Millions of dollars in potentially substandard helicopter parts have been sold to foreign military helicopter fleets, a knowledgeable industry informant has told authorities here.

These fleets provide, among other duties, NATO anti-submarine defense and personal transportation to heads of state such as the queen of England, the shah of Iran and Egyptian President Anwar Sadat, the informant has said.

Some of the parts have also been sold in the United States to civilian helicopter fleets, the informant says.

The parts were sold with forged identification and misleading inspection documents identifying them as top-quality, brand-name components, the source adds.

Senior helicopter industry officials have called the allegations "serious" and "alarming," and investigations are under way here and in England to determine if they are true. If the charges are accurate, officials say, they could cause the grounding of hundreds of European military helicopters. Correcting the problem might cost as much as $100 million, experts say.

In extensive interviews recently, the informant repeated his story to The Washington Post. The Post also interviewed other knowledgeable officials familiar with all or part of the alleged scheme, and they confirmed the informant's story. Two of the informants expressed fears for their personal safety because of the story, and all requested anonymity.

According to the allegations, company names or federally issued identification numbers have been forged on the parts indicating they came from - and met the standards of - the Bell Helicopter Co. or the Sikorsky Aircraft Division of United Aircraft Corp. Actually, neither company made or inspected the parts, which were manufactured by other firms working without critical processing specifications, according to the allegations.

he parts were given what appeared to be Federal Aviation Administration airworthiness certification. However, the certifications came from several FAAlicensed helicopter repair stations which were not equipped to give them full inspections nor authorized to issue the certifications.

Officials at one such station admitted to The Washington Post that they were not in a position to vouch for the parts' air-worthiness even though they issued the certifications.

Misleading certification also was supplied by Bell-licensed inspection stations in Southern California. The stations were licensed by Bell to install pre-tested Bell parts, but they were not equipped to do sophisticated testing on their own to prove the parts could meet Bell stress, metal-fatique or heat-testing requirements. Nor were the certifications authorized by Bell, according to a Bell official.

The suspect parts have allegedly ended up in at least 608 helicopters in the military fleets of Britain, West Germany, France, Belgium, Norway, Australia, Egypt, Qatar and Pakistan, and they also may have been sold to hte military helicopter fleets of Iran and Holland.

A Bell official and a British military official in Washington said that if the charges are accurate they could require the grounding of virtually all of England's military helicopter fleet.

British and West German helicopters play a major role in NATO anti-submarine warfare defenses, according to U.S. Defense Department officials.

The parts allegedly have also been installed on the personal helicopters of Queen Elizabeth II of England and Egyptian President Anwar Sadat and on a militar helicopter owned by the shah of Iran, according to the allegations.

In addition, the parts may also have been installed on civilian helicopters in Southern California, industry officials here said.

A large Californian helicopters parts supplier confirmed that his company purchased some of the parts, and said he believed they were resold to operators of civilian helicopter fleets on the West Coast.

Investigators for both Bell and Sikorsky have been working for over a week on the charges. They said it could take some time to determine if the allegations are correct.

"If they are correct, I would say these parts would have to be looked on as bogus and unairworthy," a senior Bell official said. "You can either ground the helicopter and find the parts or take a chance. If it happened in this country I think the helicopters would be grounded."

The FAA began its own investigation into the charges after The Washington Post requested information about unauthorized airworthiness certifications issued for the parts by FAA-licensed repairs shops in California. Copies of the certifications and other documents relating to the allegations were made available by sources to The Post.

The allegations center around Aviation Sales Corp., a New York City company that manufacturers and supplies helicopter parts here and abroad.

According to a number of sources, the alleged scheme followed this pattern:

Westland Helicopters ltd., a British firm located in Yeovil, England, builds helicopters under license from Bell and Sikorsky and sells spare parts for Bell and Sikorsky helicopters.

Westland received orders for Bell or Sikorsky helicopter parts from the British Ministry of Defense or from other European military fleets which it supplies.

Westland in turn ordered the parts from Aviation Sales, and the U.S. company relayed the order to its Chatsworth, Calif., subsidiary known as Hyfore Manufacturing Corp.

According to the allegations, Hyfore then placed the orders with independent manufacturers, who were not told the parts were to be sold as Bell or Sikorsky material. The independents - known in the trade as "vendors" - worked from technical drawings supplied by Hyfore, but those drawings did not contain the necessary information on hear treatments and stress testing.

According to top Bell and Sikorsky officials, neither company has granted Hyfore the permission or the information necessary to have parts made to their specifications.

The sources said the drawings supplied by Hyfore to the vendors were called "assembly drawings." These, they said, contained the dimensions of the parts to be made, but lacked important information on the parts metal content, their heat treaments and other critical data which determine how long the parts will hold up when they are installed.

Without this critical data, the sources said, the vendors in some cases were forced to "reverse engineer," or work back toward the unknown information from what was on the drawings. A Sikorsky official called doing this successfully "almost a statistical impossibility." In other cases, according to the allegations, the vendors weren't told they were making helicopter parts and had no way of determining their durability requirements.

After they were manufactured the parts went through a complicated series of transfers through various locations here. During those transfers, according to the allegations, the names or identifications of Bell or Sikorsky were forged on the parts and they received the misleading certifications from the FAA and Bell-licensed repair stations.

