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Michael Ohler, Ph.D., and Jean-Marc Urbani

Michael Ohler, Ph.D., and Jean-Marc Urbani’s default image

Quality Insider

Lessons of Near Failure in Fuel-Efficient Air Transport

First, carefully define how to measure improvement

Published: Tuesday, November 29, 2011 - 16:17

The objective of our improvement project was to contribute to more fuel-efficient air transportation. As explained in this article, transportation by air comes with strong regulatory constraints, and there’s a need for careful stakeholder management. We nearly abandoned the project when the efforts we had asked people to make were not quantified in the primary metric that we used. The breakthrough was only achieved when together, with careful stakeholder management, we reduced “noise” signals in that primary metric to be able to “listen to the voice of the process.” It’s what we learned from this experience that we want to share with you, a wider community.

The carbon footprint—increasingly in the focus of the logistics industry

According to the Air Transport Action Group, greenhouse gas emissions from human activities in 2010 totalled 29 gigatonnes (3,500 kg per person on the planet). About 540 megatonnes (2%) of these were related to air traffic. With the growing concern about the carbon footprint of doing business, the fuel burned for transportation is a key focus of the logistics industry.

During the structural planning of its lean Six Sigma program, TNT Airways S.A., a wholly owned subsidiary of TNT Express, launched a project to investigate and reduce the amount of fuel burned for transporting fuel. Although a driver of a car may never entertain the notion of driving with a half-full gas tank to save fuel, the careful planning of carried fuel is an important part of the diligence required to operate an aircraft.

In the past, TNT’s efforts to reduce the air traffic-related carbon footprint mainly focused on a fuel-efficient fleet, optimized loading and route planning, speed adjustment, and other best industry practices. A limit had been established for the amount of landing fuel carried, and it was monitored by observing the percentage of aircraft that landed with more fuel.

Appreciate regulatory and human factors and create a “burning platform”

To the lay person, carrying less landing fuel may seem an easy solution. However, there’s more to the reduction of fuel carried. First of all, landing with “zero fuel” is illegal. Regulations also require a certain percentage of the calculated “trip fuel” to be on board as a contingency for any unforeseen event. The equally required “holding fuel” allows aircraft to circle the airport in a holding pattern for a given amount of time, and the reserve must be sufficient for landing at a previously determined alternate airport. Besides these requirements, the stress pilots undergo when flying with minimum fuel must also be considered: Who would go for a 60-minute submarine dive with not a single extra minute of air?

A simple regression analysis for fuel consumption performed on flight data recorded over more than a year showed that on average, more than 1,000 kg of the total fuel consumed per long-haul flight could be saved if a certain type of aircraft landed with only the legally required minimum fuel in the tank. Even if that savings is a small percentage of the total fuel consumed, it correlates to an impressive quantity of carbon dioxide and operational expenses. This potential improvement further motivated the setup of the lean Six Sigma project.

Focus on demonstrating feasibility

Through financial control the potential savings were assessed to be as high as $401,700 per year. Given that the assessment had been done on a small part of the flights, it might have influenced the project goal setting to be overly ambitious. Management knew that broad initiatives like “solve world hunger” rarely succeed. Therefore, the project’s scope adhered to certain routes and to one type of aircraft. Given the ease of tracking, understanding, and communicating the amount of fuel in the tank at landing, it was chosen as a primary metric to measure progress.

The define, measure, analyze, improve, control (DMAIC) approach was chosen for the project. According to TNT Express’s experience using DMAIC for its worldwide lean Six Sigma program, the discipline of this approach prevents teams and stakeholders from overlooking important aspects, and it helps all stakeholders stay involved in the progress of the project. As a first step of the measure phase, a detailed “as is” process map was created to allow understanding of how a given amount of fuel ended up in the tank of an aircraft. Special attention was taken to draw this process map based on observations of how people “really” worked rather than taking the “should be” process from the handbooks. With that understanding and a wealth of measurements, careful analysis revealed several improvement levers. These involved multiple departments and also touched on people’s habits acquired throughout years in the business.

Significant changes in the process but no visible improvement

Having understood the cause-and-effect relation between changes in the process and the aircrafts’ fuel at landing, the team was confident about meeting the project’s target. However, day after day and week after week, improvement did not manifest in the observed data as expected. On the contrary, when staring long enough at the data-points one might even see degradation in the performance (figure 1). This caused consternation in the project team, frustration among people involved in the process, and mockery by some not-fully-engaged stakeholders and bystanders. After failed efforts to force improvement through a focus on behavior, the team went back to studying the data and the underlying assumptions.

Figure 1: Individual value plot of the landing fuel. Each data-point corresponds to one flight. (Click here for larger image)

Eureka! The new primary metric

The team got to thinking: Hadn’t the planning of alternate airports been excluded from the project’s scope? But in the fuel-at-landing data, their impact was still included. For any given route, the holding and contingency contributions to the total fuel on board varied with the transported freight (a heavier aircraft needs more fuel). All this added to the variation observed in the “fuel at landing.” In other words: The “signal” the team was looking at had “drowned in the noise” of such contributions. Changes in the policy concerning alternate airports had recently lead to some of them being at greater distance (associated with more fuel on board when aircraft did not land there). With this understanding the team deducted the contribution of alternate airports from the fuel-at-landing data (figure 2).

Figure 2: Individual value plot of the landing fuel minus alternate airport contribution (Click here for larger image)

Removing the contribution of the alternate airport in the data made the impact of the previously taken actions immediately visible. We would like to point out at this time that one should not underestimate the influence on a high-level meeting to demonstrate live the difference between plotting “landing fuel” (figure 1) vs. plotting “landing fuel minus alternate” (figure 2): The team did not need to plan communication—it “just happened.” That visible success has given the lean program a well-earned boost, and it gave management the justification that was needed to roll out the fuel-savings process to other fleets of aircraft and other routes. At the writing of this article, these activities are under way.

The lessons learned from this project are, first:
• In a project’s framework, carefully define how to measure improvement—i.e., carefully define the primary metric
• Tune the measurement system to the scope of the project
• Carefully track this metric throughout the project

And second:
• Only by following a disciplined approach (i.e., DMAIC) are teams allowed to revisit the assumptions in case of failure and deliver improvement and clear evidence of improvement. The resulting transparency allows building a proper control system, which is the precondition for lasting success.


About The Author

Michael Ohler, Ph.D., and Jean-Marc Urbani’s default image

Michael Ohler, Ph.D., and Jean-Marc Urbani

Michael Ohler, Ph.D., principal at BMGI EuropeMichael Ohler, Ph.D., is a certified Six Sigma Master Black Belt, a lean and innovation expert, and principal with Breakthrough Management Group International (BMGI), a consultancy specializing in lean Six Sigma and other disciplined methods. Ohler has collected experience in the consumer-goods, logistics, shipbuilding, semiconductor, and micromanufacturing industries. He holds a doctorate in experimental physics and has also been teaching university and post-doctoral courses in France, Italy, and Brazil.

Jean-Marc Urbani, Six Sigma Green Belt at TNT Airways S.A.Jean-Marc Urbani is a flight operations performance engineer at Belgium-based TNT Airways S.A. and a certified Six Sigma Green Belt. He has served TNT in strategic supply chain management, aircraft fleet development, ground instructor performance, and as a flight dispatcher. Urbani holds a master of science in biomechanics and has taught biology and biochemistry in Belgium high schools.