Component importance measures to identify contributions to system failure for aircraft which dispatch with known faults

The creation of Time-Limited Dispatch (TLD) followed the introduction of Full-Authority Digital Electronic Control (FADEC) systems to commercial aircraft in the 1980s. FADEC systems replaced hydromechanical control (HMC) systems and took over the role of governing engine thrust from the start of fuel metering to the point of fuel shutoff. When FADEC systems were introduced it was the first time that HMC systems would not be available to pilots in the event of electronic system failure (Larsen & Horan 2002).