Federal Register / Vol. 87, No. 12 / Wednesday, January 19, 2022 / Rules and Regulations 2689 

List of Subjects in 10 CFR Part 430 

Administrative practice and 

procedure, Confidential business 

information, Energy conservation, 

Household appliances, Imports, 

Incorporation by reference, 

Intergovernmental relations, Small 

businesses. 

Signing Authority 

This document of the Department of 

Energy was signed on January 11, 2022, 

by Kelly J. Speakes-Backman, Principal 

Deputy Assistant Secretary for Energy 

Efficiency and Renewable Energy, 

pursuant to delegated authority from the 

Secretary of Energy. That document 

with the original signature and date is 

maintained by DOE. For administrative 

purposes only, and in compliance with 

requirements of the Office of the Federal 

Register, the undersigned DOE Federal 

Register Liaison Officer has been 

authorized to sign and submit the 

document in electronic format for 

publication, as an official document of 

the Department of Energy. This 

administrative process in no way alters 

the legal effect of this document upon 

publication in the Federal Register. 

Signed in Washington, DC, on January 12, 

2022. 

Treena V. Garrett, 

Federal Register Liaison Officer, U.S. 

Department of Energy. 

For the reasons set forth in the 

preamble, DOE amends part 430 of 

chapter II, subchapter D, of title 10 of 

the Code of Federal Regulations, to read 

as set forth below: 

PART 430—ENERGY CONSERVATION 

PROGRAM FOR CONSUMER 

PRODUCTS 

■ 1. The authority citation for part 430 

continues as follows: 

Authority: 42 U.S.C. 6291–6309; 28 U.S.C. 

2461 note. 

■ 2. Section 430.32 is amended by: 

■ a. Removing paragraph (f)(1)(iii); and 

■ b. Revising paragraphs (g)(4) and 

(h)(3). 

The revisions read as follows: 

§ 430.32 Energy and water conservation 

standards and their compliance dates. 

* * * * * 

(g) * * * 

(4) Clothes washers manufactured on 

or after January 1, 2018, shall have an 

Integrated Modified Energy Factor no 

less than, and an Integrated Water 

Factor no greater than: 

Product class 

Integrated modified 

energy factor 

(cu.ft./kWh/cycle) 

Integrated water factor 

(gal/cycle/cu.ft.) 

(i) Top-loading, Compact (less than 1.6 ft 3 capacity) ............................................................. 1.15 12.0 

(ii) Top-loading, Standard (1.6 ft 3 or greater capacity) ........................................................... 1.57 6.5 

(iii) Front-loading, Compact (less than 1.6 ft 3 capacity) ......................................................... 1.13 8.3 

(iv) Front-loading, Standard (1.6 ft 3 or greater capacity) ....................................................... 1.84 4.7 

(h) * * * (3) Clothes dryers manufactured on or 

after January 1, 2015, shall have a 

combined energy factor no less than: 

Product class Combined energy factor 

(lbs/kWh) 

(i) Vented Electric, Standard (4.4 ft 3 or greater capacity) .................................................................................................. 3.73 

(ii) Vented Electric, Compact (120V) (less than 4.4 ft 3 capacity) ....................................................................................... 3.61 

(iii) Vented Electric, Compact (240V) (less than 4.4 ft 3 capacity) ...................................................................................... 3.27 

(iv) Vented Gas .................................................................................................................................................................... 3.30 

(v) Ventless Electric, Compact (240V) (less than 4.4 ft 3 capacity) .................................................................................... 2.55 

(vi) Ventless Electric, Combination Washer-Dryer .............................................................................................................. 2.08 

* * * * * 

[FR Doc. 2022–00833 Filed 1–18–22; 8:45 am] 

BILLING CODE 6450–01–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 29 

[Docket No. FAA–2021–0065; Special 

Conditions No. 29–054–SC] 

Special Conditions: Bell Textron Inc. 

Model 525 Helicopter; Fly-By-Wire 

Flight Control System 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final special conditions. 

SUMMARY: These special conditions are 

issued for the Bell Textron Inc. (Bell) 

Model 525 helicopter. This helicopter 

will have a novel or unusual design 

feature associated with a fly-by-wire 

(FBW) flight control system (FCS). The 

applicable airworthiness regulations do 

not contain adequate or appropriate 

safety standards for this design feature. 

