The damaged aircraft carrier USS Coral Sea is scheduled to return to Norfolk today for extensive repairs as Navy authorities investigate why it turned left twice before colliding with an Ecuadoran tanker near Cuba last Thursday night.

Capt. Gene Tucker, the carrier's skipper, had just left the bridge and gone to his cabin to shower after the first wave of aircraft had finished landing, officials said.

The officer of the deck ordered a left turn while Tucker was in the shower, sources said, putting the carrier on a collision course with the tanker Napo.

A Soviet electronic trawler was in the area at the time, officials said, but not close to the carrier. But its presence might have influenced the Coral Sea's course just before the collision, sources said.

Carriers steam into the wind while receiving aircraft, then usually turn right to go downwind and backtrack on their course before turning right into the wind again to receive the next wave of aircraft. When two ships are on a collision course, each is supposed to turn right to put distance between them.

The Napo, sources said, followed these rules by turning right when it saw the carrier bearing down on it 45 miles south-southeast of Guantanamo Bay. But the carrier, these sources added, turned left again, and the two ships collided.

One theory offered by experienced Navy skippers is that the tanker's lights confused the officer of the deck, who mistook the ship's direction. Official findings will not come until after an extensive Navy investigation, however.

The 574-foot, 32,000-ton Napo bumped along the right side of the Coral Sea after the ships' bows swung into each other, Navy officials said, causing extensive damage to both. The Napo was carrying 190,000 barrels of fuel oil from Ecuador to New York. The 52,500-ton Coral Sea was recently overhauled at a cost of $189.5 million and fitted with gear needed to carry the Navy's new F18 fighter-bomber. Part of the carrier's bow was crushed, and radar and communications gear on its right side were smashed.

None of its crew of about 5,000 men was injured nor any aircraft damaged, the Navy said. The carrier is expected to undergo repairs at Norfolk for at least six weeks.

The Navy traditionally holds the captain accountable for anything that goes wrong on his ship, even if he was not on the bridge at the time.

Besides delving into why the carrier made two left turns, Navy investigators are expected to probe what the navigator or assistant navigator on the bridge was doing at the time of the collision and what radio communications may have occurred between the ships before they struck.