A helicopter pilot fighting bushfires on the NSW south coast was killed when his water bucket and line became tangled in trees and pulled the chopper down, an investigation has found.
New Zealand-born Alan "Tully" Hull died in mid-August while water-bombing a blaze near Milton.
The Australian Transport Safety Bureau on Friday released its preliminary report into the incident, finding "a number of witnesses observed the bucket and longline become tangled in trees at the edge of a clearing followed by the helicopter colliding with terrain".
ATSB investigators who attended the site discovered the helicopter upside down in a clearing with the bucket and longline still attached.
The bucket was caught in trees at the edge of the clearing and the helicopter's tail rotor located about 20 metres from the main wreckage.
Transport safety executive director Nat Nagy says the investigation is ongoing.
"Investigators will now be looking at the pilot's qualifications, experience and medical records, the maintenance records from the aircraft, as well as examining recovered electronic data from the aircraft," he said in a statement.
The final report will be released in the second half of 2019.
Mr Hull was posthumously awarded the NSW Rural Fire Service commissioner's commendation for service a week after the crash.
"Tully will always be remembered as an accomplished pilot and member of the firefighting fraternity for his professionalism and courage, which will never be forgotten," the award citation read.
