Rotate a Tree to start your project

During the Logical Thinking Process training course (June 2015), Bill Dettmer took us through the whole process and the associated tools at each step.

The process starts with the famous Goal Tree, assess the current situation and focus on critical root causes with the Current Reality Tree (CRT). Conflict Resolution Diagram (AKA Evaporating Cloud) may be used to resolve conflicting objectives and find solutions (called “injections”) to turn the CRT into a Future Reality Tree (FRT).
But in order to get to the future state, some obstacles will have to be removed or by-passed. This is done with the help of a Prerequisite Tree (PRT).

Once the PRT is ready, it is a kind of logical proof of concept. In order to turn this POC into real action, Bill shows how rotating a Prerequisite Tree gives an almost ready-to-use project network. Therefore, Critical Chain Project Management (CCPM) is the sixth tool of the Logical Thinking Process.

By the end of the demonstration, Philip Marris highlights the “beauty” of this process, patching one of Critical Chain Project Management “weaknesses”: how to ensure what is to be executed as a project is meaningful? He does this by giving a sadly funny and true example in aeronautic industry.

About the authorView Christian HOHMANN's profile on LinkedIn

Schragenheim’s concise history of constraints

The definition of a constraint in Theory of Constraints (TOC) has varied as the corpus grew and matured. Still today it is confusing for newbies to sort out what is meant with “constraint”, depending how they got their basics in TOC.

Thanks to Eli Schragenheim, one of TOC’s founding fathers, and the related post on his blog, the reader can understand how and why the definition varied over time.

I strongly recommend to read Eli’s post: A concise history of constraints

Performance improvement: simple things can earn big results

Silly things can cost a lot in terms of productivity and output.  In this video interview, Philip Marris  asks me about lessons learnt while helping a pharmaceutical plant to improve productivity and deliver drugs to patients faster.

It is about how simple actions solve those silly small problems and bring big results at literally no cost.

Bandeau_CH40_smlView Christian HOHMANN's profile on LinkedIn

Stuck with continuous improvement?

This post is a kind of post scriptum to “Improving  50% is easy, improving 5% is difficult” in which I described 3 stages of improvement and ended stuck with continuous improvement as the Return On Investment (ROI) in C stage was not worth going on.

Continuous Improvement

Now assume it is not possible to radically change the process (kaikaku), because for instance it has been approved by some authority (customer, regulatory…), being on the verge of C stage does not necessarily mean this is permanent.

If the limitation to improve further are skills or experience, the situation may change over time as trainings are delivered, experience is accumulated or necessary skills hired.

If the limitation is the cost of some solution, like changing material or buying some equipment, this too may change over time and become affordable / change the ROI, thus providing opportunities to improve further without changing everything.

What wasn’t possible or reasonable at some point may become possible and meaningful.

It is therefore important to revisit the assumptions and conclusions of the improvement workshops /projects periodically and check if some conditions have changed in a favorable manner.

This is also why, after a Value Stream Mapping and/or some diagnostic was done, designing the future state should first attempt to design a perfect process. This frees the designers from actual constraints and limitations and can lead to interesting solutions.

In a second step, the constraints and limitations are brought back in and the ideal solution trimmed down to what is possible given the limitations, e.g. state of industry vs. state of art, technological or economical limitations, limited know-how, etc.

But all brainstorming ideas and drafts of a perfect process/ideal state should be kept in a kind of think tank and periodically checked. It may happen that one of the ideas, impossible at a given moment can now be envisioned, thanks to some evolution.

Bandeau_CH8View Christian HOHMANN's profile on LinkedIn

What is Kaikaku?

Kaikaku is one of these Japanese words which found their way into the Lean lingo. Kaikaku is usually translated into “radical change” or breakthrough.

my tiny Japanese dictionary proposes “reform”, “renovation” and “reorganization”.

“Doing” kaikaku means introducing a major change in a process in order to drastically improve it (quantum leap). Kaikaku is therefore “opposed” to Kaizen, which is incremental, small steps, improvement.

Kaizen is often praised for being a safe and low-cost improvement way. By changing only one thing at a time and trying allows to observe the effect of the change and to learn from this experience.

Kaikaku will discard much if not all from the existing solution and introduce big change(s). The usual set of parameters and previous accumulated learning may not be useful anymore. The new process is likely to be unstable until all new influencing parameters are fully understood and under control. Therefore Kaikaku is feared as risky.

