Architecture Level Safety Analyses for Safety-Critical Systems

Table 1

FHA report.

Component	Error	Hazard description	Functional failure	Operational phases	Severity	Likelihood	Comment
speed_sensor	“Failure on Failure”	“Faulty speed values”	“Loss of sensor readings”	“Acquire”	Critical	Probable	“Speed values are read as faulty”
speed_sensor	“Failed on Failed”	“Failure of sensor”	“Sensor failed”	“Acquire”	Catastrophic	Frequent	“Is a major hazard. Pilot cannot estimate the speed due to sensor failure”
throttle	“Failure on Failure”	“No command inputs due to actuator failure”	“Faulty or no commands”	“Output”	Critical	Remote	“Becomes a major hazard if there are command inputs to the actuator”
throttle	“Failed on Failed”	“Faulty actuator”	“Actuator in failure state”	“Output”	Catastrophic	Frequent	“Is a major hazard. Pilot cannot control the PowerBoat with proper throttle”
interface_unit	“Failure on Failure”	“Faulty or no input values and commands”	“Loss of actuator input values”	“Input”	Critical	Probable	“Becomes a major hazard if there happens to be faulty input values”
interface_unit	“Failed on Failed”	“Failure of actuator”	“Actuator in failure state”	“Input”	Catastrophic	Frequent	“Is a major hazard. Pilot cannot set proper speed value or input commands”
display_unit_inter	“Failure on Failure”	“Improper display due to faulty values or commands”	“Faulty values or commands on display”	“Output”	Marginal	Remote	“Remote possibility with display showing faulty values or commands”
display_unit_inter	“Failed on Failed”	“Display unit not working properly”	“Faulty display unit”	“Output”	Marginal	Remote	“Not a major hazard”