7/10/20

 

8900.1 CHG 712

VOLUME 4  AIRCRAFT EQUIPMENT AND OPERATIONAL AUTHORIZATIONS

CHAPTER 1  AIR NAVIGATION, COMMUNICATIONS, AND SURVEILLANCE

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Section 1  General Navigation Concepts, FAA and International Civil Aviation Organization (ICAO) Legal Framework

Source Basis:

    Administrative.

4-1    GENERAL. This section provides an explanation of navigational concepts, direction, and guidance used by Federal Aviation Administration (FAA) inspectors to evaluate requests for authorization to conduct en route operations. It also discusses methods and requirements necessary to approve or deny requests for proposed operations using aircraft and/or navigation systems new to that operator and proposed operations into new areas of en route operation using previously approved aircraft and navigational systems.

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A.    Concept of Operational Service Volume. Operational service volume is that volume of airspace surrounding an International Civil Aviation Organization (ICAO) standard airways navigation facility that is available for operational use. Within that volume of airspace, a signal of usable strength exists that is not operationally limited by co-channel interference. Within the operational service volume, an ICAO standard ground-based Navigational Aid (NAVAID) signal in space conforms to flight inspection signal strength and course quality standards including frequency protection. ICAO standard ground-based NAVAIDs are very high frequency omni-directional range stations (VOR), very high frequency omni-directional range station/distance measuring equipment (VOR/DME), and non-directional radio beacons (NDB). While the Global Positioning System (GPS) is an ICAO standard NAVAID, for purposes of defining Class I and Class II navigation, the FAA distinguishes between “standard ground-based NAVAIDs” and “standard NAVAIDs.” GPS, by virtue of its universal signal coverage, is not restricted to an operational service volume. The concept of operational service volume is critical for understanding and applying the definition of Class I navigation, as discussed in this order. For further discussion on operational service volume, refer also to the Aeronautical Information Manual (AIM).

B.    Categories of Navigational Operations. A thorough comprehension of the categories of navigational operations is essential for understanding air navigation concepts and requirements discussed in this order and other documents. Understanding the categories of navigational operations is also essential for evaluating an operator’s ability to navigate to the degree of accuracy required for the control of air traffic. In the broad concept of air navigation, two major categories of navigational operations are identified:

    Class I navigation.

    Class II navigation.

1)    Class I Navigation. Class I navigation is defined as any en route flight operation conducted in controlled or Class G airspace that is entirely within operational service volumes of ICAO standard ground-based NAVAIDs (VOR, VOR/DME, NDB).
a)    The operational service volume describes a three-dimensional volume of airspace within which any type of en route navigation is categorized as Class I navigation. For any type of navigation within this volume of airspace, instrument flight rules (IFR) navigational performance must be at least as precise as IFR navigation is required to be using VOR or VOR/DME. It is important to understand that the definition of Class I navigation is not dependent upon the equipment installed in the aircraft.

1.    For example, an aircraft equipped and approved to use GPS in the United States as the sole means of en route navigation is conducting Class I navigation when the flight is operating entirely within the operational service volume of Federal VORs and VOR/DMEs. In this example, if IFR operations are to be conducted, the IFR navigational performance of the GPS must be as precise as IFR navigation is required to be using the ICAO standard ground-based NAVAIDs.

2.    In another example, a visual flight rules (VFR) flight navigated by pilotage is conducting Class I navigation when operating entirely within the operational service volume.

b)    The operational service volumes of ICAO standard ground-based NAVAIDs determine the lateral and vertical extent of the airspace where Class I navigation is conducted (see Volume 4, Chapter 1, Section 3). Class I navigation cannot be conducted outside of this airspace. Class I navigation also includes VFR or IFR navigation operations on the following:

    Federal airways.

    Published IFR direct routes in the United States.

    Published IFR off-airway routes in the United States.

    Airways, Advisory Routes (ADR), direct routes, and off-airway routes published or approved by a foreign government, provided that these routings are continuously within the operational service volume (or foreign equivalent) of ICAO standard ground-based NAVAIDs.

c)    Generally, a Class I navigation environment is in “domestic” or “offshore” airspace (over land, extending offshore to the oceanic control area boundary). IFR separation minima used by air traffic control (ATC) are “domestic,” and also require Air Traffic Service (ATS) surveillance and very high frequency (VHF) voice communications. These domestic IFR separation minima are based on the navigational accuracy inherent in the use of ICAO standard ground-based NAVAIDs.
2)    Class II Navigation. Class II navigation is any en route operation that includes an operation or a portion of an operation that takes place outside the operational service volumes of ICAO standard ground-based NAVAIDs.
a)    Class II navigation involves operations conducted in areas where the signals from ICAO standard ground-based NAVAIDs have not been shown to meet flight inspection signal strength, course quality, and frequency protection standards. In these areas, ATC generally does not have good surveillance capabilities or direct controller-pilot VHF voice communications. Accordingly, ATC must apply larger separation criteria.
b)    When operating outside the operational service volume of ICAO standard ground-based NAVAIDs, signals from these stations cannot be relied upon as the sole means of navigating to the degree of accuracy required by ATC. Therefore, when operating outside the designated operational service volumes of ICAO standard ground-based NAVAIDs, operators must use the long-range navigation system (LRNS) approved to navigate to the degree of accuracy required for the control of air traffic.
c)    It is important to understand that the definition of Class II navigation does not address the equipment installed in the aircraft. For any type of navigation within this volume of airspace, the IFR navigational performance must be at least as accurate as the navigational performance assumed during establishment of the ATC separation minima for that volume of airspace.
d)    In the U.S. National Airspace System (NAS), it is not uncommon for VFR flights at low altitude to conduct Class II navigation while outside the operational service volumes of ICAO standard ground‑based NAVAIDs. Class II navigation includes transoceanic operations and operations in remote land areas. A more detailed discussion of Class II navigation is provided in Volume 4, Chapter 1, Section 4.