Yet Kaikaku is not all bad. Once Kaizen has given all that can be reasonably achieved (timely and in terms of Return Of Investment), a radical change may be the only option to improve further.

Kaikaku is often understood as innovation, bringing in some high-tech or top-notch technology.

Indeed, if a manufacturer changes his production way from cutting away material to additive manufacturing (3D printing to make it simple), it is a disruption and potentially a quantum leap in productivity, efficiency, lead time, customizing, etc.

Kaikaku can be more mundane than that, like reorganising the way of operating for instance.

I remember working for Yamaha music, assembling home cinema receivers and CD players, when we heard the headquarter was planning a switch from long linear conveyor belt assembly lines into small autonomous cells, it was kaikaku because it was disrupting decades of streamlined production.


Chris Hohmann in Yamaha’s headquarter, Hamamatsu city

Many Kaizen events (also called kaizen blitz) are in fact small kaikakus where drastic changes are made in short time. Those events are not the best way for try-and-learn, it’s more often one expert moderating a workgroup and leading it to a disruptive solution, hence kaikaku.

If you’d like to share your thoughts or experience, use the comments below.

View Christian HOHMANN's profile on LinkedIn

TOC, Lean and aviation MRO

In a previous post, “CCPM helps shorten aircrafts MRO”, I explained the benefits of Critical Chain Project Management (CCPM) for reducing the aircraft downtime during their mandatory and scheduled MRO.

If CCPM is great and helps a lot meeting the challenge, it will not squeeze out every potential improvement, thus time reduction, on its own.

As I explained in my post Critical Chain and Lean Engineering, a promising pair, “What CCPM per se does not is discriminate added-value tasks and non added value, the wasteful tasks listed in a project in a Lean thinking way.

Conversely, if wasteful tasks remain in the project network, chance are they will be scheduled and add their load (and duration) to the project.

That’s why in aviation MRO (as well as in other businesses), Critical Chain Project Management will not be used as a stand alone but in conjunction with other approaches, like Lean and Six Sigma.

Lean mainly will help to discriminate value-added from non value-added tasks, especially those on the Critical Chain, making them high priorities to optimize, reduce or eliminate.

We did not differently when we started with our client Embraer and while in their service center, I placed Philip Marris in front of the camcorders to present, in situ, two books related to TOC, Critical Chain and Lean in aviation MRO (aircraft Maintenance, Repair and Overhaul).

Note: Critical Chain Project Management is part of the Theory of Constraints Body of Knowledge, hence the title of this post where “TOC” is referring to CCPM.

Chris Hohmann

View Christian HOHMANN's profile on LinkedIn

CCPM helps shorten aircraft MRO


Aircrafts have to undergo periodic Maintenance, Repair and Overhaul (MRO). This is mandatory in order to insure the aircraft’s airworthiness and overall safety. During these inspections and repairs, the aircrafts are grounded.

For the owners and operators, the shorter the turnaround time*, the better. An aircraft is a huge investment and the ROI is only when it can be used in service.

*the time the aircraft is grounded, usually counted in weeks for longer in-depth inspections.

Yet aircraft operational availability is not only a question of Return On Investment, think about relief and the lives saved by medivacs or military forces brought closer to their spot during a crisis.

When an aircraft comes in for its scheduled maintenance, according to the type of inspection (ranging from Check A to Check D, according the depth and importance of inspection, the amount of time or usage…  (see Wikipedia)

The process is scheduled like a project as many tasks can’t be done prior to some others, e.g. access some hydraulic pipes before stripping the surrounding frame.

It is therefore common to use Project Management tools and techniques to organize, carry-out and monitor the whole process.

The challenge

Shortening the turnaround time is therefore a challenge for the service centers, not only to please and retain their customers, but also to attract new ones in order to grow their business and improve their profitability.

Of course the challenge is to be met while remaining compliant to the severe regulations and specific constraints, taking no chances with quality nor safety.

Furthermore, “findings” – unexpected defects of potential issues found once the aircraft is under inspection – or sudden customers requirements may add unscheduled workload.

In the traditional project management way, each task is estimated for its duration and a cautious (and generous) margin of time added. The service centers want to keep their committed due date, even if findings or any other random events (parts shortages, supplies problems…) arise.

