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process.
COMMENTS: The PHA is relatively easy to use and takes little time. Its significant power to impact
risk arises from the forced consideration of risk in all phases of an operation. This means that a key to
success is to link the PHA closely to the Operations Analysis.
EXAMPLES: The following (Figure 1.1.2B) is an example of a PHA.
List the operational phases
vertically down the page. Be sure
to leave plenty of space on the
worksheet between each phase to
allow several hazards to be noted
List the hazards noted for each
operational phase here. Strive for
detail within the limits imposed by the
time you have set aside for this tool.
FAA System Safety Handbook, Appendix F
December 30, 2000
F-7
Figure 1.1.2B Example PHA
MOVING A HEAVY PIECE OF EQUIPMENT
The example below uses an operation analysis for moving a heavy piece of equipment as the start
point and illustrates the process of building the PHA direct from the Operations Analysis.
Operation: Move a 3-ton machine from one building to another.
Start Point: The machine is in its original position in building A
End Point: The machine is in its new position in building B
ACTIVITY / EVENT HAZARD
Raise the machine to permit positioning of
the forklift
Machine overturns due to imbalance
Machine overturns due to failure of lifting device
Machine drops on person or equipment due to failure
of lifting device or improper placement (person lifting
device)
Machine strikes overhead obstacle
Machine is damaged by the lifting process
Position the forklift Forklift strikes the machine
Forklift strikes other items in the area
Lift the machine Machine strikes overhead obstacle
Lift fails due to mechanical failure (damage to
machine, objects, or people)
Machine overturns due to imbalance
Move machine to the truck Instability due to rough surface or weather condition
Operator error causes load instability
The load shifts
Place machine on the truck Improper tiedown produces instability
Truck overloaded or improper load distribution
Drive truck to building B Vehicle accident during the move
Poor driving technique produces instability
Instability due to road condition
Remove machine from the truck Same factors as “Move it to the truck”
Place machine in proper position in
building B
Same factors as “Raise the machine” except focused
on lowering the machine
1.1.3 THE ""WHAT IF"" TOOL
FORMAL NAME: The “"What If"” tool
ALTERNATIVE NAMES: None.
FAA System Safety Handbook, Appendix F
December 30, 2000
F-8
PURPOSE: The "What If" tool is one of the most powerful hazard identification tools. As in the case of
the Scenario Process tool, it is designed to add structure to the intuitive and experiential expertise of
operational personnel. The "What If" tool is especially effective in capturing hazard data about failure
modes that may create hazards. It is somewhat more structured than the PHA. Because of its ease of use,
it is probably the single most practical and effective tool for use by operational personnel.
APPLICATION: The "What If" tool should be used in most hazard identification applications, including
many time-critical applications. A classic use of the "What If" tool is as the first tool used after the
Operations Analysis and the PHA. For example, the PHA reveals an area of hazard that needs additional
investigation. The best single tool to further investigate that area will be the “What If” tool. The user will
zoom in on the particular area of concern, add detail to the OA in this area and then use the "What If"
procedure to identify the hazards.
METHOD: Ensure that participants have a thorough knowledge of the anticipated flow of the operation.
Visualize the expected flow of events in time sequence from the beginning to the end of the operation.
Select a segment of the operation on which to focus. Visualize the selected segment with "Murphy"
injected. Make a conscious effort to visualize hazards. Ask, "what if various failures occurred or
problems arose”? Add hazards and their causes to your hazard list and assess them based on probability
and severity.
The "What-If" analysis can be expanded to further explore the hazards in an operation by developing
short scenarios that reflect the worst credible outcome from the compound effects of multiple hazards in
the operation.
Follow these guidelines in writing scenarios:
·  Target length is 5 or 6 sentences, 60 words
·  Don't dwell on grammatical details
　
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