Investigation Summary
Flight 611 was a scheduled domestic service from Naha to Ishigaki. During the approach to Ishigaki Airport's Runway 22, the crew encountered crosswind conditions and touched down at 131 knots, which was 6 knots above the reference airspeed (Vref). The aircraft bounced upon initial contact. The landing was further complicated by hydroplaning, which reduced initial braking effectiveness. When the crew perceived that the spoilers and thrust reversers were not operating correctly after the second touchdown, they elected to shut down both engines. This action proved critical as it cut power to the anti-skid system. Without anti-skid protection, the inner tires on both main landing gear legs burst approximately 125 meters before the end of the runway. The aircraft skidded left, overran the threshold, and came to rest 145 meters beyond the runway end. A fire broke out 12 minutes after the stop, completely destroying the airframe.
Final Conclusions
The Aircraft Accident Investigation Commission (AAIC) concluded that the primary cause was the flight crew's inappropriate decision to shut down the engines during the landing roll and the captain's delay in applying the brakes. The investigation noted that even with the high touchdown speed, the aircraft could have stopped within the runway safety area had the engines remained running to power the anti-skid system and had maximum braking been applied immediately. The AAIC released its final report in October 1984, approximately two years and two months after the accident.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Aged 40; with the airline since 1973.
First Officer
Aged 29; with the airline since 1974.
Systems & Failure Modes
Anti-skid Braking System
A system designed to prevent wheel lock-up during braking; it was disabled when the crew shut down the engines, leading to tire bursts and reduced deceleration.
Spoilers and Thrust Reversers
Aerodynamic and engine systems used to decelerate the aircraft; the crew believed these were malfunctioning, prompting the engine shutdown.
Interesting Facts
- 01The aircraft had logged 5,056 flight hours at the time of the accident.
- 02The Ishigaki Airport runway was 4,900 feet (1,494m) long, which was later deemed insufficient for safe Boeing 737 operations.
- 03Shutting down the engines disabled the anti-skid system, reducing braking action to approximately half of its potential effectiveness.
- 0467 people were injured; while most were minor, a flight attendant and an elderly passenger required hospitalization for serious injuries.
- 05The captain had 1,666 flight hours, all on the Boeing 737.
Safety Actions & Advisories
Airport Replacement
Ishigaki Airport was eventually closed in 2013 and replaced by the New Ishigaki Airport, which features longer runways better suited for jet aircraft.
Known Controversies & Unanswered Questions
ALPA Dispute of Findings
Reference ↗The Japanese branch of the Air Line Pilots Association (ALPA) formally questioned the AAIC's findings regarding the crew's actions and the cause of the accident.
Dismissal of Criminal Prosecution
Reference ↗The Naha District Prosecutor's Office opened a criminal negligence case against the captain following the accident. However, the case was eventually dismissed due to a lack of evidence.