Douglas DC-8-33 accident at San Francisco, California, 25 Dec 1965 (JA-8006)

Accident narrative

On December 25, 1965, Japan Air Lines Flight 813, a Douglas DC-8-33, experienced a disintegrating failure of its No. 1 engine and an inflight fire shortly after departing San Francisco International Airport. The crew successfully extinguished the fire and diverted to Oakland International Airport, making a safe emergency landing. None of the 10 crewmembers and 31 passengers aboard were injured.

**The flight**

Flight 813 was a scheduled international passenger flight from San Francisco, California, to Tokyo, Japan, with an en route stop at Honolulu, Hawaii. The aircraft, registration JA-8006, carried a crew of 10 and 31 passengers, four of whom were non-revenue.

The flight crew was highly experienced. Captain Tsuneo Kato had 8,031 total flight hours, including 909 in the DC-8. Flight Engineer Harold L. Brown had 14,077 total hours, with 1,560 in the DC-8. Copilot Shinsuke Jinnaka and Navigator Susumu Kohno were also properly certificated and qualified.

At takeoff, the aircraft's gross weight was 259,330 pounds, well below the maximum allowable weight of 288,600 pounds. Weather conditions were scattered clouds at 4,500 feet, 50 miles visibility, and a 10-knot wind. The flight departed Runway 01 at 1308 P.s.t.

**The emergency**

About three minutes after takeoff, while climbing at 4,500 feet and 270 knots over the South San Francisco area, the crew felt and heard a muffled explosion. The aircraft yawed violently to the left and vibrated noticeably. Instrument indications for the No. 1 engine became erratic. Recognizing a major engine failure, the crew executed emergency procedures, and the vibration stopped.

The crew later stated that no fire warning illuminated in the cockpit. Because the No. 1 engine was difficult to see from the pilots' compartment, they were unaware of a major fire until the purser and a non-revenue passenger ran forward 15 to 20 seconds later to report it. The crew immediately executed engine fire emergency procedures. When the fuel to the engine was turned off, the fire went out. A ground witness filming the aircraft captured the fire going out, followed by the characteristic white puff of the engine fire extinguisher discharging.

Just before 1312, the flight radioed San Francisco Departure Control to declare an emergency and request an immediate landing. As the captain began a return to San Francisco, he advised the crew he was having difficulty with lateral control. Primary hydraulic pressure was fluctuating between 1200 and 1700 p.s.i., fluid quantity was decreasing, and the aileron reversion light illuminated intermittently, indicating a loss of hydraulic boost.

The engine hydraulic pumps were turned off. When the captain found he could not hold the left wing up with manual aileron, the auxiliary hydraulic pump was turned on and standby rudder power was engaged. This restored control.

At 1316, to avoid a steep left turn into San Francisco, the flight requested and was cleared to land on Runway 29 at Oakland International Airport. The captain made a safe landing at 1320 with flaps limited to 25 degrees. Using inboard engine ejectors, maximum reverse thrust from the inboard engines, and heavy braking, the aircraft stopped with about 1,800 feet of runway remaining. Passengers were evacuated using slide chutes from the right forward and aft service doors.

**What the investigation found**

The aircraft sustained substantial damage. The No. 1 engine had disintegrated, and the left wing and No. 1 pylon sustained extensive fire damage. Shrapnel from the engine pierced the fuselage, left wing, and No. 2 engine pylon. The investigation found that a piece of stator vane had penetrated the No. 2 pylon and ruptured a hydraulic line, causing the hydraulic failure.

The fire warning system failed because the disintegrating force of the engine tore away the forward portion of the engine nacelle doors, disrupting the sensor loop. The fire itself was caused when the engine breakup separated the pylon-to-engine fuel line quick disconnect. The locking lugs sheared off, jamming the valve open and releasing fuel. Because this separation was upstream of the engine fuel control, shutting down the engine did not stop the fuel flow. The fire continued until the crew actuated the emergency fuel shutoff valve located behind the firewall.

The No. 1 engine, a Pratt and Whitney JT4A-9, had accumulated 21.5 hours since it was overhauled by Japan Air Lines in Tokyo in August 1965. Overhaul records showed the low pressure compressor torque ring had been found cracked and was replaced. This ring prevents the compressor stators from rotating and is designed to be secured to the compressor case by 90 rivets.

Company mechanics stated they fitted a new ring, drilled the necessary holes, pushed rivets in, secured them with paper tape, and then riveted the ring in place. However, they stated they did not draw the rivets from the stock room, but instead used leftover rivets. Stock records confirmed a new torque ring was issued, but there was no record of rivets being issued for the job.

About 100 pieces of the No. 1 engine were recovered from the Brisbane and South San Francisco areas. No portion of the torque ring was found. Recovered segments of the compressor case showed severe rotational abrasion and frictional heat discoloration where the torque ring normally mates.

Laboratory examination of these pieces revealed no evidence of rivet material in the damaged areas, and the rivet holes showed no elongation. The Board noted that the rivets and the compressor components were made of dissimilar metals, which would have made rivet material readily identifiable under spectrochemical examination had any been present.

The Board concluded that the torque ring was not secured in place by riveting during the overhaul. The normal tight fit of the ring and three borescope inspection plugs kept it in place temporarily. When normal rotational forces overcame this friction, the stator assembly and torque ring began to turn. At high speeds, the torque ring literally ground through the compressor case until the case was so weakened that it disintegrated with explosive force.

**Probable cause**

The Board determines that the probable cause of this accident was "a disintegrating engine failure and inflight fire caused by the failure of maintenance personnel to properly secure the low pressure compressor section torque ring during engine overhaul."