5/19/16

 

8900.1 CHG 387

VOLUME 4  AIRCRAFT EQUIPMENT AND OPERATIONAL AUTHORIZATIONS

CHAPTER 1  AIR NAVIGATION, COMMUNICATIONS, AND SURVEILLANCE

Section 1 General Navigation Concepts, Policies, and Guidance

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.

A.    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 air traffic control (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.
6)    The area of proposed operation, including:

·    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.
Indicates new/changed information.
11)    Special Areas of Operation (SAO) (Reduced Vertical Separation Minima (RVSM), areas of magnetic unreliability (AMU), Required Navigation Performance (RNP), North Atlantic High Level Airspace (NAT HLA), etc.).

B.    Evaluating Operations. This chapter 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 forwarded through the regional Flight Standards division (RFSD) 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.

C.    The Objective 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.

D.    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 instrument flight rules (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 visual flight rules (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.
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.) (formerly, the Federal Aviation Act of 1958 (FA Act)). Two important sections of the act are summarized as follows:
a)    Section 40103 (formerly, § 307 of the FA Act) 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.”
b)    Section 44701 (formerly, § 601(a) of the FA Act) empowers the Secretary to “promote safety of flight of civil aircraft in air commerce by prescribing …minimum standards required in the interest of safety for …performance of aircraft…and appliances … regulations and minimum standards for other practices, methods, and procedure…necessary for safety in air commerce and national security.”
3)    Convention Articles. The Articles of the Convention represent international law and are equivalent to the FA Act. The foundation for ICAO was established on December 7, 1944, when the text of the convention was opened for signature in Chicago, Illinois. This document (DOC 7300) is referred to as the “ICAO Convention” or the “Chicago Convention.” This “Convention” contains 96 articles known as the Articles of the Convention. By signing the Convention, a government (State) agreed to abide by “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 Convention represent those certain principles and arrangements and serve as the foundation for international aviation laws, standards, recommended practices, and guidance material. Articles 44 through 66 established ICAO as a body within the United Nations. Articles 1 through 43 established general principles concerning international air navigation. 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.
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 to nationality, and shall be complied with by such aircraft upon entering or departing from or while within the territory of that state.”
d)    Article 12 is the most significant requirement related to flight operations (Rules of the Air). This Article requires that “Each contracting State undertakes to adopt measures to ensure 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 “Over 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.
4)    ICAO Annexes. The articles of the ICAO convention contain basic principles that are the foundation for ICAO annexes. ICAO annexes contain the Standards and Recommended Practices (SARP) that have been adopted through international agreement to ensure the safety, regularity, and efficiency of air navigation. An ICAO standard is worded in mandatory language (shall, must, will) and is directive in nature. A recommended practice is worded in permissive language (should, may, can) and is not directive. Recommended practices represent practices that, although internationally recognized as safe operating practices, are not sufficiently comprehensive or lack the mature development appropriate for an international standard. The following are the ICAO annexes that are most significant to FAA operations 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.
d)    Annex 11, Air Traffic Services.
5)    ICAO Annex 1, Personnel Licensing, Paragraph 3.4, Flight Radiotelephone Operator. This paragraph addresses international telecommunication conventions.
6)    ICAO Annex 2. This annex specifies international rules of the air agreed upon by ICAO member States. These rules are equivalent to the U.S. rules for operating within the territory of the United States (part 91). However, for operations over the high seas, Annex 2 is unique since it relates to flight and maneuver of aircraft within the meaning of Article 12 of the convention. Over the high seas, Annex 2 applies without exception (compliance is mandatory for all civil aircraft). 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 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.
c)    Chapter 3, paragraph 3.6.5 requires that the flightcrew of any aircraft operated as a controlled flight to maintain a continuous listening watch on and establish two-way communication as necessary with (as required for ATC) the appropriate radio frequency of 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.
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 listening watch and communicate with ATC as necessary for the purpose of ATC.
g)    ICAO Doc 7030, Regional Supplementary Procedures, forms the procedural part of the Air Navigation Plan developed by ICAO Regional Air Navigation (RAN) meetings to meet those needs of specific areas that are not covered in the worldwide provisions. Flightcrews must be aware of the regional procedures and Notices to Airmen (NOTAM) for the areas in which they plan on operating, that complement the statement of requirements for facilities and services contained in the Air Navigation Plan (ANP) publications. Procedures of worldwide applicability are either included in Annexes to the Convention as Standards and Recommended Practices (SARPs) or they form part of one of the documents titled, “Procedures for Air Navigation Services” (PANS).
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 Title 14 of the Code of Federal Regulations (14 CFR) parts 121 and 135. Part II specifies requirements for international general aviation operations. The purpose of Annex 6, 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. A State may take exception (have different criteria) to Annex 2 standards for operations conducted in its sovereign airspace; however, no State can take exception to Annex 2 standards for operations conducted over the high seas. Annex 2, which specifies the international rules of the air, applies to all operations over the high seas without exception. Under Annex 6 standards, a State may take exception for operations 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 and Navigation Equipment. This chapter contains ICAO SARPs related to navigation and communication. 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.
Indicates new/changed information. Indicates new/changed information.
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 or routes or airspaces with an RNP specification 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 or RNP routes or airspace 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.
8)    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. A clear distinction is made between ATC service, flight information service, 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. 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.

