RNAV Training Manual

and level” legs and level legs • Modern applications have aimed to increase the usefulness of RNAV by allowing very precise procedure designs that use airspace more efficiently and create more direct routes. This also has the benefit of improving terrain and traffic separation and providing better noise abatement and fuel benefit of improving terrain and traffic separation, and providing better noise abatement and fuel- efficient descent management • However, to date, no homogenous way of providing the standards and safeguards needed for accurate and consistent RNAV has emerged, and thus there are a variety of RNAV applications in different regional and national airspace and for different phases of flight (enroute, terminal, approach) – eg. B-RNAV and P-RNAV in Europe, MNPS in the North Atlantic, RNAV 1 and RNAV 2 in the US 6 What is RNP (Required Navigation Performance) ? P A • RNP terminology can be confusing, because it means slightly different things in different contexts • RNP, conceptually, is “a measure of the navigation performance accuracy necessary for operation within a defined airspace” • RNP as a performance specification is a measure of the lateral accuracy in nautical miles relative to • RNP, as a performance specification, is a measure of the lateral accuracy in nautical miles, relative to a desired flight path, that an aircraft can be expected to maintain 95% of the total time – Referred to as “RNP-X” where the “X” may be, for example, 5nm RNP i l d th f RNAV li ti th t i l d ifi RNP X i t • RNP is also used as the name for RNAV applications that include a specific RNP-X requirement – For example, RNP 10 is the name for an Oceanic RNAV application. Aircraft operating on routes designated as RNP 10 must conform to a variety of equipment, crew and operator approval requirements requirements. – However, RNAV application names are not standardised: in the North Atlantic, the RNAV application is very similar to RNP 10, but it is called “Minimum Navigation Performance Specifications” (MNPS). Europe and the USA both have Terminal RNAV applications based on p ( ) p pp RNP-1, but they are called P-RNAV and RNAV 1 respectively • ICAO is in the process of standardising RNAV and RNP applications and specifications. The general term for this is “Performance Based Navigation” (PBN); this will change, and in some cases replace, term for this is Performance Based Navigation (PBN); this will change, and in some cases replace, the use of RNP concepts 7 Summary of concepts P A RNAV Navigation capability RNP Performance capability Navigation and Performance capabilitiesNavigation capability for flight along any desired route Performance capability to remain within X nm of a desired route for 95% of the flight time combined allow RNAV procedures to be more efficient than legacy IFR “RNAV A li ti ” “RNAV Applications” Special IFR requirements in national, regional or oceanic airspace which permit the use of RNAV routes and procedures designed around an RNP X specification B RNAV P-RNAV MNPS RNP 4 RNAV 1 etc B-RNAV P RNAV MNPS RNP 4 RNAV 1 ….etc PBN Performance-based Navigation: ICAO concept to standardise current and future RNAV/RNP applications, requirements and nomenclature 8 Course contents 1. RNAV and RNP theory 4. RNAV(GPS) Approach Procedures a. Introduction b. The Path-Terminator c. RNAV procedure design a. GPS procedure types b. GPS approach requirements and approvals d. RNP principles e. RNAV and RNP applications c. GPS approach operations 5. Avionics training 2. GPS Navigators and their application to RNAV a. The GPS system b. Databases and Coding 6. Simulator and/or Flight training c. Procedures d. Error detection and warnings 3. P-RNAV Terminal Procedures a. P-RNAV requirements and approvals b. P-RNAV training topics c. P-RNAV operations 9 What is a Path-Terminator? P A • IFR routes and procedures are designed using standardised specifications and criteria – ICAO PANS-OPS Doc 8168 in Europe – TERPS (United States Standard Terminal Instrument Procedures) in the USA • Instrument procedures have always been published in chart and text form. Since the 1970s, the ARINC 424 standard has also been used to codify IFR procedures, so they can be stored and managed as records in electronic databases • A key concept in ARINC 424 is that of the “Path-Terminator” – a specific way of defining a leg or segment of an IFR procedure, based on a set of standard components that define the flight path along the leg, and the terminator or end-point of the leg the leg, and the terminator or end point of the leg • Different combinations of Path types (eg. a Heading or a Track) and Terminator types (eg. a radio beacon, RNAV waypoint or DME arc) are used to define 23 different “Path-Terminator” leg types , yp ) g yp – these 23 Path-Terminator types are, in effect, the “periodic table” of IFR procedure design and codification • In a panel-mounted GPS Navigator, an enroute flight plan consists only of one leg type: the basic “Track (from Fix) to Fix” (TF) between each of the waypoints entered. When a Departure, Arrival or Approach procedure is loaded, the flight plan will include each of the path-terminators that make up the procedure N t GPS it d t t ll th l t d t th t t d d f RNAV d i bli h d GPS “ l ” procedure. Note: some GPS units do not support all the leg types used at the start and end of RNAV procedures, or in an unpublished GPS “overlay” 10 ARINC 424 Path-Terminator leg types (1 of 3) P A ( ) IF leg type TF leg type RF leg type CF leg type • The Initial Fix Leg defines a database fix as a point in space • It is only required to define the beginning of a route or procedure • Track to a Fix defines a great circle track over ground between two known databases fixes • Preferred type for straight legs • Constant Radius Arc Leg defines a constant radius turn between two database fixes, lines tangent to the arc and a center fix • Course to a Fix Leg defines a specified course to a specific database fix • TF legs preferred over CF to avoid magnetic variation issues DF leg type • Direct to a Fix Leg defines an unspecified track starting from an undefined position to a specified FA leg type • Fix to an Altitude Leg defines a specified track over ground from a database fix to a specified FC leg type • Track from a Fix to a Distance Leg defines a specified track over ground from a database fix FD leg type • Track from a Fix to a DME Distance Leg defines a specific track from a database fix to a p p fix p altitude at an unspecified position g for a specific distance specific DME Distance from a DME Navaid 11 ARINC 424 Path-Terminator leg types (2 of 3) P A ( ) FM leg type CA leg type CD leg type CI leg type • From a Fix to a Manual termination Leg defines a specified track over ground from a database fix until Manual termination of the leg • Course to an Altitude Leg defines a specified course to a specific altitude at an unspecified position • Course to a DME Distance Leg defines a specified course to a specific DME Distance which is from a specific database DME Navaid • Course to an Intercept Leg defines a specified course to intercept a subsequent leg CR leg type • Course to a Radial termination Leg defines a course to a specified Radial from a specific AF leg type • Arc to a Fix or defines a track over ground at specified constant distance from a database DME VA leg type • Heading to an Altitude termination Leg defines a specified heading to a specific VD leg type • Heading to a DME Distance termination Leg defines a specified heading terminating at p p database VOR Navaid Navaid p g p Altitude termination at an unspecified position p g g a specified DME Distance from a specific database DME Navaid 12 ARINC 424 Path-Terminator leg types (3 of 3) P A ( ) VI leg type VM leg type VR leg type PI leg type • Heading to an Intercept Leg defines a specified heading to intercept the subsequent leg at an unspecified position • Heading to a Manual termination Leg defines a specified heading until a Manual termination • Heading to a Radial termination Leg defines a specified heading to a specified radial from a specific database VOR Navaid • Procedure Turn leg defines a course reversal starting at a specific fix, includes Outbound Leg followed by 180 degree turn to intercept the next leg HA leg type • HA leg defines racetrack pattern or course reversals at a specified database fix terminating at an HF leg type • HF leg defines racetrack pattern or course reversals at a specified database fix terminating at the fix HM leg type • HM leg defines racetrack pattern or course reversals at a specified database fix with a manual g altitude g after a single pattern termination 13 The ARINC 424 “periodic table” of 23 Path-Terminator legs P A Fix to Track from fix to Course to Heading to Direct to Racetrack DME Arc to Radius from fix Paths Fix IF TF CF DF HF AF RF Altitude FA CA VA HA Manual Termination FM VM HM Distance FC minators DME Distance FD CD VD