The government has taken a step toward regulating which passsengers may be seated in a plane beside an exit, regular or emergency.

If the Federal Aviation Administration, after listening to public responses, adopts its rule in the form that it published it on March 13, the exit rows could not be used by the blind, people traveling with small children, children traveling alone, the obese or frail, wheelchair-users, the aged, or by emotionally disturbed or retarded people, and probably others.Whether or not the rule goes through as proposed it is certain to cause an uproar. The president of the National Federation of the Blind, for example, says the proposal represents "a classic discriminatory position."

The genesis of the proposed rule is concern for passenger safety and the need to evacuate speedily a plane that is on fire or otherwise in trouble.

The FAA, which is responsible for regulations on air safety, has no rule on exit-row seating other than one allowing each airline to develop its own procedures.

The number of exits, and seats in each exit row, depends on the plane model and the airline.

The only rule that now governs the number of exits is one requiring that the plane be evacuated in a monitored test in 90 seconds.

In its new proposal, the agency says that saving passenger lives in what it calls a "survivable" emergency requires that anyone seated in an exit row be able to find the exit, see if there is an obstacle outside, recognize and use the devices that open the door, see, hear, understand and relay instructions for evacuation of the plane, unfurl the slide, exit from the plane and select a safe path away from it.

There are dozens of issues that the proposed rule discusses, including the ability to throw a heavy detachable exit door out of the way without falling out the exit or being trapped under the door panel.

Until June 12, anyone may write for a copy of the rule and the rationale for it - as published in the Federal Register, this occupied 14 pages in rather small type - and may submit written comments on it.

The comment period opened March 13. After the comment period, the responses will be addressed by the FAA in a revised document and the rule may then be put into effect as it is, changed or dropped.

If the rule is promulgated, the date it goes into effect will be published at that time; it could be as soon as 30 days or as long as two years later.

An expert in air safety regulations in the FAA said that a one-year period was a likelihood if the rule was approved.

Requests for the document containing the proposed rule should be sent to the Federal Aviation Administration, Office of Public Affairs, Public Inquiry Center, APA-430, 800 Independence Avenue SW, Washington, D.C. 20591, or made by phone to 202-267-3484.

The request must identify the document as Notice of Proposed Rulemaking, 89-8, Docket 25821.

Three weeks after the comment period opened, only four comments had been received, according to the clerk in the dockets room, Michael Triplett, but major players - the airlines, the flight attendants' union, passenger associations and advocates for the handicapped - say they intend to file comments.

The history of rules for exit-row seating has been turbulent.

An advisory committee that included representatives of groups of people with disabilities, the government and the airline industry was convened in 1987 but failed to reach a consensus on exit-row seating when the National Federation for the Blind and, according to its president, about six other disability groups, walked out of the meetings.

As a result, in mid-1988 the Department of Transportation itself, which is responsible for civil rights concerns in its area, drafted a long rule called "Nondiscrimination on the Basis of Handicap in Air Travel."

The section called "Seat Assignments" reads: "Carriers shall not exclude any person from a seat in an exit row or other location or require that a person sit in a particular seat, on the basis of handicap, except in order to comply with the requirements of an FAA safety regulation."

If this rule, which is still pending, were to be adopted without a complementary safety regulation, it would create what one lawyer at the FAA called a gap: the existing rule allowing airlines to control cabin seating would be overridden and an airline would be unable to prevent, for example, the seating of a group of children straight across an emergency exit row.

The FAA said it wanted both proposed rules, if adopted, to take effect at the same time.

The document that contains the proposed exit-row rule includes reports on evacuation tests undertaken by the FAA's Civil Aeromedical Institute in 1973.

The tests involved the handicapped , the blind, people wearing blindfolds, dolls used to simulate babies and a 200-pound dummy to simulate an immobile passenger.

"Given the results of the tests," the report said, "the researchers concluded that the average ambulatory handicapped passenger could be seated anywhere in the cabin except in an exit row or an overwing exit route, where he or she might impede the early states of an evacuation or be injured by the rush of other passengers. This approach ... serves as the basis for the present proposal."

The supporting material also cited a 1970 study by the FAA on three takeoff or landing crashes in which 105 of 261 passengers died.

"In aircraft accidents in which decelerative forces do not result in massive cabin destruction and overwhelming trauma to passsengers," this study said, "survival is determined largely by the ability of the uninjured passenger to make his way from a seat to an exit within time limits imposed by the thermotoxic environment."

The FAA said in its proposal that it also reviewed a 1987 memorandum focusing on 50 of 3,382 entries in the Civil Aeromedical Institute's cabin safety data bank.

These 50 "included problems affecting persons with disabilities, handicaps, the aged, children, the obese and others having characteristics which could affect the evacuation process," the FAA said.

"While the memorandum included some reports of successful, rapid evacuation by persons with disabilities," the FAA said, "the reports show rather dramatically that certain factors generally impede rapid evacuation - advanced age or extreme youth; parental responsibilities for minors; physical disabilities; obesity; injury or ill health."

Marc Maurer, president of the National Federation of the Blind, cites this type of statement as proving that the proposal is discriminatory.

He said: "The FAA said ... that they knew that some blind people were as capable as others in responding in an emergency. Yet they say they are going to discriminate against the whole class. This is a classic discriminatory position."

He said that some blind people were better able to function in the dark in an emergency than some sighted people but that because not all blind people could, this was not an adequate reason for barring "the whole class" of blind from the exit row.

Maurer also questioned the validity of the evacuation tests on a number of grounds. Maurer said his organization, which has 50,000 members, would submit an extensive comment on the proposal.

The Air Transport Association will support the proposal in behalf of its 21-member scheduled airlines.

"We don't want anyone in the exit row who will jeopardize passenger or crew lives," a spokesman, Leslie Rowland, said.

"The concept of whether people are able to carry out the functions needed in the exit row is the right concept. It serves our No. 1 concern, which is safety."

The International Airline Passengers Association, according to Richard Livingston, its safety consultant, said the FAA had taken the only "reasonable approach," dealing not narrowly with handicaps, but with any type of incapacity.

The National Association of Flight Attendants, the union representing crew members responsible for evacuating the plane in an emergency, said the rule would bring "much-needed uniformity" in an area where the handicapped had met varieties of rules and enforcement policies. The union will also submit a comment.

How the airlines enforce the rule, if it is adopted, will depend on them.

Some of the possibilities that have been discussed are withholding exit-row seats from the computerized sales system, asking potential passengers if they consider themselves capable of carrying out the tasks that would be needed in an emergency or filling the exit rows only after the passengers get to the airport and can be looked at and talked to.

One thing is sure: there would almost inevitably be a need to rearrange people once everyone is on the plane.