C.    Evaluation of Aircraft Navigation Equipment. Due to the complex nature of air navigation, navigational requirements of domestic and international operations, and the wide variation in ATC separation standards used in these operations, inspectors must evaluate each proposed operation while considering the following factors and assessing the underlying infrastructure to ensure that it is compatible with the aircraft navigation equipment:

1)    The aircraft.
2)    The navigational system(s).
3)    The communication system(s).
4)    The method or means of ATC surveillance used.
5)    The flightcrew’s training, skills, and recency of experience.
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6)    The area of proposed operation, including (but not limited to):

    Terrain;

    Driftdown;

    Additional passenger oxygen requirements;

    Suitable diversion/emergency airports;

    Special airports;

    Appropriate Traffic Alert and Collision Avoidance System (TCAS) requirements, if applicable; and

    Any other unique performance requirements.

7)    The operator’s experience with different aircraft and navigation, communication, and surveillance systems in the area of proposed operations.
8)    The operator’s experience with the same aircraft and navigation, communication, and surveillance systems in different areas of operations.
9)    Separation standards in the area of proposed operations.
10)    The availability of alternate navigation capabilities.
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11)    Special Areas of Operation (SAO), areas of magnetic unreliability (AMU), Required Navigation Performance (RNP), North Atlantic High Level Airspace (NAT HLA), etc.
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D.    Evaluating Operations. This section provides guidance for evaluating operations using navigational systems that have established operational characteristics and limitations within particular areas of en route operations. When an operator requests approval to use a means of navigation not addressed by this guidance, the request must be made to the Air Transportation Division (AFS-200), Aircraft Maintenance Division (AFS-300), or General Aviation and Commercial Division (AFS-800), as applicable. AFS-200, in coordination with the Flight Technologies and Procedures Division (AFS-400), will develop the necessary navigational concepts and provide national policies and guidance for evaluating such proposals.

E.    The Objectives of Air Navigation. In aviation, the following objectives of air navigation and navigational systems are necessary:

1)    The first objective is to avoid all obstacles while en route and to arrive safely and efficiently at the intended destination.
2)    The second objective is to efficiently fly an intended route with enough precision to permit ATC to safely separate aircraft.

F.    General Concepts. Early in aviation, only a few aircraft operated within any given area at the same time. The most demanding navigational requirements were to avoid obstacles and arrive at the intended destination with enough fuel remaining to safely complete a landing. As aviation evolved, the volume of air traffic grew and a corresponding need to prevent collisions increased. Today, the most significant and demanding en route navigational requirement in aviation is the need to safely separate aircraft. There are several factors that must be understood concerning the separation of aircraft by ATC.

1)    When ATC does not have a means of surveillance, such as radar or Automatic Dependent Surveillance (ADS), to verify air traffic positions, ATC must rely entirely on pilot position reports relayed from an aircraft to determine its actual geographic position and altitude. In this situation, a flightcrew’s precision in navigating the aircraft and their providing accurate position reports are critical to ATC’s ability to provide safe separation.
2)    When ATC does have a means of surveillance to verify the aircraft’s position, precise navigation and position reports, when required, are a means of providing safe separation. Flight safety in IFR operations depends directly on the operator’s ability to achieve and maintain certain levels of navigational performance. ATC radar or ADS is used to monitor navigational performance, detect navigational deviations, and expedite traffic flow.
3)    The control of air traffic requires that a certain level of navigational performance be achieved by aircraft operating under VFR to ensure safe separation of aircraft and to expedite the flow of air traffic.
a)    During cruising flight, the VFR flight altitude appropriate to the direction of flight must be maintained to ensure the required vertical separation between VFR and IFR aircraft and to assist in the prevention of collision between VFR aircraft.
b)    Any aircraft operating in accordance with ATC instructions must navigate with the level of accuracy required to comply with ATC instructions.
c)    If a clearance to enter controlled airspace has not been received, the flightcrew must navigate the aircraft with sufficient precision to avoid that airspace.
d)    A pilot must navigate VFR aircraft with sufficient precision to:

    Avoid weather conditions that would prevent visual contact with terrain and other aircraft.

    Locate a suitable airport and land safely without requiring assistance from ATC.

4-2    U.S. PUBLIC LAW, REGULATIONS, INTERNATIONAL AGREEMENTS, AND THE INTERNATIONAL CIVIL AVIATION ORGANIZATION (ICAO).

