Japan's Ministry of Transport ordered additional inspections today of the cabin pressure bulkheads in all of the Boeing 747 jumbo jets flown by Japanese commercial airlines. A rupture of the bulkhead is now thought to have led to the crash of a Japanese Air Lines 747 last Monday that killed 520 persons.
The ministry cited a "possibility that the rupture" of the rear of the pressurized passenger cabin "might have triggered the damage to the vertical stabilizer and rudders," blowing apart the tail assembly and making the plane uncontrollable.
On Friday, the Boeing Co., the manufacturer of the plane, told the world's airlines that they "may wish to inspect" the tail areas of their 747s.
Hiroshi Fujiwara, an investigator for the Transportation Ministry's Aircraft Accident Investigation Commission, said at a press conference Friday that probers had found several parts of the bulkhead and that any defect of the bulkhead could lead to a decompression in the cabin. Air from the cabin could blow into the unpressurized tail compartment and destroy the vertical tail fin from inside, he said.
The inspection ordered today by the Transport Ministry is to be performed on all 747s with more than 15,000 takeoff-and-landing cycles and is to be done within 100 flight hours, beginning last Thursday. Japanese airlines have 69 Boeing 747s.
The plane that crashed -- a 747SR, or short-range jumbo, used for domestic flights -- had reached 18,831 takeoff-and-landing cycles, a JAL spokesman said. But he said that under previous instructions from Boeing, no special inspection of the tails was due for the 747SRs until 1994. Tails of other 747s were to be inspected after 30,000 takeoff-and-landing cycles, under the Boeing instructions, the spokesman said.