ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 1

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 2

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 3

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page Contents • Definition • Types of Root Causes and why they are important • General steps to perform the RCA • History of RCA • The 5 Whys technique • The Pareto Principle • Fault Tree Analysis • Event Tree Analysis • Bow Tie Analysis ROOT CAUSE ANALYSIS (RCA) DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 4

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page Definitions Root Cause: The fundamental reason for an event, which if corrected, would prevent recurrence. (The last cause in the chain.) Contributing Cause : Any cause under the control of the enterprise that may have contributed to the non-compliance but, if addressed, could not by itself have prevented the problem Root Cause Analysis and Corrective Action Process: An effective tool for finding the true or actual cause of events, facilitating effective corrective action and preventing their recurrence. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 5

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page Definitions Specific Corrective Action: Action taken to correct or improve the condition noted in the event by changing the direct cause or the direct cause and the effect. Corrective Action Plan (CAP): A plan submitted in response to findings. The CAP outlines how the organisation proposes to address findings and ensure on-going compliance. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 6

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page What is RCA? • Root Cause Analysis (RCA) is a method that is used to address a problem or non-conformance, in order to get to the “root cause” of the problem. • It is used so we can correct or eliminate the cause, and prevent the problem from recurring. • RCA is simply the application of a series of well known, common sense techniques which can produce a systematic, quantified and documented approach to the identification, understanding and resolution of underlying causes. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 7

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page • Collective term that describes wide range of approaches, tools, and techniques used to uncover causes of problems • Some RCA approaches are geared more toward identifying true root causes than others • Some are more general problem-solving techniques, and • Others simply offer support for the core activity of root cause analysis • Enables us to determine what happened, why it happened and what to do to reduce the likelihood that it will happen again ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 8

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page • Root Cause Analysis has been called a reactive process: - It is performed after the adverse event occurs. • However, once Root Cause Analysis is applied thoroughly: - It soon becomes a proactive mechanism. - It predicts problems before they occur. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 9

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page 1. Physical causes: e.g. defective equipment 2. Human causes: e.g. maintenance not performed properly 3. Organisational causes: e.g. no clear process in place 3 Types of (Root) Causes DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 10

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page • Tackling the root causes may solve many symptoms • Cost efficiency • Organisational efficiency Why Root Causes are important DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 11

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page General steps to perform the RCA Evaluate solutions and solve the problem Collect the data Identify the possible causes Identify the root causes Define the problem DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 12

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page Now – Year 2010s • Aviation legislation now requires Root Cause Analysis ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 13

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page What does EASA say? ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 14

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page What does ICAO say? • From the ICAO Safety Management Manual (SMM) ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 15

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page History – 5 Why’s Developed by Sakichi Toyoda (founder of Toyota) • Used for development of Toyota’s manufacturing processes in 1958 ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 16

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page History – MORT NASA - Management Oversight Risk Tree (MORT) • Complex, time consuming and expensive • Reserved for the highest risks and most • mission critical activities ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 17

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page History – MORT ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 18

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page History – ASRS • Aviation Safety Reporting System (ASRS) introduced in 1975 • ASRS is funded by the FAA, but administered by NASA ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 19

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: • Some techniques to analyze problems, identify causes, and/or find solutions are listed below. Not all techniques are appropriate for every problem. Sometimes a combination of techniques may be more effective. Before using any technique, check that it is appropriate for the scope of the problem and the size/complexity of your organization. Example of RCA Tools: • Five Why’s • SHEL Model • Cause and Effect Diagram (Fishbone/Ishikawa) • Management Oversight and Risk Tree Analysis • Event and causal factor chart • Causal Mapping • Bow Tie Analysis ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 20

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: • Energy Flow / Barrier Analysis • Fault Tree Analysis / Failure Event Tree • Failure Mode and Effects Analysis • Six Thinking Hats • Pareto Analysis • Matrix Diagram • Force-Field Analysis We will explore a few of these tools. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 21

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page Possible RCA Techniques: ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 22

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: 5 Why’s • The 5 Whys is a questions-asking method used to explore the cause/effect relationships underlying a particular problem. • Ultimately, the goal of applying the 5 Whys method is to determine a root cause of a defect or problem. • 5 Why's typically refers to the practice of asking, five times, why the failure has occurred in order to get to the root cause/causes of the problem. One of the most important aspects in the 5 Why approach - the real root cause should point toward a process. You will observe that in most cases, the process is not working well or that the process does not even exist. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 23

