What happened
On 7 April 2007, a Cessna 172 operated by Alfa Flying School was conducting a training flight between Halim Perdanakusuma Airport and Budiarto Airport. The aircraft, registered PK-SDP, was carrying two instructors and one student. During the return leg to Halim Perdanakusuma, the engine experienced a sudden loss of power, dropping to idle RPM. The pilot attempted to manipulate the throttle lever to restore power, but the controls provided no response.
In response to the engine failure, the instructor performed a forced landing in a football field located southeast of Budi and Budiarto Aerodrome. During the landing roll, the aircraft struck a mound on the field. The impact caused substantial damage to the aircraft, including a broken engine mount, a broken nose wheel shock strut, and a shattered windshield. The three occupants sustained injuries, with one person suffering serious injuries and two others sustaining minor injuries.
The investigation
The investigation focused on the mechanical failure of the engine's power regulation system. Investigators examined the aircraft's carburettor to determine why the throttle lever became unresponsive. The inspection revealed that while the bolt remained on the throttle arm, the rod end, nut, and split pin had become detached from the assembly.
Findings
- The aircraft was certified as airworthy at the time of the accident.
- The engine power loss was caused by a malfunction of the butterfly valve.
- The mechanical failure occurred because the rod end, nut, and split pin were not properly attached to the throttle arm, leaving the engine power uncontrolled.
Safety action
Following the accident, Alfa Flying School conducted inspections across its entire fleet to verify the proper installation and security of the carburettor rod end, nut, and split pin attachments on all similar aircraft.