The first step in this process involved a manufacturers' agent here name H. Walker Sander-Cederlof. The agent, in an interview with The Washington Post, admitted that he was hired by Hyfore to have Bell's identification numbers placed on some of the parts. In some cases, he said, the parts already contained the Bell name cast on them by the vendors.

Sander-Cederlof said he took the parts to an industrial marking firm in east Los Angeles, where the identification was put on them.

"I was told what to do by Hyfore or Aviation Sales," Sander-Cederlof said in the interview. "They said please take these to such and such a place and here's what is to be done on them. And when they're through, bring them back to us." He said the marking firm placed a Bell identification number on the parts.

A top bell official said the company gave no permission to have its name placed on parts made by Hyfore.

According to the soruces the Sikorsky identification was placed on other parts at another location. That process did not involve Sander-Cederlof, they said.

The next step involved taking the parts from the manufacturers to several FAA-licensed repair stations. The stations provided each of the parts with a written certification. One station, for example, called Heli-parts in Porterville, Calif., issued a certification which read in part that the material inspected there was "airworthy per the Federal Aviation Administration regulations of the United States of America." It was signed and stamped at the bottom with Heli-Parts' FAA inspection station number.

Despite the official sound of the document, Edward Trupe, Heli-Parts' president, acknowledged in an interview that the certification was not official in any way. He said Heli-Parts was not equipped or requested by Hyfore to test the parts beyond the accuracy of their dimensions.

FAA officials said in interviews that the stations weren't authorized to issue the certification. Recently, FAA inspectors ordered at least one of the stations to stop issuing the certifications.

Last fall Heli-Parts broke off its business relationship with Hyfore. Trupe declined to say why the relationship was severed, but Heli-Parts officials said it was because the company began to suspect the parts it was certifying were not genuine Bell parts.

After the parts went through the FAA licensed repair stations, some of them were taken by Hyfore to several licensed Bell repair stations. THese stations issued additional written certications for the parts.

In one case a Los Angeles firm called Schultz Enterprises, Inc., certified that the parts it inspected were 'manufactured by the Bell Helicopter Co. or an approved supplier of the Bell Helicopter Co." Schultz was a Bell-licensed repair station until 1976. The certification also said the parts conformed 'visually and dimensionally" to Bell specifications, but did not say whether they met manufacturing specifications.

Paul Svitak, a Schultz official who signed the cretifications told the Post he had no way of knowing whether the arts could perform up to manufacturers' specifications. "We didn't check that," he said. "Hyfore checked that."

Svitak said he only certified the parts because they confromed to Bell dimensional drawings supplied by Hyfore and because they carried Bell identification numbers. He said he rejected many of the parts because they did not even meet the Bell dimensional specifications.

According to sources, another Bell station here has until recently been certifying parts going to Westland. Last year, sources said, an official of that station traveled to England and in two days certified thousands of parts shipped by Aviation Sales because the U.S. firm failed to send certifications with them.

The alleged scheme was completed when the parts were returned from the Bell stations to Hyfore, which then sent them to Westland in England. Westland either used the parts on its own assembly line or shipped them to military helicopter fleets around the world as spares and replacements.

Industry officials said the helicopters to receive the parts the Bell Model 47 series or the British equivalent, the Sioux. The parts also were sent for Sikorsky's Model S-58 and S-61, along with the British variations of these models manufactured by Westland known as the Sea King, the Wessex and the Commando.

U.S. Defense Department officials said the Sea King is used extensively in both the British and the West German NATO anti-Submarine warfare fleets.

So poorly made were some of the parts sent by Aviation Sales to Westland that in one case sources said a shipment of landing gear parts showed visible cracks where the metal had gone brittle during their manufacturing. The most evidently cracked parts were removed from the shipment, the sources said, and the rest of the batch was rushed to England because they were needed for the personal helicopter of Queen Elizabeth II.

According to sources, the alleged scheme allowed Aviation Sales an enormous mark-up on the parts it sent to Westland. A part that costs Aviation Sales $1 to have manufactured by a non-authorized source could be sold as a certified Bell or Sikorsky part for up to $75, the sources said.

The types of helicopter parts involved in the scheme ranged from tiny metal pins and bearings to whole landing gear assemblies, the sources said. One source familiar with the operation estimated that during the last three years between $20 million and $40 million in phony Bell or Sikorsky parts were shipped by Aviation Sales to Westland.

When some employees of Hyfore did raise objections they were overruled by Aviation Sales board Chairman Jack Dadourian. "One ofDadourian's favorite sayings when someone raised objections about the inspection process was 'No one ever inspects 100 per cent of there wouldn't be any planes that fall from the sky.'" sources said.

Aviation Sales declined to comment on any aspect of the allegations, including written questions submitted by The Post.

When these questions were provided, the company referred The Post to Richard Maystead, executive vice president of Hyfore.

"The questions [in the letter] referred to business matters pertaining solely to ourselves and a customer. We do not see that the information requested is a concern of your newspaper," Maystead replied in writing.

Under the circumstances," he continued, "we can see no reason to grant your request for an interview."