Secretary of Transportation Brock Adams yesterday said he believes the federal government should require automobile manufacturers to install air bags or other passive restraint systems in all cars, starting with model years 1980 to 1981.

Reversing the direction taken by his predecessor last December, who designed a demonstration project under which several firms were to sell 500,000 cars equipped with air bags or passive seat belts, Adams scheduled a public hearing on April 27 and promised a new air bag order by the end of May.

Former Secretary William T. Coleman Jr. had concluded that passive restraints were technologically feasible and that their use might prevent close to 10,000 fatalities a year. But Coleman said air bags should not be required in all autos because of possible consumer resistance to the added equipment and associated costs. He pointed to a citizen revolt which led Congress to revoke a previous government requirement for seatbelts with ignition interlocks.

Adams said yesterday that he "cannot agree" with Coleman's conclusion and he raised a question about the legality of Coleman's action.

The new DOT chief said the December decision was "flawed" because the Department of Transportation must answer only two questions in making a determination about mandated air bags: Does it save lives/Is it feasible?

Because the answers to those two questions were affirmative, "I cannot understand [Coleman's decision]. I do not think it is correct," Adams said."I do favor some type of passive restraint."

Once a new order is issued by DOT, Congress will have 30 days in which to overrule Adams, the secretary noted.

Officials of General Motors Corp. and Ford Motor Co., the nation's two largest auto makers, had no comment yesterday on Adams' announcement.In the past, auto makers have opposed madating the use of air bags, balloon-like devices designed to inflate instantaneously in the case of a crash and cushion passengers.

Both GM and Ford had agreed to participate in Coleman's deminstration program, which Adams described yesterday as little more than a promise "to manufacture some and try to sell them." When Adams issues his new proposed air bag order, the agreements with Coleman will be voided under terms of the contracts signed by GM, Ford and several foreign auto makers.

Yesterday, Adams emphasized his belief that auto makers could gear up to include air bags in all cars after 1980. The precise model year in which passive restraints will be required, the number of air bags in each car, and use of passive belts as an alternative will included in the proposed rule, Adams said.

With full production required for all cars, the cost to consumers should be $100 to $150 or somewhat higher, Adams told reporters yesterday.