The crew relayed the misimpressions to Capt. Will Rogers 3d, who gave the order to fire two Standard missiles at the plane when it was nine miles from the ship and still visually unsighted.
There is no evidence that the $1 billion ship's sophisticated Aegis radar system malfunctioned or that it presented technical data to justify a conclusion that the plane was "hostile," defense officials said.
But the chairman of the House Armed Services Committee, Rep. Les Aspin (D., Wis.), cautioned that human error might not entirely explain what went wrong.
Still unanswered, he said, were questions about why electronic signals that appeared to be from an F-14 fighter were picked up and why the airliner did not respond to repeated attempts to contact it.
All 290 passengers and crew aboard the Airbus A-300, on a scheduled flight to Dubai in the United Arab Emirates, died in the July 3 incident.
Pentagon officials, initially explaining Rogers' decision to shoot, cited reports from the Vincennes that the plane was diving toward the ship at high speed. Such a flight profile would not be shown by commercial airliners crossing the strait.
But since then, the officials have steadily backed away from their original assertions:
* The Pentagon retreated from its initial contention that the plane was flying outside the recognized civil air corridor linking the Iranian airport at Bandar Abbas with the Dubai airport across the strait. In its revised account, the Pentagon acknowledged that the plane was always within the corridor.
* The Pentagon retracted its early contention that no regular flight out of Bandar Abbas was scheduled around the time the airliner took off. Flight 655 was in the published airline guides, although it left Bandar Abbas about 30 minutes late. Officials said yesterday that a crew member who was asked by
Rogers to check the guides overlooked the flight.
* The Pentagon revised its initial contention that the plane was shot down during the Vincennes' battle with the gunboats. Rather, the plane was first detected five minutes after that clash ended.
Yesterday, Pentagon officials, confirming reports by the New York Times and ABC television based on leaks, said the Navy investigators, led by Rear Adm. William Fogarty, found that the ship's radar system was working properly at the time and - contrary to the crew's assertion - that the plane was not descending toward the ship or flying at an extraordinary speed.
While the Vincennes had reported that the plane was at about 9,000 feet and diving, other ships monitoring the flight - and recordings of radar, radio and other electronic signals aboard the Vincennes - put the plane at a normal altitude of about 12,000 feet and climbing.
And the Vincennes' estimate of the aircraft's speed - about 520 m.p.h. - was much faster than the airliner normally would travel at such a low altitude.
Once crew members identified a plane lifting off from the joint military- civilian airfield at Bandar Abbas as an F-14, it became difficult for them to change their minds, even when they began receiving conflicting information, the investigators reportedly conclude.
Tensions aboard the Vincennes were high at the time because the ship had been engaged in a skirmish with several Iranian speedboats. Intelligence reports alerting the crew to the possibility of an Iranian attack over the July 4 holiday weekend had elevated the crew's anxiety, defense officials said.
"We don't know whether the issue of human error is the total explanation," said Aspin, whose committee is holding hearings on compensation for the victims' relatives.
"It seems that Adm. Fogarty's report is going to say that human error is responsible for the misunderstanding about the altitude of the plane, but I don't know whether the report will say that human error is responsible for the whole problem of shooting down a civilian plane and mistaking it for a military plane."
Pentagon officials have cited three coded radio transmissions from the plane, received previously only from Iranian F-14s, as factors in the captain's decision to fire, as well as the plane's failure to respond to repeated warnings from the Vincennes and another U.S. ship.
Fogarty's team used psychologists to help in interpreting the responses of the crew members in the ship's combat information center, officials said. It was not known whether the team has recommended disciplinary action.
Officially, the Pentagon declined to discuss the report, which is not expected to be released until late this month. Defense officials said the inquiry findings were still being reviewed by Gen. George B. Crist, the head of the U.S. Central Command at MacDill Air Force Base in Tampa, Fla., and have not yet been sent to the Pentagon.
President Reagan, in a brief exchange with reporters, also declined to comment on the matter.
"I have read and heard and seen what is being said about the report and assigning the blame to the people in the radar room interpreting the signals and all," Reagan said. "I don't think that we can consider the report final until it has been submitted. . . . I have to feel the process hasn't been completed."