Intercept CI VI Term Each leg type has a two letter name based on the path and terminator combination Radial CR VR Procedure Turn PI 14 Fly-By and Fly-Over RNAV waypoints P A • The “fix” in Path-Terminator legs is either based on radio aids or it is an RNAV waypoint. ICAO define a waypoint as “a specified geographical location used to define an RNAV route or the flight path of an yp p g g p g p aircraft employing RNAV” • There are 2 kinds of RNAV waypoint: Fly-By and Fly Over Fly-By waypoint Fly-Over waypoint Jeppesen symbol Jeppesen symbol ICAO symbol ICAO symbol Note: Jeppesen sometimes depict the curved Note: radio aid or other symbols may be • A waypoint which requires turn anticipation (start of turn before the waypoint) to allow tangential • A waypoint at which a turn is initiated fly-by track, sometimes the two straight tracks are joined under the fly-by symbol Note: radio aid or other symbols may be overlaid on waypoint symbol interception of the next segment of a route or procedure • The aircraft navigation system calculates the start of the turn onto the next route leg before the waypoint • The aircraft starts to turn onto the next route leg as it passes over the waypoint • Fly-Over waypoints are most often used as the first fix in the missed approach procedure and in depicting the turn onto the next route leg before the waypoint • This is the preferred type of waypoint for all Area Navigation (RNAV) Standard Instrument Departures/Standard Instrument Arrivals (SIDs/STARs) in the missed approach procedure and in depicting traditional procedures designed around overflying radio aid fixes • RNAV Procedure designers are increasingly avoiding th f Fl O i t Source: Eurocontrol http://elearning.eurocontrol.int/IANS/NAV/prnav/prnav_free_access/firstwin.htm the use of Fly-Over waypoints 15 Aircraft trajectory in Fly-By and Fly-Over waypoints P A Fly-By Fly-Over trajectory more consistent and controlled trajectory less consistent and controlled • Turn is a Rate 1 curved path tangential to both the inbound and outbound track • Turn consists of roll-in, Rate 1 turn, roll-out and intercept elements • Both types of trajectory are subject to variations in wind, aircraft speed and bank angle, navigation system logic and Pilot or Autopilot performance. However, flight paths resulting from Fly-By turns are, in practice, much more consistent and predictable, and thus preferred in RNAV procedure design (eg. they require a smaller protected area) they require a smaller protected area) • Although the Fly-By turn is a simple concept, it is important for the pilot to understand exactly how turns are annunciated and displayed on the GPS navigator and how lateral guidance is provided to the autopilot in Nav or Roll Steer (GPSS) modes in order to consistently and provided to the autopilot in Nav or Roll-Steer (GPSS) modes, in order to consistently and accurately achieve the tangential path the procedure requires 16 Course contents 1. RNAV and RNP theory 4. RNAV(GPS) Approach Procedures a. Introduction b. The Path-Terminator c. RNAV procedure design a. GPS procedure types b. GPS approach requirements and approvals d. RNP principles e. RNAV and RNP applications c. GPS approach operations 5. Avionics training 2. GPS Navigators and their application to RNAV a. The GPS system b. Databases and Coding 6. Simulator and/or Flight training c. Procedures d. Error detection and warnings 3. P-RNAV Terminal Procedures a. P-RNAV requirements and approvals b. P-RNAV training topics c. P-RNAV operations 17 Principles of ‘traditional’ Instrument Procedure design 1. The Protected Area • Instrument procedures in Europe are designed using the specifications and criteria in ICAO PANS- OPS Doc 8168 The US equivalent standard is “TERPS” (United States Standard Terminal Instrument OPS Doc 8168. The US equivalent standard is TERPS (United States Standard Terminal Instrument Procedures) Full width of Protected Area ¼ width ¼ width ½ width Profile of Protected Area Plan View of Protected Area Secondary Area Primary Area Secondary Area Full Secondary Area Primary Area Secondary Area MOC declines u MOC to zero • The key design criteria is to provide safe obstacle and terrain clearance whilst an aircraft is flown in accordance with the published procedure – horizontally, within a Protected Area o o ta y, t a otected ea – vertically, with a specified Minimum Obstacle Clearance (MOC) 18 Principles of ‘traditional’ Instrument Procedure design 2. Track and Fix tolerances, and MOC , • The horizontal width of the Protected Area is determined by various tolerances relating to where an aircraft could be located whilst flying the procedure aircraft could be located whilst flying the procedure • The key tolerance is based on the type of radio aid being tracked and distance from it. An angular splay is used that widens the protected area as the aircraft travels further from the fix Illustrative plan view of the Protected Area in a leg from a VOR • Protection in a descent or a turn initiated at a fix is also provided by including a Fix Tolerance VOR NDB DME LOC Examples Protected Area widens at an angle of 7.8 O relative to the leg track, in the case of a VOR VOR NDB DME LOC System Tolerance 4.5 O 6.2 O 0.25nm plus 1.4 O Fli ht T h i l Examples Protected Area width The angle is 10.3 O for an NDB and 15 O for flying a heading plus 1.25% of the DME distance Flight Technical Tolerance 0.7 O 0.7 O 1.0 O Total Fix Tolerance 5.2 O 6.9 O 2.4 O is initially 2nm Note that fix tolerances are different from path tracking tolerances Note: FTT excluded when fix is based on an intersect. These are illustrative examples, the full definition of fix tolerances (eg. overhead a beacon, radar fixes) is beyond the scope of this course • The Minimum Obstacle Clearance (MOC) is 984’ or 300m up to the Initial Approach Fix, and declines during the Approach and Missed Approach (down to a minimum of 98’ or 30m on the missed) Source: Jens Gerlev’s book, “Instrument Flight Procedures” 19 Principles of ‘traditional’ Instrument Procedure design 3. Fly-Over Turns y • The protected area around a turn is necessarily greater than the “sum” of the track protection required to and from a fix: it must take into account to and from a fix: it must take into account – the fix tolerance – the time it takes a pilot to react to crossing the fix and establish the turn the effect of worst case wind pushing the aircraft to the outside of the turn – the effect of worst-case wind pushing the aircraft to the outside of the turn – the turning radius of different aircraft types “Nominal” track : ie. the zero error, zero wind track an aircraft would follow Illustration of traditional Fly-Over turn wind track an aircraft would follow Fix tolerance Reaction time 6s Fix tolerance time, 6s Extra protected area required in traditional Fly-Over turns Source: Jens Gerlev, “Instrument Flight Procedures” 20 Principles of ‘traditional’ Instrument Procedure design 4. Aircraft Approach Categories pp g • Aircraft speed is the key criteria for the design of any manoeuvring elements of an instrument procedure (turns, procedure turns, holds, missed approaches, landing and circling minima) p ( , p , , pp , g g ) • Procedures are designed around 5 aircraft categories, based on a notional approach speed of 1.3x the stalling speed in the landing configuration at maximum landing mass (V AT) Aircraft Category VAT Initial Approach speeds Final Approach speeds Max Circling speed A <91 90-150 70-100 100 B 91-120 120-180 85-130 135 C 121-140 160-240 115-160 180 C 121 140 160 240 115 160 180 D 141-165 185-250 130-185 205 E 166-210 185-250 155-230 240 All speeds are KT IAS • Most general aviation aircraft are Categories A or B. However, in busy Terminal airspace, ATC will often request a higher than normal speed from light aircraft. If appropriate, the pilot should also elect to follow a higher-Category procedure and observe the corresponding minima – note that GPS databases usually only include the Category C&D procedures 21 How are RNAV Procedures different? 1. Definition of Protected Area based on RNAV system performance or RNP P A Based on RNAV system type Based on RNP Based on RNAV system type Based on RNP • RNAV procedures designated for specific navigation systems, eg • PANS OPS protected area width is 2x RNP + a buffer navigation systems, eg – RNAV(GNSS) – RNAV(DME-DME) – RNAV(EXCEPT CLASS A GNSS) RNP a buffer • Buffer is 2nm for arrival, 1nm for initial and intermediate approach and 0.5nm for final, missed approach and departure ie. FMS GPS only, not panel mount GPS RNAV(EXCEPT CLASS A GNSS) • Each procedure type has a system- specific “semi area width”, which is the l t l t ti ith id f th Full width of Protected Area buffer 4x RNP buffer lateral protection either side of the nominal track, eg. 3nm for GPS STARs • Modern approach is to define procedures based on RNP not on specific navigation Buffer Area Buffer Area MOC based on RNP, not on specific navigation systems • Fix Tolerance is based on system- specific linear Along Track (ATT) and • Fix Tolerance is simply a 1x RNP radius Cross-Track (XTT) tolerances, rather than angular splays around the waypoint See the Eurocontrol publication “Guidance Material for the Design of Terminal Procedures for Area Navigation”, at http://www.ecacnav.com/downloads/iss3 0.pdf p g g , p _ p This is an excellent document, with detailed content on many topics that are only briefly touched upon in this manual. It is well worth downloading and saving as a reference. 