An ATSB investigation has concluded that a Robinson R44 that crashed south-west of Newman WA in late 2022 was probably over its maximum take-off weight, according to an investigation report published this week.
VH-OCL was departing from a cultural heritage site in the Collier ranges in November 2022 with three members of a survey team on board. When the aircraft was at tree-top level and a forward speed of 27 kt, the aircraft performance dropped sharply and a rotor low speed alarm sounded. The pilot attempted to recover the aircraft, then conduct an emergency landing, but OCL crashed into terrain and rolled onto its side.
The pilot and two passengers were slightly injured and one passenger was seriously injured in the crash.
Investigators found that the pilot used estimated weights supplied to him by a member of the survey team rather than actual weights, and that the aircraft took off with a density altitude of 4210 feet.
The estimated weights put the aircraft below its maximum take-off weight, but ATSB calculations based on actual weights had it 30 kg over the MTOW.
“More power than the engine could provide was needed to safely conduct the take-off, given the overweight helicopter condition, confined take-off area and high-density altitude,” ATSB Director Transport Safety Stuart Godley said.
“This highlights the importance of using accurate figures when calculating weight and balance, and expected performance, especially when operating at full capacity and near the maximum gross weight.”
Investigators also noted that the drop-off in performance coincided with the moment the helicopter transitioned from ground effect.
The ATSB also found that the operator had conducted the flight under CASR Part 138 (air work) rules, but it should have been under CASR Part 133 (air transport), which the operator had no approval for.
The full investigation report is on the ATSB website.