At about 1,000 feet over the Pacific between Oahu and Kauai, the Marine Corps KC-130J Super Hercules had to slow way down to let a Kaneohe-­based CH-53E Super Stallion helicopter catch up.

With Rim of the Pacific in its final week, the four-engine turboprop Super Hercules was serving Friday in its role as an aerial refueler during the tactical, less scripted “free play” phase of the military exercise.

Two of the big Super Stallion choppers each took on 8,000 pounds of fuel — rotor blades whirling about 30 feet from the refueler’s tail as it slowed to about 126 mph.

While Marine Corps F/A-18 Hornet aircraft knife through the sky at supersonic speeds, its refuelers such as the Super Hercules keep them airborne longer.

Air Force KC-135 tankers are also participating in the five-week RIMPAC exercise, which wraps up Thursday.

The Marine Corps version, which first entered U.S. service in 1956, doubles as a cargo and troop carrier, and after the refueling mission, the Super Hercules was headed to Hawaii island for multiple troop and cargo runs for Marines who have been in the field.

“It’s a great mission,” said Capt. Charles Buckley, the aircraft commander for Friday’s flight. “It’s a huge enabler for Marine Corps aviation and ground units. We enable the (Marine Air-Ground Task Force) to reach out farther by providing them in-­­­ flight refueling.”

The Navy and Marines use a hose and drogue system for refueling that plays out from pods on the wing, while the Air Force uses a boom that telescopes from the rear of big jets. However, the Air Force’s newer KC-46A Pegasus, based on a Boeing 767 airliner, has both.

The Hawaii helicopters extend their own boom off the cockpit and try to thread that needle into a small basket attached at the end of 90 feet of hose.

For any aircraft, there can be a challenge trying to “plug” the basket, Buckley said.

“On a calm day like today, it shouldn’t be too much of a challenge,” he said before the flight. “However, if there’s turbulence or any other really adverse condition, it can make the refueling process challenging.”

Helicopter pilots will have a junior co-pilot practice refueling, and “watching them make plays for the basket is actually pretty interesting,” Buckley said.

On Friday, one helicopter nosed forward, missed the center of the basket by inches and had to retry. It takes five to 10 minutes to pump thousands of gallons of fuel into the receiving aircraft, the Marines said.

Buckley said the single Marine Corps Super Hercules has been flying six to eight sorties a day during RIMPAC.

“We’ve been very busy,” said Buckley, who is from Virginia. “A lot of aerial refueling missions and a lot of movement of troops and cargo from island to island.”

The free-play phase tests military unit skills during a specific scenario.

“Component commanders and subordinate units respond to scenarios that become more and more intense. These include realistic situations that nations could face in the Pacific Rim,” according to Canada’s armed forces, one of 25 international fighting forces represented at RIMPAC. “As a result, military units and members that take part experience challenging, full-spectrum operations. These cover surface, submarine, air and land threats.”

An amphibious assault at Marine Corps Base Hawaii in Kaneohe is planned for Sunday. It dovetails with an earlier effort that included humanitarian assistance as part of “Operation Restore Griffon,” officials said.

Under the training scenario, a 7.9-magnitude earthquake and subsequent tsunami hit the fictitious island nation of Griffon on July 4. A friend to the United States, Griffon’s government requested international assistance and the RIMPAC commander provided help, which also required dealing with radical insurgent forces, according to exercise plans.