Transfer of C-130s from USACOM to USTRANSCOM
A significant issue for the C-130 entailed the reassignment of CONUS-based active duty C-130s from USACOM to USTRANSCOM. As the single manager for DoD transportation, the consolidation of these air mobility assets under USTRANSCOM lent further credence to USTRANSCOM's single manager charter. Furthermore, as the Air Force component of USTRANSCOM, Air Mobility Command subsequently exercised both service authority (i.e., train, organize, equip, and provide) and operational control over these forces. This arrangement eliminated confusion and yielded more effective and efficient service to the air mobility customer. Theater CINCs would continue to exercise combatant command and operational control of overseas-assigned C-130 forces.
Although service life computations have not been used to determine grounding or airframe restrictions, the Air Force has used service life estimates as a planning tool to anticipate when major aircraft structural events can be expected. A key issue was the structural service life of the C-130 airframes, which was dependent on mission severity, fatigue, and corrosion factors.
A severity factor accounted for the difference between normal civilian flying and military flying (low level, short-field landings, etc.). Mission profile determined the severity factor, which was averaged over each aircraft's most recent two year history. This calculation translated airframe clock hours into equivalent airframe damage hours which would indicate the higher aging rate of the military airframes. On average, active C-130 aircraft were found to be flying approximately 600 hours per year, while ARC C-130E and C-130H aircraft were flying about 375 hours and 450 hours per year, respectively.
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 airframe fatigue 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 operations tempo. Based on the current operations tempo, the fleet will begin to lose airworthiness in 2013.
The average age of the active duty C-130 fleet as of 2000 is over 25 years old, while the average age of Guard and Reserve C-130s is 15 years old. The average age of the C-130E model is over 28 years and average flying time is approximately 19,800 hours, with the newest E-model being produced in 1972. Based on projected operations tempo and overall mission severity, C-130E aircraft were said to have an average remaining service life of 15 years. Material solutions such as selective repair, a service life extension program (SLEP), or procurement of new aircraft were some of several ways investigated to influence and resolve aging of the C-130 fleet.
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