22 How are RNAV Procedures different? 2. Fly-By turn Protected Area is smaller than that of conventional turns P A • The Fly-By turn design assumes fi t l f RNP X ( 1 i P RNAV) – a fix tolerance of RNP-X (eg. 1nm in P-RNAV) – aircraft turn at Rate 1 (3 O/sec), up to a maximum bank angle of 25 O, whichever is lower – a 5 seconds allowance, from the time the aircraft’s navigation system computes that a turn should start for either the pilot or autopilot to react and to establish the appropriate bank angle should start, for either the pilot or autopilot to react and to establish the appropriate bank angle • The Fly-By turn design thus uses the same bank angles, fix tolerances, wind effects and pilot/autopilot reaction times as the Fly-Over design However the diagrams below illustrate how much inherently reaction times as the Fly Over design. However, the diagrams below illustrate how much inherently smaller the Fly-By protected area is with those same safety margins built-in Identical turns drawn to scale : Fly-Over vs Fly-By Protected Areas Illustration of a delay in initiating the turn until Secondary Area Secondary Area g approx 1 minute after waypoint crossed Primary Area Primary Area Area Secondary Area Secondary Area Fly-Over Fly-By Source: based on diagrams in “Guidance Material for the Design of Terminal Procedures for Area Navigation”, at http://www.ecacnav.com/downloads/iss3_0.pdf 23 How are RNAV Procedures different? 3. Procedures use only a few of the most “predictable” Path-Terminators P Paths Fix to Track from fix to Course to Heading to Direct to Racetrack DME Arc to Radius from fix Fix IF Initial TF Track to CF Course to DF Direct to HF Racetrack AF RF Radius to Initial Fix Track to Fix Course to Fix Direct to Fix Racetrack to Fix AF Radius to Fix Altitude FA Fix to Altitude CA Course to Altitude VA Heading to Altit d HA Racetrack to Altitude R d “b t ti ” Altitude Altitude Altitude to t tude Manual Termination FM Fix to man. term. VM Heading to man. term. HM Racetrack to man. term. nators Red: “best practice” RNAV leg types term. term. Distance FC DME Distance FD CD VD Termin Orange: RNAV leg types used Distance Intercept CI VI Course to Intercept R di l mainly at the start and end of procedures when required (eg. VA as the first leg of a SID) Radial CR VR Procedure Turn PI Blue: non-RNAV leg types 24 How are RNAV Procedures different? 4. There is a distinct RNAV procedure “style” P • “Style” features typical of RNAV procedures: RNAV STARs start with a conventional Fix which the pilot should “traditional” Entry Fix • RNAV STARs start with a conventional Fix, which the pilot should use to cross-check with radio aid raw data to avoid gross errors • RNAV SIDs require a nav accuracy check on the runway • RNAV(GPS) approaches may require a user-defined check for gross error, since they often start with a ‘pure’ RNAV waypoint Conventional initial fix Use of many Waypoints g y p yp • After the initial Fix, all subsequent leg terminators are RNAV waypoints, rather than radio-referenced fixes • 6-10 waypoints are common in an RNAV arrival procedure, d t 3 6 fi i t diti l multiple waypoints Turns are Fly-by compared to 3-6 fixes in a traditional one • Generally, all turns will be Fly-By, with Fly-Over waypoints avoided • Turns may also use the “Fix to Fix via a Constant Radius” (RF) leg W i t d f h t t ll t bl t k Fly-By yp Fly by Legs are TF, • Waypoints are spaced far enough apart to allow stable track capture between turns • TF (and, in the future, RF) legs are used to provide the most predictable flight paths and the most FMS/GPS-“friendly” coding, except at the start/end of procedures TF predictable flight paths and the most FMS/GPS friendly coding, sequencing and guidance • By necessity, procedures may start or end with non-TF legs, eg. a SID may begin with VA (Heading to Altitude) then CF (Course to Fix) followed by a TF sequence Examples: Many altitude and speed constraints Fix), followed by a TF sequence • RNAV arrivals, in particular, include more specific altitude and speed constraints than a typical conventional procedure. This is designed to allow efficient traffic flows and descent profiles and 3000 3000 “or above” “at” 4000 2000 “between” Max IAS 220KT speed limit p constraints reduced radio communications 3000 “or below” IAS 180KT speed target 25 How are RNAV Procedures different? 4. …..RNAV procedure illustration P All turns are Fly-by Example: NEMAX2B trial P-RNAV Arrival to Rwy 27 ILS at Nottingham y g East Midlands (EGNX) Extract from UK CAA AIP SUP S1/2008 Many altitude and speed constraints GAM 235 radial DO NOT USE FOR NAVIGATION “traditional” Entry Fix 49.0 DME Note: QNH setting instruction ft i All legs are TF (after the IF) after passing waypoint Many Waypoints 26 How are RNAV Procedures different? 5. Arrival vertical profile often optimised for jet aircraft “continuous descent” P • Unlike most conventional procedures, RNAV STARs are often “closed”, terminating at the final approach point, rather than an initial or intermediate one (“open”) pp p , ( p ) • The vertical profile is usually designed to allow jet aircraft to commence descent late and then descend continuously, at 220KIAS and flight idle power, from the start of the procedure until the final approach waypoint and speed. This corresponds to a gradient of approximately 300’ per nm. – this is the most efficient and environmentally friendly method, known as CDA (Continuous Descent Approach). Otherwise, for jet aircraft, the earlier descent and power/configuration changes in a “step-down” arrival involve unnecessary fuel burn and a greater noise footprint Example: Vertical profile of NEMAX1B trial P-RNAV Arrival procedure at Nottingham East Midlands (EGNX) FL100 FL80 FL100 min FL120 max FL70 min FL60 4000’ FL55 min 4000’ min 3500’ min At 3000’ At 2000’ Gradient approximately 300’ per nm 2000’ 0’ nm to runway High target speed: advise ATC if unable when assigned the procedure and offer best speed to FAP • Note the aircraft performance and pilot workload required during the transition to the final approach – descending at ~300’ per nm whilst decelerating from 190KIAS (or speed attainable) to approach speed – no distinct level-off available for slowing down 0 10 20 30 40 50 60 y – no distinct level-off available for slowing down – cockpit transition of CDI, GPS course guidance and autopilot mode from RNAV to ILS/DME 27 How are RNAV Procedures different? Summary P A Traditional Procedures RNAV Procedures Traditional Procedures RNAV Procedures • Execution is demanding – selecting identing and displaying • Execution is easy – following the GPS guidance from – selecting, identing and displaying navaids – following track, distance and timing from raw data – following the GPS guidance from waypoint to waypoint • Management is more complex – repeated for each leg • Management is easy Management is more complex – valid database, correct procedure loaded and verified – RAIM availability checked; GPS, CDI g y – select the right chart and then follow the execution steps y ; , and Autopilot mode selection – avoidance of gross errors and “WIDN?” (what’s it doing now?) f i ith GPS i confusion with GPS receivers • The focus of most of the following sections of this course is on the proficient and safe management of RNAV flight 28 Course contents 1. RNAV and RNP theory 4. RNAV(GPS) Approach Procedures a. Introduction b. The Path-Terminator c. RNAV procedure design a. GPS procedure types b. GPS approach requirements and approvals d. RNP principles e. RNAV and RNP applications c. GPS approach operations 5. Avionics training 2. GPS Navigators and their application to RNAV a. The GPS system b. Databases and Coding 6. Simulator and/or Flight training c. Procedures d. Error detection and warnings 3. P-RNAV Terminal Procedures a. P-RNAV requirements and approvals b. P-RNAV training topics c. P-RNAV operations 29 Objectives of the RNP concept P Traditional procedure design RNAV procedures pre-RNP RNP procedure design p g • Standard infrastructure of ground radio aids p p • Proliferation of different RNAV navigations systems p g • Standard performance specifications established: ground radio aids • Aircraft carry a standardised suite of navigation receivers and instruments navigations systems • Even within one type of aircraft and one make of avionics, a variation in the FMS or GPS specifications established: “RNP-X” • Procedure tolerances designed