B.    Relationship Between 14 CFR, ICAO Annexes, and Foreign National Regulations. Title 49 U.S.C. is the authority for 14 CFR. Title 14 CFR represents the regulatory implementation of the responsibilities assigned by the U.S.C. and the implementation of the principles derived from the ICAO convention. The relationship between 14 CFR, ICAO Annexes, and foreign national regulations are discussed in the following subparagraphs.

1)    Title 14 CFR 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:
a)    Section 91.703 requires each person operating a U.S. aircraft to comply with ICAO Annex 2 when over the high seas and to comply with the regulations of a foreign country when operating within that country’s airspace.
b)    Section 91.703(a)(3) requires compliance with part 91 when not in conflict with the regulations of a foreign nation or Annex 2.
2)    In addition to part 91 requirements in paragraph 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:
a)    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:
a)    Rules of the country concerned and any local airport rules that may be in force.
b)    All rules of 14 CFR 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 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:
a)    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.
5)    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. For program managers conducting operations under part 91K, § 91.701 requires compliance with that part while operating within the United States. 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.

1)    Title 14 CFR related to air navigation have been promulgated and frequently changed 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.
2)    Examples of operational 14 CFR 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; Section 91.143, Flight Limitation in the Proximity of Space Flight Operations;
g)    Section 91.157, Special VFR Weather Minimums;
h)    Section 91.159, VFR Cruising Altitude or Flight Level;
i)     Section 91.169, IFR Flight Plan: Information Required;
j)     Section 91.173, ATC Clearance and Flight Plan Required;
k)    Section 91.179, IFR Cruising Altitude or Flight Level;
l)     Section 91.181, Course to Be Flown;
m)   Section 91.511, Communication and Navigation Equipment for Overwater Operations;
Indicates new/changed information.
n)    Section 91.703, Operations of Civil Aircraft of U.S. Registry Outside Of the United States; and
o)    Section 91.706, Operations Within Airspace Designated as Reduced Vertical Separation Minimum Airspace.

D.    Regulations Specifying Air Navigation 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 14 CFR 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.

1.    Section 91.205(d)(2) requires air navigation equipment to be appropriate to the ground facilities used. The current NAS is based on Very high frequency Omnidirectional Range (VOR) and VOR/distance measuring equipment (DME) ground facilities. Therefore, this regulation requires that VOR and/or VOR/DME equipment or an Area Navigation (RNAV) system that meets the en route criteria be installed in the aircraft and operable if it is to be used for IFR flight in the U.S. NAS. This navigational equipment is necessary to navigate to the degree of accuracy required for ATC. If the route to be flown is predicated on nondirectional radio beacon (NDB), then automatic direction finder (ADF) airborne equipment is also required.

2.    Section 91.205(e) requires approved DME equipment 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.
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.
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 specified in §§ 121.93 and 121.113 are not applicable to Class II navigation. Certain OpSpecs stipulate requirements for operations in Class G airspace.
b)    Sections 121.95 (domestic/flag) and 121.115 (supplemental), Route Width, specify the lateral navigation considerations necessary for the control of air traffic in Class I navigation. Certain Part B OpSpecs address these requirements (see Volume 3, Chapter 1, Section 4).
c)    Sections 121.103 and 121.121, En Route Navigational Facilities.

