An investigation into a fatal helicopter crash off the northern WA coast has found the configuration of the helicopter's controls and fatigue were factors in the crash. 

The Australian Transport Safety Bureau has made 21 findings in its final report into the March 2018 crash, which occurred when the helicopter was on its way to pick up a marine pilot from a bulk carrier ship off the Port Hedland coast.

The report said the pilot of the helicopter had been recently recruited by operator Heli-Aust Whitsundays Pty Ltd and was being supervised by a company instructor while carrying out his first night-time marine pilot transfers.

When approaching the bulk carrier ship for a second time, the helicopter descended rapidly, hitting the water.

The instructor was able to escape and was rescued shortly after, but the pilot was trapped in the cockpit as it flooded.

The pilot's body was recovered from the wreckage several days later.

The ATSB said the instrument panels were set up for a single pilot and the configuration had a detrimental effect on the instructor's ability to monitor the helicopter's flight path.

The helicopter's instruments were set up for a single pilot in the right seat," ATSB Chief Commissioner Angus Mitchell said.

"For any operation that relies on the instrument flying skills of a second pilot, consideration should be given to the adequacy of flight instrumentation for that pilot."

Mr Mitchell said since the 2018 crash, the Civil Aviation Safety Authority has updated regulations requiring single-pilot cockpits to be carefully assessed before they are used for training.

Escape training concerns

The ATSB investigation also found the newly recruited pilot last completed helicopter underwater escape training (HUET) in 2011, seven years before the incident.

"HUET provides familiarity with a crash environment and confidence in an emergency, for this type of accident.

"Interviews with survivors from helicopter accidents requiring underwater escape frequently mention they considered that HUET had been very important in their survival."

The report said the operator rostered the pilot on for marine pilot transfer flying without ensuring that helicopter underwater escape training had been done in line with the operations manual.

Fatigue flagged as safety risk

The ATSB also found the pilot had limited sleep in the 48 hours before the accident and probably experienced a level of fatigue that would affect their performance.

"The investigation found technical and methodological flaws in the operator's fatigue risk management system, and that the operator did not conduct a formal risk assessment of its roster prior to commencing marine pilot transfer operations at Port Hedland," Mr Mitchell said.

"Management of fatigue risk is a shared responsibility between operators and pilots and relies on sound principles, effective systems, and accurate recording."

The report said since the incident the operator had undertaken a safety investigation and made changes to it its fatigue management system and its training and checking specifications for marine pilot transfers. 

It said the operator had also added emergency breathing systems to pilot life jackets and introduced a requirement for underwater escape training every two years.