Quiero saber acerca de...

khammond on DSKJM1Z7X2PROD with RULES

Federal Register / Vol. 86, No. 234 / Thursday, December 9, 2021 / Rules and Regulations emissions. The FAA determined that, at this time, no information has been presented that shows radio altimeters are not susceptible to interference caused by C-Band emissions permitted in the United States.
Additionally, the deployment of CBand wireless broadband networks is occurring globally. In certain countries, deployment has already occurred in CBand frequencies. In some countries, temporary technical, regulatory, and operational mitigations on C-Band systems have been implemented while aviation authorities complete their safety assessments. Under the FCC rules adopted in 2020, base stations in rural areas of the United States are permitted to emit at higher levels in comparison to other countries which may affect radio altimeter equipment accuracy and reliability.
The radio altimeter is an important aircraft instrument, and its intended function is to provide direct heightabove-terrain/water information to a variety of aircraft systems. Commercial aviation radio altimeters operate in the 4.24.4 GHz band, which is separated by 220 megahertz from the C-Band telecommunication systems in the 3.7
3.98 GHz band. The radio altimeter is more precise than a barometric altimeter and for that reason is used where aircraft height over the ground needs to be precisely measured, such as autoland or other low altitude operations. The receiver on the radio altimeter is typically highly accurate, however it may deliver erroneous results in the presence of out-of-band radiofrequency emissions from other frequency bands.
The radio altimeter must detect faint signals reflected off the ground to measure altitude, in a manner similar to radar. Out-of-band signals could significantly degrade radio altimeter functions during critical phases of flight, if the altimeter is unable to sufficiently reject those signals.
Many operators need to be able to land in low visibility conditions. These operators employ specially certified equipment and flightcrew training in order to be able to fly closer to the ground during approach in instrument conditions, in some cases all the way through the landing phase, without visual reference to the runway environment. These operations can only be conducted with reference to actual height above the ground, as measured by a radio altimeter.
Additionally, automatic and/or manual flight guidance systems on airplanes facilitate low visibility operations and rely on accurate radio altimeter inputs. These inputs determine when and where the aircraft
VerDate Sep<11>2014

16:33 Dec 08, 2021

Jkt 256001

flares for landing, when power reductions are made for landing, and when automated crosswind controls and other control inputs are made.
Anomalous missing or erroneous radio altimeter inputs to these systems may cause the aircraft to be maneuvered in an unexpected or hazardous manner during the final stages of approach and landing, and may not be detectable by the pilot in time to maintain continued safe flight and landing. Inaccurate radio altimeter data can result in pilots not trusting their instruments, eroding the foundation on which all instrument flight training is built.
Although the FAA has determined the operations immediately at risk are those requiring a radio altimeter to land in low visibility conditions, a wide range of other automated safety systems rely on radio altimeter data. Harmful interference to the radio altimeter could cause these systems to operate in an unexpected way. The FAA continues to work with inter-agency and industry stakeholders to collect data on potential effects to these systems to determine whether additional mitigations are necessary. The FAA determined, however, that mandatory action is not immediately required for these systems.
The FAA plans to use data provided by telecommunications providers to determine which airports within the United States have or will have C-Band base stations or other devices that could potentially impact airplane systems.
NOTAMs will be issued, as necessary, to state the specific airports where the data from a radio altimeter may be unreliable due to the presence of 5G CBand wireless broadband signals.6 For this reason, this AD requires flight manual limitations that prohibit certain operations requiring radio altimeter data at locations that will be identified by NOTAMs. Due to the dynamic nature of both the base station activation and the ongoing process of identifying the resulting affected airspace, including potential consideration for variability in C-Band deployment conditions such as radiated power levels and locations, the FAA has determined that NOTAMs are the best means to communicate changes in restrictions at affected airports.
Finally, the FAA notes that in accordance with paragraph h of this AD, any person may propose and request FAA approval of an alternative method of compliance AMOC. The proposed AMOC must include specific conditions that would address the unsafe condition e.g., by providing 6 The FAAs process for issuing NOTAMs is described in FAA Order 7930.2S, Notices to Air Missions NOTAM, December 2, 2021.

PO 00000

Frm 00009

Fmt 4700

Sfmt 4700

69985

information substantiating that certain aircraft or altimeter models are not susceptible to C-Band radiofrequency interference.
FAAs Determination The FAA is issuing this AD because the agency has determined the unsafe condition as described previously is likely to exist or develop in transport and commuter category airplanes with a radio altimeter as part of their type design.
AD Requirements This AD requires revising the limitations section of the existing AFM
to incorporate limitations prohibiting certain operations requiring radio altimeter data when in the presence of 5G C-Band wireless broadband signals as identified by NOTAM. These limitations could prevent dispatch of flights to certain locations with low visibility, and could also result in flight diversions.
Compliance With AFM Revisions Section 91.9 prohibits any person from operating a civil aircraft without complying with the operating limitations specified in the AFM. FAA
regulations also require operators to furnish pilots with any changes to the AFM 14 CFR 121.137 and pilots in command to be familiar with the AFM
14 CFR 91.505.
Interim Action The FAA considers this AD to be an interim action. If final action is later identified, the FAA might consider further rulemaking.
Justification for Immediate Adoption and Determination of the Effective Date Section 553b3B of the Administrative Procedure Act APA 5
U.S.C. 551 et seq. authorizes agencies to dispense with notice and comment procedures for rules when the agency, for good cause, finds that those procedures are impracticable, unnecessary, or contrary to the public interest. Under this section, an agency, upon finding good cause, may issue a final rule without providing notice and seeking comment prior to issuance.
Further, section 553d of the APA
authorizes agencies to make rules effective in less than thirty days, upon a finding of good cause.
An unsafe condition exists that requires the immediate adoption of this AD without providing an opportunity for public comments prior to adoption.
The FAA has found that the risk to the flying public justifies forgoing notice and comment prior to adoption of this
E:FRFM09DER1.SGM

09DER1