around these RNP-X • Procedure tolerances designed around these standards software release installed can make an important difference to the system’s capabilities for executing a particular standards • Navigation and autopilot systems certified to RNP-X executing a particular procedure • Procedure design increasingly complex and restricted criteria • RNP is a ‘standard interface’ between the complex worlds of IFR airspace complex and restricted p p and procedure design, avionics and autopilot design/certification and the development of flight training and operating procedures • The new PBN model aims to further improve upon the benefits of the RNP concept 30 Definition of RNP accuracy requirement P A • There are five main navigation performance criteria: 1. Accuracy is the difference between the true and indicated position and track 2. Integrity is the ability to provide timely warnings when the system is not safe to use 3. Availability is the ability of the total system to perform its function at the initiation of the intended operation 4. Continuity is the ability of the navigation system to provide its service without interruption during an operation 5 Vulnerability is the susceptibility to unintentional or deliberate interference 5. Vulnerability is the susceptibility to unintentional or deliberate interference • The key requirement of RNP-X is an accuracy specification expressed as a Total System Error (TSE) of X nm or less for more than 95% of the total flight time • TSE is defined as follows: Total System Error (TSE) is the vector sum of• TSE is defined as follows: Desired Path Path Definition Total System Error (TSE) is the vector sum of – Path Definition Error (PDE) – Path Steering Error (PSE) – Position Estimation Error (PEE) Defined Path Error (PDE) Path Steering Error (PSE) Position • Path Definition Error is the difference between the path intended by the procedure designer and the path the aircraft is guided along as a result of database coding and navigator processing • Path Steering Error is the sum of display error in Nav systems and Flight Technical Error (FTE); ie. the errors in manual flight by pilots or autopilot performance in True Position Position Estimation Error (PEE) following a desired path. FTE includes reaction times and wind/turbulence induced errors, it does not include human “conceptual” errors eg. selecting the wrong procedure, waypoint or autopilot mode, or simply turning in the wrong direction • Position Estimation Error is the combination of navigation system/sensor (GPS) error and computation error (GPS software). PEE is expressed as a 95% confidence radius, ll d th E ti t f P iti U t i t (EPU) A t l N i ti P f Estimated Position • In practice, the Path Definition and Position Estimation errors are negligible, the key concerns for the GA pilot are FTE and the human factor errors in selecting RNAV procedures using GPS units interpreting guidance True Position called the Estimate of Position Uncertainty (EPU) or Actual Navigation Performance (ANP). PEE is sometimes also called Navigation System Error (NSE) are FTE and the human factor errors in selecting RNAV procedures, using GPS units, interpreting guidance and in manual flying or operating the autopilot 31 The current RNP-X specifications published in Europe (see next section for future PBN specs) Used for RNAV(GPS) Approaches Used for P-RNAV US RNAV 1 Oceanic & t t Used for B-RNAV remote enroute Oceanic Source: Eurocontrol publication “Guidance Material for the Design of Terminal Procedures for Area Navigation” 32 Course contents 1. RNAV and RNP theory 4. RNAV(GPS) Approach Procedures a. Introduction b. The Path-Terminator c. RNAV procedure design a. GPS procedure types b. GPS approach requirements and approvals d. RNP principles e. RNAV and RNP applications c. GPS approach operations 5. Avionics training 2. GPS Navigators and their application to RNAV a. The GPS system b. Databases and Coding 6. Simulator and/or Flight training c. Procedures and guidance d. Error detection and warnings 3. P-RNAV Terminal Procedures a. P-RNAV requirements and approvals b. P-RNAV training topics c. P-RNAV operations 33 Current RNAV applications in Europe: an overview P A Enroute/Terminal Terminal Approach pp • Requires RNP-5 capable navigation • Requires RNP-1 capable navigation • Requires RNP-0.3 capable (Basic) B-RNAV (Precision) P-RNAV RNAV (GPS) Approaches q p g equipment (sufficient condition) • Compulsory, since 1998, in almost all European airways and TMAs P i t GA t t q p g equipment (necessary but not sufficient) • Europe is in the early stages of implementing P-RNAV procedures q p navigation equipment • Europe is in the early stages of implementing GPS approaches P i t GA t i t • Private GA operators can meet requirements through carriage of an approved IFR GPS installation (for UK registered aircraft, AFM supplement must specify BRNAV approval; for US aircraft implementing P RNAV procedures and all such TMAs currently offer conventional alternatives • Private GA operators must obtain a Letter of Authorisation from their • Private GA operators requirements for equipment carriage are similar to B-RNAV: (E)TSO C129a or C146a GPS with installation conforming to FAA AC20 138 or EASA AMC 20 5 must specify BRNAV approval; for US aircraft, requirements are similar – see AC90-96A Appendix 1) • B-RNAV SIDs and STARs are implemented which meet en-route Letter of Authorisation from their state of registry. JAA TGL10 and FAA AC90-96A Appendix 2 specify requirements for navigation system function database approval pilot FAA AC20-138 or EASA AMC 20-5 and AFM approval for Approaches • National air law generally requires GA pilots to have some theoretical p design criteria (eg. are above MSA) and which start & end at a conventional fix (note: both B-RNAV and P-RNAV procedures function, database approval, pilot training and operating procedures and flight training specific to GPS Approaches are designated “RNAV”. Check approach plate detail, airport text pages and AIPs/AICs as appropriate – some RNAV terminal procedures formerly requiring only B-RNAV are migrating to needing P-RNAV approval) See Section 3 See Section 4 Source: see website of the Eurocontrol Navigation Domain http://www.ecacnav.com/Home which has a comprehensive set of documents and HTML resources 34 Future RNAV applications in Europe: The new Performance-Based Navigation (PBN) model P g ( ) • PBN is the new formal model of how RNAV is implemented • It is a move from a limited statement of required performance accuracy (ie. basic RNP-X) to more extensive statements of required performance in terms of accuracy, integrity, continuity and availability, together with descriptions of how this performance is to be achieved in terms of aircraft and crew requirements. • The Required Navigation Performance (RNP) concept has been replaced by the PBN concept. Therefore, a lot of RNP terminology has been replaced by PBN terminology • The ICAO 'Performance Based Navigation Manual (Final Draft)' replaces the • The ICAO Performance Based Navigation Manual (Final Draft) replaces the 'Manual on Required Navigation Performance (RNP) ICAO Doc 9613-AN/937'. • Global definitions of terms are provided that are aimed at removing any previous regional differences. Available from • A set of globally compatible Navigation Specifications are also provided. These are to be used as a basis for local or regional Navigation Applications in the en route, terminal and approach environments Available from http://www.ecacnav.com/Document_Library Source: the ECACNAV free online course on PBN http://www.ecacnav.com/WBT/PBN/frames/firstwin1.htm • PBN has no current or imminent relevance to European IFR operations. However, because a GA pilot may increasingly encounter the terminology and specification of f t PBN li ti i i ti l d d t thi ti id b i f p future PBN applications in various articles and documents, this section provides a brief overview for the sake of completeness and orientation • This Manual will revert to the current RNAV terminology in sections 2-6, and no further reference to PBN will be necessary reference to PBN will be necessary 35 Performance-Based Navigation (PBN) specifications PBN i t d 2 l f ifi ti ….introduces 2 new classes of specification “on board performance monitoring” is not a problematic requirement for modern GPS units RNAV specifications ..do not include a requirement for on-board performance monitoring and alerting RNP specifications ..do include a requirement for on-board performance monitoring and alerting • These are essentially a re naming of existing • These add some (modest) extra • These are essentially a re-naming of existing specifications with a new RNAV X convention, in which the X is 95% lateral accuracy in nm • These add some (modest) extra “containment”/alerting requirements to existing RNP specs, and introduce some new applications Current name PBN name RNP 10 RNAV 10 PBN name Used in: RNP 4 