After five years of study, the Federal Aviation Administration has abandoned an attempt to write a regulation designed to reduce the chances of an airplane crashing for unusual reasons.

The "main reason" for withdrawing an advance notice of proposed rule-making was "we didn't have any support for it," said Charles R. Foster, director of the FAA's Northwest Mountain Region in Seattle, which is responsible for passenger aircraft certification standards.

The regulatory docket at the FAA contains letters of opposition to most or all of the FAA's proposal from, among others, Boeing, McDonnell Douglas, the Aerospace Industries Association (a manufacturers' lobby) and the Air Transport Association (the lobby of major airlines).

Perhaps the most influential letter in opposition came from James W. Mar, a professor at the Massachusetts Institute of Technology who was a member of a National Academy of Sciences panel that recommended the regulation be written.

The FAA withdrew its proposal Aug. 6, six days before a Japan Air Lines Boeing 747 slammed into a mountain after suffering severe damage in the tail section for undetermined reasons. Five hundred twenty people were killed in that, the world's worst single-plane accident.

The genesis of the debate was the worst accident in U.S. history, the May 25, 1979, crash in Chicago of an American Airlines McDonnell Douglas DC10 that killed 273 people. The accident occurred as an engine and its supporting pylon ripped from the wing as the plane's nose was lifting off a Chicago O'Hare runway.

As the pylon and engine tore loose, hydraulic lines in the wing were severed, which permitted the slats on the forward edge of the left wing to retract. Slats are curved metal plates that extend to permit an airplane to fly at slow speeds, especially during takeoffs and landings.

The slats on the right wing remained extended; thus the DC10 was flying on the right wing, but not on the left. Warning systems to alert the pilot were also knocked out. The plane rolled to the left and crashed into a field.

A National Transportation Safety Board investigation traced the crash to maintenance at American Airlines, where one of the major attachment plates for the pylon was cracked accidentally. The crack was not detected, it grew, then the plate split. During the investigation, the FAA grounded all DC10s for 30 days until it was certain there was no design problem with the pylon.

Airplanes are supposed to be able to fly safely after an engine fails at the instant the nose lifts off the runway. What the regulators had not anticipated was the subsequent breakdown in hydraulic systems, the slat retraction and the malfunctioning warning systems.

After the accident, the Transportation Department asked the National Academy of Sciences to study the way the FAA certified aircraft. A panel of experts was convened under the late Dr. George M. Low, president of Rensselaer Polytechnic Institute and a former NASA administrator. The panel's June 1980 report contained several mostly administrative recommendations about how the FAA could improve.

But one recommendation went to the heart of the DC10 crash: "The committee recommends that the FAA develop a rule requiring assurance that an aircraft is designed to continue to fly after structural failure, unless that failure itself prevents the aircraft from flying."

In other words, if a wing is torn off in a collision, it is expected that the plane will crash. If, however, an engine pylon or an aft pressure bulkhead fails because of fatigue or damage that occurs during maintenance, it is expected that the plane's vital systems will survive sufficiently for the aircraft to land safely.

The proposed regulation said, "The aircraft must be designed to successfully complete a flight after failure of any single, principal structural element . . . regardless of the improbability of the failure's occurrence . . . . "

The rule would have been in addition to an existing regulation that says manufacturers "must show that catastrophic failure due to fatigue, corrosion, or accidental damage will be avoided throughout the operational life of the airplane."

Mar's letter and those from the manufacturers primarily attacked the proposal for mandating a specific philosophy of structural design at a time when manufacturing technology is advancing, both in methods and materials. "The Low Committee was concerned with overall system effects rather than with structural design philosophy," Mar wrote.

Another member of the Low Committee was Donald W. Madole, a Washington attorney who represents the estates of aircraft accident victims in liability cases. Madole was disappointed in the decision not to proceed.

"It was my understanding that the Low Committee felt the manufacturer should identify . . . the structurally significant items to assure that the aircraft is designed to continue to fly after structural failure," he said. " . . . Why do we have an FAA if they're not going to do their job?"

Anthony J. Broderick, the FAA's associate administrator for aviation standards and a man who, like Foster, spent weeks working on the DC10 investigation, said the abandoned rule "required complete redundancy of structure . . . . That is not really what the Low Committee intended. There might be other ways to modify the rules, but I don't know any way to improve on them."