The Federal Aviation Administration, which has been all over the lot on the question of whether airlines could reduce the number of doors on the Boeing 747 jumbo jet from 10 to eight, has decided to study the problem yet again.

FAA Administrator Donald D. Engen, testifying last week at the House Public Works subcommittee on investigations and oversight, promised to review his agency's decision permitting the reduction in the number of doors that could be used in an emergency evacuation.

The FAA first approved the reduction in 1983, then upheld it again in April. But the National Transportation Safety Board and the Association of Flight Attendants (AFA) opposed it, saying chances of successfully evacuating the 747 are greater with 10 doors.

The 747 was originally certificated by the FAA with 10 doors, in compliance with an FAA standard saying that there must be at least two doors for every 110 passengers and that the manufacturer must demonstrate that a fully loaded aircraft can be evacuated in the dark within 90 seconds, assuming half the doors are inoperable.

U.S. airlines use no more than 440 seats on their 747s. Therefore, under the rule, eight doors would be enough to meet the standard, assuming the evacuation test could be met. Using that reasoning, the FAA's regional office in Seattle amended the original 747 certificate to permit the reduction in planes with no more than 440 seats.

The FAA says the amendment was proposed for public comment, but consumer advocate Ralph Nader characterized the change as a "secret law" and the AFA noted it was made without the evacuation demonstration. Regulations permit "analysis and tests" as an alternative to a demonstration, an FAA spokesman said yesterday.

The AFA also said that the reduction in doors would increase the distance between emergency exits from 36 to 72 feet. That is "the widest distance between exits in any aircraft you can find," said Matthew Finucane, director of air safety for the flight attendants.

The furor continued. Engen sent U.S. airlines a letter June 12 that said, "I cannot legally prevent you from taking out these doors without going the route of changing our regulations, but I strongly encourage you to maintain the currently available exits on your passenger-carrying Boeing 747 aircraft, even though the minimum standards of the aircraft certification requirements may not require this action."

That's where the issue stood when Rep. James L. Oberstar (D-Minn.), subcomittee chairman, scheduled the hearings. Oberstar said, "I'm appalled by the potential for tragedy and astonished by the process by which this decision was reached."

In its testimony, the Boeing Co. said: "Evacuation time is governed not by the distance between exits but by the number of people seeking egress. Eight doors for a maximum of 440 people afford the same ratio of safety as 10 doors for 550."