These special conditions contain the 

additional safety standards that the 

Administrator considers necessary to 

establish a level of safety equivalent to 

that established by the existing 

airworthiness standards. 

DATES: Effective February 18, 2022. 

FOR FURTHER INFORMATION CONTACT: John 

VanHoudt, FAA, Dynamic Systems 

Section, AIR–627, Technical Innovation 

Policy Branch, Policy and Innovation 

Division, Aircraft Certification Service, 

10101 Hillwood Parkway, Fort Worth, 

TX 76177–1524; telephone and fax 817– 

222–5193; email John.G.Van.Houdt@

FAA.Gov. 

SUPPLEMENTARY INFORMATION: 

Background 

On December 15, 2011, Bell applied 

for a type certificate for a new transport 

category helicopter, designated as the 

Model 525, under Title 14, Code of 

Federal Regulations (CFR) part 29. Bell 

applied for multiple extensions, with 

the most recent occurring on November 

12, 2020. The date of the updated type 

certification basis is December 31, 2016, 

based upon the applicant’s proposed 

type certificate issuance date of 

December 31, 2021. The Model 525 is a 


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2690 Federal Register / Vol. 87, No. 12 / Wednesday, January 19, 2022 / Rules and Regulations 

medium twin-engine rotorcraft. The 

design maximum takeoff weight is 

20,500 pounds, with a maximum 

capacity of 19 passengers and a crew of 

two. 

The Bell Model 525 helicopter will be 

equipped with a four axis full authority 

digital FBW FCS that provides for 

aircraft control through pilot input and 

coupled flight director modes. The 

design of the Bell Model 525 FBW 

controls, which provides no direct 

hydro-mechanical linkage between the 

primary cockpit flight controls or 

inceptors and the main and tail rotor 

actuators, is a first for commercial 

rotorcraft use. Therefore, the regulations 

do not contain adequate or appropriate 

safety standards for this new design 

feature. 

The rotorcraft industry is producing 

new generations of helicopters, and 

gradually increasing size, speed, load 

capacity, and technical sophistication. 

In recent years, an accelerated trend has 

occurred using rotorcraft for a wide 

range of commercial and industrial 

applications. This has resulted in 

increased complexity of modern control 

systems and increased use of 

automation in flight control systems, 

including the implementation of 

advanced flight control systems such as 

FBW FCS. 

Section 29.671(c), which provides 

requirements for transport category 

rotorcraft control systems, does not 

contain adequate or appropriate safety 

standards for this new design feature. 

Section 29.671(c) requires, in part, a 

means to allow the pilot to determine 

that full control authority is available 

prior to flight. This command control 

authority is typically achieved by 

verifying movement of the control 

quadrant through an unassisted 

mechanical pilot-initiated manipulation 

of the primary flight controls prior to 

flight. Although this approach does not 

guarantee that 100% maximum control 

movement of the flight controls has 

been achieved prior to flight, it has been 

deemed appropriate for mechanical 

flight control systems. 

Unlike traditional mechanical flight 

control systems, the FBW FCS reduces 

the opportunity for jamming of the flight 

controls due to mechanical bind, 

improper servo adjustment resulting 

from faulty maintenance, or presence of 

a foreign object in the control 

mechanism that will impair safety. This 

reduced exposure for jams is due to the 

replacement of the mechanical linkages 

between the primary cockpit flight 

controls or inceptors and the main and 

tail rotor actuators with digital signal 

processing wiring. However, the FBW 

FCS does increase the potential for 

latent failures or faults that could impair 

full control authority, unless a means 

exists to ensure the FBW FCS is fully 

functional and free of control authority 

impairment prior to flight. A FBW 

system may have the ability to verify 

full control authority without having to 

move the primary flight controls. 

Although part 29 does not contain 

adequate or appropriate safety standards 

for this novel or unusual design feature, 

14 CFR 25.671, amendment 25–23, 

provides these requirements for 

transport category airplanes. 