1.    Sections 121.103(a) and 121.121(a) implement the concept of “navigation performance” when conducting IFR Class I navigation and certain types of Class II navigation that use nonvisual ground aids. Nonvisual ground aids are electronic Navigational Aids (NAVAID), but not necessarily limited to VOR, DME, or NDB. Long-range navigation-C system (LORAN-C) is an example of a navigation system considered to be a nonvisual ground aid. Each part 121 operator must show that nonvisual ground aids are available and located to allow navigation to the degree of accuracy required for ATC and the type of operation involved.

2.    Area navigational systems that are certified for IFR flight in areas where domestic ATS procedures are applied meet the intent of §§ 121.103 and 121.121 when conducting Class I navigation (including space-based systems such as global positioning system (GPS)).

3.    Certain long-range operations may be conducted under these regulations using the following navigational equipment:

·    Automatic LORAN-C systems approved in reference to Advisory Circular
(AC) 20-121, Airworthiness Approval of LORAN-C Navigation Systems for use in the U.S. National Airspace System (NAS) and Alaska, current edition.

·    Operations using approved satellite-based systems such as GPS.

·    When operating in the U.S. Class A airspace, RNAV systems that have not been demonstrated to meet the criteria for IFR flight in areas where domestic ATS procedures are applied also meet the intent of these rules, provided the ATC radar is serviceable and dual airborne VOR/DME equipment is installed and operable. OpSpecs provide authorization to conduct operations in the U.S. Positive Control Area (PCA) using these RNAV (or long-range navigation) systems.

4.    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, 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, Instrument 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.

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).

3.    This rule does not apply to Class II navigation.

NOTE:  Section 121.347(b) specifies that for night VFR pilotage operations, the airplane must be equipped with the radio equipment necessary to receive radio navigational signals applicable to the route flown.

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.

1.    The intent of this regulation is to require redundant airways navigation capability (VOR, VOR/DME, and NDB) to ensure the ability to navigate to the degree of accuracy required for ATC when conducting Class I navigation. Sections 121.103 and 121.121 clearly state that nonvisual ground aids are not required for operations over routes where celestial or other means of navigation are approved by the Administrator. Since all IFR primary en route and approach navigation facilities have historically been nonvisual ground aids (Standard ICAO ground-based NAVAIDs), § 121.349 is intended to apply only to operations over routes predicated on VOR, VOR/DME, or NDB.

2.    Section 121.349 applies to both Class I and Class II navigation operations. Sections 121.103, 121.121, and 121.389 apply to Class II navigation operations. The intent of § 121.349 is met when any Class I navigation operation is predicated on the following:

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

4.    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.

5.    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.

6.    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.

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. Sections 121.103, 121.121, and 121.389 apply to all other Class II navigation operations.
k)    Section 121.357, Airborne Weather Radar Equipment Requirements, apply to weather radar normally used for thunderstorm detection and avoidance.
l)    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. GPS, INS, and IRS are long-range navigation systems (LRNS) that can be used to satisfy the requirements of Class II navigation.
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.

1.    “Reliably fixed,” as defined in the OpSpecs, is a station passage of a VOR, Collocated VOR and Tactical Air Navigational Aid (TACAN) (VORTAC), or NDB waypoint. A “reliable fix” also includes a VOR/DME fix, an NDB/DME fix, a VOR intersection, an NDB intersection, and a VOR/NDB intersection, provided course guidance is available from one of the facilities and the fix lies within the operational service volume of both facilities that define the fix. A “reliable fix” also includes positioning information obtained from an IFR-certified area navigation system, such as GPS, LORAN-C, or DME/DME updated flight management system (FMS).

2.    Section 121.389 does not apply to those situations where the airplane’s position can be reliably fixed, at least once each hour to the degree of accuracy required for the control of air traffic. If the operator can show compliance with § 121.103/121.121, the requirements of § 121.389 are automatically met by providing fixes more frequently than once an hour. Therefore, Class II navigation operations using a GPS system meets the requirements of § 121.103 or 121.121 and are approved under these regulations.

3.    Class II operations with an INS system are approved under § 121.355 and Appendix G.

4.    Class II navigation systems are divided into two categories.

5.    INS, Inertial Reference Units (IRU), and IRS (inertial systems) are defined as “specialized means of navigation,” as addressed in §§ 121.389 and 121.355. They are self-contained, electronic dead reckoning systems that have no “position fixing” capabilities.

