The ATSB’s investigation into a collision with terrain of an amateur-built Sling 4 aircraft at Caloundra aerodrome, in Queensland, found that due the use of incorrect weight and balance data, the flight was conducted with the centre of gravity aft of its rear limit.
Before its flight on the morning of 12 August 2017, the pilot used the average or standard weights of each occupant to calculate the aircraft’s weight and balance with its electronic flight instrument system.
ATSB Executive Director Transport Safety Nat Nagy says that to reduce the risk of overloading the Civil Aviation Safety Authority recommends that load calculations for aircraft with less than seven seats should be based on the actual weight of occupants and baggage rather than standard or average weights.
Using actual weights for the load calculations would have prevented it operating with its centre of gravity aft of its rear limit.
“Using actual weights for the load calculations of the Sling 4 would have prevented it operating with its centre of gravity aft of its rear limit,” Mr Nagy said. “Operating like this meant it was less stable and more susceptible to an aerodynamic stall and harder to recover if a stall occurred.”
While descending, the Sling 4 deviated from its desired flight path. Attempts to continue the approach by manoeuvring the aircraft at low level and speed coupled with its loading outside of the permissible centre of gravity range reduced the remaining margins of controllable flight.
The aircraft stalled and entered an incipient spin. Recovery from the stall was not possible and the aircraft collided with terrain. The fuselage fractured at the engine firewall and the engine was pushed rearward into the cabin. The aircraft was destroyed. The pilot and three passengers suffered serious injuries.
Further information: Guidance on the use of standard passenger and baggage weights for the calculation of aircraft weight and balance is available in the Civil Aviation Safety Authority’s advisory publication CAAP 235-1(1) Standard passenger and baggage weights. Pilots can also refer to the United States Federal Aviation Administration publication Pilot’s Handbook of Aeronautical Knowledge Chapter ten, Weight and Balance for advice on correctly calculating aircraft weight and balance.
Read the report: Collision with terrain involving The Airplane Factory Sling 4, VH-BEG, Caloundra Aerodrome, Queensland, on 12 August 2017