A.    General.

1)    Protection. The need to ensure protection of persons and property both in-flight and on the ground is fundamental to the regulations. Many of the design and performance requirements in aircraft certification rules are established to provide this protection. This protection is also extensively addressed in the operating and equipment rules related to air navigation. It is important that the regulations provide this protection equally to persons and property in-flight and on the ground. Approvals of route and areas of en route operation must take into account the need to protect persons and property in-flight and on the ground.
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2)    FAA Powers. The authorities and responsibilities of the FAA related to air navigation and navigation systems, practices, and procedures originate in Title 49 of the United States Code (49 U.S.C.) (originally passed as the Federal Aviation Act of 1958; recodified in 1994). Two important sections of the act are summarized as follows:
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a)    Section 40103 (formerly § 307 of the Federal Aviation Act of 1958) states that “The Administrator of the Federal Aviation Administration shall develop plans and policy for the use of the navigable airspace and assign by regulation or order the use of the airspace necessary to ensure the safety of aircraft and the efficient use of airspace.”
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b)    Section 40105 states that the Secretary of Transportation and the Administrator “shall act consistently with obligations of the United States Government under an international agreement.”
c)    Section 44701 (formerly § 601(a) of the Federal Aviation Act of 1958) mandates that the Administrator of the FAA “shall promote safe flight of civil aircraft in air commerce by prescribing …minimum standards required in the interest of safety for appliances and for the …performance of aircraft… and… regulations and minimum standards for other practices, methods, and procedure…necessary for safety in air commerce and national security.”
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3)    Chicago Convention Articles. The Convention on International Civil Aviation of 1944 (Chicago Convention) established the International Civil Aviation Organization (ICAO), a specialized agency of the United Nations charged with setting the standards and recommended practices for international aviation (ICAO Doc 7300, Convention on International Civil Aviation). By ratifying the Chicago Convention, a government (State) agrees on “certain principles and arrangements in order that international civil aviation may be developed in a safe and orderly manner and that international air transport services may be established on the basis of equality of opportunity and operated soundly and economically.” The articles of the Chicago Convention represent those certain principles and arrangements and serve as the foundation for international aviation laws, standards, recommended practices, and guidance material. Articles 1 through 42 established general principles concerning international air navigation. Articles 43 through 66 established ICAO as an organization tasked to develop principles and techniques of international air navigation and to foster the planning and development of international air transport. The following are some of the more significant articles that relate to air navigation:
a)    Article 1 recognizes that each State has complete and exclusive sovereignty over the airspace above its territory.
b)    Article 3 states that the convention applies only to civil aircraft and that each State will require their state aircraft to operate with due regard for the safety of navigation of civil aircraft.
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c)    Article 11 requires that the international air navigation laws and regulations of a contracting State relating to “the operation and navigation of such aircraft while within its territory, shall be applied to the aircraft of all contracting States without distinction as to nationality, and shall be complied with by such aircraft upon entering or departing from or while within the territory of that State.”
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d)    Article 12 relates to flight operations (Rules of the Air). This article requires that “[e]ach contracting State undertakes to adopt measures to insure that every aircraft flying over or maneuvering within its territory and that every aircraft carrying its nationality mark, wherever such aircraft may be, shall comply with the rules and regulations relating to the flight and maneuver of aircraft there in force.” This article also requires that “[o]ver the high seas, the rules in force shall be those established under this Convention. Each contracting State undertakes to insure the prosecution of all persons violating the regulations applicable.”
e)    Article 37 requires each contracting State to achieve the highest practicable degree of uniformity with ICAO standards and recommended practices, in matters related to the safety, regularity, and efficiency of air navigation.
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f)    Article 38 requires each contracting State to “give immediate notification” of differences between its own practice and that established by the international standard.
4)    ICAO Annexes. The articles of the Chicago Convention contain basic principles that are the foundation for ICAO annexes. ICAO annexes contain the Standards and Recommended Practices (SARPs) that have been adopted with international agreement to ensure the safety, regularity, and efficiency of air navigation. An ICAO standard is stated in mandatory language (shall, must, will) and is directive in nature. A recommended practice is stated in permissive language (should, may, can) and is not directive. Recommended practices represent practices that the uniform application of which are recognized as desirable, but not necessary, in the interest of safety, regularity, or efficiency of international air navigation. The following are the ICAO annexes that are most significant to FAA inspectors:
a)    Annex 1, Personnel Licensing, Paragraph 3.4, Flight Radiotelephone Operator.
b)    Annex 2, Rules of the Air.
c)    Annex 6, Operation of Aircraft.
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d)    Annex 8, Airworthiness of Aircraft.
e)    Annex 11, Air Traffic Services.
5)    ICAO Annex 1, Personnel Licensing, Paragraph 3.4, Flight Radiotelephone Operator. This paragraph addresses international telecommunication conventions.
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6)    ICAO Annex 2. This annex specifies international rules of the air agreed upon by ICAO Member States. Annex 2 applies to the extent that it does not conflict with the rules published by the State with jurisdiction over the territory flown. Article 38 of the Chicago Convention allows departures from international standards, so long as the State notifies ICAO of such differences. The U.S. rules for operating within the airspace over the territory of the United States are contained in Title 14 of the Code of Federal Regulations (14 CFR) part 91. However, over the high seas, Annex 2 applies without exception (compliance is mandatory for all civil aircraft; see Article 12 and the foreword to Annex 2). Annex 2 is incorporated by reference into part 91. Part 91, § 91.703(a) requires each person operating a civil aircraft of U.S. registry outside of the United States to comply with Annex 2 when operating over the high seas. The sections of Annex 2 most relevant to the discussion of air navigation are Chapter 3, General Rules, and Chapter 5, Instrument Flight Rules.
a)    Chapter 3, paragraph 3.3 specifies requirements for ATC flight plans, and paragraph 3.6 specifies requirements for ATC services.
b)    Chapter 3, paragraph 3.6.2 requires an aircraft to adhere to its “current flight plan” (currently effective ATC clearance), to operate along the defined centerline of any Air Traffic Service (ATS) route used, and on any other route to operate directly between the points defining that route.
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c)    Chapter 3, paragraph 3.6.5 requires that the flightcrew of any aircraft operated as a controlled flight to maintain a continuous air-ground voice communication watch on the appropriate communication channel of, and establish two-way communication as necessary with, the appropriate ATC unit.
d)    Chapter 5, paragraph 5.1.1 requires aircraft to be equipped with suitable instruments and navigational equipment appropriate to the route the pilot will fly.
e)    Chapter 5, paragraph 5.2.1 requires all IFR flights to comply with the provisions of paragraph 3.6 when operating in controlled airspace.
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f)    These requirements, as specified in Chapters 3 and 5 of Annex 2, mean that the aircraft must be navigated to the degree of accuracy required for ATC. Flightcrews must maintain a continuous communication watch and communicate with ATC as necessary for the purpose of ATC.
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g)    ICAO Doc 7030, Regional Supplementary Procedures, forms the procedural part of the Air Navigation Plans (ANPs) developed by ICAO Regional Air Navigation (RAN) meetings to meet those needs of specific areas that are not covered in the worldwide provisions. Procedures of worldwide applicability are either included in Annexes as SARPs or they form part of one of the documents titled, “Procedures for Air Navigation Services” (PANS). Flightcrews must be aware of the regional procedures and Notices to Airmen (NOTAM) for the areas in which they plan on operating.
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7)    ICAO Annex 6. ICAO Annex 6 has two parts applicable to fixed-wing aircraft. Part I specifies requirements for airplanes engaged in scheduled international air services and nonscheduled international air transport operations for compensation or hire. Part I applies to airplanes operated under 14 CFR parts 121 and 135. Part II specifies requirements for international General Aviation (GA) operations. The purpose of Part I is to facilitate safety in international airspace by providing standards for safe navigational operating practices. Part I also contributes to the efficiency and regularity of international air navigation by encouraging States to facilitate passage of other States’ airplanes over their territories by operating in conformity with such standards. The application of Annex 2 to international operations differs slightly from Annex 6. As mentioned above in subparagraph 4-2A6), a State may take exception to Annex 2 standards (file a “difference” in accordance with Article 38) for operations conducted in its sovereign airspace; however, any differences a State files to Annex 2 are applicable in that State’s sovereign airspace only. Annex 2 applies to all operations over the high seas without exception. Under Annex 6 standards, a State may take exception for operations of its aircraft in its sovereign airspace and for operation of its aircraft over the high seas. For air navigation, the most relevant section of Annex 6 is Chapter 7, Aeroplane Communication, Navigation and Surveillance Equipment. This chapter contains ICAO SARPs related to Communication, Navigation, and Surveillance (CNS). Pertinent elements of these SARPs are described as follows:
a)    Each airplane must have radio communication equipment capable of receiving meteorological information during the flight and conducting two-way communication at any time during the flight with aeronautical stations on frequencies prescribed by the appropriate authority. This requirement cannot be routinely satisfied by relaying reports through other aircraft.
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b)    Each airplane must have navigational equipment that enables it to proceed in accordance with its operational flight plan and the requirements of ATC services. Operations in NAT HLA require navigational equipment that continuously provides information to the flightcrew of adherence to or departure from track with respect to the required degree of accuracy at any point along that track. Any operation in NAT HLA must be authorized by the State responsible for that operator.
c)    Each airplane must have enough navigation equipment installed and operational to ensure that, if one item of equipment fails at any time during the flight, the remaining equipment will be sufficient to enable navigation to the degree of accuracy (and to ensure continuity of service) required for ATC. Additionally, failure of any single unit required for communication or navigation purposes, or both, must not result in the loss of another required unit.
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8)    ICAO Annex 8. ICAO Annex 8 specifies uniform procedures for the certification and inspection of aircraft.
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9)    ICAO Annex 11. ICAO Annex 11 pertains to the establishment of airspace, units, and services necessary to promote a safe, orderly, and expeditious flow of air traffic. Annex 11 states: “[a] clear distinction is made between ATC service, Flight Information Services (FIS), and alerting service. Its purpose, together with Annex 2, is to ensure that flying on international air routes is carried out under uniform conditions designed to improve the safety and efficiency of air operation.” Further, the SARPs in Annex 11 apply in those parts of the airspace under the jurisdiction of a Contracting State where ATSs are provided and a Contracting State accepts the responsibility of providing ATSs over the high seas or in airspace of undetermined sovereignty. A Contracting State accepting such responsibility may apply the SARPs in a manner consistent with that adopted for airspace under its jurisdiction.
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B.    Relationship Between 14 CFR, ICAO Annexes, and Foreign National Regulations. Title 49 of the United States Code (49 U.S.C.) is the codification of the laws regarding transportation in the United States. The implementation of such transportation laws related to aviation is contained in 14 CFR. The relationship between 14 CFR, ICAO Annexes, and foreign national regulations are discussed in the following subparagraphs.

