History of the Flight
On 12 September 2013, a Cessna 152 aircraft registered PK-KFC, operated by PT Aviasi Solusi Prima (FlyBest Flight Academy), was conducting a local training flight from Hang Nadim Airport, Batam. The aircraft was destined for the Bridge 5 training area. On board were a student pilot acting as Pilot Flying (PF) and a flight instructor acting as Pilot Non Flying (PNF).
After taxi and takeoff at 23:50 UTC, the aircraft climbed normally. At approximately 1,500 feet, the student pilot increased engine power but noted the RPM was only 2,200 instead of the expected 2,500. Shortly thereafter, engine power decreased further to 2,000 RPM. The pilot requested to return to Hang Nadim Airport. Subsequently, oil pressure dropped to zero, and the engine continued running for about 15 seconds before stopping. The crew performed emergency procedures and attempted to restart the engine unsuccessfully. They decided to make an emergency landing over the sea. The aircraft ditched on a radial of 158° at 8 nautical miles from the BTM VOR.
Injuries and Aircraft Damage
The instructor and student pilot sustained minor injuries. The aircraft came to rest upside down and floated on the sea.
Aircraft and Maintenance History
The Cessna 152 was registered PK-KFC. The flying school began operations in January 2013 and introduced a lean air mixture procedure. In June 2013, the school changed the fuel type from aviation gasoline (AVGAS) to motor gasoline (MOGAS), while continuing to apply the lean takeoff procedure. Maintenance records indicate the aircraft was grounded on 7 and 11 September 2013 due to loss of power during engine power checks.
Engine and Fuel Issues
The investigation found that the engine had been overheating for a period of several days. This was the result of a combination of lean mixture at high engine power and the use of lower octane fuel, which placed the engine in an area of heavy detonation. The change from AVGAS to MOGAS was classified as an alteration and was not performed in accordance with CASR sub part 43.13. Additionally, discrepancies that appeared after the introduction of MOGAS were not resolved within the management.
Contributing Factors
The investigation concluded that the contributing factors to the accident were: 1. Engine overheating due to the combination of lean mixture at high engine power and the use of lower octane fuel, leading to heavy detonation. 2. The fuel change from AVGAS to MOGAS was not carried out in accordance with applicable regulations. 3. Management failed to address the discrepancies that arose after the use of MOGAS.