Fail-safe

Redundancy, fault tolerance, or contingency plans are used for these situations (e.g. multiple independently controlled and fuel-fed engines).

[11][12] "Safe to fail" refers to civil engineering designs such as the Room for the River project in Netherlands and the Thames Estuary 2100 Plan[13][14] which incorporate flexible adaptation strategies or climate change adaptation which provide for, and limit, damage, should severe events such as 500-year floods occur.

Fail-secure, also called fail-closed, means that access or data will not fall into the wrong hands in a security failure.

For example, if a building catches fire, fail-safe systems would unlock doors to ensure quick escape and allow firefighters inside, while fail-secure would lock doors to prevent unauthorized access to the building.

[16] The design was to prevent any single failure of the American command system causing nuclear war.

Globe control valve with pneumatic diaphragm actuator. Such a valve can be designed to fail to safety using spring pressure if the actuating air is lost.
Railway semaphore signals. "Stop" or "caution" is a horizontal arm, "Clear to Proceed" is 45 degrees upwards, so failure of the actuating cable releases the signal arm to safety under gravity.
An aircraft lights its afterburners to maintain full power during an arrested landing aboard an aircraft carrier . If the arrested landing fails, the aircraft can safely take off again.