Investigation Summary
The accident occurred three minutes after takeoff while the aircraft was climbing through 4,500 feet. The number one engine suffered a catastrophic failure of the low-pressure compressor, which shattered the outer casing and forward cowling. Debris from the engine struck the airframe, tearing away a large section of the left aileron and damaging the number two engine pylon and hydraulic lines. The crew was initially unaware of the resulting fire because the engine was not visible from the cockpit and no fire warnings were triggered; they were alerted 15 to 20 seconds later by the purser and a non-revenue passenger who ran forward to the cockpit. Facing deteriorating hydraulic pressure and lateral control issues, the captain opted for a direct approach to Oakland's Runway 29 rather than attempting a complex turn back to San Francisco.
Final Conclusions
The National Transportation Safety Board determined the probable cause was the failure of maintenance personnel to properly secure the torque ring on the low-pressure compressor during a recent engine overhaul. The engine had been returned to service only one day prior to the accident after fatigue cracks in the torque ring were addressed at the Japan Air Lines factory in Tokyo.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Tsuneo Kato, age 40.
First Officer
Shinsuke Jinnaka, age 30.
Flight Engineer
Harold L. Brown, age 41.
Navigator
Susumu Kohno, age 41.
Systems & Failure Modes
Low-Pressure Compressor
The component that suffered an uncontained failure after its torque ring was not properly secured during maintenance.
Hydraulic System
Debris from the engine explosion severed hydraulic pipes, leading to a loss of pressure and making lateral control difficult.
Fire Warning System
The system failed to issue a warning to the pilots despite an active fire in the No. 1 engine nacelle.
Interesting Facts
- 01The aircraft was named Kamakura and had logged 13,423 flight hours.
- 02The No. 1 engine had been installed on the aircraft on November 20, 1965, and returned to service just one day before the accident.
- 03Nearly half of the left aileron was torn off by debris from the engine explosion.
- 04The crew learned of the engine fire from a flight attendant rather than cockpit warnings.
- 05All 41 occupants survived without injury.
Safety Actions & Advisories
Maintenance Procedure Review
Source ↗The investigation emphasized the critical importance of properly securing the torque ring on the low-pressure compressor during engine overhauls to prevent uncontained failures.