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page ROOT CAUSE ANALYSIS 5 Whys Process Flow Chart DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 24

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: 5 Why’s – Rules of Performing the 5 Why’s ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 25

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: 5 Why’s Limitations: • Tendency for investigators to stop at symptoms rather than going on to lower level root causes. • Inability to go beyond the investigator's current knowledge - can't find causes that they don't already know. • Lack of support to help the investigator to ask the right "why" questions. • Results aren't repeatable - different people using 5 Whys come up with different causes for the same problem. • Tendency to isolate a single root cause, whereas each question could elicit many different root causes. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 26

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page ROOT CAUSE ANALYSIS – 5 Whys Technique Here’s an example Toyota offers of a potential 5 Whys that might be used at one of the plants DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 27

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: 5 Why’s Example: Controlled MOE copy in hangar is revision 11, current revision in library is revision 12 (the finding) Why? – MOE revision 12 is not implemented in the hangar copy. (First why) Why? – MOE revision 12 package was never received in the hangar. (Second why) Why? – It got lost in company mail. (Third why) Why? – Co-mail department does not have full traceability of shipments which makes lost mail possible. (Fourth why) Why? – Company’s internal mail process does not require traceability of shipments. (Fifth why, a root cause) ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 28

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: 5 Why’s – Group Activity Situation - An apprentice engineer at an aircraft maintenance organization installed the landing gear pins in the main landing gear so the aircraft could be jacked up for a retraction test of the nose gear. When the gear switch was selected up, the main and nose gear retracted. The main jacks (which had been lowered but not removed) punched through the bottom of the wings as the aircraft came to rest on its belly on the hangar floor. The incident took place at 3:00 AM and the aircraft was to be on line at 6:00 AM. 1. Tabulate the handout using the 5 Why Technique 2. Identify 3 short term corrective actions and 3 long term corrective actions ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 29

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Pareto Principle • In the late nineteenth century, Italian economist Vifredo Pareto noted that most of the wealth of the community was held by a small proportion of the population • From this insight he developed the 80/20 rule, or the Pareto Principle, which, in the case of community wealth, meant that about 20% of any population owns about 80% of the wealth • His principle is widely observed to be true in many fields of human activity • It can be applied to the topic of risk analysis in the process industries. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 30

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Pareto Principle Examples of the principle’s applications in an industrial context include: • 80% of a company’s sales come from 20% of its customers. • 80% of a company’s sales are made by 20% of the sales force. • 20% of the workers are involved in 80% of the accidents. • 20% of the equipment items cause 80% of the facility shutdowns. • 20% of a company’s products will account for 80% of the total product defects. • 80% of weight loss during a diet is achieved with the first 20% of the effort ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 31

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Pareto Principle • In each of the above examples, an “important few” or the “vital few” have a great impact on the business, whereas the “unimportant many” are much less significant • Therefore, a safety manager should direct his or her program toward that minority of incident-creating workers. • Spending time on the “unimportant many” is not likely to have much benefit. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 32

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Pareto Principle – Importance Ranking • Pareto Principle expresses itself in an industrial context in the form of “importance ranking.” Example • Assume an electrically driven pump in a facility has a probability of failure to start of 0.1, i.e., it will not start one times in ten. • Management may decide that this failure rate is too high; they wish to reduce the rate to lower than 0.02, i.e., one time in 50. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 33

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Pareto Principle – Importance Ranking A survey of facility records for this and similar pumps is made. The following reasons for a pump of this type failing to start immediately are identified: • Operator busy elsewhere • Electrical power not available • Start switch does not work properly • Pump motor fails • Discharge valve sticks closed • Operator starts the wrong pump. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 34

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Pareto Principle – Importance Ranking The number of occurrences of each of the six steps listed above is shown in the table below. The events are sorted by importance ranking. ROOT CAUSE ANALYSIS Analysis of Pump Failing to Start Reason for Failure Number of Incidents % of Total Cumulative % Rank Operator busy elsewhere 123 60.6 60.6 1 Electrical Power not available 44 21.7 82.3 2 Motor fails 18 8.9 91.1 3 Operator starts the wrong pump 12 5.9 97.0 4 Start switch does not work 5 2.5 99.5 5 Discharge valve sticks closed 1 0.5 100.0 6 Total 203 100.0 DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 35