6.    LORAN-C and GPS are “position fixing” or “position keeping” devices that receive their signals from an external source. LORAN-C and GPS are nonvisual ground and space-based aids, respectively, and are addressed in §§ 121.103 and 121.121, En route navigational facilities.

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.
d)    Section 135.161, Communication and Navigation Equipment for Aircraft Operations VFR at Night or Under VFR Over-the-Top Conditions, requires radio navigational equipment able to receive radio signals from the ground facilities to be used. 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.

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 systems or one independent GPS 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.

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(d) allows for the installation and use of a Single Long-Range Navigation System (S-LRNS) in specific geographic areas. This may be authorized by the issuance of OpSpec B054, Class II 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.

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 its 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.”

NOTE:  Various ICAO Planning and Implementation Regional Groups (PIRG) are considering the implementation of strategic lateral offset procedures, to be used at the pilot’s option, whereby properly equipped aircraft can be flown offset 1 or 2 nautical miles (NM) to the right of centerline based on direction of flight. This procedure is designed to decrease the technical collision risk in the applicable airspace. An operational trial of this procedure is ongoing in the West Atlantic Route System (WATRS).

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 already been shown to provide a number of advantages over more conventional forms of navigation.
3)    RNP is intended to provide 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. RNP is a concept that applies to navigation performance within an airspace, and therefore affects both the airspace and the aircraft. RNP is intended to characterize an airspace through a statement of the navigation performance accuracy (RNP type) to be achieved within the airspace. The RNP type is based on a navigation performance accuracy value that is expected to be achieved by the population of aircraft operating within the airspace 95 percent of the time. Required levels of navigation performance (standards) vary from area to area, depending on traffic density and complexity of the routes flown. The implementation of RNP is part of ICAO’s Global Air Navigation Plan for Communication, Navigation, and Surveillance (CNS) and supports ICAO’s air traffic management (ATM) concepts. The end state of the transition is the implementation of free flight, allowing user-defined trajectory. The development of the RNP concept recognizes that current aircraft navigation systems are capable of achieving a predictable level of navigation performance accuracy and that a more efficient use of available airspace can be realized on the basis of this navigation capability. The carriage of specialized navigation equipment is a requirement in some regions and may become a requirement in others.

B.    Concept of Operational Service Volume. Operational service volume is that volume of airspace surrounding an 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 this volume of airspace (the operational service volume), an ICAO standard ground-based NAVAID signal in space conforms to flight inspection signal strength and course quality standards including frequency protection. ICAO standard ground-based NAVAIDs are VOR, VOR/DME, and NDB. GPS has been accepted by ICAO as a standard NAVAID, however, a distinction is made between “standard ground-based NAVAIDs” and “standard NAVAIDs.” “Standard ground-based NAVAIDs” have an operational service volume and “standard NAVAIDs” do not. The NAS of ICAO contracting member States are based on the operational service volume of these ground-based facilities, but GPS, by virtue of its universal signal coverage, is not restricted to an operational service volume. Navigational performance within the operational service volume and ATC separation minima can be predicated by the use of both standard ground-based NAVAIDs and standard NAVAIDs. The concept of operational service volume is critical for understanding and applying the principles of air navigation, as discussed in this handbook. Refer also to the Aeronautical Information Manual (AIM) for further discussion on operational service volume.

C.    Categories of Navigational Operations. A thorough comprehension of the categories of navigational operations is essential to understand air navigation concepts and requirements discussed in this handbook 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, 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. For example, an aircraft equipped and approved to use LORAN-C or 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 LORAN-C or GPS must be as precise as IFR navigation is required to be using the ICAO standard ground-based NAVAIDs. In another example, a VFR flight navigated by pilotage is conducting Class I navigation when operating entirely within the operational service volume.
b)    A determination of the lateral and vertical extent of the airspace where Class I navigation is conducted is determined solely by the operational service volumes of ICAO standard ground-based NAVAIDs (see Section 3 of this chapter). 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 (ADRs), 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)    Class I navigation requirements are directly related to separation minima used by ATC. IFR separation minima applied in the United States. NAS and most other countries are based on the use of ICAO standard ground-based NAVAIDs. However, these separation minima can only be applied by ATC within areas where the ground-based NAVAID signal in space meets flight inspection signal strength and course quality standards. An ICAO standard ground-based NAVAID signal in space conforms to flight inspection signal strength and course quality standards, including frequency protection, within its designated operational service volume. Therefore, air navigation and the safe separation of aircraft within that service volume can be predicated on the use of these facilities.
d)    Within areas where the safe separation of aircraft is based on the use of ICAO standard ground-based NAVAIDs, any IFR operation must be navigated with at least the same accuracy as the accuracy specified by the appropriate national separation minima. The illustration following this paragraph provides several examples of Class I navigation.
Indicates new/changed information.