Accordingly, these special conditions 

are based on § 25.671 to provide 

requirements for a FBW FCS on the Bell 

Model 525 helicopter. Section 25.671(c) 

provides the same level of safety as 

intended by § 29.671(c) when 

employing a FBW FCS by including 

requirements for jamming and failure 

analysis. These special conditions 

require a comprehensive safety analysis 

of the aircraft’s FBW FCS to include 

failures due to command logic 

(software), mechanical and electronic 

interfaces to other systems, jamming, 

and maintenance. Therefore, in 

conjunction with § 29.671(a) and (b), 

these special conditions incorporate 

provisions from § 25.671(c) to establish 

a level of safety equivalent to that 

established in the regulations. 

Type Certification Basis 

Under the provisions of 14 CFR 21.17, 

Bell must show that the Model 525 

helicopter meets the applicable 

provisions of part 29, as amended by 

Amendments 29 through 55 thereto. The 

Bell Model 525 certification basis date 

is December 31, 2016. 

If the Administrator finds that the 

applicable airworthiness regulations 

(i.e., part 29) do not contain adequate or 

appropriate safety standards for the Bell 

Model 525 because of a novel or 

unusual design feature, special 

conditions are prescribed under the 

provisions of § 21.16. 

Special conditions are initially 

applicable to the model for which they 

are issued. Should the type certificate 

for that model be amended later to 

include any other model that 

incorporates the same or similar novel 

or unusual design feature, the special 

conditions would also apply to the other 

model under § 21.101. 

In addition to the applicable 

airworthiness regulations and special 

conditions, the Bell Model 525 

helicopter must comply with the noise 

certification requirements of 14 CFR 

part 36, and the FAA must issue a 

finding of regulatory adequacy under 

§ 611 of Public Law 92–574, the ‘‘Noise 

Control Act of 1972.’’ 

The FAA issues special conditions, as 

defined in 14 CFR 11.19, in accordance 

with § 11.38, and they become part of 

the type-certification basis under 

§ 21.17(a)(2). 

Novel or Unusual Design Features 

The Bell Model 525 helicopter will 

incorporate the following novel or 

unusual design features: A FBW FCS. 

This new design feature has no direct 

hydro-mechanical linkage between the 

primary cockpit flight controls or 

inceptors and the main and tail rotor 

actuators, thereby eliminating the more 

complex elements of either a manual 

movement of the controls by the pilot, 

or another manual means. 

Discussion 

These special conditions require that 

a means be available to show full 

control authority for all powered control 

systems. 

These special conditions contain the 

additional safety standards that the 

Administrator considers necessary to 

establish a level of safety equivalent to 

that established by the existing 

airworthiness standards. 

Discussion of Comments 

The FAA issued Notice of Proposed 

Special Conditions No. 29–054–SC for 

the Bell Model 525 helicopter, which 

published in the Federal Register on 

January 29, 2021 (86 FR 7516). The FAA 

received one response, from the 

European Union Aviation Safety Agency 

(EASA). 

The FAA proposed the special 

conditions, which are based on current 

§ 25.671(c), in lieu of § 29.671(c). EASA 

requested the FAA explain its rationale 

for replacing § 29.671(c), which requires 

a means to allow either full movement 

of all primary flight controls or a 

determination by the pilot that full 

control authority is available prior to 

flight. EASA stated that although FBW 

reduces the risk of jamming, it does not 

alleviate the need to allow checking the 

full control movement prior to flight 

and thus a pre-flight check is still 

necessary. 

The FAA is not replacing the 

requirement for a pre-flight check. 

Instead, these special conditions 

include a requirement for a 

comprehensive safety analysis to ensure 

the FBW FCS is fully functional and free 

of control authority impairment prior to 

flight. The comprehensive safety 

analysis should address failures due to 

command logic (software), mechanical 

and electronic interfaces to other 

systems, jamming, and maintenance. 

The safety analysis should also identify 

the existence of any latent faults. 


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Federal Register / Vol. 87, No. 12 / Wednesday, January 19, 2022 / Rules and Regulations 2691 

Therefore, the means to ensure the FBW 

FCS is fully functional and free of 

control authority impairment prior to 

flight is based on the results of the 

comprehensive safety analysis. The 

means to ensure the safety objective of 

the special conditions is met may 

consist of design, analysis, test, built in 

test, and limited pre-flight checks. 

