Final answer:
The necessary separation for a Cessna 152 landing behind a H/C-17 conducting a touch-and-go can vary and is determined by aviation authorities or air traffic control to ensure safety from wake turbulence.
Step-by-step explanation:
The question you are asking pertains to the separation required when a Cessna 152 is landing behind a H/C-17 performing a touch-and-go on the same runway. The specific separation required can vary depending on the airport and traffic control measures in place. Typically, air traffic controllers will require increased separation behind a large aircraft like the H/C-17 because it generates significant wake turbulence. However, the exact number of miles needed for safe separation is defined by the pertinent aviation authority, such as the FAA in the United States, and can be found in their regulations or by direct communication with air traffic control.