The Boeing Co. said yesterday that casts of a faulty bulkhead splice found in the wreckage of a Japan Air Lines 747 will be shipped to Boeing headquarters in Seattle to determine if incorrect repairs contributed to aviation's worst single-plane disaster.

Jim Boynton, a Boeing spokesman, said a team of engineers will examine the parts from the jumbo jet, which slammed into a mountain in central Japan with 524 people aboard Aug. 12. Only four survived.

The company acknowledged the faulty repairs Friday in a letter to airlines that fly its 747 jets and said an investigation of the crash indicates "a decompression occurred during the flight due to a rupture" of the bulkhead.

Japanese officials expressed astonishment and anger over the Boeing report. Satoru Totoki, JAL managing director and vice president, said that "Boeing is known the world over and is among the best of the best. I am astonished to hear that Boeing might have made faulty repairs."

JAL's chief Boeing 747 technician, Hiroaki Kohno, was quoted by airline spokesman Satohiko Hotta as saying, "It would be unbelievable if Boeing conducted a defective repair."

The chairman of the Transport Ministry's accident investigation commission, Keizo Hatta, was quoted by Kyodo News Service as saying, "Can they really have said that? Without any notification to us probing into the crash, this one-sided announcement of the cause of the accident amounts to breaking the basic principle of an accident investigation."

Boynton said from Boeing headquarters that the Boeing team would "look fully at this repair to get to the heart of what caused the accident. Although, you've got to remember the splice may not have had any effect on the crash."

The pressure bulkhead of a 747 separates the pressurized cabin from the depressurized tail section.

Boeing experts made the repair on the JAL jet after inspecting the bulkhead at the request of airline officials following a rough landing in 1978. The accident caused the jet's tail section to drag on the runway for 1,200 feet.

Boeing conceded that about 17 percent of the bulkhead surface was incorrectly assembled during the repair but disputed a published report Friday that the problem involved a single line of rivets instead of the double line mandated by the plane's manual.

"Contrary to published reports, this misassembly does not involve a missing row of rivets," the company said. "A splice plate added during the repair was incorrectly installed in this small section of the bulkhead splice such that one of three rows of rivets did not pass through the splice plate."

In another aviation-related safety announcement, British Airways said yesterday it has withdrawn from service 22 Pratt & Whitney engines similar to the one that exploded and led to a fire on a Boeing 737 at Manchester Airport last month, killing 55 people.

The state-owned airline said the 22 JT8D-15 engines are being fitted with new combustion chambers to replace those found to be suspect in X-ray checks ordered after the Aug. 22 crash of the British Airtours jet.

British Airways, which along with its British Airtours subsidiary owns 44 Boeing 737s, said all other JT8D-15 engines now have been cleared for service after stringent tests.