A well-known veterinarian and his son who died last week in a plane crash near Ka'au Crater in East Honolulu were off course, and a preliminary examination of the plane wreckage showed no mechanical problems, according to a National Transportation Safety Board report.

Zoe Keliher, an NTSB investigator, said yesterday afternoon that while investigations continue and the cause of the crash that killed Dr. Nicholas Palumbo, 81, and his 20-year-old son, Timothy, won't be known for at least six months, no mechanical anomalies were found on the single-engine Piper that crashed after 1 p.m. Jan. 10 in rugged terrain during rainy, cloudy conditions.

"We did not find any anomalies, or engine problems, that would contribute to a pre-impact cause," Keliher said.

Investigators will look at physiological issues of the pilot, for fatigue, medications or "other human factors," Keliher said.

The Palumbo family could not be reached for comment last night.

The last recorded messages between Palumbo and FAA controllers showed that he "was in the rain at golf course (and) proceeding to Punchbowl," according to the report. But ground air navigation showed that the plane was heading toward the mountains and was actually near 'Äina Haina. That last recorded message was at 1:44 p.m., according to the report.

Investigators gave this chronology of Palumbo's flight in their preliminary report:

• At 1:15 p.m., Palumbo and his son left Läna'i Airport for the 63-nautical-mile flight to Honolulu. Palumbo had not filed a flight plan, but family members told investigators that he was a seasoned pilot with an "extensive history of flying on the island and had performed thousands of flights between Läna'i and Honolulu."

• At 1:32 p.m., the air traffic controller told the pilot to proceed to Koko Head and gave Palumbo the direction and a runway number.

• At 1:39 p.m., the pilot reported he was passing Koko Head and the controller told him to descend at his discretion.

• At 1:42 p.m., the pilot reported "he was in the rain at golf course (and) proceeding to Punchbowl."

• At 1:44 p.m., the pilot reported he was at Punchbowl at an altitude of 1,900 feet and was inbound for landing. The controller told the pilot he was actually off course and gave the pilot information "to vector him to intercept landing."

That was the last transition made.

• At 1:45 p.m., the plane is believed to have crashed. Hikers near the accident site said they saw the plane just before it crashed, the report said. One hiker described conditions as cloudy, with poor visibility. He said he heard the plane crash into a ridge about 50 yards from where he was standing.

"He further stated that visibility was so bad that he was not able to see the airplane," the report said.

Other hikers reported hearing the plane's engine running until it crashed.

Investigators found the plane intact, with the main section burned and the wings and tail attached, in a remote area of rocky outcroppings and thick vegetation with an 80-degree slope. Because of the steep terrain, NTSB used Honolulu Fire Department search and rescue crews to secure the plane.

The plane was removed Saturday by a helicopter that lifted it off the slope and put it onto a flatbed truck at the top of Laukahi Street in the Wai'alae Iki area. It was then taken to a hangar at the airport.

The crash site was below the Lanipo Trail.

A specialist from NTSB headquarters in Washington is to arrive in Honolulu on Wednesday to perform a routine, detailed investigation of the air traffic control facility's involvement with the airplane, Keliher said.