The Federal Communications Commission is planning to solicit comment shortly on the “appropriate treatment” of 121.5 MHz emergency locator transmitters (ELTs).

The agency has released a notice that is expected to be printed in the Federal Register in upcoming weeks that questions whether, how and when the continued use of the 121.5 MHz ELTs should be phased out. The Aircraft Owners and Pilots Association calls FCC’s notice a measured approach to the issue.

The internationally supported Cospas-Sarsat satellite system stopped processing signals from the 121.5 MHz frequency in 2009, and FAA is banning development of new units that rely on the frequency. But FAA has not banned continued production, nor has it required that operators equip their aircraft with 406 MHz ELTs, which are satellite supported.

The National Transportation Safety Board last summer held a panel session on ELT use, finding that 180,000 general aviation aircraft were still equipped with the 121.5 MHz ELTs. Signals form those ELTs can only be processed through ground-based receivers or from aircraft flying overhead.

FCC in 2010 planned to ban manufacture and use of the 121.5 MHz, but stayed that ban after industry and FAA expressed opposition. FAA told FCC that 121.5 MHz ELTs can still help locate missing aircraft without satellite monitoring because the search and rescue community – including the Civil Air Patrol – still monitors the frequency. FAA and the aviation community had also expressed concerns about costs and the availability of replacements.

“We continue to believe that a phaseout of 121.5 MHz ELTs is in the public interest,” FCC says in its new notice. “While nothing in the record disputes the conclusion … that 406 MHz ELTs are superior to 121.5 MHz ELTs, or that a transition to 406 MHz ELTs would promote aviation safety, we seek further comment on these tentative conclusions,” the agency says.

FCC specifically seeks comment on timing and implementation of any such transition.

Since FAA has already prohibited production approval of new 121.5 MHz ELTs, FCC says it sees no reason to certify new models.