The ATSB report into the incident in February last year, which killed a 60-year-old pilot, concluded VH-SEH struggled to clear the trees at the end of the runway in Seaview, Victoria.
“The pilot was taking off for the first run of the day, so had almost full fuel on board,” the safety bureau’s director of transport safety, Dr Michael Walker, said.
“While the amount of fertiliser on board could not be determined, it was likely the aircraft’s weight exceeded the performance-limited maximum take-off weight for the strip, as well as the aircraft’s documented maximum take-off weight.”
The Piper PA-25-235/A9 was damaged when the outboard section of its left wing hit the trees and detached on 23 February 2022.
The pilot had conducted take-offs on the Seaview runway strip in previous years, but an increased height of trees at the northern end of the strip since it was last used by the pilot had reduced safety margins to some extent.
“Aircraft operators and pilots should remind themselves of the hazards associated with operations from small landing areas that are not prepared as permanent runways,” Dr Walker said.
“In any case, pilots should ensure aircraft loads are within specified limits, appropriate for the environmental conditions, and will result in the required performance to maintain safety margins.”
Physical and recorded evidence analysed by the ATSB indicated the power generated by the engine during the take-off may have been slightly lower than normal. However, there was insufficient evidence to reach a firm conclusion.
“It is possible the engine was negatively impacted by the volume of water present within the air, affected by carburettor ice, or the carburettor heat selector may have been inadvertently left on during take-off,” Dr Walker said.
The ATSB’s final report also noted the pilot likely initiated a jettison of the hopper contents shortly after becoming airborne, but any effect this had on the aircraft’s performance was probably negligible.