The Reagan administration may be pushing ahead with deregulation in other quarters, but it is clamping down on the cosmic experience of soaring through the air. The Federal Aviation Administration has issued new rules, effective Oct. 4, for hang gliders and light recreational aircraft, including a requirement that heavier gliders and their pilots be licensed.

And the FAA warned that manufacturers and pilots of the smaller craft had better develop voluntary compliance programs for safety certification and pilot proficiency, or the FAA would do it. In taking the action, the agency expressed concern about the growing number of light aircraft and their increased capabilities, and said their unrestricted use would pose a threat to other air traffic.

The rules designate a new category of aircraft -- ultralights -- which includes hang gliders and their powered counterparts. Because motorized ultralights have features that allow them to be operated much like regular aircraft, the new rules require that those that exceed certain weight and performance limits must be certified by the FAA like regular aircraft. And people who fly the heavier or high-performance powered versions will now need a pilot's license.

The FAA said it will not require certification or registration of hang gliders under 155 pounds or powered ultralights that are under 254 pounds and have a fuel capacity of five gallons or less. Motorized ultralights in that category will be limited to a top speed of 55 knots with a power-off stall speed of not more than 24 knots.

In addition to limits on weight and performance, the new rules set up right-of-way and minimum visibility standards, ban flights over congested areas, ban most flights between sunset and sunrise and authorize on-the-spot inspections by FAA personnel.