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.

FCC is proposing to prohibit future certifications. The agency is also proposing to ban continued manufacture, importation or sale of the 121.5 MHz model one year after the effective date of a rule release. FCC believes a one-year grandfather period “will enable manufacturers, importers and distributors of 121.5 MHz ELTs to largely avoid any significant economic burden associated with stranded inventory.”

But FCC asks for comment on whether one year is too short, too long or if there should be a transition period at all from a cost and safety standpoint. FCC also asked that if it were to permit the continued sale of the units, should there be additional requirements – such as special labeling – to ensure purchasers are aware that 121.5 MHz ELTs are not satellite monitored.

FCC also explores whether it should adopt a date prohibiting the use. “Should they be grandfathered indefinitely so that they would need to be replaced only at the end of their useful life or for a specific limited period of time?” FCC asks.

FCC requests information on costs associated with a mandatory transition to 406 MHz. Past estimates have ranged between $300 million -$500 million. The agency is also seeking comment on potential problems with available inventory.

Other areas where FCC is seeking information include whether continued used of 121.5 MHz fosters an “unwarranted reliance on the ELTS, whether education outreach is necessary, and whether other equipment – such as ADS-B – could be used in place of 406 MHz ELTs.

While FCC is hoping to push forward with a ban, it is also looking for comment on residual safety benefits of 121.5 MHz.