Which of the following aircraft is not a training aircraft?

The C-130 Hercules is primarily designed as a military transport aircraft, primarily used for cargo transport, medical evacuation, and aerial refueling missions. It serves a vital role in logistics and support rather than as a training aircraft for pilots. The other options listed are specifically designed for training purposes.

The T-45A Goshawk is used by the Navy for training Navy and Marine Corps aviators, particularly in carrier operations. The T-6A Texan is a fundamental training aircraft for the Air Force that prepares pilots for advanced flight training. The EA-18G Growler, while primarily an electronic warfare aircraft, is also used to train pilots for advanced combat operations, but it is still more aligned with operational roles rather than basic training.

Thus, the designation of the C-130 Hercules as a transport aircraft distinguishes it from the others, which are all specifically intended for pilot training or related purposes.