EASA noted the proposed special 

conditions, although derived from 

§ 25.671(c), are not aligned with EASA’s 

latest Certification Specifications (CS) 

25.671 (Amendment 24). 

Under § 21.16, special conditions 

prescribed by the FAA must establish a 

level of safety equivalent to that 

established in the FAA’s existing 

regulations. Accordingly, the FAA based 

these special conditions on 14 CFR 

25.671(c) and not on EASA’s 

certification specifications. 

EASA requested the FAA clarify its 

use of the term ‘‘continued safe flight 

and landing’’ used in the proposed 

special conditions. EASA stated the 

term has a specific definition for flight 

control failures on large airplanes and 

asked whether the FAA will use a 

consistent definition for failure 

conditions under § 29.1309. EASA also 

asked whether the FAA will provide a 

definition of ‘‘continued safe flight and 

landing’’ in the context of flight control 

failures. 

Advisory Circular 29–2C, Certification 

of Transport Category Rotorcraft (AC 

29–2C), contains a definition for 

‘‘continued safe flight and landing.’’ The 

FAA plans to use this definition for the 

purposes of these special conditions. 

EASA stated the proposed special 

conditions introduce the term ‘‘normal 

flight envelope,’’ which is not present in 

EASA’s CS 29 regulation. EASA 

questioned whether it is relevant only to 

the Bell Model 525 and whether it 

means the same as ‘‘operating’’ 

envelope. 

When § 25.671 was incorporated, the 

‘‘normal flight envelope’’ was the 

aircraft approved operating limitations 

contained in the aircraft flight manual. 

This proposed special condition has the 

same intent. In order to provide clarity 

and consistency in the language 

between this special condition and 

§ 29.672, the wording will be revised to 

approved operating limitations. 

EASA asked what the FAA means by 

the proposed requirement that 

‘‘probable failures have only minor 

effects.’’ Specifically, EASA asked 

whether a probable failure is greater 

than 1E¥5 per flight hour and whether 

‘‘no safety effect’’ would be a 

noncompliance. 

In AC 29–2C, the upper part of the 

range previously applied to the term 

‘‘probable’’ has been redefined as 

‘‘reasonably probable.’’ Accordingly, the 

FAA has revised these special 

conditions by replacing ‘‘probable’’ with 

‘‘reasonably probable.’’ As provided in 

AC 29–2C, reasonably probable events 

are based on a probability on the order 

of between 10¥3 to 10¥5. If a failure is 

classified as ‘‘no safety effect,’’ then no 

further showing of compliance would be 

required. 

EASA requested the FAA change the 

language in paragraphs (1) and (2) of the 

proposed special conditions to reference 

failures as defined in § 29.671(c)(3). 

EASA states its suggested language will 

avoid a gap between EASA CS 

29.671(c)(1) and 29.671(c)(3). 

The FAA agrees and made the 

suggested change in the special 

conditions. 

EASA stated that if the FAA’s special 

conditions have a no single failure 

criterion under § 29.1309, then jams 

under § 29.671(c)(3) may need to be 

excluded. EASA referenced CS 25.1309 

(Amendment 24) for no single failure. 

EASA is correct; there is no criteria 

for single failure in § 29.1309. As such, 

the FAA has removed the ‘‘single’’ 

descriptor from the special conditions 

language to be consistent with § 29.1309 

safety objectives. The FAA does not 

agree that jams under § 29.671(c)(3) 

need to be excluded. Any failure 

condition that can be shown to be 

extremely improbable isn’t limited by 

failures that occur from a single source. 

EASA stated that using language from 

§ 25.671(c), which is applicable to 

transport category airplanes, is overly 

ambitious for rotorcraft. EASA asked 

several hypothetical questions 

concerning how an applicant would 

show compliance and requested the 

FAA provide further guidance. 

Section 29.671(c), which these special 

conditions replace as a certification 

requirement for the Model 525, requires 

either a means to allow full control 

movement of the primary flight controls 

prior to flight or a means that will allow 

the pilot to determine that full control 

authority is available prior to flight. The 

language utilized from § 25.671(c) for 

these special conditions ensures 

verification of the control authority 

prior to flight via a comprehensive 

safety analysis. This analysis is 

necessary to address failures that could 

not be detected by full control 

movement of the digital primary flight 

controls. 

