The FAA issued an emergency Airworthiness Directive (AD)-2011-01-53 on December 20 to owners and operators of the Piaggio Avanti twin turboprop. The AD supersedes AD 2011-01-51, issued December 18. The latest FAA-issued AD follows previous ADs issued by both the FAA and the EASA in response to reports of clogged drain holes in the environmental control unit condenser that cause water to accumulate in the belly of the aircraft and freeze, subsequently jamming the flight controls.

AD 2011-01-51 requires an immediate functional test of the drain holes and a report of the results to the FAA. Because the issue affects safety of flight, the FAA is working this AD concurrently with the EASA instead of waiting for the European agency, as the state of design, to issue an AD. This action is considered unilateral AD action. The FAA is also working with the EASA and Piaggio on this unsafe condition.