The HH-53B was essentially an interim type, with production quickly moving on to the modestly improved Air Force HH-53C CSAR variant. The most visible difference between the HH-53B and HH-53C was that the HH-53C dispensed with the fuel-tank bracing struts. Experience with the HH-53B showed that the original tank was too big, adversely affecting performance when they were fully fueled, and so a smaller 450 US gal (1,703 L) tank was adopted in its place. Other changes included more armor and a more comprehensive suite of radios to improve communications with C-130 tankers, attack aircraft supporting CSAR actions, and aircrews awaiting rescue on the ground. The HH-53C was otherwise much like the HH-53B, with the more powerful T64-GE-7 engines.

A total of 44 HH-53Cs were built, with introduction to service in August 1968. Late in the war they were fitted with countermeasures pods to deal with heat-seeking missiles. As with the HH-53B, the HH-53C was also used for covert operations and snagging reentry capsules, as well as snagging reconnaissance drones. A few were assigned to support the Apollo space program, standing by to recover an Apollo capsule in case of a launchpad abort, though such an accident never happened.

In addition to the HH-53Cs, the Air Force obtained 20 CH-53C helicopters for more general transport work. The CH-53C was apparently very similar to the HH-53C, even retaining the rescue hoist, the most visible difference being that the CH-53C did not have an in-flight refueling probe. Since CH-53Cs were used for covert operations, they were armed and armored like HH-53Cs. A good number of Super Jollies were converted into Pave Low special-operations helicopters. PAVE or Pave is an Air Force code name for a number of weapons systems using advanced electronics.

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