Oceanic Basic RNP 1 & 2 Various flight B-RNAV RNAV 5 RNAV 2 (USA) RNAV 2 P-RNAV (Europe) Basic RNP 1 & 2 Advanced RNP 1 Various flight phases RNP APCH Similar to RNAV(GPS) More demanding P-RNAV (Europe), RNAV1 (USA) RNAV 1 RNP AR APCH More demanding “Authorisation Required” approaches RNP “3D”, “4D” ..to be defined 36 Reference: extract from ICAO PBN Manual Table 1-1: Application of Navigation Specification by Flight Phase 37 Course contents 1. RNAV and RNP theory 4. RNAV(GPS) Approach Procedures a. Introduction b. The Path-Terminator c. RNAV procedure design a. GPS procedure types b. GPS approach requirements and approvals d. RNP principles e. RNAV and RNP applications c. GPS approach operations 5. Avionics training 2. GPS Navigators and their application to RNAV a. The GPS system b. Databases and Coding 6. Simulator and/or Flight training c. Procedures d. Error detection and warnings 3. P-RNAV Terminal Procedures a. P-RNAV requirements and approvals b. P-RNAV training topics c. P-RNAV operations 38 The Global Satellite Navigation System (GNSS) The general term for the global navigation satellite and ground station infrastructure P A GNSS GNSS Note that the terms GNSS and GPS are sometimes used interchangeably Note: there are other national GNSS programmes and proposals , eg. India, China GPS • The USA’s “Navstar” Global GLONASS • Russian “Global Navigation Satellite “Galileo” • The European Union’s GNSS Positioning System • A military system that became fully operational for worldwide civilian use in 1995 System” • Introduced during the Soviet era for military applications • At present only partially operational project • After some controversy, formally approved in Nov 2007 • Should be operational by ~2013 • Designed around a network of 24 medium-earth orbit satellites • “Selective Availability” (SA) d d ti f i ili i l • At present, only partially operational, with 13 of 24 required satellites functioning and approx ~60% global coverage R i i t d t f ll t • Should be operational by ~2013 • USA/EU agreement that Galileo and GPS will be “interoperable” • Will use a 30 satellite constellation; degradation of civilian signal accuracy ended in 2000 • Russia intends to fully restore GLONASS by ~2011, in partnership with the Indian government ; some service and accuracy improvements over current GPS • The concept is that receivers should be able to operate with multiple systems, creating in GNSS a single ‘virtual’ system capable of providing a high degree of resilience when used as a sole source of navigation data for aircraft • The rest of this manual will refer only to GPS 39 How does GPS work? 1. Overview of the system’s three “segments” P A Space Segment (SS) • The system is designed for a minimum of 24 satellites (abbreviated as “SV”, Satellite Vehicle): The system is designed for a minimum of 24 satellites (abbreviated as SV , Satellite Vehicle): 4 in each of 6 orbital planes, at a height of ~20,000km and completing one orbit every 12hrs • Currently there are 31 satellites, the 7 additional ones improve accuracy and resilience. The constellation is arranged so that at least 6 satellites are always line-of-sight visible from almost any point on the Earth • Each satellite broadcasts a “ranging code”, used to establish distance from the GPS receiver, and its own “Navigation Message” containing • The Master Control Station feeds back a navigational update to each satellite synchronising its internal – Clock data at the time of transmission – Data on the satellite’s orbital position (“ephemeris”) – “Almanac” data on the status of the entire satellite network Th l ti f th G d St ti satellite, synchronising its internal clock and adjusting the ephemeris model of its orbit • Occasional maneuvers are commanded which maintain a satellite in its proper orbit (detailed in following pages) • The location of the Ground Stations is very accurately established and used to calibrate the satellites’ position and clock data based on the navigation messages they send satellite in its proper orbit Control Segment (CS) • A Master Control Station in Colorado and 4 Monitor stations across the globe • They establish the exact orbital position of User Segment (US) • Navigation devices which typically include an antenna, an accurate clock, receiver, processor and control/display components • The receipt of ranging codes and navigation messages from multiple satellites They establish the exact orbital position of each satellite, and maintain the reference atomic clocks for the system • Modern ‘multi-channel’ receivers can simultaneously monitor 12-20 satellites p g g g g p allows GPS Receivers to compute accurate 3D position, speed and time 40 How does GPS work? 2. The satellites broadcast a signal for civilian receivers called “L1” P A The Navigation Message consists of 5 subframes of 10x 30bit words The Navigation Message C/A (Coarse/Acquisition) code The Navigation Message consists of 5 subframes of 10x 30bit words (1500bits total) transmitted at 50bits/s, ie. every 30 seconds. See next page for detail. ..is the ranging code, used by the GPS receiver to measure distance to the satellite; also called “the “Standard Positioning Service” or SPS The C/A code is a 1,023bit “pseudorandom number” (PRN) transmitted at 1 023Mbit/s ie repeating every millisecond C/A (Coarse/Acquisition) code The 1023Mbits/s is sometime also referred to as the “chipping” rate, and each BPSK modulated bit of data as a “chip” (change in phase) 1.023Mbit/s, ie. repeating every millisecond. The PRN is unique to each satellite, and all the PRNs are stored in GPS Receiver memory. Because they are long pseudorandom numbers designed to be “orthogonal”, any two different PRNs will “correlate” poorly (ie. when multiplied together, give a value near zero). The Receiver isolates any given satellite’s transmission by multiplying the incoming L1 signal by that satellite’s PRN at different time shift intervals, within the 1 millisecond sequence, until it finds a match or ‘lock-on’ (when a particular time shift results in a high multiplication value). It can thus “filter out” all the other satellites from the L1 frequency and use the time “Modulo 2 Adder” The Navigation Message is encoded onto the C/A at 50bits/s by changing its sign L1 Carrier filter out all the other satellites from the L1 frequency, and use the time shift required for lock-on to calculate the satellite’s range and also extract (demodulate) the Navigation Message from the C/A code. See later pages for detail. Broadcast Signal The Navigation message is encoded onto the C/A code, and the C/A is then modulated on to a carrier frequency of 1575.42 MHz, called “L1” L1 Carrier A digital (binary) signal is transmitted by changing (modulating) a (sinusoidal) carrier wave in one of three ways: amplitude, frequency or phase. The latter is ll d Ph K Shifti (PSK) Bi i th i l t PSK th d (BPSK) “BPSK” Modulation The fundamental frequency of the system, Fo, is 10.23Mhz. The carrier and code frequencies called Phase Key Shifting (PSK). Binary is the simplest PSK method (BPSK) which “switches” between 2 carriers 180 O out of phase Reference: Colorado Centre for Astrodynamics Research, R.S. Nerem & E. W. Leuliette, lecture #25, http://ccar.colorado.edu/asen5060/lectures.html. are multiples of this , eg. L1 = Fo x 154. All radio frequencies and codes generated in the satellite are from the same 10.23MHz crystal, controlled by an atomic clock 41 How does GPS work? 3. The structure of the Navigation Message P A Frame Frame:1500 bits long; 30s @ 50bps • The Navigation Message is transmitted as a stream of digital data organised into a sequence of Frames Subframe 3 Subframe 4 Subframe 1 Subframe 2 Subframe 5 5 Subframes each 300 bits long: 6s @ 50bps • Each satellite begins sending a Frame exactly on the minute and half-minute, according to its internal clock • Each Frame is made up of 5 Subframes Subframe 3 Subframe 4 Subframe 1 Subframe 2 Subframe 5 – Subframes 1,2 and 3 are repeated in consecutive Frames and updated every 1-2 hours, on the hour – The almanac data in Subframes 4 and 5 is “sub commutated”; it takes a cycle of 25 Frames (with different Subframe 4&5 data) for the receiver to Clock data for this satellite Ephemeris data for this satellite Almanac data common to all GPS satellites • Data that allows the GPS receiver to calculate the small • The almanac consists of basic orbit and status information for all satellites an • An “ephemeris” is a table of values that gives the position of ) assemble the full almanac – The almanac is thus repeated every 25 Frames and is updated approximately every 24hrs receiver to calculate the small offset between the satellite's internal clock time and GPS time defined by the ground station atomic clocks status information for all satellites, an ionospheric model, and information to relate GPS time to UTC that gives the position of astronomical objects in the sky. In a GPS context, it means the detailed model of a satellite’s orbit E h S bf i d f 10 W d Word 3 Word 4 Word 1 Word 2 Word 5 Word 8 Word 9 Word 6 Word 7 Word 10 A Subframe is made up of 10 Words, each 30 bits long: 0.6s @ 50bps • Each Subframe is made up of 10 Words – Words 3-10 carry the data content of the frame as described above – Word 1 is called the “Telemetry” word and contains a sync pattern used by the receiver to 30bits in a word .. .. 