Figure 4-1.  Examples of Lateral Separation in the North Atlantic High Level Airspace and Lateral Separation on Federal Airways

Figure 4-1. Examples of Lateral Separation in the North Atlantic High Level Airspace (NAT HLA) and Lateral Separation on Federal Airways

2)    Class II Navigation. Class II navigation is any en route operation that is not categorized as Class I navigation and includes any operation or portion of an operation that takes place outside the operational service volumes of ICAO standard ground-based NAVAIDs. For example, an aircraft equipped with only VOR conducts Class II navigation when the flight operates in an area outside the operational service volume of a VOR.
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. Therefore, ATC cannot predicate aircraft separation on the use of these facilities alone and 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 conducting long-range operations to the degree of accuracy required for the control of air traffic or as the sole means of obstacle avoidance. Therefore, when operating outside the designated operational service volumes of ICAO standard ground-based NAVAIDs, operators must use LRNS approved to navigate to the degree of accuracy required for the control of air traffic and to avoid obstacles
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. 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 Section 4 of this chapter.

D.    GPS and Wide Area Augmentation System (WAAS) Navigation. GPS is a satellite-based radio navigation system that uses precise range measurements from GPS satellites to determine a precise position anywhere in the world. The GPS constellation consists of a minimum of 24 satellites in various orbital planes approximately 11,000 NM above the earth. The satellites broadcast a timing signal and data message that the airborne equipment processes to obtain satellite position and status data and to measure how long each satellite’s radio signal takes to reach the receiver. By knowing the precise location of each satellite and precisely matching timing with the atomic clocks on the satellites, the receiver can accurately measure the time the signal takes to arrive at the receiver. Thus, the receiver can determine the satellite’s precise position. A minimum of three satellites must be in view to determine a two-dimensional position. Four satellites are required to establish an accurate three-dimensional position. GPS equipment determines its position by precise measurement of the distance from selected satellites in the system and the satellite’s known location. The accuracy of GPS position data can be affected by various factors. Many of these accuracy errors can be reduced or eliminated with mathematics and sophisticated modeling, while other sources of errors cannot be corrected. The following are examples of those errors that cannot be corrected:

·    Atmospheric propagation delays can cause relatively small measurement errors, typically less than 100 feet. Ionospheric propagation delays can be partially corrected by sophisticated error‑correction capabilities.

·    Slight inaccuracies in the atomic clocks on the satellites can cause a small position error of approximately 2 feet.

·    Receiver processing (such as mathematical rounding and electrical interference) may cause errors that are usually either very small, which may add a few feet of uncertainty into each measurement, or very large, that are easy to detect. Receiver errors are typically on the order of 4 feet.

·    Conditions that cause signal reflections before the satellite’s transmitted signal gets to the receiver can cause small errors in position determination or momentary loss of the GPS signal. While advanced signal processing techniques and sophisticated antenna design are used to minimize this problem, some uncertainty can still be added to a GPS measurement.

·    A satellite’s exact measured orbital parameters (ephemeris data) can contain a small error of approximately 4 feet.