1)    Part 91 regulates the operation of all civil and public aircraft within the United States and specifies minimum capabilities necessary to navigate to the degree of accuracy required for ATC. It also regulates the operation of civil aircraft of U.S. registry outside the United States. The following are examples of part 91 regulations applicable outside the United States:
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a)    Section 91.703 requires each person operating a civil aircraft of U.S. registry to comply with ICAO Annex 2 when over the high seas and to comply with the regulations of a foreign country relating to the flight and maneuver of aircraft when operating within that country’s territorial airspace.
b)    Section 91.703(a)(3) requires compliance with part 91 (except for §§ 91.71, 91.117(a), 91.307(b), 91.309, and 91.323) when not in conflict with the applicable regulations of a foreign country or Annex 2.
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2)    In addition to the part 91 requirements in subparagraph 1) above, for operators conducting operations under part 121, § 121.1 requires compliance with that part while operating within or outside the United States. Section 121.11 specifies that these operators, when operating within a foreign country, must comply with the following:
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a)    Air traffic rules of the country concerned and any local airport rules that may be in force.
b)    All rules of part 121 that are more restrictive than a foreign country’s rules must be followed, if it can be done without violating the rules of that country.
c)    Annex 2 when over the high seas, in accordance with § 91.703.
3)    The regulations listed below are in addition to part 91 requirements. For operators conducting operations under part 125, § 125.23 requires compliance with that part while operating within and outside the United States and specifies that these operators, when operating within a foreign country, must comply with the following:
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a)    Air traffic rules of the country concerned and any local airport rules that may be in force.
b)    All rules of parts 61, 91, and 125 that are more restrictive than a foreign country’s rules must be followed, if it can be done without violating the rules of that country.
c)    Annex 2 when operating over the high seas, in accordance with § 91.703.
4)    The following regulations are in addition to the part 91 requirements. For operators conducting operations under part 135, § 135.3 requires compliance with that part while operating within the United States. It also specifies that while operating outside the United States, these operators must comply with the following:
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a)    Air traffic rules of the country concerned and any local airport rules that may be in force, when operating within that country.
b)    All the regulations of parts 61, 91, and 135, which are more restrictive than Annex 2 or regulations of a foreign country when compliance with these U.S. regulations would not violate requirements of Annex 2 or the foreign country.
c)    Annex 2, when operating over the high seas, in accordance with § 91.703.
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5)    Part 91 subpart A regulates the operation of all civil and public aircraft within the United States and specifies minimum capabilities necessary to navigate to the degree of accuracy required for ATC. Sections 91.1 and 91.101 specify that part 91 prescribes rules governing the operation of aircraft in the United States. This includes aircraft used in fractional ownership program operations under part 91 subpart K (part 91K). In addition to the sections of part 91 that regulate civil aircraft of U.S. registry outside the United States, the program managers must comply with the following:
a)    Rules of the country concerned and any local airport rules that may be in force.
b)    All regulations of parts 61, 91, and 91K that are more restrictive than a foreign country’s rules must be followed, if it can be done without violating the rules of that country.

