Question

An aircraft system is modeled as being comprised of (3) independent subsystems - each critical - with reliability as follows

: – Electrical => 15% probability of failure

– Mechanical/Hydraulic => 10% probability of failure

– Fuel/Powerplant => 5% probability of failure

Question 1: What is the overall reliability of the aircraft system?

Two identical Electrical subsystems are installed side-by-side in a hot-swap backup configuration.

Question 2: Assuming all independent subsystem components have the same reliability as previously stated, what is the overall reliability of this modified aircraft system?

Answer 1

Answer:

1.

To determine the overall reliability of the aircraft system

Required probability = Probability of electrical survival * probability of mechanical survival * probability of fuel survival

substitute given values

= (1 - 0.15)*(1 - 0.10)*(1 - 0.05)

[since Probability(system failure) = 1 - P(system survival) ]

= 0.85*0.90*0.95

= 72.68%

2.

To determine the overall reliability of this modified aircraft system

Here if there are 2 same electrical subsystems are found then the probability of survival of at least one electrical system

i.e.,

= 1 - P(Both of them were failed)

= 1 - 0.15*0.15

= 1 - 0.0225

= 0.9775

Now the probability of system survival = Probability of electrical survival * probability of mechanical survival * probability of fuel survival

substitute given values

= 0.9775 * 0.90 * 0.95

= 83.58%