EASA requested the FAA clarify 

whether § 29.691 is sufficient for an 

FBW system or whether specific 

guidance is needed for FBW flight 

controls after a power failure at entry 

into and during autorotation. 

The requirements in § 29.691, and the 

accompanying guidance in AC 29–2C, 

are sufficient for an FBW system. 

Section 29.691 requires that the flight 

control design allow rapid entry into 

autorotation after a power failure. AC 

29–2C provides that applicants may 

comply with this rule through an 

evaluation as part of the Type 

Inspection Authorization test program. 

EASA requested the FAA clarify the 

meaning of ‘‘normally encountered’’ in 

paragraph (3) of the proposed special 

conditions. Specifically, EASA asked 

whether there are jams that are not 

considered normal and are therefore 

excluded from the assessment. EASA 

further noted that the flight conditions 

listed in paragraph (3) of the proposed 

special conditions are contrary to the 

maneuvers required by §§ 29.141 and 

29.143. 

The FAA intended these special 

conditions to address jams encountered 

during any flight condition including 

transitions between flight conditions. 

The FAA has revised paragraph (3) 

accordingly. 

EASA requested the FAA clarify the 

relationship between the proposed 

special conditions and § 29.685(a), 

which addresses flight control jamming. 

EASA noted the approach in § 29.685(a) 

is different from the one proposed in the 

special conditions, as § 29.685(a) 

requires the design of the control system 

to prevent jamming. EASA states the 

proposed special conditions would not 

provide credit for jamming that may 

result in a condition where continued 

safe flight is guaranteed. 

Section 29.685(a) contains a design 

requirement for mechanical controls 

and is limited in scope. These special 

conditions are broader and include FBW 

primary flight controls that did not exist 

when § 29.685 was promulgated in 

1964. Regarding EASA’s statement 

about credit, paragraph (3) of these 

special conditions require reducing 

jamming in any phase of flight to a level 

capable of continued safe flight and 

landing. 

Applicability 

These special conditions are 

applicable to the Bell Model 525 

helicopter. Should Bell apply at a later 

date for a change to the type certificate 

to include another model incorporating 

the same novel or unusual design 

feature, these special conditions would 

apply to that model as well. 

Conclusion 

This action affects only a certain 

novel or unusual design feature on the 

Bell Model 525 helicopter. It is not a 

rule of general applicability. 


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1The FCC’s rules did not make C-Band wireless 

broadband available in Alaska, Hawaii, and the U.S. 

Territories. 

2The regulatory text of the AD uses the term ‘‘5G 

C-Band’’ which, for purposes of this AD, has the 

same meaning as ‘‘5G’’, ‘‘C-Band’’ and ‘‘3.7–3.98 

GHz.’’ 

List of Subjects in 14 CFR Part 29 

Aircraft, Aviation safety, Reporting, 

and recordkeeping requirements. 

Authority Citation 

The authority citation for these 

special conditions is as follows: 

Authority: 49 U.S.C. 106(f), 106(g), 40113, 

44701–44702, 44704. 

The Special Conditions 

Accordingly, pursuant to the 

authority delegated to me by the 

Administrator, the following special 

conditions are issued as part of the type 

certification basis for the Bell Textron 

Inc. Model 525 helicopter. Unless 

otherwise stated, the following special 

conditions will be used in lieu of 

§ 29.671(c). 

The rotorcraft must be shown by 

analysis and tests, to be capable of 

continued safe flight and landing after 

any of the following failures or jamming 

in the flight control system for any 

speed or altitude within the approved 

operating limitations, without requiring 

exceptional piloting skill or strength. 

Reasonably probable failures must have 

only minor effects. 

(1) Any failure, excluding a jam as 

listed in paragraph (3). 

(2) Any combination of failures not 

shown to be extremely improbable, 

excluding a jam as listed in paragraph 

(3). 

(3) Any jam in a control position 

encountered during any flight 

condition, including transitions, within 

the approved operating limitations, 

unless the jam is shown to be extremely 

improbable, or can be alleviated. 

