One of the engines of a Cessna that crashed on the NSW mid north coast, killing two people, was likely producing no power at the time of the accident, air safety investigators believe.
The light plane took off from Toowoomba in Queensland on October 28 in good weather conditions.
It came down near the Pacific Highway, north of Johns River, south of Port Macquarie, later that afternoon.
Witnesses saw the plane flying at low altitude, roll to the left and descend rapidly before the fatal crash. The landing gear was reportedly extended.
The crash claimed the life of Sydney businessman Grant Burley and his partner.
Australian Transport Safety Bureau investigators combed through the wreckage for clues and took a number of aircraft components and electronic devices away.
"Examination of the engines and propellers indicated the left engine was producing no power and the right engine was likely producing low power at the time of the accident," a preliminary report on the incident said on Friday.
"The aircraft was not equipped with a flight data recorder or a cockpit voice recorder, nor was it required to be."
The ATSB said ongoing investigations will include the pilot's qualifications, experience and medical information along with fuel planning for the flight.