The following is a battery level Fault Tree Analysis (FTA) of a primary power supply for an aircraft.
Non-Solid State Primary Power Supply
System Architecture
Fault Tree Analysis: Loss of Overcurrent Protection When Required
Fault Tree Analysis: Inability to Start Engine
Fault Tree Analysis: No Avionics Voltage When Required
Non-Solid State Primary Power Supply
System Architecture
Fault Tree Analysis: Loss of Overcurrent Protection When Required
Fault Tree Analysis: Inability to Start Engine
Fault Tree Analysis: No Avionics Voltage When Required
Conclusions
- For overcurrent protection, a BIT will reduce exposure time, consequently, despite the failure rate of the FET being worse than the fuse, the probability of the “loss of overcurrent protection when required” failure condition would be better for the new system than the old system
- FET and microcontroller required to mimic response of fuse to hard and soft shorts
- In the event of a hard short, it is possible for the FET to be damaged before it trips?
- Control of FET via a microcontroller will allow for parallel and series arc protection
- FET and microcontroller, in addition to overcurrent protection, can provide switching