Issued in Kansas City, Missouri, on January 

12, 2022. 

Patrick Mullen, 

Manager, Technical Innovation Policy 

Branch, Policy and Innovation Division, 

Aircraft Certification Service. 

[FR Doc. 2022–00862 Filed 1–18–22; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2022–0004; Project 

Identifier AD–2022–00036–T; Amendment 

39–21913; AD 2022–02–16] 

RIN 2120–AA64 

Airworthiness Directives; The Boeing 

Company Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final rule; request for 

comments. 

SUMMARY: The FAA is adopting a new 

airworthiness directive (AD) for all The 

Boeing Company Model 787–8, 787–9, 

and 787–10 airplanes. This AD was 

prompted by a determination that radio 

altimeters cannot be relied upon to 

perform their intended function if they 

experience interference from wireless 

broadband operations in the 3.7–3.98 

GHz frequency band (5G C-Band), and a 

recent determination that, during 

landings, as a result of this interference, 

certain airplane systems may not 

properly transition from AIR to 

GROUND mode when landing on 

certain runways, resulting in degraded 

deceleration performance and longer 

landing distance than normal due to the 

effect on thrust reverser deployment, 

speedbrake deployment, and increased 

idle thrust. This AD requires revising 

the limitations and operating 

procedures sections of the existing 

airplane flight manual (AFM) to 

incorporate limitations prohibiting 

certain landings and the use of certain 

minimum equipment list (MEL) items, 

and to incorporate operating procedures 

for calculating landing distances, when 

in the presence of 5G C-Band 

interference as identified by Notices to 

Air Missions (NOTAMs). The FAA is 

issuing this AD to address the unsafe 

condition on these products. 

DATES: This AD is effective January 19, 

2022. 

The FAA must receive comments on 

this AD by March 7, 2022. 

ADDRESSES: You may send comments, 

using the procedures found in 14 CFR 

11.43 and 11.45, by any of the following 

methods: 

• Federal eRulemaking Portal: Go to 

https://www.regulations.gov. Follow the 

instructions for submitting comments. 

• Fax: 202–493–2251. 

• Mail: U.S. Department of 

Transportation, Docket Operations, M– 

30, West Building Ground Floor, Room 

W12–140, 1200 New Jersey Avenue SE, 

Washington, DC 20590. 

• Hand Delivery: Deliver to Mail 

address above between 9 a.m. and 5 

p.m., Monday through Friday, except 

Federal holidays. 

Examining the AD Docket 

You may examine the AD docket at 

https://www.regulations.gov by 

searching for and locating Docket No. 

FAA–2022–0004; or in person at Docket 

Operations between 9 a.m. and 5 p.m., 

Monday through Friday, except Federal 

holidays. The AD docket contains this 

final rule, any comments received, and 

other information. The street address for 

the Docket Operations is listed above. 

FOR FURTHER INFORMATION CONTACT: 

Dean Thompson, Senior Aerospace 

Engineer, Systems and Equipment 

Section, FAA, Seattle ACO Branch, 2200 

South 216th St., Des Moines, WA 98198; 

phone and fax: 206–231–3165; email: 

dean.r.thompson@faa.gov. 

SUPPLEMENTARY INFORMATION: 

Background 

In March 2020, the United States 

Federal Communications Commission 

(FCC) adopted final rules authorizing 

flexible use of the 3.7–3.98 GHz band 

for next generation services, including 

5G and other advanced spectrum-based 

services.1 Pursuant to these rules, CBand wireless broadband deployment is 

permitted to occur in phases with the 

opportunity for operations in the lower 

0.1 GHz of the band (3.7–3.8 GHz) in 

certain markets as early as January 19, 

2022. This AD refers to ‘‘5G C-Band’’ 

interference, but wireless broadband 

technologies, other than 5G, may use the 

same frequency band.2 These other uses 

of the same frequency band are within 

the scope of this AD since they would 

introduce the same risk of radio 

altimeter interference as 5G C-Band. 

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 

4.2–4.4 GHz band, which is separated 

by 0.22 GHz 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, manual landings, 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 outof-band radio frequency 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. 


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