The copilot and the bodies of three other crewmen of a U.S. helicopter shot down over Communist territory three days ago were released today by North Korea.

The release underlined efforts of North Korea and the United States not to let the incident grow to a confrontation. The copilot, CWO Glenn M. Schwanke, 23 of Spring Green, Wis., walked to freedom at the Panmunjom truce village as a senior U.S. officer said. "I acknowledge receipt of Chief Warrant Officer Schwanke."

Schwanke was placed under medical observation but his only visible injuries were a bruise under the chin and scratches on his face. Three other crew members who died in the crash were carried back in wooden coffins draped with the Stars and Stripes.

On Thursday, the four Army fliers unwittingly crossed the military demarcation line and headed north in a Chinock helicopter. They became the latest casualties in a war that theoretically ended 24 years ago.

Their return after seven hours of calm, business-like negotiations, unparalleled in Panmunjom'sdiscord scarred history, according to experienced observers may mark a new era in North Korea's attitude toward the United States. President Carter voiced regret for the unarmed helicopter's accidental intrusion and North Korea decided to "settle leniently" what it termed "a dangerous incident."

In previous incidents, U.S. military personnel who fell into North Korean hands spent months in captivity. The crewmen of the intelligence ship USS Pueblo were beaten. Before today, no one had been released in less than a week.

The North Koreans refused to return the CH-47 Chinook helicopter, however, saying it was destroyed and they did not want it used for anti-Communist propaganda.

In Washington, President Carter welcomed the release but said through a spokesman that he "deplored the loss of life and the excessive reaction in an unarmed and inadvertent intrusion."

The North Korean radio quoted copilot Schwanke as telling a press conference that his fellow crewmen would not have died and he would not, have been wounded if they had not attempted to escape after the helicopter landed in response to a warning shot.

According to the radio, Schwanke said: "The full responsibility for the latest intrusion case rests with us." He then apologized, the radio said.

[Schwanke said he received excellent treatment and medical assistance and expressed his gratitude, the North Korean radio added.]

Rear Adm. Warren C. Hamm of the U.S. Navy, who led the negotiating team as senior U.N. member of the Military Armistice Commission, said North Korea's prompt response was welcome."We deplore the loss of life and the use of force against an unarmed and inadvertent intrusion," he said. "However, it is encouraging that the matter was handled by both sides in a manner consistent with the armistice agreement."

Discussions began at 11 a.m. as Hamm and his North Korean counterpart. Maj. Gen. Han Ju Kyong, faced each other across a green baize table in the commission's Panmumjom headquarters, a cramped, single-story prefabricated structure.

As the mercury climbed to 90. the delegations found the basis of agreement -- the crewmen would be returned without conditions in return for signed receipts.

Schwanke stayed in captivity another seven hours as a working-level meeting summoned to arrange the mechanics of transfer bogged down in procedural wrangles. The U.N. side offered a series of minor concessions to speed the pace.

With the aim of recovering schwanke, whose medical condition was then unknown, Col. Terence McClain, secretary to the U.N. delegation, yield to North Korean wishes on the time, place and conduct of the handover.

The atmosphere, however, was encouraging. The North Korean guards still goose-stepped to the conference room, slamming their jackboots into the concrete. But after years of angry faces and hostile acts, they relaxed occasionally smiled, and offered cigarettes to the U.S. Army military policemen.

Inside the discussions were devoid of the usual propaganda and accusations.

A U.N. spokesman described the North Korean stance as "very mild and very low-key."

Gen. Han told Adm. Hamm:

"No conditions are applicable to their return. All your side has to do is write a receipt for the delivery of the crew and the bodies."

Han said that since the United States had said the intrusion into the north was unintentional. "We are going to settle it leniently so that a complicated situation will not develop."

(The North Korean radio said Han "clarified the truth of the incident and demanded the enemy side -- take steps lest similar incidents should occur again." Han, the radio said, took "note of the fact that the enemy side admitted the intrusion of the U.S. military helicopter into the air space of our side and expressed regret for it . . ."))

The last scenes of a dramatic day were played out at sunset. A camouflaged North Korean truck backed up slowly in the main courtyard of Panmunjom. Six North Korean medical attendants in white gowns, masks and gloves lowered the three coffins to the ground. Except for the whir of movie cameras, there was absolute silence as Col. McClain raised each of the shrouds.

CWO Thomas Savage identified the remains as those of three men from his unit, the 213th Aviation Co., based at Camp Humphreys, 40 miles south of Seoul.

Because the North Koreans had refused to let U.S. soldiers cross to their side to retrieve the coffins, six officers from Australia, Canada, the Philippines, South Korea, Thailand and Great Britain carried them over the thin concrete slab that divides the two Koreas in Panmunjom.

As U.S. joint security area guards carried the coffins away, a black sedan drew into the courtyard. The windows were curtained, presumably to prevent Schwanke, who was inside from seeing North Korean defenses.

The red-haired, Schwanke, a 2,000-hour pilot, was Ashen and Haggard. He had on the rumpled flight suit he was wearing when shot down. He walked stiffly over the demarcation live saluted McClain and climbed into an ambulance.

McClain signed receipts for Schwanke and his three dead colleagues. A North Korean colonel accepted the papers and McClain said: "I accept your proposal that we conclude the meeting."

The North Koreans scored a public relations success through the swift release of the crew with emphasis on humanitarian concern. North Korea thus may have gone some way toward changing its public image in the United States which seen it as a nation of bullies.

"They (the North Koreans) were very, very low-key, very moderate," a veteran Panmunjom-watcher said. The negotiation also showed that where Pyongyang and Washington see reconcilable objectives, cooperation is possible. Both governments were anxious to solve the incident without endangering Carter's plan to withdraw U.S. ground forces from South Korea.

His brother. Steve, said:

"We saw Robert a few weeks ago. He was supposed to be coming home next month."

Two weeks ago CWO Joseph A. Miles was home on leave in Washington, Ind. He told his parents not to worry about his return to duty in South Korea.

"He told us not to worry, that there wasn't a war going on," his mother, Mrs. John A. Miles, said. "I feel a little better knowing. When I heard one of the crew was still alive, not knowing if he was the one was something I couldn't handle."

Sgt. Ron Wells, 22, of El Paso, Tex. was on his second tour of duty when he was killed.

"He wanted to spend more time with his family," his father. Marvin Wells, a retired Army sergeant, said. "This was his second trip to Korea since 1974."

The younger Wells was married and had two children, Laurie Ann, 3, and Ronnie, 2.