Amid growing speculation that the pilot of a Japan Air Lines jet that crashed into the waters off Tokyo's Haneda Airport last Tuesday may have been mentally unstable, Japanese authorities today launched a wide-ranging probe into JAL's pilot inspection and overall safety procedures.

Civil aviation and police officials, who are conducting separate investigations, have declined to pinpoint possible specific causes of the crash, which killed 24 persons and seriously injured 78. But the widespread speculation here about the pilot, Seiji Katagiri, 35, has brought calls from the public and the press for the airline to adopt more stringent methods of screening flyers for signs of severe emotional stress.

JAL officials have acknowledged that Katagiri, who is now undergoing treatment for crash injuries and pyschiatric testing at a Tokyo hospital, had a history of stress-related disorders that kept him largely grounded from November 1980 until August last year and under continued observation by JAL doctors and flight inspectors until the day of the crash.

According to press reports, Katagiri told police that he felt out of sorts on the flight. Newspaper photos and television films also have shown him inexplicably dressed in what appear to be civilian clothes and among the first of the survivors rescued.

Local police, meanwhile, have confirmed that the pilot complained that his home outside Tokyo had been bugged in August 1980 and that his conversations were being monitored. After checking the pilot's home, they said, they found no evidence to support the claim but did discover a hole the pilot had apparently punched in the ceiling to look for bugging devices.

Top JAL executives have acknowledged that the DC8, carrying 174 passengers on a flight from Fukuoka in southern Japan, had been making a normal landing approach until it descended to an altitude of 200 feet, went into a sharp dive and slammed into Tokyo Bay about 1,000 yards short of the runway. A simple loss of power, they have suggested, would not explain the steep angle of the crash.

Japanese investigators have so far made public only sketchy details of the accident. But they are believed to have narrowed the causes to the possibility that Katagiri pushed forward on the control stick, causing the aircraft's nose-section to dip, threw one or more of its four engines into reverse thrust, or did both.

Reverse controls are normally only applied after touchdown to brake the aircraft's forward speed. Photographs of the wreckage show signs that two of the engines were in reverse propulsion, but aviation experts said that the situation may have resulted from the shock of the crash.

Japanese press reports, meanwhile, have pieced together a bizarre tapestry of events in the cockpit minutes before the crash. Quoting police investigators, the reports say that Katagiri began yelling loudly as the aircraft made its final approach to Haneda and that copilot Toshifumi Ishikawa and flight engineer Yoshiaki Ozaki, who also survived, tried to subdue the pilot. Ishikawa, the reports add, struggled with the pilot, trying to regain control of the plane.

After the jet hit the water, Ishikawa is quoted by Mainichi, a major daily, as telling Katagiri, "Look what you've done," pointing to the seriously injured Ozaki who had apparently unfastened his seatbelt before the crash in an effort to forcibly restrain Katagiri.

The senior pilot, Mainichi reported, stared blankly out the front window of the crushed fuselage, saying unemotionally, "Oh, I've done it." Ishikawa also reportedly told investigators that on the flight to Fukuoka a day earlier, Katagiri executed a wild, banking turn, forcing the copilot to bring the aircraft under control. Investigators declined to confirm these reports, but they have acknowledged that the tape from the voice recorder aboard the aircraft has a series of abnormally loud noises in the cockpit shortly before the crash. The noises are undergoing a voice-pattern analysis, according to the investigators.

Company officials have said that Katagiri approached JAL doctors in November 1980 complaining of nausea. The doctors diagnosed his ailment as chronic gastritis, a stress-related disorder, but cleared him for flight duty as a copilot the following month when they say his condition had improved.

Last year between January and August, Katagiri underwent repeated examinations by company and private doctors and was checked out at the controls by JAL flight inspectors, company officials said.

By the time he resumed more regular flight duties in August, they acknowledged, he had developed an unspecified disorder of the nervous system. But he was reinstated as a flight captain in November on the condition that he be kept under close company watch. On the day of the crash, he had been scheduled to undergo another inflight inspection after returning from Fukuoka.

Between March and October 1981, doctors advised Katagiri on three separate occasions to see specialists and a psychiatrist, JAL officials said. JAL records do not indicate whether Katagiri did in fact consult a psychiatrist, they said.

Japanese civil aviation authorities, who require airlines to file medical reports on pilots twice a year, said today that the documents received from JAL concerning Katagiri indicated nothing abnormal. They said the reports were currently under investigation.

In the press photos of the rescue operation, Katagari is among the first wave of survivors aboard the DC8's life rafts and, later, is seated upright and looking alert on a bus ride to a nearby hotel, which had been converted into a relief operations center.

JAL officials said that Katagiri was originally listed among the dead in the immediate aftermath of the crash. Because of the chaotic circumstances following the crash, JAL President Yasumoto Takagi told reporters yesterday that he found it "incredible" that a pilot should be among the first group of rescued passengers.

According to accounts in the Japanese press, Katagiri has declined to discuss details of the accident with police and he agreed to sign a written statement last weekend only after consulting a lawyer. Asahi, a major daily, has reported that Katagiri told police he remembered pushing forward on the control stick but could not remember anything else about the crash.

JAL has prided itself on its record for passenger safety in recent years, logging a million hours in the air without a serious mishap since one of its aircraft crashed at Kuala Lumpur, Malaysia, in September 1977. The company requires its 1,841 flight crew members, including pilots, to submit to medical and operational tests every six months. JAL doctors have asserted that it is difficult to detect signs of pilot stress unless the pilots take the initiative.