1)    System Operation.
a)    The Department of Defense (DOD) is responsible for operating the GPS satellite constellation and constantly monitors the GPS satellites to ensure proper operation. Every satellite’s ephemeris data are sent to each satellite for broadcast as part of the data message sent in the GPS signal. The GPS is a system of Cartesian earth-centered, earth-fixed coordinates, as specified in the DOD World Geodetic System 1984 (WGS-84). Navigation values, such as groundspeed and distance and bearing to a waypoint, are computed from the aircraft’s latitude/longitude and the location of the waypoint. Course guidance is usually provided as a linear deviation from the desired track of a great circle course between defined waypoints.
b)    GPS navigation capability from the 24-satellite constellation is available 24 hours a day anywhere in the world. GPS status is broadcast as part of the data message transmitted by the satellites. Additionally, system status is available through NOTAMs and from the U.S. Coast Guard.
c)    GPS signal integrity monitoring will be provided by the GPS navigation receiver, using receiver autonomous integrity monitoring (RAIM). For GPS sensors that provide position data only to an integrated navigation system (e.g., FMS, multi-sensor navigation system), a level of GPS integrity equivalent to that of RAIM may be provided by the integrated navigation system. Availability of RAIM capability to meet non-precision approach requirements in the United States with the 24-satellite constellation is expected to exceed 99 percent.
2)    Selective Availability (SA). SA is a method by which the DOD can artificially create a significant clock and ephemeris error in the satellites. This feature is designed to deny an enemy nation or terrorist organization the use of precise GPS positioning data. SA is the largest source of error in the GPS system. When SA is active, the DOD guarantees horizontal position accuracy will not be degraded beyond 100 meters, 95 percent of the time, and beyond 300 meters, 99.99 percent of the time. The United States began discontinuing the use of intentional degradation, SA, May 1, 2000 until 2006 with an annual assessment of its continued use. Civilian users will realize a dramatic improvement in GPS accuracy with the discontinuation of SA. It is envisioned that SA will not be turned on unless a national emergency exists or is imminent.
3)    GPS Performance. TSO-C145a/C146a, Avionics Equipment for Wide Area Augmentation Systems (WAAS), has been developed to improve the accuracy, integrity, availability, and reliability of GPS signals. It is a safety-critical system consisting of a ground network of reference and integrity monitor data processing sites that assess current GPS performance, as well as a space segment that broadcasts that assessment to Global Navigation Satellite System (GNSS) users to support IFR navigation. WAAS equipment has been designed to automatically use the WAAS data and ranging signal. The operational availability of navigation for WAAS-equipped operators in any given area may be ascertained by accessing the FAA NOTAM system (refer to TSO-C145a/C146a and RTCA DO229B, Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System Airborne Equipment).
a)    Recent developments in navigation technology include the availability of WAAS-capable navigation systems approved under TSO-C145a/C146a. This equipment constitutes a significant improvement over the older GPS standards (TSO-C129) by the incorporation of new technology to provide enhanced signal integrity using WAAS, fault detection and exclusion (FDE), and RAIM. The improved navigation accuracy and flexibility of WAAS equipment will ultimately produce an increase in both system capacity and overall flight safety.
b)    TSO-C145a provides the certification standards for airborne navigation WAAS sensors, while TSO-C146a refers to a WAAS standalone airborne navigation system. TSO-C145a/C146a equipment must be installed in accordance with the current edition of AC 20-138, Airworthiness Approval of Positioning and Navigation Systems.
c)    For TSO-C145a equipment, the FMS must comply with TSO-C115b, Airborne Area Navigation Equipment using Multi-Sensor Inputs, and be installed in accordance with the current edition of AC 20-138, Airworthiness Approval of Positioning and Navigation Systems. When all provisions are met, including the installation of dual independent systems, these systems may be authorized for use as the only means of conducting IFR RNAV in the U.S. NAS.
d)    FDE technology allows WAAS equipment to automatically detect a satellite failure that effects navigation and to exclude that satellite from the navigation solution.
e)    RAIM is a function that considers the availability of satisfactory signal integrity broadcasted from the particular GPS satellites used during a given flight. Onboard GPS/WAAS navigators accomplish this automatically as the aircraft proceeds along its route. When insufficient signal integrity is detected, a ‘loss of integrity’ or RAIM alert is provided to the flightcrew. To support preflight planning, operators can identify outages that impact WAAS equipment through NOTAMs or by accessing an FAA-approved prediction program.
f)    Under present regulations, operators certificated in accordance with 14 CFR part 119 proposing to use WAAS equipment as the only means of IFR navigation must have a TSO-C145a/C146a approach-capable navigation system installed and operating in their aircraft. In the event of a complete failure of WAAS and GPS navigation capability, operators must provide for reversion to another form of radio navigation or the navigation system must provide for an automatic positioning capability to ensure the flight can be safely continued to its destination or a suitable alternate.
4)    Use of WAAS in Alaska Operations.
a)    POIs should refer to 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. OpSpec paragraph B030 is issued to those certificate holders identified in Section 1 of Special Federal Aviation Regulation (SFAR) 97 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.

