Pressure Wall Found, May Be Key to Jet Crash

Japanese investigators today found a badly damaged pressure wall from a crashed Japan Air Lines jetliner, supporting a theory that the wall burst during flight, causing the plane’s tail fin to disintegrate and the jet to crash.

All but four of the 524 people aboard Monday’s JAL Flight 123 died in the crash, aviation’s worst single-plane disaster.

Hiroshi Fujiwara, deputy investigator of the Transport Ministry’s Aircraft Accident Investigation Commission, said at a news conference that the pressure bulkhead his team found at the crash site was “peeled like an orange.”

The bulkhead is an umbrella-like aluminum-alloy partition that seals the rear of the passenger cabin from the unpressurized tail section. If cracked or broken, JAL technical manager Hiroaki Kohno told reporters, it could allow air from the cabin to rush in and burst the hollow vertical stabilizer.

JAL’s chief 747 pilot, Capt. Yoshio Iwao, said such a chain of events could damage the plane’s hydraulic systems, leaving the pilot with no way to control the aircraft except for engine power.

Fujiwara said investigators are concentrating on the bulkhead and “linkage” between the body and the vertical stabilizer.

In Seattle today, Boeing Co. issued a service advisory to 747 jetliner operators, saying they may wish to inspect tail sections of the giant planes.

Spokesman Richard Schleh said today that Boeing sent telex messages to 747 operators late Thursday saying: “Until the cause of the accident is determined, operators may wish to inspect the vertical fin and rudder structure due to the reported decompression (of the JAL plane’s cabin). Operators may also wish to visually inspect the external and aft portions of the pressure shell structure.”