenance.

While the focus is on speed, speed must be mindful of quality and safety. The execution model consists of eight horizontal bars that, taken collectively, operationalize the Red Queen effect to improve performance.

The first bar, “road to …” establishes the tone for achieving and sustaining the art of the possible results. Simplistically, the plan shows current and future targets, delineates milestones of achievements and develops an action plan to sustain performance improvements. The second bar represents “networks,” which lays out an electronic path (e.g., Concerto, a proprietary information system) to perform aircraft maintenance activities. The path consists of a sequence of task dependencies which includes well-defined predecessors and successors, and clearly identifies routing information to complete all aircraft maintenance activities.

The third bar, “gates/DBR,” provides control or stability in managing aircraft maintenance activities. Specifically, gates introduce breaks, or manageable chunks of work, through the networks, and DBR, which stands for drum buffer rope, controls the release of work, prevents multitasking (or stretching resources too thinly) and concentrates resources to gain speed. A schedule or drum is set for the constraint so that the constraint can dictate the pace of the system. The buffer is established prior to the constraint to protect the constraint from variations, while the rope is a communication mechanism to release or authorize work to the system.

The fourth bar, “release points,” establishes elaborate checklists or rules at gates for releasing work under the drum buffer rope to ensure steady progress in completing aircraft maintenance. The ideas promoted in the previous two bars emphasize controlled release, which is an important tenet of the theory of constraints (TOC) principles.

The fifth bar, “visual displays,” displays important information regarding aircraft maintenance performance (e.g., speed or quality) on the shop floor for the mechanics and the supervisors. The displays should be relevant, simple and an accurate reflection of how the aircraft maintenance is progressing. The sixth bar, “standard work” (scripting), delineates repeatable steps for accomplishing a task on the shop floor.

While a network establishes task dependencies, standard work, also known as scripting, breaks down the tasks into a sequence of steps that are more meaningful for a mechanic to use to complete the tasks. The concepts embedded in the previous two bars are anchored in lean principles.

The seventh bar, “tools/tech data,” emphasizes the importance of providing the right tools and equipment, along with appropriate technical orders. To avoid any delays in completing aircraft maintenance, when there is a discrepancy between a technical order and a task at hand, an engineering resolution must be found expeditiously by filing a noncompliance form.

The eighth bar, “touch time,” promotes keeping a mechanic’s hands on an aircraft. In order to increase the touch time, opportunities must be explored to improve supportability functions that could meticulously stage parts (e.g., fasteners), tools (e.g., torque wrench), consumables (e.g., gloves) and equipment (e.g., fuel quantity tester) close to the aircraft.

The Red Queen logic

Using the execution model, F-15 maintenance implemented Red Queen logic to evolve continuously. The objective is to sustain improvement performance, stay competitive and generate additional F-15 maintenance work.

The effort required modifications in almost every aspect of the F-15 processes, and it would impact the entire system’s workforce. In the past, many of these modifications were carried out haphazardly. Processes either did not exist, or processes were operated based on experience.

This time, the leadership decided to apply the execution model systematically. The F-15 team’s leadership consists of a director, two deputies and flight chiefs, who are responsible for running different areas of maintenance activities.

Leadership decided to establish a cross-functional team to apply the Red Queen logic to redesign many of their processes. The team consisted of management, process engineers, the transformation office and mechanics. The team recognized that the top four bars of the execution model, taken together, deal with macro decisions that affect F-15 maintenance.

For example, networks determine how every activity should be coordinated to complete F-15 aircraft maintenance. The team recognized that focused or smaller teams may be necessary to coordinate any alterations or upgrades in networks. The team also recognized that the bottom four bars of the execution model involve micro decisions that affect only parts or specific areas of the organization. These decisions and their outcomes may be different from one area to the other.

With maintenance leadership, the team coordinated implementing Red Queen logic using the execution model, which proceeded by using eight overlapping sequential phases.

The execution

Phase I, road to …: The F-15 maintenance’s leadership coordinated the determination of current and future targets. Leadership noted that after several months of excellent due date performance, declines started in late 2013, with performance particularly bad (grade of D+) from July 2014.

Numerous other problems affected many areas of F-15 maintenance. F-15 throughput was declining, and carry-over aircraft from previous years were in double digits, which meant fewer aircraft were available to fly missions. Several processes were out of control or there was lack of process synchronization, and many quality problems were threatening the future F-15 workload.

After understanding the current situation, the F-15 leadership proceeded to set improvement targets. There was general consensus that F-15 maintenance functions must show improvement in due date performance and sustain those improvements by the middle of 2015. Leaders agreed that F-15’s due date performance should be excellent (A+), and the target for improvement was set at 90 percent.

There was also consensus that throughput of F-15s had to increase and the WIP level should decrease through improved networks. Leadership developed milestones of improvements and a detailed action plan for improving performance.

