Originally Posted by Star Trek Viewer
Is a safe-life approach "safer" than a fail-safe approach, in your opinion, or is it the other way around? Just curious.
Personally I prefer fail-safe, but safe-life can have applications.
In a safe-life design, the product is designed to survive a specific "design life" usually with a reserve built in. So typically Airbus planes are designed to function for approximately 20 years. After which the plane is to be replaced, however the drawback is that the plane could technically probably maintain service longer. The idea in a safe-life design is that a critical system is designed to work for years without the need for repairs, this is usually done in systems that are difficult to access and/or repair.
Fail-safe is a design philosophy where should a failure actually take place in a component, the system as a whole can respond in a way to minimize harm to other components or personnel. So basically if a component were to fail, that one failure should not lead to the destruction of the whole system. This is also similar to "fault-tolerant" designs.
This is why generally you don't normally see Airbus planes in service that are over 20 years old. There are probably exceptions.
In a way, I guess you could say that in safe-life, the component isn't supposed to fail in the first place. Fail-safe takes steps to be ready in case a failure does take place.
But like I said earlier, you can design the hell out of something but there are still limits to what a design can take, even one that uses a fail-safe design philosophy.