C.    Relationship of U.S. 14 CFR to Air Navigation.

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1)    Title 14 CFR related to air navigation were written to accommodate the need to efficiently handle a continuous growth in air traffic. Significant advances in air navigation technology, ATC techniques, and ATC equipment have permitted and required these regulations to evolve to their current status. Over the past years, numerous operational regulations have been adopted to specifically satisfy the critical air navigation objective of safely separating aircraft. Certain regulations, such as those requiring filing an ATC flight plan and complying with ATC clearances, are clearly related to this objective. Other 14 CFR provisions are not as clearly related, but have a direct bearing on the overall plan used to separate aircraft. The ATC system presumes compliance with all of the regulations related to air navigation. Any noncompliance with these regulations can seriously degrade the ability to separate aircraft.
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2)    Examples of operational 14 CFR provisions related to air navigation and the objective of safely separating aircraft include the following:
a)    Section 91.123, Compliance with ATC Clearances and Instructions;
b)    Section 91.129, Operation in Class D Airspace;
c)    Section 91.130, Operation in Class C Airspace;
d)    Section 91.131, Operation in Class B Airspace;
e)    Section 91.135, Operations in Class A Airspace;
f)    Section 91.137, Temporary Flight Restrictions in the Vicinity of Disaster/Hazard Areas;
g)    Section 91.143, Flight Limitation in the Proximity of Space Flight Operations;
h)    Section 91.157, Special VFR Weather Minimums;
i)    Section 91.159, VFR Cruising Altitude or Flight Level;
j)    Section 91.169, IFR Flight Plan: Information Required;
k)    Section 91.173, ATC Clearance and Flight Plan Required;
l)    Section 91.179, IFR Cruising Altitude or Flight Level;
m)    Section 91.181, Course to be Flown;
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n)    Section 91.511, Communication and Navigation Equipment for Overwater Operations (applicable to subpart F, Large and Turbine-Powered Multiengine Airplanes and Fractional Ownership Program Aircraft, as described in Section 91.501, Applicability);
o)    Section 91.703, Operations of Civil Aircraft of U.S. Registry Outside Of the United States; and
p)    Section 91.706, Operations Within Airspace Designated as Reduced Vertical Separation Minimum Airspace.
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D.    Regulations Specifying Air Navigation and Surveillance Equipment Requirements. Many regulations require specific aircraft equipment. These requirements relate directly to the air navigation objective of safely separating aircraft. Some of these equipment rules specifically relate to the operational requirement of navigating to the degree of accuracy required for ATC. The air navigation equipment rules of parts 121, 125, and 135 are often supplemented by operations specifications (OpSpecs) that contain specific authorizations, limitations, and conditions which must be complied with by operators conducting flights under those parts. The following discussion references air navigation equipment requirements and provides direction, guidance, and clarification, when appropriate.

1)    Certain subparts of part 91 specify navigation and communications equipment necessary for operations in the U.S. National Airspace System (NAS). The following are examples of part 91 equipment requirements, with clarification when appropriate. Inspectors should read the appropriate 14 CFR in conjunction with this material.
a)    Section 91.171, VOR Equipment Check for IFR Operations.
b)    Section 91.205, Powered Civil Aircraft with Standard Category U.S. Airworthiness Certificates: Instrument and Equipment Requirements.
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1.    Section 91.205(d)(2) requires communication and navigation equipment to be suitable for the route to be flown. Some airways are based on VOR and VOR/DME ground facilities. To fly those airways, this regulation requires that VOR and/or VOR/DME, or an Area Navigation (RNAV) system that meets the en route criteria be installed and operable. This navigational equipment is necessary to navigate to the degree of accuracy required for ATC.

2.    Section 91.205(e) requires approved DME or a suitable RNAV system when operating at or above 24,000 feet mean sea level (MSL) if the route or route segment is predicated on VOR. DME is not required, for example, when navigation is based on the use of an RNAV system that meets the appropriate Airworthiness Certificate or equivalent en route performance and reliability criteria (or equivalent) without input from DME.

c)    Section 91.209, Aircraft Lights.
d)    Section 91.215, ATC Transponder and Altitude Reporting Equipment and Use.
e)    Section 91.217, Data Correspondence Between Automatically Reported Pressure Altitude Data and the Pilot’s Altitude Reference.
f)    Section 91.219, Altitude Alerting System or Device: Turbojet-Powered Civil Airplanes.
g)    Section 91.221, Traffic Alert and Collision Avoidance System Equipment and Use.
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h)    Section 91.225, Automatic Dependent Surveillance-Broadcast (ADS-B) Out Equipment and Use.
i)    Section 91.227, Automatic Dependent Surveillance-Broadcast (ADS-B) Out Equipment Performance Requirements.
2)    Part 121 specifies the navigational equipment necessary for all operations conducted under that part, including operations outside the United States. These requirements are in addition to the navigational equipment requirements of part 91, but do not require duplication of any equipment specified in part 91. All of part 121 en route requirements reflect the concept of “demonstrated ability.” The following are examples of part 121 navigation equipment requirements. Inspectors should read the appropriate 14 CFR in conjunction with this material.
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a)    The air carrier must show that it is able to conduct satisfactory operations over the routes and areas in which it operates. Approvals in areas and on specific routes are granted in OpSpecs and listed by “area of en route operation” and specific route, when appropriate. The general requirements are specified in §§ 121.93 and 121.113. Certain OpSpecs stipulate requirements for operations in Class G airspace.
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b)    Sections 121.95 (domestic/flag) and 121.115, Route Width, (supplemental) specify the considerations in determining route width. Certain Part B OpSpecs address these requirements (see Volume 3, Chapter 18, Section 4).
c)    Sections 121.103 and 121.121, En Route Navigational Facilities.
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1.    Sections 121.103(a) and 121.121(a) require operators to show that “suitable navigation aids are available to navigate the airplane along the route within the degree of accuracy required for ATC.”

