Flight History
On 20 June 2016, a Cessna 172P aircraft, registration PK-NIV, operated by Nusa Flying School, was conducting a mutual flight training area from Ahmad Yani International Airport (WAHS), Semarang to the Wedung area, Demak. Prior to the accident flight, the aircraft had flown a dual cross country training from Budiarto Airport, Tangerang to Semarang, with a flight instructor, two student pilots, and one company engineer on board. The aircraft was loaded with full fuel tanks for that leg. Upon arrival in Semarang, the aircraft was scheduled for a mutual training flight. Before departing, the two student pilots performed a preflight check and found no abnormalities. The fuel quantity indicator showed 120 liters of fuel, sufficient for a two-hour flight. No additional fuel was added at Semarang.
At 1249 local time (0549 UTC), the aircraft departed Semarang with two student pilots; one acted as Pilot Flying (PF) and the other as Pilot Monitoring (PM). The flight to the Wedung area was uneventful. After approximately 55 minutes of area training, the PM requested to leave the Wedung area and was instructed to hold over the area at 1,000 feet due to another aircraft returning from Jepara at 2,000 feet.
Engine Failure and Emergency Landing
While holding, the pilots noticed engine problems indicated by decreasing propeller rotation and aircraft vibration. The pilot performed the procedure to identify the cause: the ignition was on BOTH, master switch ON, carburetor heater on STAND BY, mixture on FULL RICH, and the fuel selector valve was slightly to the right of the ON/BOTH position. The pilot was unable to restart the engine after several cranking attempts and decided to make an emergency landing. The PM informed Semarang Approach of the emergency, and another training aircraft relayed that PK-NIV was performing an emergency landing in the Wedung area.
At approximately 0636 UTC, the aircraft landed in a fishpond at coordinates 6°48’5.64” S 110°35’0.66” E, about 16 nautical miles from Semarang on radial 050°. Both student pilots evacuated with minor injuries. The aircraft sustained substantial damage, and the fishpond was contaminated with aviation fuel.
Investigation Findings
The investigation concluded that the engine failure in flight was caused by improper fuel flow to the engine because the fuel selector valve was in an intermediate position between BOTH and RIGHT. Additionally, a deviation in the pilots' understanding of the aircraft fuel system prevented them from reselecting the proper valve position during the troubleshooting procedure, leading to the failure to restart the engine.
The investigation also noted that the fuel system design required the selector valve to be positively in the detent of the desired position; intermediate positions could restrict fuel flow. The fuel selector valve was found after the accident in a position that did not correspond to any labeled detent.