Arm 55 Chapter 2 Incomplete Draft Version

Front 1

definition: root cause

Back 1

The event or circumstance that directly leads to an occurrence

Front 2

definition: root cause analysis (RCA)

Back 2

A systematic procedure that uses the results of the other analysis techniques to identify the predominant causes of the accident

Front 3

acronym: RCA

Back 3

root cause analysis

Front 4

the 4 basic characteristics of root causes

Back 4

• Expressed as a specific underlying cause, not a generalization
• Can be reasonably identified
• Must be expressed as something that can be modified
• Must produce effective recommendations for prevention of future accidents that stem from the root cause

Front 5

the 5 broadly-defined RCA approaches

Back 5

• Safety-based (originated from accident analysis and occupational safety & health)
• Production-based (evolved from quality control procedures for industrial manufacturing
• Process-based (like production-based, but includes business processes)
• Failure-based (from failure analysis; used primarily in engineering and maintenance
• Systems-based (combines above four approaches with change management, risk management, and systems analysis concepts)

Front 6

definition: causal factors

Back 6

The agents that directly result in one event causing another

Front 7

the 4 steps in the RCA process

Back 7

1. Data collection
2. Causal factors charting
3. Root cause identification
4. Recommendation determination and implementation

Front 8

definition: failure mode and effect analysis (FMEA)

Back 8

An analysis that reverses the direction of reasoning in fault tree analysis by starting with causes and branching out to consequences

Front 9

acronym: FMEA

Back 9

failure mode and effect analysis

Front 10

definition: failure mode

Back 10

The manner in which a perceived or actual defect in an item, process, or design occurs

Front 11

definition: effects analysis

Back 11

The study of a failure’s consequences to determine a risk event’s root cause(s)

Front 12

definition: indenture level

Back 12

An item’s relative complexity within an assembly, system, or function

Front 13

definition: local effect

Back 13

The consequence of a failure mode on the operation, function, or status of the specific item or system level under analysis

Front 14

definition: next-higher-level effect

Back 14

The consequence of a failure mode on the operation, function, or status of the items in the indenture level immediately above the indenture level under analysis

Front 15

definition: end effect

Back 15

The consequence of a failure mode on the operation, function, or status of the highest indenture level

Front 16

FMEA’s primary goal: ensure customer safety & production of quality products through these 5 outputs:

Back 16

• Improvement in the design of procedures and processes
• Minimization or elimination of design characteristics that contribute to failure
• Development of system requirements that reduce the likelihood of failures
• Identification of human error modes and their effects
• Development of systems to track and manage potential future design problems

Front 17

the 5 steps of the FMEA process

Back 17

1. Determine scope and objective(s)
2. Assemble team
3. Define system components and their functions
4. For each component, identify potential causes and effects of failure
5. Develop responses to prevent or mitigate failure

Front 18

definition: criticality analysis

Back 18

An analysis that identifies the critical components of a system and ranks the severity of losing each component

Front 19

the 4 categories of failures used in criticality analysis

Back 19

Category 1 – results in excessive unscheduled maintenance
Category 2 – results in delay or loss of operational availability
Category 3 – results in potential mission failure
Category 4 – results in potential loss of life

Front 20

definition: risk priority number (RPN)

Back 20

The product of rankings for consequence, occurrence, and detection used to identify critical failure modes when assessing risk within a design or process

Front 21

acronym: RPN

Back 21

risk priority number

Front 22

the 3 components of a RPN

Back 22

• Consequence – rate the severity of the effect of the failure
• Occurrence – rate the likelihood that the failure will occur (failure rate)
• Detection – rate the likelihood that the failure will NOT be detected before it reaches the customer

Front 23

definition: criticality

Back 23

A combination of the risk priority number elements of consequence and occurrence, used to determine the relative risk of a failure mode and effects analysis item

Front 24

4 advantages of FMEA

Back 24

• Widely applicable to many different system modes
• When used early in design phase, can reduce costly equipment modifications
• Can improve quality, reliability, and safety of a product or process; can improve organization’s image and competitiveness by possibly reducing scrap in production
• Emphasizes problem prevention by identifying problems early in the process and eliminating potential failure modes

Front 25

3 disadvantages of FMEA

Back 25

• When used as top-down tool, may only identify major failure modes in system
• Other analysis methods might be better suited for this type of analysis
• Analyzing complex multilayered systems can be difficult and tedious with FMEA; studies that are not adequately controlled and focused can be time-consuming and costly

Front 26

definition: fault tree analysis (FTA)

Back 26

An analysis that takes a particular system failure and traces the events leading to the system failure backwards in time

Front 27

acronym: FTA

Back 27

fault tree analysis

Front 28

p(S and T and U)

Back 28

p(S) x p(T) x p(U)

Front 29

p (H or I or both)

Back 29

p(H) + p(I) - p(H and I)
p(H) + p(I) - [p(H) x p(I)]

Front 30

the 5 steps of FTA

Back 30

1. Identify a specific harmful event to construct the fault tree; be as specific as possible so that events contributing to the failure can be fully described
2. Diagram, in reverse order, the events that led to the harmful event
3. Determine whether the events leading to any other event on the fault tree are connected by an “and” gate or an “or” gate
4. Evaluate fault tree to determine possible system improvement
5. Suggest risk control measures to management that can treat the identified hazards

Front 31

3 underlying assumptions of FTA

Back 31

• All components exist in only 1 of 2 conditions (success/operational vs. failure/not operational)
• Any system component’s failure is independent of any other component’s failure
• Each failure has an unchanging probability of occurrence

Front 32

5 limitations of FTA

Back 32

• If uncertainty about probabilities of underlying/base events, probability of top event will also be uncertain
• Important pathways to top might not be explored if causal events are omitted from the fault tree
• Because fault tree is static, it may need to be reconstructed if circumstances or procedures change
• Human error is difficult to characterize in a fault tree
• “Domino effects” or conditional failures are not easily included in a fault tree

Front 33

4 steps of a 5 Whys analysis

Back 33

1. Completely describe the specific problem under investigation
2. Ask why that particular problem occurred; determine the answer
3. If answer does not reveal problem’s root cause, ask why it occurred
4. Repeat steps 2 & 3 until root cause of original problem is determined

Front 34

3 advantages of 5 Whys analysis

Back 34

• Can determine root cause of a problem
• When several root causes are found, can help determine relationship among them
• Usually does not require statistical analysis or data collection

Front 35

5 disadvantages of 5 Whys analysis

Back 35

• Investigators tend to stop analysis after first determination instead of asking additional questions to discover problem’s root cause
• Investigators tend to focus on only one answer to each question
• Organizations sometimes do not help the investigator ask the right why questions [what?]
• An uninformed investigator cannot ask relevant questions
• Different investigators will discover different causes for the same problem (this can be an advantage if several root causes exist for the same problem)

Front 36

9 steps of developing a fishbone diagram

Back 36

1. Team agrees on problem statement
2. Write problem statement on far right of diagram, encircle, draw horizontal arrow from L to R pointing to statement
3. Team brainstorms major causes of problem
4. Facilitator writes categories of causes as branches off main arrow
5. Team brainstorms possible specific causes (may use 5 Whys)
6. Facilitator writes specific causes as branches off categories
7. For each specific cause, brainstorm sub-causes
8. Before ending, focus on areas with the fewest ideas
9. Develop and implement remedies to prevent recurrence of problem