5 Whys vs Fishbone vs ICAM vs Apollo RCA
Root Cause Analysis
Method Comparison
- 5 Why - fast, simple linear problem solving
- Fishbone (Ishikawa) - brainstorming of possible causes
- ICAM - regulatory incident investigation framework
- Apollo RCA - detailed cause-and-effect analysis for complex problems
When to use each RCA Tool
Quick Overviews
5 Whys – A simple questioning technique suited to straightforward, relatively linear problems where the causal chain can be tested quickly. Rarely solves complex problems.
Fishbone (Ishikawa) – A visual brainstorming tool used to organise possible causes into categories. Useful for exploring possibilities, but additional evidence is needed to establish whether a proposed cause actually contributed to an event. Forces teams to “vote” on favorite solutions or popular causes.
ICAM – A structured, systems-based approach common in aviation, mining, and rail industries. It is particularly useful where organisations have established ICAM governance and reporting requirements. ICAM is strong on incident classification but can miss underlying causal pathways.
Apollo Root Cause Analysis (ARCA) – A structured cause-and-effect methodology suited to complex, recurring or significant problems involving multiple interacting causes and the need for evidence-based causal validation. This method uncovers true root causes and develops effective, lasting solutions.
Where Apollo RCA Differs
Apollo RCA is designed to represent multiple cause-and-effect relationships rather than reducing a complex event to a single linear chain.
The method encourages teams to:
- develop causal relationships explicitly
- distinguish assumptions from evidence
- identify gaps in the current explanation
- consider multiple interacting causes
- link proposed solutions back to identified causes
This makes Apollo particularly useful where the problem is complex, recurring, high consequence or cross-functional.
Comparison Guide
Ready Reference Chart
| Criteria | 5 Whys | Fishbone / Ishikawa | ICAM | Apollo RCA |
|---|---|---|---|---|
| Typical time | Minutes to ~1 hour | ~1–2 hours | Several hours or longer | Several hours to multiple sessions depending on complexity |
| Analysis style | Linear questioning | Categorised brainstorming | Regulatory incident investigation | Cause-and-effect pathways |
| Typical problem complexity | Low | Low to moderate | Moderate to high | Moderate to high / complex |
| Team size | 1-2 | Small group | Multi-disciplinary | Multi-disciplinary |
| Evidence requirement | Low to moderate | Low during brainstorming | Moderate to high | Moderate to high |
| Documentation | Notes / short record | Diagram + notes | Investigation report | Cause-and-effect chart + investigation record |
| Training required | Minimal | Minimal | Formal ICAM training commonly required | Formal Apollo Facilitator training required to run, no training required to participate. |
| Main strength | Speed and simplicity | Broad generation of possible causes | Regulatory governance structure | Detailed causal logic across multiple pathways |
| Main limitation | Oversimplifies complex problems and misses cause pathways | Brainstorming does not prove causation. Don't imagine what happened. | Can be resource-intensive and process-heavy. Focuses on regulatory action rather than fixing the problem | Requires more preparation, evidence gathering and facilitation effort than simpler methods. |
| Best use | Simple/local issues | Exploring possible causes | Incident investigation within ICAM-based organisations | Complex, recurring, significant or multi-causal problems |
Which RCA Method Should You Choose?
Use 5 Whys when:
- the issue is simple
- consequences are limited
- causality is relatively linear
- evidence can be checked quickly
Use Fishbone when:
- you need to explore possible causes
- the event is not yet well understood
- broad team brainstorming is useful
Use ICAM when:
- your organisation requires ICAM
- the event is safety/incident focused
- governance and incident classification are important
Use Apollo RCA when:
- the problem is recurring
- multiple causal pathways are likely
- consequences are significant
- the problem spans several systems or teams
- management needs a defensible causal explanation
Stop Addressing the Symptoms. Start Solving the Cause
Why Organisations Choose Apollo RCA
Apollo RCA is designed for organisations that need a structured approach to complex, recurring or high-consequence problems. Its cause-and-effect framework helps teams make investigation logic visible, test important assumptions against evidence and develop solutions linked to identified causes.
Globally Recognised
Recognised globally as one of the most effective incident investigation methods
Expert Training
Delivered by experienced facilitators with engineering and reliability backgrounds.
Flexible Delivery
Flexible training formats: online sessions, in-person workshops, and customised in-house delivery.
Professional Certification
Certification included, with access to RealityCharting software and exclusive investigation templates.
When Apollo RCA Training Makes Sense
If your organisation regularly deals with complex, recurring or high-consequence problems, building internal Apollo RCA capability can provide a more structured approach than relying on ad hoc investigation methods.
Root Cause Australia delivers practical Apollo RCA training for engineering, reliability, maintenance, operations and safety teams.
Participants learn to:
- define problems clearly
- build cause-and-effect charts
- test important assumptions against evidence
- identify multiple causal pathways
- use RC Pro™
- develop solutions linked to identified causes
- participate in or facilitate structured RCA investigations
Root Cause Analysis FAQs
Is 5 Whys a root cause analysis method?
Yes but not reliable for complex problems. It is a simple problem-solving method suitable for relatively straightforward issues, but it may not provide enough depth for complex or multi-causal problems.
When should I use Fishbone instead of 5 Whys?
Fishbone is useful when the team needs to explore a broad range of possible causes rather than follow one linear questioning chain.
Can I use more than one RCA method?
Yes. Organisations often use simple methods for low-consequence issues and escalate to more structured methods when complexity, consequence or recurrence increases.
Which method should my team use?
Use the simplest method capable of addressing the problem adequately. Complex, recurring or high-consequence problems usually justify a more structured investigation approach.
Is ICAM better than Apollo RCA?
Neither is universally “better”. ICAM is well suited to organisations using regulatory incident-investigation frameworks, while Apollo RCA is particularly useful for detailed cause-and-effect analysis of complex or recurring problems.
Why is Apollo RCA suited to complex problems?
Because it can represent multiple interacting causal pathways and allows important causal relationships to be tested against evidence. You don't vote on a favorite root cause, you discover it.
Is Apollo RCA suitable for every problem?
No. Simple, low-consequence problems may only require a lightweight method such as 5 Whys. Apollo RCA is particularly valuable where the problem is complex, recurring, significant or involves multiple interacting causes.
