Investigation Summary
The investigation focused on the flight crew's management of the Xian MA60's power levers. The First Officer, who was the pilot flying, had previously experienced delays when attempting to move the levers into Ground Idle after touchdown. To prevent this, he pre-emptively lifted the mechanical power lever stop slots during the final approach. Because the airline's specific procedures (revised in 2008 without a formal risk assessment) required the Electric Magnetic Power Lever Lock to be in the 'OPEN' position before landing, there was no remaining safeguard to prevent the levers from moving behind the Flight Idle gate. At approximately 112 feet, the left power lever entered the Beta range, followed by the right at 90 feet. This caused the propellers to move to a low pitch angle, acting as massive air brakes. The aircraft slammed onto the runway 58 meters from the threshold, shearing the landing gear and causing the wing structure to fail and the fuselage to break in two.
Final Conclusions
The National Transportation Safety Committee (NTSC) concluded the accident was caused by the movement of power levers to the Beta range at 90 feet, which produced significant drag and loss of lift. Contributing factors included an operator procedure that required opening the Power Lever Lock during approach without a comprehensive risk assessment, and the pilot's intentional lifting of the mechanical stop slots to avoid perceived mechanical delays, which led to the unintentional entry into Beta mode.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Qualified as route instructor.
First Officer
Under training; had 58 hours with the company.
Systems & Failure Modes
Power Lever Lock System
An electric magnetic lock designed to prevent the power levers from moving from Flight Idle to Ground Idle (Beta range) while in flight.
Mechanical Power Lever Stop Slot
A physical gate that requires the pilot to manually lift a trigger to move the power levers into the reverse/ground range.
Beta Mode
A propeller state where the blade pitch is controlled directly by the power lever, typically used for ground operations to provide reverse thrust or high drag.
Interesting Facts
- 01The aircraft experienced a vertical acceleration of +5.99 G upon impact.
- 02The First Officer was a Malaysian national, correcting early media reports that identified him as South Korean.
- 03The First Officer had only 58 hours of total flying time with the company and was in a training program.
- 04While 25 people were reported injured, the NTSC officially classified 5 (1 crew member and 4 passengers) as having sustained serious injuries.
- 05The airline's Normal Checklist had been revised in 2008 to keep the Power Lever Lock 'OPEN' during landing due to previous mechanical reliability issues.
- 06The aircraft was written off due to severe structural damage, including a broken fuselage and failed wing structure.
- 07The crash contributed to the financial collapse of Merpati Nusantara Airlines, which suspended operations eight months later.
Safety Actions & Advisories
Special Audit
The Indonesian Transportation Ministry initiated a special audit of Merpati Nusantara Airlines' maintenance and airworthiness procedures for the Xian MA60 fleet.
Checklist Revision Review
Investigators highlighted that the 2008 revision to the Normal Checklist (opening the power lever lock in flight) was made without a comprehensive risk assessment and contradicted manufacturer procedures.
Known Controversies & Unanswered Questions
First Officer Nationality Confusion
Reference ↗Following the accident, multiple media outlets incorrectly reported that the First Officer was a South Korean national. The investigation later confirmed he was a Malaysian national named Au Young Vunpin.
Unauthorized Checklist Revision
Reference ↗The investigation revealed that Merpati Nusantara Airlines had revised its Normal Checklist in 2008 to require the Power Lever Lock be set to 'OPEN' during approach. This change was made to bypass mechanical reliability issues where the lock failed to disengage after landing, but it was implemented without a formal risk assessment and directly contradicted the manufacturer's safety procedures, removing a critical safeguard against accidental Beta range entry in flight.