BRUNSWICK – Brunswick Naval Air Station has issued a noise alert in conjunction with the arrival of a squadron of Marine Corps H-53 “Sea Stallion” helicopters at the base for a 10-day training mission.

The 100-foot-long, heavy-lift aircraft are the U.S. military’s largest helicopters and can be heard several minutes before they appear in view.

After their arrival late Wednesday, the six Sea Stallions will spend the next 10 days on training flights over mountainous and remote terrain in northern Maine.

The mission will include day and night training in high mountain rescue operations, air-to-air refueling and coordinated flight operations with A-10 “Warthog” attack aircraft from the Massachusetts Air National Guard.

The helicopters, accompanied by a support staff of more than 100 Marines, will practice low-level flights and terrain avoidance for possible overseas operations, said John James, public affairs director at BNAS.

“Due to our unencumbered air space,” he said, “the naval air station is one of the few bases in the country that can offer this type of invaluable training in a northern climate.”

The exercises will take place in Federal Aviation Administration-designated military airspace that has been used for low-level flights for more than 30 years. All air refueling will take place above 6,000 feet.

The Sea Stallions, which are used to transport Marines from ships to combat operations on land, make more noise than other helicopters, James said.

“These have seven blades,” he said. “The search and rescue helicopters most people are used to have four. These are huge machines, about the same size as our P-3,” a reference to the submarine-hunting patrol planes based at Brunswick.

Brunswick Town Councilor Tom Crimmins said noise alerts “come with the territory” and are not cause for concern.

“The base has always warned us when they’ve had special operations,” Crimmins said. “There’s never been a problem.”