1 2 .. 29 .. 30 synchronize itself with the Navigation Message and thus decode the data content – Word 2 is the “Handover” word, analogous to a counter that increments by 1 in each Subframe • Each Word is made up of 30 Bits of data • The Navigation Message is the ‘real-time reference manual’ for the GPS receiver, First 6 bits are parity data Final 24 bits carry the data content Source: Article by Ed Weston, http://gpsinformation.net/gpssignal.htm. which helps it calculate an accurate position based on the C/A Code ranging signals 42 How does GPS work? 4. Other (non-civilian) signals and future enhancements to the system Non-civilian GPS transmissions Future enhancements L1 Carrier 1575.42 MHz C/A Code 1.023 MHz Civilian-use signal L1 Carrier 1575.42 MHz C/A Code Existing Future • L1C New version of C/A code M (Milit ) d Nav.Msg. 50 Hz P(Y) Code 10.23 MHz L2 Carrier 1227.60 MHz • C/A Code • P(Y) Code • L2C signal CM (civilian moderate) code • M (Military) code L2 Carrier 1227.60 MHz P(Y) Code Same P(Y) Code transmitted on L1 and L2 • P(Y) Code CL (civilian long) code • M (Military) code L5 Carrier 1176 45 MH • “Safety of Life” signal 10.23 MHz • The P (Precise) code is a 10,230bit psuedo-random number, it is a 10x more accurate version of the C/A code 1176.45 MHz • These new signals are being implemented progressively by new satellite launches over the next 5 years • Normally, the P code is encrypted by a “Y” code, creating the 10.23 MhZ P(Y) signal which can only be decrypted by military users – known as the “Precise Positioning Service” (PPS) • The encryption is an “anti-spoofing” technique ,which provides some assurance that the signal received is not being sent by a • L1C will be compatible with existing receivers but include better interoperability with other GNSS systems and other improvements • L2C is the more accurate “v2.0” civilian GPS signal and allows civilian ionospheric compensation through comparison of L1C and L2C signals some assurance that the signal received is not being sent by a non-GPS “spoofing” transmitter. The C/A code is potentially vulnerable to such spoofing. • The ionosphere delays or “disperses” radio signals differently according to their frequency. Military (and some specialised • The M code is the improved military signal • The L5 “Safety of Life” signal is specifically for civil aviation use and is transmitted in the protected Aeronautical Radio Navigation Services (ARNS) band civilian) receivers can compensate for this by comparing P(Y) signal reception between the L1 and L2 carriers. • Author’s note: Existing GPS receivers will be supported for very many years. It is likely that after ~2013, some RNAV applications will begin to require new GPS receivers, capable of using the more accurate signals and multiple GNSS systems Source: Royal Observatory of Belgium GNSS website http://www.gps.oma.be/gb/modern_gb_ok_css.htm and US Air Force GPS fact sheet http://www.losangeles.af.mil/library/factsheets 43 How does GPS work? 5. International time and the GPS time system P A International Atomic Time (TIA) Universal Coordinated Time (UTC) “GPS Time” (TIA) • The standard international scientific time scale • The length of a second is defined by (UTC) • “Earth time” (“UT1”) defines the earth’s angular position with respect to the celestial sphere; this is the most useful • The GPS system uses a time reference (“GPS Time”) maintained by the Master Control ground• The length of a second is defined by a frequency property of the cesium- 133 atom, and atomic clocks are used to “count” or “accumulate” seconds p ; time scale for navigation and astronomy • Fluctuations in the earth’s spin mean that UT1 deviates from the precise TIA y g station’s atomic clocks • GPS time uses the TIA second, and was set equal to UTC in 1980. It does not introduce leap seconds, and today is 14s ahead of UTC (the difference between TIA & UTC was 19s in 1980, hence today’s 33s-19s=14s). seconds • TIA is derived from 230 atomic clocks in 65 sites around the world, and 11 different laboratory caesium f t d d that UT1 deviates from the precise TIA reference • UTC, the “official world time” is a compromise between Earth time and TIA it th TIA d b t , y ) The Navigation Message transmits a correction for UTC, so that GPS receivers can display UTC and local time zones. • Each satellite carries its own atomic clock which will have a small error orfrequency standards • The data is collated by the BIPM (Bureau International des Poids et Mesures) in Paris, who calculate TIA; it uses the TIA second, but introduces leap seconds to account for changes in the earth’s spin and maintain a useful consistency with UT1 clock, which will have a small error or “offset” from GPS Time. This is known as SV (Satellite Vehicle) time • SV clock offset information is broadcast in each satellite’sTIA and promulgate the results to various international centres • At any given time, UTC equals TIA minus an integer number of seconds. In January 2008, UTC was 33s behind. Typically, a leap second is subtracted broadcast in each satellite s Navigation Message • The GPS “calendar” is a counter of weeks and days of the week. ‘Date • Time measurement is the basis for GPS navigation, because the range from a satellite to a receiver can be determined by the time delay in receiving a signal, once a year zero’ was 6 January 1980 y y g g , and with multiple range fixes, a position can be calculated Source: “The Science of Timekeeping”; DW Allen, N Ashby, C Hodge (Hewlett Packard Application Note 1289) www.allanstime.com/Publications/DWA/Science_Timekeeping See also the US Naval Observatory Time Service Department website, http://tycho.usno.navy.mil/ 44 How does GPS work? 6. The GPS Receiver: Overview P A Th t i d i d t id Simplified GPS receiver diagram (not Garmin specific, photos are illustrative) • The antenna is designed to provide equal sensitivity to all satellite signals above (typically) 5 degrees of elevation, and is shielded from lower elevation signals to avoid “multi path” error (reflections from • Preamplifier: amplifies the Radio Frequency (RF) signal and sets the noise level to reject other RF interference • Down Converter: converts the RF • A modern multi-channel receiver simultaneously detects and processes signals from all visible satellites • Locks on to the PRN code and extracts the Navigation message • Calculates the relationship between GPS time and Receiver time • Determines position and velocity (method described on next page) Navigation Message Antenna Nav functions and user interface p ( terrain or from the airframe) signal to an Intermediate Frequency (IF) • Determines position and velocity (method described on next page) Preamplifier and Down Converter Demodulation and Code control Navigation and Signal Processor Data decoding C/A d Message C/A Code Position, Velocity, Time g Satellite positions Pseudo-range calculation Receiver position, velocity and time calculations C/A code generator Measurement Time Measurement Clock Measurement Aviation navigation database and charts. Radios and other sensors. • Oscillator provides the receiver’s time and frequency reference • Frequency synthesiser converts this reference to a signal providing clock i f ti t th P information to the Processor • The Navigation processor’s task is complicated, because the GPS receiver has no accurate time or position reference other than the satellite signals it decodes. These specify the exact “GPS Time” of transmission but the receiver doesn’t directly “know” Sources: Peter H. Dana article 29/7/95 and Jeppesen JAA ATPL Manual Edition 2, Radio Navigation volume. specify the exact “GPS Time” of transmission – but the receiver doesn’t directly “know” its own GPS Time of reception. The calculation method is described on the next page. 45 How does GPS work? 7. The GPS Receiver: Calculation of time and position P A Stage 1: The “pseudorange” Stage 2: The accurate fix Wh th GPS i i t t d it i t l “l l” l k ill b Th R i th th h i ( bit l) d t i h • When the GPS receiver is started-up, its internal or “local” clock will be inaccurate by an unknown error, called clock bias or offset, compared to the reference GPS Time • A modern quartz clock may be accurate to one part in a million (ie. drift by one microsecond every second). This means that after only 1s, the internal clock error can be th i l t f h d d f t (1 300 t th d f li ht) A it th t’ • The Receiver then uses the ephemeris (orbital) data in each satellite’s Navigation Message to establish the satellite’s position in space at the time of the Pseudorange