The Australian Transport Safety Bureau (ATSB) has identified retracted flap as a major contributor into the 2016 fatal crash of an Air Tractor AT-502.
Air Tractor VH-LIK was on crop-spraying operations near Cryon, NSW, in November 2016 when it crashed on take-off after re-loading for another run. The pilots was fatally injured and the aircraft destroyed by fire.
The ATSB investigation found that the flaps were retracted on impact, but couldn't say if they weren't used for take-off or were selected up after the aircraft became airborne.
"The flaps were retracted at some point during the take-off, which significantly degraded the take-off and climb performance," the ATSB found. "This effect was compounded by the estimated weight of the aircraft, the local temperature and wind conditions at the time of the flight.
"The combined effect probably resulted in the aircraft having insufficient take-off performance. The reason the flaps were retracted was not able to be determined.
"The aircraft reached a height above the ground where the reduced benefit of ground effect further degraded the aircraft’s performance. The low height and airspeed precluded the pilot from turning the aircraft towards a clear area and the aircraft descended into trees.
"Recorded data from the aircraft indicated that the pilot attempted to dump the hopper contents after becoming airborne, which would have achieved significant gains in climb performance, however a complete dump was not achieved. The reason for this could not be determined."
In it's safety message, the ATSB reminded agricultural pilots to be constantly aware of the need to consider dumping the hopper load should it be necessary.
Air Tractor is also updating the maintenance manual for the aircraft type to specify regular inspection of the emergency dump controls.
The full investigation report is on the ATSB website.