Merpati Nusantara Airlines Flight 6517
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On 4 January 2013, a Britten-Norman BN-2A-27 Islander, registration YV2615, operated by Transaereo 5074, went missing during a flight from Los Roques Airport to Caracas Airport, both in Venezuela.The plane took off about midmorning, in decent weather conditions.
Accident
Flight 6517 departed Bajawa Turulelo Soa Airport at 09.00 a.m local time carrying 46 passengers and 4 crews on board with an ETA of 9:40 a.m. The flight was uneventful until its landing. First Officer Vunpin was the pilot flying and Captain Aditya was the Pilot Monitoring. At 09:22, the flight crews made first communication with El Tari Control Tower controller (El Tari Tower) and reported their position and maintaining 11,500 ft. The pilot received information that the runway in use was 07 and the weather information. Flight 6517 later descended approved their descent clearance of 5.000 ft. At 09.38 local time, the crew reported the aircraft was passing 10,500 ft and stated that the flight was on Visual Meteorological Condition (VMC). El Tari Airport then obtained visual contact with Flight 6517 and issued a landing clearance. At 09.51 a.m, the crew reported that their position was on final and the El Tari Tower re-issued the landing clearance. Flight 6517 then retracted its landing gear.
On 10.15 a.m, Flight 6517 bounced for three times[16] and slammed onto the tarmac. It broke into two sections. Both the left wing and the right wing were bent forward and both propellers were destroyed. Eyewitness recalled that there was a massive explosion when the crash occurred. It then skidded for several meters. After the aircraft stopped, the flight attendants assessed the situation and decided to evacuate the passengers through the rear main entrance door.
A total of 25 people were injured in the crash. One pilot and four passengers who seated on row number three, seven and eight suffered serious injury. Several injured passengers suffered shock from the crash and was taken into El Tari's VVIP Lounge. Several people were admitted to the airport's military hospital, the Kupang Military Hospital, located on the west of the airport. Several of the injured were taken to the Prof. Dr. WZ Johannes Public Hospital. Military personnel immediately assisted the survivors and sterilized the crash site. A police line then extracted by authorities.
On 10.15 a.m, Flight 6517 bounced for three times[16] and slammed onto the tarmac. It broke into two sections. Both the left wing and the right wing were bent forward and both propellers were destroyed. Eyewitness recalled that there was a massive explosion when the crash occurred. It then skidded for several meters. After the aircraft stopped, the flight attendants assessed the situation and decided to evacuate the passengers through the rear main entrance door.
A total of 25 people were injured in the crash. One pilot and four passengers who seated on row number three, seven and eight suffered serious injury. Several injured passengers suffered shock from the crash and was taken into El Tari's VVIP Lounge. Several people were admitted to the airport's military hospital, the Kupang Military Hospital, located on the west of the airport. Several of the injured were taken to the Prof. Dr. WZ Johannes Public Hospital. Military personnel immediately assisted the survivors and sterilized the crash site. A police line then extracted by authorities.
Investigation
The Vice Minister of Transportation Ministry Bambang Susanto immediately ordered three main things in response to the crash, which were evacuation process of the survivors, immediate investigation by the National Transportation Safety Committee, and immediate clean-up at El Tari Airport.
Most survivors stated that before the plane touched the runway, the aircraft "swayed and shook" for several times. Shortly afterwards the aircraft bounced and slammed onto the tarmac. Investigators then analysed the FDR and CVR. The FDR was downloaded in Surabaya on 13 June with good quality. Further analysis was conducted in Jakarta. Based on the FDR analysis of the flight's approach, the approach was not on profile as published for runway 07, while the approach angle greater than 2.9°. Investigators then noticed that the left power lever was in the range of BETA MODE while the aircraft altitude was approximately 112 ft and followed by the right power lever at 90 ft until hit the ground. The FDR also recorded a vertical acceleration of +5.99 G followed by -2.76 G and stopped recording 0.297 seconds after touchdown. The CVR was downloaded at NTSC facility on 12 June 2013 and contained 120 minutes of good quality recording. The audio files were examined found to contain the accident flight. The recording showed that First Officer Vunping intended to reduce the power to correct the speed. Then, sounds similar to changing of engine and propeller were heard in the recording. First Officer Vunpin then exclaimed "Oops", possibly realizing his mistake. The aircraft then impacted terrain.
Noticed by the abnormal situation on the thrust lever, investigators then examined it. The power levers should have prevented to move from flight idle to ground idle during flight by the function of Electric Magnetic Lock Systems and Mechanical Power Lever Stop Slot. At the accident aircraft was found that the electric magnetic lock system (Power Lever lock) was on open position. With power lever lock on open position, the solenoid of the electric magnetic lock system disengage and allow the power lever moves to ground idle in flight whenever the mechanical power lever stop slots lifted. Based on simulator test conducted by the NTSC, if the engine entered this condition, the aircraft would lose lift and eventually descended rapidly. The movement of power lever to ground idle will result to the propeller pitch angle changes to low pitch angle which produces significant drag. The NTSC stated that because it happened on 112 ft, it was impossible to not crash.