calculation • It requires a minimum of 4 satellite pseudoranges to determine a 3D navigational fix for the Receiver. the equivalent of hundreds of metres (1μs = ~300m at the speed of light). A unit that’s been switched off for a week or two could be inaccurate by ~1s or hundreds of thousands of km. • The first stage of the navigation problem is to calculate “pseudoranges” from the visible satellites to the GPS, ignoring the local clock offset. Th “ d ” b th ll k t b b a gat o a o t e ece e • The GPS system specification is that 5 satellites should always be available above a mask (elevation) angle of 7.5 degrees (usually it is 6 or more) • With 4 satellite positions known and 4 pseudo ranges calculated, the navigation problem can be expressed as 4 equations with 4 ( f These ranges are “pseudo” because they are all known to be wrong by the same (unknown) local clock error • For any given satellite, the Receiver generates the satellite’s PRN code internally, based on its “code book”, and starts the code sequence at the time its local clock says the satellite should have started its PRN unknowns (the unknowns being the x,y,z position of the receiver and t, the clock bias error) • The Receiver calculates a solution to these equations and establishes a position fix With t ( th th d ) it ld l i 3 t llit iti t e ts oca c oc says t e sate te s ou d a e sta ted ts transmission. The internal PRN code is then time-shifted until it matches (locks-on) to the PRN code signal from the satellite. This time-shift, or offset, is the (pseudo) elapsed time between transmission and the reception Time of Arrival (TOA) Th P d i d i d f th TOA i i d f • With true (rather than pseudo) ranges, it would only require 3 satellite position spheres to determine a fix intersect. However, with pseudoranges, a 3 sphere solution would give the wrong range. 4 pseudoranges spheres won’t intersect at a point – because the ranges are not true and consistent with a single point in space. The receiver, in effect, solves the equations to determine which value of local clock error creates the best intersect of the 4 spheres • The Pseudorange is derived from the TOA, assuming a given speed for radio wave travel and the decoded time of transmission from the satellite • The 1023 bit PRN code is transmitted at 1000 times per second, and the Receiver can judge the “start” of a bit to about 1%, so the maximum accuracy of the C/A code is ~3m • By decoding the Navigation Message, the Receiver gets data that allows it to correct • The receiver also calculates a Geometric Dilution of Precision (GDOP), based on the relative position of the satellites (satellites close together provide a weaker fix) • When more than 4 satellites are available, modern receivers use various other algorithms to provide a better fix Fi ll th iti f th t f th th i t l t d y g g g , g Pseudorange for the following errors – The SV (Satellite Vehicle) time offset from GPS time – Basic ionospheric corrections from the Almanac – Relativistic effects and receiver noise • The Receiver calculates pseudoranges from different satellites • Finally, the x,y,z position from the centre of the earth is translated into latitude, longitude and altitude using the WGS84 datum, and GPS Time is converted into UTC. (See later pages on WGS84) • Velocity (ie. ground speed and ground track) is calculated using a combination of rate of change of position and Doppler shift simultaneously, so they are all subject an identical local clock error combination of rate of change of position and Doppler shift measurement of the L1 carrier frequency of different satellites, compared to the receiver’s L1 oscillator frequency 46 How does GPS work? 8. Illustration of the GPS navigation calculation Stage 1: The “pseudorange” 1023 bits Sample of the C/A PRN codes 31 rows Each row is the code from one satellite 1 0 1 1 0 0 1 0 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 0 0 0 0 1 0 0 0 The Receiver generates the C/A PRN code for the satellite it is trying to lock on to…. • All 31 satellites use the same L1 carrier frequency to transmit their C/A codes using the Code Division Multiple Access (CDMA) method of multiplexing that allows them to “share” the same carrier. • A particular C/A code can be extracted from the “noise” of 31 superimposed signals by multiplying the inbound carrier with th d i d PRN d t d i t ll d ti hifti …and seeks a time-shift that will provide the best correlation between the L1 C/A signal and the internally generated code the desired PRN code generated internally, and time-shifting the internal PRN until a correlation “spike” is achieved • A full description is beyond the scope of this course. The diagrams are illustrative rather than technically rigorous • Low correlation: wrong PRN code 1 0 0 1 1 0 1 1 0 1 1 0 0 1 1 1 1 0 0 1 0 1 1 1 0 0 1 1 1 1 1 1 0 1 1 0 0 1 0 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 0 0 0 0 1 0 0 0 X 1 0 1 1 0 0 1 0 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 0 0 0 0 1 0 0 0 1 0 1 1 0 0 1 0 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 0 0 0 0 1 0 0 0 X • Better correlation: correct PRN code, but time shift wrong 1 0 1 1 0 0 1 0 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 0 0 0 0 1 0 0 0 1 0 1 1 0 0 1 0 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 0 0 0 0 1 0 0 0 X • Best correlation: correct PRN code and best time shift ti hift Sources: Peter H. Dana, University of Colorado website: http://www.colorado.edu/geography/gcraft/notes/gps/gps.html and Id prior pages (R.S. Nerem & E. W. Leuliette, lecture #25) time shift 47 How does GPS work? 9. Illustration of the GPS navigation calculation Stage 2: The accurate fix Two dimensional illustration of the GPS navigation calculation Determining pseudorange from 3 satellites results in 3 equations with 3 unknowns: the x,y position of the receiver and t, the local clock bias The navigation processor solves these equations to determine a clock bias which gives the best intersect between the three bias-adjusted “true” range arcs Pseudoranges calculated from Satellite position known from Navigation Message ephemeris data Best fit local clock bias (all three black arrows represent the same clock bias) g PRN correlation time shift Pseudorange arc Clock bias unknown, thus receiver position unknown Best fit position True range arc • The actual method used is analogous to this; 4 satellites provide 4 range spheres and thus unknown p solution • The actual method used is analogous to this; 4 satellites provide 4 range spheres, and thus 4 equations to solve for the unknown 3D x,y,z position of the receiver and its clock bias 48 How does GPS work? 10. The WGS84 map datum What is WGS84? Definition of WGS84 • Geodesy (or geodetics) is the science concerned with the study of the geometric shape and size of the earth. It defines the coordinate systems and references used in surveying, mapping, and navigation. Typically, such systems have 3 elements: – a “Cartesian” reference or datum, defining the origin as the centre of the earth’s mass d th i t f l t i l d i idi l • From the Eurocontrol WGS84 Implementation Manual: • The World Geodetic System - 1984 (WGS 84) coordinate system is a Conventional Terrestrial System (CTS), realized by modifying the Navy Navigation Satellite System (NNSS), or TRANSIT, Doppler Reference Frame (NSWC 9Z-2) in origin and scale and rotating it to bring its reference meridian into and the x,y,z axes in terms of polar, equatorial and prime meridian planes – an “Ellipsoidial” datum for latitude and longitude; based on the Cartesian datum and an ellipsoid model of the earth’s surface – a “Geoid” datum for elevation, determined by local variations in the earth’s gravity, hi h t M S L l d diff f th id li d lli id (“ id scale, and rotating it to bring its reference meridian into coincidence with the Bureau International de l’Heure (BIH)- defined zero meridian. – Origin and axes of the WGS 84 coordinate system are defined as following: – Origin: Earth’s centre of mass which represents Mean Sea Level and differs from the idealised ellispoid (“geoid undulation”). See later page on GPS and VNAV. • Many different global, regional and national geodetic systems are used for different applications. National mapping coordinate systems tend to use a “local” ellipsoid model of the earth’s surface, which is a more accurate mathematical approximation for a – Z axis: The direction of the Conventional Terrestrial Pole (CTP) for polar motion, as defined by BIH – X axis: Intersection of the WGS 84 reference meridian plane and the plane of the CTP’s equator, the reference meridian being the zero meridian defined by the BIH – Y axis: Completes a right-handed, Earth Centred, Earth Fixed , pp particularly country than any global ellipsoid. • In 1960, the US Department of Defense combined the different global reference systems used by the US Navy, Army and Air Force into a standard “World Geodetic System” known as WGS60. As