RooT Cause Analysis (RCA)

by Christopher Vallee from the TapRooT® RooT Cause Analysis People

System Improvements, Inc.238 S. Peters RdKnoxville, TN 37931865.567.0378vallee@taproot.com

In Honor of Our Service MembersOur members of the United States Military continue to support and defend our country with honor.

The faces used for this presentation are actual members of the U.S. Military.

Please take a moment to honor our military members (past and present).

2

When you hear Root Cause Analysis…

What is it?

Who uses it?

When do people use it?

What is it NOT used for?

3

A Little about Chris Vallee

Teach Root Cause Analysis Facilitate investigations to include industrial

injury and accidents, medical events, quality issues and equipment failures.

Human Factors in Psychology Background 18 years in Aviation from the Air Force to

Commercial Aircraft Assembly But has RCA always been part of my life??

4

Life of An Aircraft Fuels Mechanic... 24+ Years Ago

And RCA?

5

Let's look at the F-16 Aircraft Fuel SystemFuel Capacity: 7,000 pounds internal; 12,000 pounds with two external tanks

6

Typical Problem = Fuel Imbalances

Auto-Trim designed to correct aft heavy imbalances.

When the fuel difference is above/below the normal values parts of the red paint on the AL pointer become visible.

7

A Typical Day for an F-16 Fuel Systems Mechanic

MOC, I am coming in with a slow to transfer external left wing tank.

Roger that, we will have Fuel

Cell debrief you.

8

A Typical Day for an F-16 Fuel Systems Mechanic

Fuel Cell, we have a fuel

transfer issue with SW 456.

Roger that, we will send Airman

Vallee to start the RCA.

9

A Typical Day for an F-16 Fuel Systems Mechanic

An RCA?????

An RCA???

10

When Equipment Breaks…..

What is the proper term to use by the mechanic when called to fix a problem?

Troubleshoot

Trace and correct fault

See what’s broke

RCA

11

A Typical Day for an F-16 Fuel Systems Mechanic

Roger that, we will send Airman Vallee to debrief

the pilot and troubleshoot the problem.

• Trust me, when I started working F-16’s, I was not taught the term “Root Cause Analysis”.

• Is RCA really that different? Does it differ from true equipment troubleshooting? Is it confused with “Broke-Fix”?

12

Step 1: Debriefing the Pilot

Which option is the right way to debrief:

AAsk the pilot to tell you what

they saw and did?

BStart using a troubleshooting

fault tree to ask questions first?

13

Step 1: Debriefing the Pilot

Tell me about how the fuel transferred.

Ask the pilot to tell you what they saw and did?

• Let the pilot tell you what he/she knows• Don’t interrupt• Don’t corrupt the debriefing with your own biases• Interrupt too much and the pilot will shutdown. (Yes, I did this

more than once early in my career!)

14

Step 1: Debriefing the Pilot

Do you need to be a fuels systems mechanic to debrief a pilot on a fuels problem?

Could anyone take good notes if the fuel systems mechanic was not available?

What are the con’s and pro’s of both?

15

Step 1: Debriefing the Pilot

In this particular case the pilot told us this:

“When I took off I had a full load in my internal and external fuel tanks. Took off in afterburner and 30 minutes later, I noticed that my left external wing tank had more fuel than my right external wing tank.” 16

Step 2: Troubleshooting the Aircraft

• The Fuel Systems Mechanic removed the left external tank, replaced and tested the defective tank.

• The defective tank tested good and the aircraft flew and came down with another “slow to transfer left external tank” with the new tank installed.

• Why? What went wrong? 17

Step 2: Troubleshooting the Aircraft

Expert Troubleshooting and effective RCA have similarities in that they:

1. Do not remove the components from the system prior to testing.

2. Test the components in the same environment as they failed in when the defect occurred. 18

Step 2: Troubleshooting the Aircraft• The Fuel Systems Mechanic tested

the defective left external tank on the aircraft this time.

• The defective tank tested good, the aircraft was allowed to fly and again came down with another “slow to transfer left external tank”.

• Why? What went wrong?

19

Step 2: Troubleshooting the Aircraft

Expert Troubleshooting and effective RCA have similarities in that they:

1. Use schematics to map out the flow of the process.

2. Verify statements received during debrief against system design.

20

Step 2: Troubleshooting the AircraftThe 3rd time they used a schematic and traced the fuel flow.

Simple: Fuel must have space for fuel to transfer into. The left internal wing tank was receiving fuel from the right external wing tank that had a failed fuel shutoff valve.While this was a type of aft heavy, the differential was not enough to trigger the auto-trim.

21

Summary of the Good RCA Hints

I did not realize it 24+ years ago, but I had started my path to RCA without a name for it:

1. Ask the pilot to tell you what they saw and did?◦ Let the pilot tell you what he/she knows◦ Don’t interrupt◦ Don’t corrupt the debriefing with your own biases◦ Interrupt too much and the pilot will shutdown.

2. Do not remove the components from the system prior to testing.

3. Test the components in the same environment as they failed in when the defect occurred.

4. Use schematics to map out the flow of the process.

5. Verify statements received during debrief against system design.22

Step 3: Do we Troubleshoot the Valve Failure now?

• Was the valve defective before install?

• Did the airman install it incorrectly?

• Did it break during transport to the aircraft?

• Why brainstorm this, why not do a proper RCA to figure out what happened?

23

Is this the First Trigger to start an RCA? Is an RCA and Troubleshooting the same? Good Troubleshooting is needed to find

out what happened to a component.

The evidence must be collected on the spot before disturbed.

But does Troubleshooting stop at the fix and not why it occurred?

What is the probability of this happening again?

24

RCA Cautions before going forward1. Your root cause analysis is only as good as the info you collect.

2. Your knowledge (or lack of it) can get in the way of a good root cause analysis.

3. You have to understand what happened before you can understand why it happened.

4. Interviews are NOT about asking questions.

5. You can’t solve all human performance problems with discipline, training, and procedures.

6. Often, people can’t see effective corrective actions even if they can find the root causes.

7. All investigations do NOT need to be created equal (but some investigation steps can’t be skipped).

25

Let’s break down the F-16 Fuel Issue

The question is why did it take 3 actions to find the actual problem?1. The pilot did not indicate what the other

fuel tanks contained (quantity wise)

2. The external fuel tanks were tested either off the aircraft or with an empty internal fuselage.

26

What if we used a structured process to Troubleshoot the Fuel Issue?

27

Steps 1-2: Create a SnapCharT® during or after the debrief

Aircraft Fueled to 12,000 lbs

by POL Mechanic

Pilot pulls aircraft up in afterburner

Aircraft consumes fuel

Right external Tank empties faster than left external tank

Internal right and left wings

stay full

Left external tank continues

to transfer very slowly

28

Define the actions or lack of actions that caused the transfer issue or made it worse:

The Right External Fuel Tank Shutoff Valve did not close.

The Defective Right External Fuel Tank Shutoff Valve was not identified during troubleshooting

Steps 3: Define the Causal Factors

29

Now we can take each Causal Factor through a root cause tree analysis:

Equipment Difficulty: The Right External Fuel Tank Shutoff Valve did not close.

Human Performance Difficulty: The Defective Right External Fuel Tank Shutoff Valve was not identified during troubleshooting

Steps 4: Root Cause Analysis

30

Contact me for an introvallee@taproot.com

The TapRooT® Root Cause TreeAnd

Equifactor®

Steps 4: Root Cause Analysis

31