What is the difference between a contributing factor and a probable cause?

• A. Probable cause is the primary reason; contributing factors are additional conditions that increased risk or severity.
• B. They are the same.
• C. Contributing factors are the primary cause.
• D. Probable cause is always a human error.

Answer: (A)

In an investigation, the probable cause is the primary factor that started or directly led to the sequence of events causing the accident. Contributing factors are other conditions or actions that increased the risk or severity of the outcome but aren’t the main driver. So, the probable cause is the central issue you’d address to prevent a repeat, while contributing factors are the surrounding conditions that made the situation worse or more likely. For example, a cockpit crew’s mismanagement of airspeed during approach might be the probable cause, while fatigue, poor crew coordination, and high workload could be contributing factors that aggravated the situation. This distinction helps investigators prioritize corrective actions: fix the primary cause, and also mitigate those additional factors to reduce risk in the future.