The report is focused on factual information from the investigation's early evidence collection phase, and contains no analysis or findings, which will be detailed in the investigation's final report.

The crash occurred on December 2, 2020, in the Shoalhaven Gorge region of Morton National Park, and killed both Goulburn helicopter pilot Nicolaas Brink and Moama Shire councillor and businessman Andrew Goldman, who was in training as a pilot.

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The report states that on December 2, at 3.58pm, a Robinson Helicopter Company (RHC) R44 Raven I, registered VH-HGU, departed Goulburn Airport with a trainee pilot and an instructor on board.

The helicopter flew east from Goulburn Airport, and the last recorded automatic dependent surveillance broadcast (ADS-B) detected it descending into a valley in the Morton National Park at 4.11pm.

"Later that evening, when VH-HGU had not returned to Goulburn as expected, the chief pilot began an aerial search of the training area in another helicopter," the report said

"The wreckage of VH-HGU was found in a valley, approximately 4 km northwest of its last ADS-B transmission.

"Wreckage examination indicated that the main rotor struck the helicopter's fuselage in flight. This resulted in a loss of control and subsequent collision with terrain. Both pilots were fatally injured and the helicopter was destroyed.

"The engine and fuselage were exposed to a fire at the main wreckage site, which self-extinguished before emergency services arrived."

The aircraft track at its last transmission point was calculated from ADS-B data, while the direction at impact was estimated based on the direction of wreckage and damage to trees around the accident site.

The investigation has so far found that instructor held a Grade 3 helicopter flight instructor rating, and had 690 hours of flying experience, predominantly in R44 helicopters.

The trainee pilot was undergoing intensive flight training for the issue of a private pilot licence and was 11 days into the course with the operator at the time of the accident. The trainee had accrued a total of 38 hours of dual flying on VHHGU. The trainee pilot's first solo flight was conducted on the morning of the accident.

The Robinson R44 is a four-seat, single piston engine helicopter, first certified in December 1992. In January 2000, RHC introduced the R44 Raven I. At the end of 2020, there were 566 R44 helicopters on the Australian civil aircraft register.

The R44 Raven I helicopter involved in the accident, serial number 2615, was built in May 2020 in the United States. The helicopter was first placed on the Australian register as VH-HGU on 10 July 2020. VH-HGU was being maintained in accordance with the RHC R44 manual suite. The most recent maintenance release was not recovered from the wreckage, but the helicopter had an estimated 150 hours total time in service.

On October 14, 2020, RHC issued a safety alert for engine intake valves installed on O-540-F1B5 engines. RHC reported they had been advised of burned intake valves on engines whose serial number ended in '40E', with less than 500 hours' time-in-service, which included VH-HGU.

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A periodic inspection of VH-HGU was completed on November 18, at 100.57 hours total time in service, which addressed matters raised in the alert. The intake valves were inspected and the valve covers were reinstalled with new gaskets. A compression check was conducted and no issues were identified.

The two closest automatic weather stations showed significantly different weather one hour prior to, and at the time of the accident.

The half-hourly weather report at Goulburn Airport (31 km west of the accident site) recorded the wind from a north-westerly direction, up to 9 knots. The visibility remained greater than 10 km, and the temperature was 25C. There was no other significant weather observed.

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The half-hourly weather report at Moss Vale (43 km north-east of the accident site) recorded the wind from an easterly direction, up to 14 knots.

Based on the Moss Vale observations, a special weather report was first issued at 3.38pm, due to a significant deterioration of weather conditions in the area. These conditions continued for several hours, with descending cloud and reduced temperatures.

To date, the ATSB has attended the accident site on two occasions for wreckage assessment and evidence collection, completed a subsequent examination of the helicopter's engine and tail rotor driveshaft and conducted interviews with relevant parties, including the operator.

The investigation is continuing.

Future areas of scrutiny will include consideration of factors that contributed to a rotor blade impacting the fuselage in flight, such as turbulence, pilot input, engine issues, and aircraft controllability, as well as a review of the performance and handling characteristics of the helicopter.

Analysis of the weather conditions at the time of the accident, detailed technical examination of the engine and other retained components/electronic devices, and a review of available training and aircraft maintenance documentation will also be taken into account.

There will also be an assessment of related occurrences in Australia and overseas.

"Should a critical safety issue be identified during the course of the investigation, the ATSB will immediately notify relevant parties so appropriate and timely safety action can be taken," the report said.

A final report will be released at the conclusion of the investigation.