It is therefore no surprise that major Checks ground an aircraft for weeks.

The new approach

It wasn’t long before some service centers spotted the improvement potential (turnaround time reduction) with Critical Chain Project Management (CCPM). Delta TechOps, Lufthansa Technik, US Navy and Air Force, French SiAé are cases I’m aware of.

Compared to traditional Critical Path Method (CPM), Critical Chain Project Management takes the resources’ limited capacities into account at once and has a completely different approach regarding margin of time. In short, all margins are shortened based on a statistical rationale and a share of it put into a global protective time buffer.

Chris Hohmann

CCPM provides also a simple but very effective visual indicator to monitor both project’s achievement and protective buffer consumption, thus indicating instantly when the project may be late. This robust and early warning allows project managers to focus on a very limited number of issues instead of trying to control every single task.

This allows also the mechanics to work in a quieter atmosphere, an important additional benefit in a trade that considers human stress as a major risk for quality.

CCPM has proven great for consistently meeting due dates and often shortening a whole project duration compared to its original estimations.

Our client testimony

I was fortunate to be involved in Embraer’s Business Jets Service Center’s project to reduce turnaround time in Paris (Le-Bourget) and pleased to produce a series of videos of their testimonies about their achievement.

In this video, Sébastien Albouy, Director of Embraer Executive Jets Services center in Paris Le Bourget executive airport, explains how Critical Chain Project Management helped to drastically shorten the aircraft turnaround time, thus increasing aircraft availability and the center’s capacity.

>Related: TOC, Lean and aviation MRO

View Christian HOHMANN's profile on LinkedIn

TOC-based decision for best product mix

Theory of Constraints (TOC) provides a framework to identify, exploit, set pace and elevate* the constraint, or put in simpler words: identify the bottleneck in the process and make the best with it.

*Identify, exploit, subordinate, elevate and prevent inertia are known as the “five focusing steps” of Theory of Constraints.

In this constraint or bottleneck-centered approach, the aim is to give this peculiar resource a privileged treatment as it controls directly the whole system Throughput, hence the profit.

But working on the constraint capacity is not enough to maximize Throughput, the product mix is also very important.

Theory of Constraints therefore developed Throughput Accounting in order to cope with issues when making decisions based on traditional accounting and a new way to make decisions regarding product mix.

This video is a 49mn course about TOC-based decision for best product mix by Prof G. Srinivasan, IIT Madras


View Christian HOHMANN's profile on LinkedIn

Improving  50% is easy, improving 5% is difficult

It is with this enigmatic sentence that one of my Japanese mentors introduced the growing difficulty with continuous improvement.

What it means is that at the beginning of an improvement program or when starting in a new area, the first and usually the easiest actions bring big improvement, hence the “easy” 50%.

This is also known as “reaping the low hanging fruits“, another metaphor for earning easy results with very reasonable effort.

Once these easy and quick wins are done, what is left to improve requires more effort, more time or more investment.

The improvement curve is therefore asymptotic and it is increasingly difficult and expensive to squeeze out the last improvement potential, hence the “difficulty to improve (the last) 5%”

The graph shows the 3 stages of improvement

Continuous ImprovementA: quick and easy, few actions, visible results, big leverage, usually a leap in performance. Excellent Return On Investment (ROI).

B: second stage in continuous improvement, more effort and investment is necessary, but the ROI is still worth it

C: “chasing the decimals” : huge efforts and investment are required to squeeze out the last potential. The ROI is not worth it.

At some point, the Return On Investment (ROI) is not worth going on. This means that improving further what exists and/or the way it has been done until now is no more meaningful. What is required is a breakthrough, a radical change.

This is where kaizen (continuous incremental improvement) must give way to kaikaku (radical change), or in other words: as the old process or usual way cannot be further reasonably improved, it must be totally reconsidered.

Yet in many cases this is the upper limit of improvement as the process cannot be changed. Too often redesigning the product or process is not possible:

  • Design has to be approved or the new product/process has to undergo lengthy and costly qualification (pharma, automotive, aerospace…)
  • Remaining life is not long enough to pay for
  • Facilities are not flexible, can’t be modified
  • The modification would break some contract

The continuous improvement is often limited by options and decision made in early design and development stages, a fact I discuss in >this post<

Related: Stuck with continuous improvement?

Bandeau_CH11View Christian HOHMANN's profile on LinkedIn