2.    Area navigational systems that are certified for IFR flight are compliant with §§ 121.103 and 121.121 when relying on space-based Navigation Aids (NAVAID), such as the U.S. GPS.

3.    Sections 121.103 and 121.121 do not specifically state or imply a redundant navigation equipment capability. In addition, these regulations do not apply to VFR pilotage operations, or “other operations approved by the responsible Flight Standards office” (e.g., operations with a flight navigator or long-range navigation operations using an inertial navigation system (INS)).

d)    Section 121.305, Flight and Navigational Equipment.
e)    Section 121.323, Instruments and Equipment for Operations at Night.
f)    Section 121.325, Instruments and Equipment for Operations Under IFR or Over-the-Top.
g)    Section 121.345, Radio Equipment.
h)    Section 121.347, Communications and Navigation Equipment for Operations Under VFR Over Routes Navigated by Pilotage.

1.    If the route is navigated using an area navigational system, radio navigational signals compatible with the airborne area navigational system must be available if required for the system to perform its intended function. Unless the route is navigated using an area navigation system certified for IFR flight in accordance with criteria in the appropriate guidance, airborne VOR equipment is required when the route is predicated on VOR. Airborne ADF equipment is required when it is predicated on NDB.

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2.    Although § 121.611 permits VFR en route operations, part 121 operators are generally prohibited from conducting VFR en route operations by Part B of the OpSpecs. Certain part 121 operators may be specifically authorized to conduct VFR en route operations in special situations (see Volume 3, Chapter 1).

i)    Section 121.349, Communication and Navigation Equipment for Operations Under VFR Over Routes Not Navigated by Pilotage or For Operations Under IFR or Over the Top, requires that airplanes be equipped to receive radio navigational signals from all primary en route and approach navigational facilities intended to be used.
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1.    The intent of this regulation is to require redundant navigation capability (VOR, VOR/DME, NDB, or GNSS) to ensure the ability to navigate to the degree of accuracy required for ATC. Sections 121.103 and 121.121 state that NAVAIDs are not required for “other operations approved by the responsible Flight Standards office.” This could include operations where celestial or other means of navigation are approved by the Administrator.

2.    Section 121.349 applies to both Class I and Class II navigation operations. The intent of § 121.349 is met when any navigation operation is predicated on the following:

a.    VOR, provided dual independent VOR equipment is installed and operable in the airplane.

b.    NDB, provided dual independent ADF equipment is installed and operable in the airplane. However, if one ADF system and a dual independent VOR system are installed and operable, the intent of § 121.349 is met provided VOR NAVAIDs are located at ground positions that would permit the flight to safely proceed (from any point along the route) to a suitable airport and complete an instrument approach without using ADF equipment.

c.    RNAV systems, provided either dual independent RNAV systems certified under the appropriate guidance are installed and operable or if the capability exists to revert to VOR or NDB, a single RNAV system is installed and operable.

3.    Part B of the OpSpecs permits (under specified conditions) an RNAV system fix to be substituted for an ICAO ground-based NAVAID when that facility is temporarily out of service.

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j)    Section 121.351, Communication and Navigation Equipment for Extended Overwater Operations and for Certain Other Operations, Applies to Both Class I and Class II Navigation Operations.
k)    Section 121.355, Equipment for Operations on Which Specialized Means of Navigation Are Used, limits the definition of “specialized means of navigation,” such as INS operations, when operating outside the United States. Section 121.355 is referenced in § 121.389 which requires “specialized means of navigation” (INS or inertial reference system (IRS)) to be approved in accordance with § 121.355. GNSS, INS, and IRS are LRNSs that can be used to satisfy the requirements of Class II navigation.
l)    Section 121.357, Airborne Weather Radar Equipment Requirements, apply to weather radar normally used for thunderstorm detection and avoidance.
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m)    Section 121.389, Flight Navigator and Specialized Navigation Equipment, applies to situations when the aircraft position cannot be reliably fixed for a period of more than 1 hour.
3)    Part 125 specifies the navigation and communications equipment necessary for all operations under part 125, including part 125 operations outside the United States. These requirements are in addition to the navigation and communications equipment requirements of part 91, but do not require duplication of any equipment specified in part 91. The following are examples of part 125 navigation and communications equipment requirements, with clarification, when appropriate. Inspectors should read the appropriate 14 CFR in conjunction with this material.
a)    Section 125.203, Communication and Navigation Equipment.
b)    Section 125.224, Collision Avoidance System.
c)    Section 125.225, Flight Data Recorders.
d)    Section 125.226, Digital Flight Data Recorders.
e)    Section 125.227, Cockpit Voice Recorders.
f)    Section 125.267, Flight Navigator and Long-Range Navigation Equipment.
4)    Part 135 specifies the navigation and communications equipment necessary for all operations under part 135, including part 135 operations outside the United States. These requirements are in addition to the navigation and communications equipment requirements of part 91, but do not require duplication of any equipment specified in part 91. The following are examples of part 135 navigation and communications equipment requirements, with clarification, when appropriate. Inspectors should read the appropriate 14 CFR in conjunction with this material.
a)    Section 135.143, General Requirements.
b)    Section 135.149, Equipment Requirements: General.
c)    Section 135.159, Equipment Requirements: Carrying Passengers Under VFR at Night or Under VFR Over-the-Top Conditions.
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d)    Section 135.161, Communication and Navigation Equipment for Aircraft Operations VFR at Night or Under VFR over Routes Navigated by Pilotage, requires navigational equipment suitable for the route to be flown. The ground facilities and airborne equipment used must enable navigation to the degree of accuracy required for ATC. Airborne equipment requirements must also comply with Part B of the OpSpecs.