Phase II, networks: The F-15 maintenance’s leadership focused on upgrading the network of maintenance activities. The purpose was to reduce WIP, gain resource concentration and increase speed.

The network provided an electronic footprint to complete aircraft maintenance activities. The footprint consisted of a sequence of task dependencies with clearly defined steps of predecessors and successors. Essentially, the F-15’s networks consisted of two overlapping lines. One involved programmed depot maintenance (PDM) of planes, where, every 18 months or so, each F-15 fighter jet visits Warner Robins maintenance for routine upkeep. The other involved rewire, or rewiring planes. PDM and rewiring were broken down into four steps. The end step is a gate, and within each step are milestones.

Pre-dock is the first step for both programmed depot maintenance and rewiring. After removing the fuel, workers strip the plane of most of its components, including engines, flight controls, ramps, doors and panels. They perform a detailed inspection of corrosion, cracks and high stress areas.

In the second step, both the PDM and rewiring lines go separate ways. For the PDM line, the second step is repair, where most repair activities are performed. For rewire, the second step is also repair, but this step includes upgrading electrical wiring.

For both PDM and rewire, the next two steps overlap. The third step is buildup, which consists of putting the aircraft together, assembling and replacing the engines, flight controls, ramps, doors and panels. The fourth step is post-dock, where green runs on the aircraft’s engines and flight controls are operated while the aircraft is still on the ground.

The aircraft then begins functional tests and a functional check flight. After passing the functional check flight, the aircraft returns to service. These steps are supported by parts routed from back shops, tooling of needed components, equipment, engineering, flight test, and de-paint and paint operations, as shown in Figure 2.

Phase III, gates/DBR: To break gates into manageable chunks of work, F-15 maintenance applied Little’s law. The law provides that the association between work in process (WIP), throughput (TH) and flow time (FT) can be stated as WIP = TH multiplied by FT. The definition of WIP is the average number of aircraft. TH is throughput per unit of time in days. And FT is the average time an aircraft spends in repair.

The law can be restated as FT = WIP multiplied by takt time, where takt time is the time interval between two successive productions of aircraft. For example, if maintenance handles 48 aircraft in 365 days, the F-15 PDM’s takt time is eight (365/48). If we want to establish the F-15 PDM’s target FT as 100 days and have a takt time of eight, the WIP requirement is 13 (100/(365/48)).

Please note that 100 days roughly translates into 125 calendar days, including the weekends. All gates have to be designed not to exceed an FT of 100 days and a WIP of 13 aircraft. For gate one, pre-dock, flow time is 17 days, taking into account all the milestones.

Using a flow time of 17 days, the pre-dock WIP for gate one is two (17/8) aircraft. Likewise, gate two’s repair WIP is five (37/8) aircraft. Gate three’s buildup WIP is three (24/8) aircraft. Gate four’s post-dock WIP is three (22/8).

Phase IV, release points: Release points that involved multiple activities were established at each gate, and these typically are reviewed by a master scheduler.

An elaborate checklist is used to review an aircraft at a gate, and the activities that must occur can be described in three categories. First, find out if all the requisite forms have been completed.

Examples include incoming aircraft field reports received, all technical changes/technical orders (TCTO) correctly identified, all parts ordered (form 95) and engineering changes processed (form 202).

Second, establish that all tasks are complete and no jobs left unfinished. In addition, all the technical books, which specify the jobs, are stamped, and all the supporting information technology systems have been updated. Third, ensure that all of the issues or problems were recorded. The problems may relate to equipment, tools, back shop operations, other concerns and possible opportunities for improvements.

Phase V: visual displays: Visual displays on the shop floor helped mechanics and supervisors gauge the progress of aircraft maintenance through the gates. If mechanics or supervisors don’t have information about how well they were performing relative to a gate’s requirements, they cannot assess if they were having a good day, a bad day or were somewhere in between.

Any shop floor control chart must connect the specific gate’s requirements with the daily work schedule. Even though Warner Robins Air Logistics Complex is a maintenance environment, management referred to this chart as a production control board. It is difficult, if not impossible, to display all the shop floor activities, so the production control board only included the major jobs.

The production control board is displayed prominently near the plane’s nose or in another conspicuous place. The script on the board must be large enough, and the board must have sufficient space for the mechanics to write notes on it detailing their progress. As mechanics start or complete a major job, they check the corresponding activity on the production control board. In addition, they can write about major issues or problems they encounter on the shop floor.

This helps speed up solutions. For example, if the mechanics are having problems related to tools, equipment or parts, schedulers or supervisors walking through the shop can quickly determine which aircraft needs immediate help.

Phase VI, standard work (scripting): Traditionally, mechanics followed different sequences of steps to complete many tasks, adding to the variability of aircraft maintenance environment. This led to routine delays, along with safety and quality problems.

Standard work or scripting is a repeatable sequence of steps needed to complete a task. Scripting establishes consistency, which increases speed and improves safety and quality. F-15 leadership initiated scripting to break down many of the tasks into a sequence of steps that mechanics could follow easily.

