Follow-Up & Survival Analysis Flashcards

Post-repair verification of an electronics assembly primarily confirms that:

Answer: The repaired unit meets original performance specifications

Post-repair verification tests the unit against its original performance specs to ensure the repair fully restored function.

System availability A is correctly calculated as:

Answer: A = MTBF / (MTBF + MTTR)

Availability is the fraction of time the system is operational: A = MTBF / (MTBF + MTTR).

Mean Time To Repair (MTTR) is best defined as:

Answer: The average elapsed time from failure detection to return to service

MTTR includes diagnosis, repair, and verification time—all activities from failure recognition until the system is back in service.

Corrective Maintenance (CM) is distinguished from Preventive Maintenance (PM) in that CM is:

Answer: Triggered by an actual failure event

CM restores a failed item to service and is unplanned, whereas PM is scheduled to prevent failure before it occurs.

In depot-level maintenance, a unit is declared 'Beyond Economical Repair' (BER) when:

Answer: Estimated repair cost exceeds a defined percentage of replacement cost

BER thresholds (often 65–75% of replacement cost) ensure repair resources are not wasted on units that would cost nearly as much to fix as to replace.

A field return rate metric is used by manufacturers to measure:

Answer: The fraction of sold units returned due to defects or failures

Field return rate (returns ÷ units shipped) tracks real-world product quality and directly feeds back into reliability improvement programs.

Fault isolation in electronics troubleshooting is best accomplished by:

Answer: Systematically applying signal tracing and half-split techniques to narrow the fault location

Half-split and signal-tracing methods minimize the number of diagnostic steps needed to isolate a fault to the defective component.