Interviews from Merpati officials revealed that the first two aircraft had several problems on the Power Lever Lock System, whereas the automatic power lever lock system sometimes failed to open after landing. In May 2008, the board of instructors had agreed to revise the Normal Checklist that the Power Lock system selects to “OPEN” before landing. However, further analysis revealed that there were no faults in the engines.
Investigators then turned on the pilot who flew the plane, First Officer Vunpin. First Officer Vunpin have some experiences of delay on moving the power lever to Ground Idle during landing. On the accident flight, he aware to previous experienced and lifted the mechanical power lever stop slots during approach. He realized that he retarded the Power Lever backward at about 70 ft of aircraft altitude and unintentionally entered the Beta Range. Interviews with First Officer Vunpin revealed that he have some experiences of delay on moving the power lever to Ground Idle during landing. This experience became his belief (cognitive). First Officer Vunpin has been planned to do the flight check to be qualified First Officer, and he wanted to prove that he was qualified as a First Officer. Knowing that he had repeated the errors in the past flights, he tried to prove that he had overcome his errors. However, he unintentionally moved the power lever beyond flight idle (behavioral). The aircraft lost lift and subsequently crashed.
Most survivors stated that before the plane touched the runway, the aircraft "swayed and shook" for several times. Shortly afterwards the aircraft bounced and slammed onto the tarmac. Investigators then analysed the FDR and CVR. The FDR was downloaded in Surabaya on 13 June with good quality. Further analysis was conducted in Jakarta. Based on the FDR analysis of the flight's approach, the approach was not on profile as published for runway 07, while the approach angle greater than 2.9°. Investigators then noticed that the left power lever was in the range of BETA MODE while the aircraft altitude was approximately 112 ft and followed by the right power lever at 90 ft until hit the ground. The FDR also recorded a vertical acceleration of +5.99 G followed by -2.76 G and stopped recording 0.297 seconds after touchdown. The CVR was downloaded at NTSC facility on 12 June 2013 and contained 120 minutes of good quality recording. The audio files were examined found to contain the accident flight. The recording showed that First Officer Vunping intended to reduce the power to correct the speed. Then, sounds similar to changing of engine and propeller were heard in the recording. First Officer Vunpin then exclaimed "Oops", possibly realizing his mistake. The aircraft then impacted terrain.
Noticed by the abnormal situation on the thrust lever, investigators then examined it. The power levers should have prevented to move from flight idle to ground idle during flight by the function of Electric Magnetic Lock Systems and Mechanical Power Lever Stop Slot. At the accident aircraft was found that the electric magnetic lock system (Power Lever lock) was on open position. With power lever lock on open position, the solenoid of the electric magnetic lock system disengage and allow the power lever moves to ground idle in flight whenever the mechanical power lever stop slots lifted. Based on simulator test conducted by the NTSC, if the engine entered this condition, the aircraft would lose lift and eventually descended rapidly. The movement of power lever to ground idle will result to the propeller pitch angle changes to low pitch angle which produces significant drag. The NTSC stated that because it happened on 112 ft, it was impossible to not crash.
Interviews from Merpati officials revealed that the first two aircraft had several problems on the Power Lever Lock System, whereas the automatic power lever lock system sometimes failed to open after landing. In May 2008, the board of instructors had agreed to revise the Normal Checklist that the Power Lock system selects to “OPEN” before landing. However, further analysis revealed that there were no faults in the engines.
Investigators then turned on the pilot who flew the plane, First Officer Vunpin. First Officer Vunpin have some experiences of delay on moving the power lever to Ground Idle during landing. On the accident flight, he aware to previous experienced and lifted the mechanical power lever stop slots during approach. He realized that he retarded the Power Lever backward at about 70 ft of aircraft altitude and unintentionally entered the Beta Range. Interviews with First Officer Vunpin revealed that he have some experiences of delay on moving the power lever to Ground Idle during landing. This experience became his belief (cognitive). First Officer Vunpin has been planned to do the flight check to be qualified First Officer, and he wanted to prove that he was qualified as a First Officer. Knowing that he had repeated the errors in the past flights, he tried to prove that he had overcome his errors. However, he unintentionally moved the power lever beyond flight idle (behavioral). The aircraft lost lift and subsequently crashed.
| Incident summary | |
|---|---|
| Date | 10 June 2013 |
| Summary | Pilot error, wrong thrust position during landing led to structural failure |
| Site | El Tari Airport, Kupang, East Nusa Tenggara, Indonesia |
| Passengers | 46 (including 1 infant) |
| Crew | 4 |
| Fatalities | 0 |
| Injuries (non-fatal) | 25 (5 seriously) |
| Survivors | 50 (all) |
| Aircraft type | Xian MA60 |
| Operator | Merpati Nusantara Airlines |
| Registration | PK-MZO |
| Flight origin | Turelelo Soa Airport, Bajawa, East Nusa Tenggara, Indonesia |
| Destination | El Tari Airport, Kupang, East Nusa Tenggara, Indonesia |
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