What happened
On 11 February 2010, an ATR 42-300, registration PK-YRP, operated by Trigana Air Service, was performing a scheduled passenger flight from Berau to Samarinda. The aircraft was carrying 52 people, including 46 passengers and 6 crew members.
During the final approach to Samarinda, the crew observed the left engine ECU light illuminate, followed by a drop in oil pressure and torque. Due to the short runway and nearby residential areas at Samarinda, the pilot decided to divert to Balikpapan. While climbing through 3,800 feet toward Balikpapan, the right engine also experienced an ECU light illumination, low oil pressure, and low torque, resulting in a total loss of power from both engines. The crew declared a MAYDAY and executed a forced landing in a clear field in the Samboja area. While there were no fatalities, one passenger sustained serious injuries, and the aircraft suffered substantial damage, including a nose wheel that penetrated the cabin floor.
The investigation
The investigation focused on the engine systems and fuel management to determine why both engines failed sequentially. Investigators examined the fuel tanks, filters, and engine components, as well as the functionality of the flight recorders.
Analysis of the fuel system revealed that the left wing tank was nearly empty, with only two liters of fuel drained, while the right tank contained 4/00 liters. The investigation found that during the diversion, the crew had used the cross-feed valve, which caused the left engine to draw from the right tank, eventually leading to fuel starvation. Additionally, the investigation revealed that both the Flight Data Recorder (FDR) and the Cockpit Voice Recorder (CVR) were unserviceable and had not been recording data for a significant period prior to the accident.
Findings
- The primary cause of the dual engine flame-out was fuel starvation.
- The fuel quantity indication was likely misleading, as the crew was unaware of the critical fuel levels.
- The FDR was non-functional due to a faulty acquisition processor circuit board.
- The CVR was inoperable due to extremely worn recording heads and a motor failure.
- Significant debris, dirt, and uncured sealant were found inside the wing tanks.
- Maintenance procedures for verifying fuel system modifications were not performed according to the correct functional test requirements.