Three Navy men overpowered a sailor after he held them hostage at gunpoint for three hours yesterday demanding a long-range antisubmarine aircraft, Whidbey Island Naval Air Station authorites said.

One of the hostages, CPO Gerald A. Walker, of Oak Harbor, cut his hand grabbing the gun from the captor, identified as James C. LeBlanc. LeBlanc had threatened to kill the three if he wasn't given the sophisticated plane, a crew and fuel, authorities said.

No motive had been established, said Lt. J. W. Kennedy, a base spokes man. The hostages said the man never gave them a motive.

The drama began at a change of watch, about 7:30 a.m. PST, when the gunman entered the duty office and threatened to shoot the people there with a .22-caliber rifle. He ordered Walker and two officers into the front seat of a military station wagon, climbed into the back, fired two or three shots at a security van which was driving by, then at gunpoint ordered the captives to drive to a runway.

He demanded a four-engine turboprop anti-submarine aircraft, fuel, a crew and charts of Puget Sound and Western Canada.

When the hostages persuaded LeBlanc that it was impossible to get the plane and crew prepared quickly, he agreed to let them drive him out of the base.

The four drove to a gate. As they waited for it to open, the gunman glanced away, and Walker grabbed his gun. The others jumped the gunman and subdued him.

In an unrelated incident, military police in Spokane, Wash., shot an Air Force sergeant to death after a two-hour siege in which authorities said he took over his barracks and began firing a rifle at random targets, including passersby.

Authorities said Sgt. Ernest Holsopple, 32, of Holyoke, Mass., began his rampage about 10:40 p.m. Sunday at a Fairchild Air Force Base barracks and fired about 100 rounds from a .22-caliber rifle before he himself was killed.

One witness said Holsopple had been drinking. A six-year veteran, he was a structural repair quality control inspector in a maintenance squadron.