E.    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.
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. Examples of particular categories of navigational operations and specified areas include navigation on airways in the national airspace of ICAO member States and long-range navigation (LORAN) in oceanic or remote land areas.
3)    For operations where ATC services are provided by the United States, separation minima are established by 14 CFR and ATC directives. For operations where ATSs are provided by contracting ICAO member States, separation minima are established by the national regulations of the member States (if established) and 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 Chapter 2, Section 3.
4)    Separation minima applied for operations in the U.S. NAS can be found in the current edition of FAA Order 7110.65, Air Traffic Control. FAA Order 7110.83, Oceanic Air Traffic Control, prescribes separation minima in international oceanic airspace delegated to the United States by ICAO. ICAO Document 7030/4, Regional Supplementary Procedures, also prescribes separation minima in international airspace.

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

A.    ADS-B System. The ADS-B system:

1)    Automatically and periodically transmits position, velocity, and other information with no pilot or controller action required for the information to be transmitted;
2)    Is dependent on the aircraft position source (e.g., GNSS/GPS);
3)    Is used for surveillance services, much like traditional radar; and
4)    Is used to broadcast aircraft position and other data to any aircraft or ground station equipped to receive ADS-B.

B.    ADS-B System Elements. The ADS-B system consists of three elements:

1)    Avionics. Installed aircraft avionics gather, format, and transmit the message elements from the aircraft via a discrete frequency. ADS-B messages include at least the following elements:

·    Aircraft horizontal position (latitude/longitude).

·    Aircraft barometric altitude.

·    Aircraft identification: the assigned, unique ICAO 24-bit address.

·    Flight ID.

·    Special Position Indicator (SPI).

·    Emergency status.

NOTE:  Flight ID, SPI, and the emergency status are the only message elements that can be modified by the flightcrew.

2)    Positioning Source. Position data is typically derived from GNSS/GPS to provide an aircraft’s position.
3)    Ground Radio Stations. The ground infrastructure must be in place to receive and process the message elements from aircraft and to provide the air traffic automation system with the necessary information for ATC surveillance and separation services.

C.    ADS-B Out (Transmit) Functions. Different avionics packages and suites are available to support ADS-B Out. The transmission of message elements by ADS-B-equipped aircraft is known as ADS-B Out.

D.    Position Source Dependency.

1)    ADS-B derives horizontal and vertical position information from the positioning source on the aircraft, which is typically the GNSS/GPS navigation system. This can mean that the accuracy of the ADS-B system is directly related to the availability of the GPS constellation of satellites. In some installations, the altimeter is also used as an added vertical cross-check referred to as baro-aiding. The navigation service and the altimeter must be available and of sufficient quality in order to provide the required level of safety to meet air traffic separation services standards.
2)    The ADS-B system is heavily dependent on the continued high performance of the avionics and position source. This dependency requires an operator to ensure that the planned operation can meet the performance requirements for the entire route and time of the flight. For this reason, certificate holders/operators should check the availability of the ADS-B service and GNSS/GPS (e.g., NOTAM) to ensure that ADS-B performance is available.

E.    Air Traffic Separation Services.

1)    Air traffic separation services using ADS-B enhances operations in several ways. ADS-B data is provided to ATC at a higher rate than existing radar surveillance, resulting in more accurate position information to the controller. This increased position accuracy enables more efficient and effective use of airspace.
2)    Air traffic separation services using ADS-B are dependent on the quality and performance of the individual aircraft and the ground system. It is critically important that each piece of the system is operated and maintained in a manner that ensures design performance, supporting the approved safety levels associated with the operation.

F.    Contingency Operations. A failure of any one component of the ADS-B system requires ATC to “fallback” to procedural separation standards. Therefore, service provider or certificate holder/operator reliance on ADS-B must be carefully weighed for the contingency operations, which may be required should the ground service, avionics, or positioning source fail.

