The critical fatigue component for the C-130 fleet is the center wing box, which is structurally more susceptible to the stresses of mission profile and payload.
The center wing box has a limit of 60,000 relative baseline hours (flight hours multiplied by the mission severity factor).
A corrosion limit of 40,000 flight hours was based on historical data and engineering judgment.
This data took into account corrosion factors not considered in airframefatigue analysis.
Actual airframe service life depends on which limit, fatigue or corrosion, is reached first.
For instance, the service-life of the HC-130N/P was based upon the aircraft's wing box and operationstempo.
Based on the current operations tempo, the fleet will begin to lose airworthiness in 2013.