1.    If the route is navigated using an RNAV system installed in accordance with the appropriate guidance, the installed RNAV equipment must be operable. VOR and/or ADF equipment are not required for en route operation dispatch where an RNAV system certified for IFR flight is installed, in accordance with the applicable guidance, and operable. Additionally, all ground-based or space-based elements of the support system must be operational at dispatch.

2.    Unless the route is navigated using an RNAV system certified for IFR flight in accordance with appropriate ACs, VOR equipment must be installed and operable if the route is predicated on VOR. ADF equipment must be installed and operable if the route is predicated on NDB.

e)    Section 135.163, Equipment Requirement: Aircraft Carrying Passengers Under IFR.
f)    Section 135.165, Communication and Navigation Equipment: Extended Over-Water or IFR Operations.

1.    The requirements of § 135.165 apply to both Class I and Class II navigation equipment requirements. Part 135 Class II navigation requirements are specified in Part B of the OpSpecs.

2.    This regulation requires two independent systems for navigation compatible with the facilities to be used. For en route navigation (excluding terminal operations), the facilities that must be used, whether self-contained, ground-based, or space-based, must enable navigation to the degree of accuracy required for ATC. Airborne equipment requirements must also comply with Part B of the OpSpecs.

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3.    If the route is navigated using an RNAV system installed and approved in accordance with the en route criteria of the applicable airworthiness certificates, two independent RNAV systems must be installed and operable. Dual VOR and/or dual ADF equipment is not required for en route operations when two independent RNAV systems, certified for IFR flight in accordance with the applicable ACs, are installed and operable and all elements of the support facilities are serviceable. For example, two independent GPS/GNSS systems or one independent GPS/GNSS system and some other approved independent RNAV system would be acceptable configurations.

4.    Part B of the OpSpecs permits (under specified conditions) an approved RNAV system fix to be substituted for an ICAO ground-based NAVAID when that facility is temporarily out of service.

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5.    Unless routes are navigated using an RNAV system certified for IFR flight in accordance with the appropriate airworthiness certificates, two independent VOR systems must be installed and operable if the route is predicated on VOR and two independent ADF systems must be installed and operable if the route is predicated on NDB. Section 135.165(g) allows for the installation and use of a Single Long-Range Navigation System (S-LRNS) in certain geographic areas. This may be authorized by the issuance of OpSpec B054, Oceanic and Remote Airspace Navigation Using Single Long-Range Navigation System (S-LRNS).

g)    Section 135.175, Airborne Weather Radar Equipment Requirements.
h)    Section 135.215, IFR: Operating Limitations, specifies the degree of accuracy required when operating IFR outside of controlled airspace (e.g., Class G airspace and/or at an airport without an operating control tower). It also reflects the concept of “demonstrated ability” to safely conduct operations.

4-3    NAVIGATION CONCEPTS.

A.    Concept of Navigation Performance. The concept of navigation performance involves the precision that must be maintained for both the assigned route and altitude by an aircraft operating within a particular area. Navigation performance is affected by the deviation (for any cause) from the route of flight specified in the ATC clearance. This includes errors due to degraded accuracy and reliability caused by the design and maintenance of airborne and ground-based navigational equipment and the flightcrew’s competency.

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1)    The concept of navigational performance is fundamental to the regulations and is best defined in §§ 121.103 and 121.121, which state that each aircraft must be navigated to “the degree of accuracy required for air traffic control.” Section 91.123 requirements related to compliance with ATC clearances and instructions also reflect this fundamental concept. The concept of navigational performance is also inherent in ICAO SARPs. For example, Annex 2 states that the aircraft “shall adhere to the current flight plan” (comply with the currently effective ATC clearance) and “when on an established ATS route, operate along the defined centre line of that route.”
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NOTE:  Strategic Lateral Offset Procedures (SLOP), to be used at the pilot’s option, allow properly equipped aircraft to be flown offset up to 2 nautical miles (NM) to the right of the center line based on direction of flight. This procedure is designed to decrease the collision risk and avoid wake turbulence.

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2)    RNAV operations permit flight in any airspace with prescribed accuracy tolerances without the need to fly directly over ground-based navigation facilities. The application of RNAV techniques in various parts of the world has been shown to provide a number of advantages over more conventional forms of navigation.
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3)    RNP provides RNAV performance standards that can be used and applied by aircraft and aircraft equipment manufacturers, airspace planners, aircraft certification and operations, pilots and controllers, and international aviation authorities. RNP, along with other aspects of communications, navigation, and surveillance, can be applied to obstacle clearance or aircraft separation requirements to ensure a consistent application level. For further information on RNP, refer to Advisory Circular (AC) 90-105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace, and/or ICAO Doc 9613, Performance-based Navigation (PBN) Manual.

B.    Global Positioning System (GPS) and Wide Area Augmentation System (WAAS) Navigation. GPS is a Global Navigation Satellite System (GNSS) operated by the United States. WAAS is an air navigation aid developed to augment the GPS, with the goal of improving its accuracy, integrity, and availability. For a full and up-to-date description on these systems and current navigation policy, please see the U.S. AIM, in particular Section 1, “Navigation Aids.” For airworthiness topics associated with GPS/GNSS and WAAS, refer to AC 20‑138, Airworthiness Approval of Positioning and Navigation Systems. Also refer to AC 90-105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace.

