• A way to structure risk descriptions is the ECE Risk Expression, which gives a simple, clear description and assists risk assessment by identifying the adverse Event, likely Cause and the expected Effect. It is structured as follows:

    E – what is the adverse EVENT?

    C – what is the likely CAUSE? (hazards)

    E – what is the expected EFFECT? (outcomes / consequences)

    Example:

    • Event: aircraft control restriction
    • Likely Cause: loose tools in the cockpit
    • Effect: loss of control in flight 
    • Risk description: loose tools left in the cockpit cause control restriction which leads to loss of control in flight
    LIKELIHOOD: how often the Cause could potentially lead to the stated Event and result in the stated harmful Effect
    Likelihood level Frequency descriptor: use available evidence and appropriate judgment to estimate the potential likelihood level
    5 – Almost certain The Safety Risk (stated CEE) could occur at least once a month
    4 – Likely The Safety Risk could occur at least once a year
    3 – Possible The Safety Risk could occur once in 2 years
    2 – Unlikely The Safety Risk could occur once in 3 years
    1 – Rare The Safety Risk could occur once in 4+ years


    IMPACT: estimation of potential harm, to how many people as a result of the stated effect
    Impact level Descriptor: use available evidence and appropriate judgment to estimate the potential harm below
    First and second parties Third parties
    5 – Very High Such as following the loss of passenger carrying aircraft (est. 50+ fatalities) 10+ fatalities
    4 – High Such as following the loss of  passenger carrying  aircraft (est. 20-49 fatalities) 3-9 fatalities
    3 – Medium Such as following the loss of smaller passenger carrying aircraft (est. 10-19 fatalities) 1-2 fatalities
    2 – Low Such as following the loss of smaller passenger carrying aircraft (est. 6-9 fatalities) Any serious injuries
    1 – Very Low Such as following the loss of a small GA aircraft (est. 0-5 fatalities and/or any number of injuries) Any non-serious injuries


    Note 
    Each Impact Level is derived from the result from the First/Second Parties column AND/OR the Third Parties column.