Summary
The FAA proposes to supersede Airworthiness Directive 2021-23- 12, which applies to all transport and commuter category airplanes equipped with a radio (also known as radar) altimeter. AD 2021-23-12 requires revising the limitations section of the existing airplane/ aircraft flight manual to incorporate limitations prohibiting certain operations requiring radio altimeter data when in the presence of 5G C- Band interference as identified by Notices to Air Missions. Since the FAA issued AD 2021-23-12, the FAA determined that additional limitations are needed due to the continued deployment of new 5G C-Band base stations whose signals are expected to cover most of the contiguous United States at transmission frequencies between 3.7-3.98 GHz. This proposed AD would require revising the limitations section of the existing airplane/aircraft flight manual to incorporate limitations prohibiting certain operations requiring radio altimeter data, due to the presence of 5G C-Band interference. This proposed AD would also require modifying certain airplanes to allow safe operations in the United States 5G C-Band radio frequency environment. The FAA is issuing this AD to address the unsafe condition on these products.