Robinson R44 helicopters that have not been fitted with upgraded fuel tanks face being grounded from April 30 this year.
CASA has issued a direction to all affected R44 helicopter operators about the installation of flexible fuel tanks to reduce the risk of post-accident fires.
The move comes in the wake of an R44 crash on March 21 near Bulli Tops, NSW, that claimed four lives.
During lift-off, the helicopter turned to the right and the main rotor struck a tree. The helicopter descended and then rolled over onto its right side. A fire started on the grass under the rotor mast and the cabin. All on board died.
Although investigation is still at the preliminary stage, the ATSB has said "The circumstances of this accident are consistent with two recent R44 accidents in Australia involving low-energy impacts that resulted in the all-aluminium fuel tanks being breached and a fuel-fed fire. R44 accidents result in a significantly higher proportion of post-impact fires than for other similar helicopter types."
The accident helicopter was equipped with an all-aluminium tank.
CASA has made it clear that R44 helicopter operators following the Robinson maintenance program are required to install the new fuel tanks.
Any operators not covered by the Robinson maintenance program will be directed by CASA to fit the tanks if the upgrade has not already been completed.
Robinson issued a service bulletin in September 2012, which set April 30, 2013 as the deadline for the fitting of the flexible fuel tanks.