A four-seat Big Island tour helicopter was substantially damaged last month after landing at Kona Airport, according to a preliminary study by the National Transportation Safety Board.

No one was injured in the accident that occurred on Aug. 26 at 7:45 a.m. after the Robinson R44 II helicopter landed at the Kailua-Kona Airport with two helicopter instructor pilots on board.

According to the NTSB report released this week, one of the two flight instructor pilots reported problems after the helicopter landed and the aircraft “began to gently oscillate fore and aft about its longitudinal axis.”

The pilot said the oscillating became more severe where one main rotor blade, the tail boom and the lower vertical fin hit the ground.

“The tail boom and lower vertical fin were substantially damaged as the result of the impact with terrain,” according to the NTSB report.

The flight had left the Kona airport at 7:15 a.m.

The two certified flight instructors were not injured.

Federal Aviation Administration records show the helicopter, which was manufactured in 2005, is owned by Hawaii Pacific Aviation. The company runs aerial tours of Oahu, the Big Island and Kauai under the name of Mauna Loa Tours and operates a flight school.