History of the Flight
On 8 March 2014, at approximately 13:15 UTC, a Beechcraft A-36 Bonanza, registration HA-ARB, operated by JetStream Kft., was on a flight from Tököl Airport (LHKK) to Sofia International Airport (LBSF). During the approach phase, the autopilot was engaged. The aircraft suddenly pitched nose-down without any pilot input. The pilot immediately disconnected the autopilot and manually recovered the aircraft to a normal attitude. The flight continued and landed safely at Sofia Airport.
Injuries to Persons
No persons were injured. The report states zero deaths and zero severe injuries.
Damage to Aircraft
The aircraft sustained slight damage as a result of the incident.
Other Damage
No other damage was reported.
Personnel Information
The pilot held a Private Pilot Licence (A) with a Single Engine Piston (SEP) rating and was current. A passenger was also on board. Both were interviewed by the investigating committee.
Aircraft Information
The aircraft was a Beechcraft A-36 Bonanza, registration HA-ARB. The operator was JetStream Kft. The aircraft was equipped with an autopilot system.
Tests and Research
The investigating committee inspected the aircraft at Kiskunlacháza Airport (LHKK) and conducted tests on the autopilot operation. They measured the force required for automatic shut-off and assessed the operating mechanism.
Cause of the Serious Incident
The direct cause of the serious incident was an erroneous signal from the autopilot's pitch channel due to a software error in the autopilot computer.