Investigation Summary
The flight was the final leg of a multi-stop domestic route. The journey was plagued by technical delays; on the initial leg from Jakarta on February 15, the No. 4 engine failed to synchronize, and upon landing at Surabaya, an oil leak was discovered on the No. 1 propeller. After repairs, the flight attempted to reach Makassar but diverted back to Surabaya due to poor weather, where the No. 1 propeller oil leak was again noted for rectification. The flight finally reached Makassar the following morning before departing for Manado. Upon arrival, the crew encountered a cloud base of 900 feet and visibility of 2 km. The approach to Runway 18 required navigating over a hill 200 feet above runway elevation, located approximately 2,720 feet from the threshold. After clearing this obstacle, the captain realized the aircraft was poorly positioned. In an attempt to salvage the landing, he lowered the nose and banked right to intercept the glide path. This aggressive correction caused the airspeed to decay below the 125-knot target. The investigation highlighted that the pilot was likely unaware of the specific relationship between negative thrust and high sink rates at low speeds on the Electra. The narrow runway (98 feet wide) and uneven pavement further complicated the pilot's depth perception and touchdown target, contributing to the decision to attempt a tight, steep circuit.
Final Conclusions
The investigation concluded the primary cause was an awkward landing technique that resulted in an excessive rate of sink on touchdown. Contributing factors included marginal weather requiring a tight circuit, the narrow appearance of the 98-foot wide runway, and uneven pavement that incentivized the pilot to land as close to the threshold as possible. Additionally, the investigation noted a lack of knowledge regarding the Electra's sink rate characteristics when operating with negative thrust at low speeds.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
36 years old; held ATR license; passed proficiency check Nov 1966.
First Officer
36 years old; held ATR license.
Systems & Failure Modes
Lockheed L-188C Propulsion
The investigation noted that the relationship between negative thrust and sink rate at low speeds was not fully understood by the pilot or operator, contributing to the heavy landing.
Landing Gear
The undercarriage suffered a complete structural failure upon impact 156 feet short of the threshold due to the excessive rate of sink.
Interesting Facts
- 01The aircraft, named Tjandi Borobudur, had accumulated 12,359 flight hours at the time of the crash.
- 02The captain was the only pilot on the flight with previous experience landing an Electra at Manado.
- 03The runway at Mapanget Airport was only 98 feet wide, which may have created an optical illusion of being higher than actual altitude.
- 04The aircraft landed while still in a right-hand bank.
- 05All 22 fatalities were passengers; all 8 crew members and 62 passengers survived out of the 92 total souls on board.
- 06A total of 69 survivors sustained injuries during the crash and subsequent fire.
Safety Actions & Advisories
Pilot Training Enhancement
The investigation emphasized the need for pilots to better understand the aerodynamic relationship between negative thrust and sink rates at low speeds on the L-188 Electra.