G.    Automatic Dependent Surveillance-Broadcast (ADS-B)-Related Definitions.

1)    ADS-B. A surveillance system in which an aircraft or vehicle to be detected is fitted with cooperative equipment in the form of a data link transmitter.
a)    The aircraft or vehicle periodically broadcasts its GPS-derived position and other information such as velocity over the data link, which is received by a ground-based transmitter/receiver (transceiver) for processing and display at an ATC facility.
b)    ADS-B is a system for airborne or surface aircraft, or other surface vehicles operating within the airport surface movement area, that periodically transmits a state vector (horizontal and vertical position, horizontal and vertical velocity) and other information.
c)    ADS-B is a function on an aircraft or surface vehicle operating within the surface movement area that periodically broadcasts its state vector and other information. ADS-B is automatic because no external stimulus is required to elicit a transmission; it is dependent because it relies on onboard navigation sources and onboard broadcast transmission systems to provide surveillance information to other users.
d)    ADS-B is an advanced surveillance technology where ADS-B Out-equipped aircraft share position, altitude, velocity, and other information with ATC and other appropriately equipped aircraft.
2)    ADS-B Out.
a)    The capability of an aircraft to periodically broadcast its position, velocity, and other information. ADS-B Out is automatic in the sense that no flightcrew or controller action is required for the information to be transmitted. It is dependent surveillance in the sense that the surveillance information depends on the navigation and broadcast capability of the source.
b)    Transmission of an aircraft’s position, altitude, velocity, and other information to other aircraft and ATC ground-based surveillance systems.
3)    Extended Squitter (ES). A long message (e.g., format DF=17) that Mode S transponders transmit automatically, without need for interrogation by radar, to announce the own ship aircraft’s presence to nearby ADS-B-equipped aircraft.
4)    Global Navigation Satellite System (GNSS).
a)    A worldwide position, velocity, and time determination system that includes one or more satellite constellations, receivers, and system integrity monitoring, augmented as necessary to support the RNP for the actual phase of operation.
b)    The generic term for a satellite navigation system, such as GPS, that provides autonomous worldwide geospatial positioning and may include local or regional augmentations.
5)    Global Positioning System (GPS).
a)    A space-based radio positioning, navigation, and time transfer system. The system provides highly accurate position and velocity information, and precise time (on a continuous global basis) to an unlimited number of properly equipped users. The system is unaffected by weather and provides a worldwide common grid reference system. The GPS concept is predicated upon accurate and continuous knowledge of the spatial position of each satellite in the system with respect to time and distance from a transmitting satellite to the user. The GPS receiver automatically selects appropriate signals from the satellites in view and translates these into three‑dimensional position, velocity, and time. System accuracy for civil users is normally 100 meters horizontally.
b)    A space-based position, velocity, and time system composed of space, control, and user segments. The space segment, when fully operational, will be composed of 24 satellites in 6 orbital planes. The control segment consists of five monitor stations, three ground antennas, and a Master Control Station (MCS). The user segment consists of antennas and receiver processors that provide positioning, velocity, and precise timing to the user.
c)    A U.S. satellite-based radio navigation system that provides a global positioning service. The service provided by GPS for civil use is defined in the GPS Standard Positioning System Performance Standard, 4th Edition.
6)    International Civil Aviation Organization (ICAO) 24-Bit Address. Address assigned to each aircraft transponder of an ADS-B transmitter. For aircraft equipped with Mode S transponders, their replies to TCAS interrogations and their ADS-B transmissions should use the same 24-bit address, allowing correlations by Airborne Surveillance and Separation Assurance Processing (ASSAP).
7)    Mode S. A Secondary Surveillance Radar (SSR) system that operates using addressed interrogation on 1030 megahertz (MHz), and the transponder replies on 1090 MHz. Mode S systems interrogate for aircraft identity (Mode A), altitude (Mode C), and other aircraft-specific information. The aircraft transponder replies with the requested information. Mode S supports a two-way data link that provides ADS-B data through an ES.
8)    Position Source.
a)    The onboard avionics equipment that provides the latitude, longitude, geometric altitude, velocity, position and velocity accuracy metrics, and position integrity metrics. Additionally, the position source may provide the vertical rate parameters.
b)    Within this OpSpec, RAIM is a synonym for Aircraft-Based Augmentation System (ABAS) and is used to refer to both RAIM and RAIM-equivalent algorithms.
9)    Secondary Surveillance Radar (SSR). A radar sensor that listens to replies sent by transponders carried onboard airborne targets. SSR sensors, in contrast to primary surveillance radar (PSR) sensors, require the aircraft under surveillance to carry a transponder.
10)    Surveillance. Detection, tracking, characterization, and observation of aircraft, other vehicles, weather, and airspace status information and phenomena for the purposes of conducting flight operations in a safe and efficient manner. The primary purposes of traffic surveillance (as distinct from all surveillance functionality) are to control the flow of aircraft, to provide SA for pilots and controllers, and to separate aircraft.

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.

D.    Nonradar or Non-ADS Environment. In a nonradar or non-ADS 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.