MOUNT PLEASANT — Ralph Brown loved to fly. But even more, he loved to give veterans like Jim Powers a taste of their glory days in open-cockpit airplane tours over Charleston.

What caused Brown's vintage World War II training biplane to suddenly crash Wednesday night in Charleston Harbor, killing both men, remains a mystery.

The National Transportation Safety Board offered no clues Thursday as to why the 1943 Boeing Stearman PT-17 two-seater smashed into Crab Bank during a scenic sunset flight in heavy winds.

"Right now we're trying to get as many facts as we can without drawing any conclusions," said Luke Schiada, a New Jersey-based senior air-safety investigator with NTSB.

A preliminary report should be available by the end of next week, he said, though it will not include a probable cause for the accident.

Authorities doubt there was any communication with air-traffic controllers around the time of the crash, but they will look into that as well, Schiada said.

The flight was not related to the Medal of Honor celebration on the aircraft carrier Yorktown that was going on at the same time at Patriots Point, officials said Thursday.

Biographical sketches on the two victims showed both were avid air enthusiasts. Brown, 61, of James Island, was an

Air Force veteran, a fixture at the Johns Island Executive Airport and co-owner of the Air Tiger aerial tour company based there.

The company advertises guests should "pull on a helmet and goggles, feel the rushing breeze on your forehead, hear the rumble of the massive radial engine, the song of the wind through the flying wires."

Powers, 76, was an Air Force veteran who flew the mighty, V-winged F-86 Sabre class of jets out of Charleston in the mid-1950s, after the Korean War.

Much of the investigation into the crash will focus on the performance of the crashed plane, a restored PT-17 rebuilt about seven years ago.

A local pilot who has flown a Stearman says it probably was a strong and reliable craft during its World War II-era prime. A weakness, however, was the danger of stalling.

"You have to keep the airplane moving to keep it flying," said pilot Pat Waters. "It's a lot of airplane; it has a tremendous engine," he added.

Witnesses reported the plane flipped upside down about 30 feet above the water, just before the crash.

Waters surmised Wednesday's heavy wind gusts played a factor.

Otherwise, "it's a wonderful airplane," he said. "Everybody wants one but nobody can afford one."

The yellow-and-blue painted airplane had over time also collected the nickname "Yellow Peril" — a generic reference to several classes of World War II training planes given because of the dangers they presented during novice flight training.

Powers, the passenger, retired as a leading national sales manager for Sylvania/GTE before returning to Charleston in 1996, his family said. He was active in the Lions Club.

Ray Bronk of the Austin, Texas, area was Powers' roommate when both were stationed in Charleston. He said Powers flew the Sabre F-86D and L, an all-weather interceptor.

"Jim was a good, careful pilot," he said. "I'm very surprised that's how he met his end" even though he wasn't at the controls Wednesday, he said.

When Powers had his own plane in California, he flew medicines and went on other relief missions to Mexico and Central America, Bronk said.

Friends at the executive airport said Brown was so glued to the flying world that he would drop by three or four times a week just to hang out, even if he wasn't taking to the air that day.

"He loved the airport; it was his home," Linda Benson, manager of the ProFlight training school, said.

Brown wasn't one to take risks, she added.

"He was an experienced pilot. He would not have gone out in winds beyond the capability of his plane," she said.