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Pareto Principle – Importance Ranking • The data in the table show that the items “Operator busy elsewhere” and “Electrical power not available” contribute 82% of the overall failure rate. • In terms of the Pareto Principle, these two items are the “important few,” with the others being the “unimportant many. Therefore, to improve the system reliability, all efforts should be directed toward ensuring that the operator has sufficient time to start the spare pump • If this failure mode can be removed from the system, the system reliability will increase by 60%. If the second high ranked item, “Electrical Power Not Available” can also be eliminated, the system reliability will improve by more than 80% over the initial value • However, if management works on correcting one of the “unimportant many,” say the “Start switch does not work,” the overall failure rate moves from 0.1 to 0.098, a trivial improvement ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 36

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Fault Tree Analysis • Is a widely used top down, deductive failure analysis in which an undesired state of a system is analyzed using Boolean logic ("true”/”false” values with operators "and”, "or” and "not”) to combine a series of lower-level events. • This analysis method is mainly used in the fields of safety engineering and reliability engineering to understand how systems can fail or have failed, to identify the best ways to reduce risk. • Results of each event are presented in a tree-like diagram using logic symbols to show dependencies among events ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 37

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Fault Tree Analysis • Events are related to mechanical components, software and/or electronics used in the design of the product • Top level, undesired events are the primary topic being studied in the FTA • FTA provides valuable trouble shooting information when applied to problem solving • FTA diagram often utilizes failure probabilities at each level, from components and software to the undesirable Top-level event. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 38

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Fault Tree Analysis – How to make a Fault Tree 1. Define the undesired event: the primary fault or failure being analysed 2. Deduce the event’s immediate causes 3. Keep stepping back through events until the basic causes are identified 4. Construct a fault tree diagram 5. Evaluate your fault tree analysis ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 39

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Fault Tree Analysis ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 40

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Fault Tree Analysis ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 41

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Event Tree Analysis • Is a forward, bottom up, logical modeling technique for both success and failure that explores responses through a single initiating event and lays a path for assessing probabilities of the outcomes and overall system analysis. • This analysis technique is used to analyze the effects of functioning or failed systems given that an event has occurred • ETA is a powerful tool that will identify all consequences of a system that have a probability of occurring after an initiating event that can be applied to a wide range of systems. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 42

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Event Tree Analysis • ETA uses the same logical and mathematical techniques as FTA • However, whereas a Fault tree analyses how an undesirable top event may occur, an Event tree considers the impact of the failure of a particular component or item in the system, and works out the effect such a failure will have on the overall system risk or reliability • Event trees use an inductive approach, whereas fault trees are deductive. Event trees were developed for the nuclear industry. They are much less used in the process industries. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 43

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Event Tree Analysis • An ETA shows all possible outcomes resulting from an accidental (initiating) event, taking into account whether installed safety barriers are functioning or not, and additional events and factors • By studying all relevant accidental events (that have been identified by a preliminary hazard analysis, or some other technique), the ETA can be used to identify all potential accident scenarios and sequences in a complex system • Design and procedural weaknesses can be identified, and probabilities of the various outcomes from an accidental event can be determined. ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 44

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Event Tree Construction 1. Identify (and define) a relevant accidental (initial) event that may give rise to unwanted consequences 2. Identify the barriers that are designed to deal with the accidental event 3. Construct the event tree 4. Describe the (potential) resulting accident sequences 5. Determine the frequency of the accidental event and the (conditional) probabilities of the branches in the event tree 6. Calculate the probabilities/frequencies for the identified consequences (outcomes) 7. Compile and present the results from the analysis ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 45

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Event Tree Analysis ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 46

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Event Tree Analysis ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 47

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Combining Event Trees and Fault Trees ROOT CAUSE ANALYSIS • Fault Trees and Event Trees can be combined • The gates in the event tree are treated as top events of multiple fault trees • The figure shows how the fault trees are linked into event trees DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 48

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Combining Event Trees and Fault Trees ROOT CAUSE ANALYSIS • Event Trees and Fault trees can also be linked as shown in the next slide • The Fault tree (which is left to right rather than the normal bottom to top) generates a top event • This event is, in turn, the initiating event for the event tree that follows • The bow tie technique uses the same structure DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 49

Property of Dviation Training Centre For Training Purpose Only QA & RCA Page RCA Tools: Combining Event Trees and Fault Trees ROOT CAUSE ANALYSIS DTC - Root Cause Analysis ISS 01 REV 00 Date : 14 October 2021 50