1)    Use of WAAS in Alaska Operations.
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a)    Aviation safety inspectors (ASI) should see Volume 3, Chapter 18, Section 4, OpSpec B030, IFR Navigation Using GPS/WAAS RNAV Systems, for issuance of OpSpecs that authorize WAAS RNAV operations in Alaska. In accordance with Special Federal Aviation Regulation (SFAR) 97, OpSpec paragraph B030 is issued for IFR en route RNAV operations in Alaska and its airspace on published air traffic routes using TSO-C145a/C146a navigation systems as the only means of IFR navigation. The OpSpec also authorizes TSO‑C145a/C146a navigational systems to be used for IFR en route operations at special minimum en route altitudes (MEA) that are outside the operational service volume of ground-based NAVAIDs, if the aircraft operation meets the requirements of Sections 3 and 4 of SFAR 97.
b)    SFAR 97 is applicable to U.S. and foreign operations conducted in Alaska under parts 91, 121, 125, 129, and 135. The SFAR allows IFR operations using dual TSO-C145a/C146a GPS/WAAS systems as the only means of navigation on Federal airways and other published ATS routes in domestic airspace, both within and outside the operational service volume of ground-based NAVAIDs. The rule also authorizes the use of GPS-designated MEA for aircraft using TSO-C145a/C146a systems. These GPS MEAs along applicable routes are indicated on IFR charts in blue followed by the letter “G.” The SFAR also establishes training requirements for operators of TSO-C145a/C146a-equipped aircraft including training in service degradation and equipment failure modes.

C.    Concept of the Degree of Accuracy Required for Control of Air Traffic. The fundamental concept for all IFR navigation standards, practices, and procedures is that all IFR aircraft must be navigated to the degree of accuracy required for control of air traffic.

1)    When a flight adheres to the clearance assigned by ATC at all times, that aircraft is considered to be navigated to the degree of accuracy required for the control of air traffic. If an aircraft makes an unauthorized deviation from its assigned clearance, that aircraft has not been navigated to the degree of accuracy required for control of air traffic.
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2)    ATC separation minima establish the minimum lateral, vertical, and longitudinal distances that are used to safely separate aircraft operating within a specified area. Separation minima also represent the minimum level of overall navigation performance and a buffer that can be accommodated at any time without jeopardizing safety of flight. These separation minima have been established for IFR operations in controlled airspace. These standards are usually established through international agreement and implemented through national regulations. These minima are established for particular categories of navigational operation and specified areas.
3)    For operations where ATC services are provided by the United States, separation minima are established in accordance with ATC directives, and associated operator requirements are published in the 14 CFR. For operations where ATSs are provided by contracting ICAO Member States, separation minima are established in accordance with criteria of the Member States, which are generally aligned with procedures for air navigation services published in ICAO documents. Operations in Class G airspace are not provided ATC services (aircraft are not separated by ATC). Separation minima are not normally established for Class G airspace. The prevention of collision is dependent upon the “see and avoid” concept and other practices discussed in Volume 4, Chapter 1, Section 3.
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4)    FAA Order 7110.65, Air Traffic Control, describes separation minima applied for operations in the U.S. NAS and in international oceanic airspace delegated to the United States by ICAO pursuant to regional air navigation agreements. ICAO Doc 4444, Procedures for Air Navigation Services – Air Traffic Management, and ICAO Doc 7030/4, Regional Supplementary Procedures, address separation minima in international airspace.

4-4    AUTOMATIC DEPENDENT SURVEILLANCE-BROADCAST (ADS-B).

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A.    ADS-B. ADS-B is a surveillance technology where aircraft automatically and periodically transmit position, velocity, and other information with no pilot or controller action required for the information to be transmitted. For a full description of ADS-B, see AC 90-114, Automatic Dependent Surveillance-Broadcast Operations, and the U.S. Aeronautical Information Manual, in particular Section 5, Surveillance Services. See Volume 6, Chapter 15, Section 1 for guidance on regulatory oversight of ADS-B equipment.

B.    Space-Based ADS-B. New separation standards for application in oceanic airspace rely on the Iridium satellite network, where satellites with ADS-B receivers downlink surveillance information to ATC. In 2019, the “Advanced Surveillance Enhanced Procedural Separation (ASEPS)” project began using space-based ADS-B to support applications in the North Atlantic (NAT). For further information and updates, see current “NAT OPS Bulletins” in the “EUR and NAT Documents” section of the ICAO North Atlantic web page, here: https://www.icao.int/EURNAT/Pages/welcome.aspx.

4-5    THE CONCEPT OF AN ATC CLEARANCE. Issuance of an ATC clearance by a controller and the acceptance of this clearance by a pilot is a negotiation process that establishes conditions for the prevention of collision hazards (in-flight and terrain).

A.    Controller-Issued IFR Clearance. When a controller issues an IFR clearance, the controller agrees to reserve a three-dimensional block of airspace for that aircraft along the route defined in that clearance. The controller also agrees to issue clearances to all other controlled air traffic, ensuring safe separation.

B.    Pilot-Accepted ATC IFR Clearance. When a pilot accepts an ATC IFR clearance, the pilot agrees to continuously remain within that three-dimensional block of airspace assigned by ATC, and adhere to the rules of flight for that operation. The pilot is obligated to comply with the clearance unless amended or an emergency is declared.

C.    Expected Degree of Pilot Accuracy. The pilot is expected to navigate to the degree of accuracy required for ATC. A failure to navigate to the degree of accuracy required may create a flight safety hazard.

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D.    Non-Surveillance (Nonradar or Non-ADS-B) Environment. In a non-surveillance (nonradar or non-ADS-B) environment, ATC has no direct knowledge of the actual position of an aircraft or its relationship to other aircraft in adjacent airspace. Therefore, ATC’s ability to detect a navigational deviation and resolve collision hazards is seriously degraded when a deviation from an agreed-to clearance occurs.

RESERVED. Paragraphs 4-6 through 4-20.