HW6.1: Fault Tree Analysis

This problem focuses on the functional success or failure of a simplified airplane consisting of two major independentsubsystems: the propulsion subsystem and the electrical-power supply subsystem. In this problem, you are asked to focus on the failure of this airplane, formulate the problem as a fault tree in which the top event is the failure of this airplane and identify all minimum cur-sets for the fault tree.

The propulsion subsystem of an airplane has three engines, and they can provide 100 units, 60 units and 60 units of thrust, respectively. Suppose that the airplane needs 150 units of thrust to be considered operational. The airplane uses electrical power to control all the equipment and instruments, except the propulsion subsystem. (Recall the simplifying assumption of independence of the two subsystems.) The electrical-power supply subsystem has built-in redundancy and has two identical modules. As long as one of the two modules works, the subsystem works. Each of the two modules consists of one dedicated battery and the required circuitry. Suppose that each battery has sufficient charge to last the entire flight in absence of its failure, so that the operation of the electrical-power supply subsystem does not need to draw power from any of the engines and hence does not depend on whether the propulsion subsystem works or not. (This is consistent with the independence assumption of the two subsystems.) Further suppose that all components fail independently.

Develop a fault tree to represent the system consisting of these components in which the top event is the failure of the airplane. Use E100, E60-1 and E60-2 to denote the three engines, B1 and B2 to represent the two batteries, C1 and C2 to represent the two circuitries, respectively. If needed, you can use P and E to denote the propulsion and the electrical-power supply subsystem, respectively.

Use the MOCUS Algorithm to find all minimum cut-sets. (A cut-set that is not contained in any other cut-set is a minimum cut-set. Only such minimum cut-sets are root causes. FTA identifies all root causes as input to FMEA.)