Scripting the process was not easy. Often, tasks included a complex sequence of steps, and mechanics didn't agree about which sequence provided the best outcomes. After several meetings and deliberations, however, the mechanics reached consensus and scripted many tasks throughout the F-15 network. Scripting significantly improved supportability functions, or the availability of parts, equipment and facilities.

Phase VII, tools/tech data: With engineering support, the F-15 maintenance program continually upgraded tools and equipment to gain speed and mitigate quality and safety problems.

At times there was considerable delay in obtaining an engineering resolution for two reasons. First, the process of obtaining the resolution was not streamlined, and second, engineering or tech support was inadequate. Delays frustrated mechanics because they could not add value or contribute toward aircraft maintenance, although they kept busy with other activities, such as cleaning the shop floor.

F-15 leadership worked on tightening the process of obtaining an engineering resolution. In addition, the F-15 maintenance program obtained additional engineering support.

Phase VIII, touch time: In order to increase touch time, F-15 leadership carefully studied how mechanics spent their time performing aircraft maintenance activities. The purpose was to identity opportunities for improvements, even if small, that would increase mechanics’ touch time. It is important to understand that small improvements made throughout the F-15 network, with hundreds of tasks being performed, could add up to large improvements.

Many such opportunities for improvements were pursued simultaneously. First, F-15 leadership explored ways to enhance supportability functions by staging parts and equipment closer to mechanics. This kept mechanics from wasting time looking for parts or equipment. Second, to reduce mechanics’ idle time, leadership installed better technology or provided laptops to facilitate faster accessibility to tech data. Third, minor adjustments or tweaking of the processes were done to improve touch time.

While individually these changes had a small impact of an hour or less, cumulatively they had an impact of a day or more.


Objective results from implementing the Red Queen effect were very encouraging.

As Figure 3 shows, the speed of completing programmed depot maintenance (PDM) and rewire has increased significantly. PDM flow days continue to decrease and are wavering around 125 days, compared with 200 days previously. Rewire flow days are fluctuating around 187 days compared with 270 days. The F-15 maintenance program’s WIP decreased from 44 to 24 aircraft, quality of finished products increased and the cost of maintenance decreased.

Subjective results from the Red Queen effect logic were also reassuring. In an effort to measure the F-15 maintenance program’s journey of improvement, leadership created a maturity matrix for all the bars in the Air Force Sustainment Center execution model.

The matrix is a subjective evaluation created by the leadership to gauge the program’s progress toward attaining world-class status. Values ranging from one to five are assigned to each bar. A value of one implies an organization is at an initial setup level, and a value of five implies world-class level. The change in score over time shows improvement or regression.

Figure 4 shows an example of a maturity matrix where most bars are increasing in value over time, implying progress toward attaining world-class status.

Two lessons stand out from pairing Red Queen effect logic with the execution model and its eight horizontal bars. The first lesson is that the top four bars (road to ..., networks, gates/DBR and release points) taken together deal with macro decisions, which often impact the whole organization. Meanwhile, the bottom four bars (visual displays, standard work (scripting), tools/tech data and touch time) cumulatively involve micro decisions, which generally impact only parts of the organization.

When leadership is contemplating macro decisions or establishing overall direction for an organization, management should consider input from everyone. Since macro decisions affect everyone, leaders need to present an effective message to their workforce at a set periodic interval, such as once every month. Macro decisions should be undertaken thoughtfully and implemented infrequently, about once every three years.

For micro decisions, not everyone needs to be involved, general consensus is not always necessary and these decisions can be implemented frequently, or about once every month.

The second lesson is that the execution model suggests a sequence to implement improvement strategies (theory of constraints, lean and Six Sigma). As operating conditions change, all organizations or systems become unstable or display a high amplitude of oscillations in their performance.

First, when oscillations are at high levels, gates/DBR or theory of constraints (TOC) concepts are used to stabilize the system. Application of TOC dampens these oscillations through controlled release of work or WIP reduction, and that gives rise to resource concentration and increased speed (or throughput).

Second, as the oscillations reach medium levels, visual displays or lean principles are more applicable. During this period, operations are still messy and variables are unknown. The lean tools identify value-added activities and non-value-added activities. Traditionally, there are seven categories of non-value-added activities or waste: overproduction, inventory, defects, motion, overprocessing, waiting and transportation. Applying the lean tools repeatedly removes the clutter, streamlines operations and makes the variables known.

Third, when the oscillations are reduced to low levels, or the system is stable and variables are known, engineering /Six Sigma principles are most applicable.

Satya S. Chakravorty is Caraustar Professor of Operations Management at Kennesaw State University. His Ph.D. in production and operations management is from the University of Georgia. His research has been published in more than 50 articles that include MIT Sloan Management Review and The Wall Street Journal.