Aircraft and Flight Details
The prototype GA-8 aircraft was conducting test flying from the manufacturer's facility at Latrobe Valley airfield. The test flying was scheduled by the designer under the provisions of a permit to fly approved by the Civil Aviation Safety Authority. For a series of spin tests, the aircraft was equipped with fixed and jettisonable ballast, a jettisonable pilot's door, and a tail-mounted anti-spin parachute attached to a long lanyard.
On the accident flight, the aircraft was configured at 9,000 feet above ground level with full power, flaps fully down, an extreme aft center of gravity, and maximum all-up weight. The test pilot was the only occupant.
Spin Test and Emergency Procedures
The test pilot applied full left rudder and full right aileron to initiate a spin. After the aircraft entered a spin to the left, the pilot applied standard control inputs to effect a recovery to normal flight. The aircraft did not respond. At 6,500 feet, 13 seconds after the spin commenced, the pilot jettisoned the ballast and deployed the anti-spin parachute. The aircraft still did not respond.
Accident Sequence
At about 32 seconds into the spin, at 5,200 feet, the pilot initiated release of the jettisonable door, released his harness, bailed out, and was clear of the aircraft as it passed through 3,600 feet. At 1,800 feet, the aircraft was observed to stop spinning. Fifty seconds after the commencement of the spin, the aircraft dived into the ground and was destroyed. The pilot sustained minor injuries during his landing.
Probable Cause
The official findings stated that as this was a prototype aircraft, some deficiencies and/or problems during testing are to be expected. With this particular aircraft, the fact that the inadequate rudder hinge moment was masked throughout flight testing meant that the inadequate rudder performance during critical spin recovery was not clearly detected until it combined with other factors to become critical. These other factors included an ineffective anti-spin parachute, extensive blanking of the fin and rudder, and flight at the extremes of the weight and C of G envelope. It is not known what, if any, effect the previous rerigging of the elevator controls had on this flight. The following factors were reported: 1. The rudder and fin effectiveness was inadequate for the spin test being undertaken. 2. The anti-spin protection systems were ineffective. 3. The aircraft was not able to be recovered from an intentional spin.