terrestrial and space survey data improved, and working with i ti t d i tit ti f th t i th D D bli h d i d d t i p g , , (ECEF) orthogonal coordinate system, measured in the plane of the CTP equator, 90° East of the x-axis • WGS 84 is an earth-fixed global reference frame, including an earth model defined by the shape of an earth ellipsoid, its angular velocity, and the earth-mass which is included in the ellipsoid of reference scientists and institutions from other countries, the DoD published improved datums in 1966, 1972 and 1984 (WGS66, WGS72, WGS84). • WGS84 was selected as the Datum for the GPS system, and is now a fixed standard; minor subsequent updates have had no practical impact C t i ti t ti l di t t lth h h h d ellipsoid of reference. • Countries continue to use national coordinate systems, although some have changed theirs to conform more closely to WGS84. However, there can be differences of hundreds of metres between WGS84 maps and other, relatively modern, national and regional maps. For example, the UK’s Ordnance Survey grid (OSGB36) meridian is 6m west of the historical meridian monument at Greenwich and the WGS84 meridian is 103 t f it Source: WGS84 Implementation Manual, Eurocontrol & IfEN, University of Munich 1998 http://www.icao.int/pbn/Docs/Eurocontrolwgsman24.pdf . Appendix B of this excellent document has a detailed overview of Geodesy. 103m east of it 49 How does GPS work? 11. Aviation charts and WGS84 P A Aviation charting datums GPS Navigators and WGS84 • Aviation charts use 3 types of position data – Surveyed positions for topographic and terrain features, navaid positions and physical references, like runway thresholds – Declared positions, defined by latitude and longitude (rather than any surveyed point) for airspace boundaries and oceanic entry/exit points – Calculated points, defined by a geometric relationship to a surveyed position (eg. a • The source of approved aviation GPS navigation and map data are the ICAO-compliant charts published in national AIPs. • These are encoded into electronic databases and maps using the ARINC 424 standard; proprietary standards may also be used for dditi l f t lik t i d b t l d t d th l t i Calculated points, defined by a geometric relationship to a surveyed position (eg. a fix based on a VOR/DME radial and distance) • RNAV waypoints are either calculated relative to navaids or at declared latitudes and longitudes (although, of course, charts will often show both the navaid reference and the lat/long of a waypoint) additional features like terrain and obstacle data and the electronic depiction of paper charts • Aviation GPS receivers establish the aircraft's position in terms of the WGS84 datum. The aircraft position is then used as the reference for the GPS navigation and map display • Historically, each country used its own geodetic datum for aviation charts. Navigating with ground-based aids, an aircraft could fly between countries that used datums hundreds of metres apart without any problem, since IFR terminal and approach charts used in the cockpit were published with the appropriate local datum g p p y • In “map display mode”, objects such as waypoints, ground features and airspace boundaries are displayed on the map relative to the aircraft WGS84 position – based on the objects’ stored WGS84 coordinates. Navigation data (eg. track and distance to waypoint, t k ) i l l l t d f th l ti WGS84 • However, work in Europe on radar and navaid trajectories in the 1970s demonstrated the inconsistency of national datums. For example, an aircraft could appear on one county’s radar exactly at the declared longitude of an airspace boundary and 1km away from it on an adjacent country’s radar cross-track error) is also calculated from the relative WGS84 co- ordinates of the aircraft and the waypoint or flight plan track. • In most aviation GPS Receivers the WGS84 country s radar • In 1989, ICAO adopted WGS84 as the standard aviation geodetic reference system Thi h b f ll i l t d i E d Receivers, the WGS84 datum can not be changed • In non-aviation GPS, the datum may be changeable (eg. to be consistent with • This has been fully implemented in Europe and North America; so that GPS-derived WGS84 positions, approved electronic charts used in GPS receivers and approved paper-based aviation charts are self consistent maps used for hiking or marine navigation) Example from Garmin GNS530 Pilot’s Guide Source: ibid, WGS84 Implementation Manual are self-consistent Note: see http://www.jeppesen.com ..Online Publications..IFR Pilot Information for an online status report of countries whose AIPs conform to WGS84 50 How does GPS work? 12. GPS mapping illustration P A Satellite C/A Code and Navigation Message Data card with current database Navigation and Si l P Navigation Message Aircraft’s position relative to WGS84 GPS map objects coded with WGS84 Database supplier encodes AIP data from the current AIRAC cycle Signal Processor Using WGS84 datum datum GPS map objects, coded with WGS84 datum, depicted relative to aircraft’s position Chart supplier publishes paper charts for in-flight use based on the current AIP National AIS publishes WGS84- referenced charts and procedures in ICAO format in the AIP, updating them GPS satellite orbits, GPS-derived aircraft position, electronic charts, in-flight paper charts and AIP h t ll f d t th WGS84 d t based on the current AIP according to the AIRAC schedule charts all referenced to the same WGS84 datum • The use of current, approved WGS84 charts and databases assures the consistency of GPS navigation with radio aids, paper charts and surveyed airport, terrain and obstacle positions • If non-approved, non-WGS84 or outdated charts or data are used, inconsistencies may arise that could exceed the protection designed into IFR routes and procedures 51 GPS and Vertical Navigation (VNAV) P A Definition of the “geoid” and Mean Sea Level Aviation vertical navigation • The reference ellipsoid (global or local) for mapping datums is • In aviation, altitude is measured from an MSL datum and pressure • The reference ellipsoid (global or local) for mapping datums is necessarily a geometric shape – so that latitude and longitude lines may be perfectly regular • Measures of elevation (or, in aviation terminology, altitude) also need a datum; which, by convention, is Mean Sea Level (MSL). This is both a , p altitude is measured from the ISA pressure datum of 1013.25 hectopascals • In an aircraft, a barometric altimeter is used to indicate – pressure altitude, directly, when set to 1013mb or 29.92” Hg vertical reference to measure from and a (gravitationally defined) direction of up and down to measure along • Climactic, tidal, weather, current and local topographic effects cause the sea level to fluctuate. At any given point, the actual sea level may be measured over time to determine its mean However measured mean – altitude, indirectly, by using a local pressure setting (QNH) that approximates to the MSL datum • Under ICAO, the WGS84 datum is widely used as the standard for lateral navigation (LNAV). There is no corresponding standard datum f M S L l i ti l i ti (VNAV) A i ti h t d measured over time to determine its mean. However, measured mean sea levels do not fit well with any ellipsoid model of the earth - because of the gravitational effect of irregularities in the earth’s shape and composition (eg. variations in the density of the earth’s crust). • In effect, where gravity is locally “stronger”, MSL will be higher. Why? ater flo s do nhill nder the infl ence of gra it A still bod of ater ill establish a for Mean Sea Level in vertical navigation (VNAV). Aviation charts and procedure designs tend to be based on a local MSL datum • Using barometric altimetry, these variations in MSL datum are not observable to the pilot, because QNH is always referenced to the local MSL datum used for charts and procedures– water flows downhill under the influence of gravity. A still body of water will establish a surface which, at all points, is perpendicular to the “down” direction – in a perfect, ellipsoid planet of uniform density, “down” would always be towards its geometric centre. In the case of an irregular body like the earth, the gravitational “down” direction varies locally, rather than always pointing to the earth’s centre of mass. Hence, the global MSL datum is an irregular surface of gravitational “equipotential”. At any point on this surface a plumb line or spirit level (simple devices for identifying local p • Although modern aviation GPS receivers can display an altitude derived from GPS position data and referenced to EGM96 Mean Sea Level, this can vary significantly from the local MSL datum Thus all IFR VNAV uses barometric altimetry on this surface, a plumb line or spirit level (simple devices for identifying local, gravitationally “true” down ) would indicate a down perpendicular to the surface. • A “geoid” is the representation of the earth whose surface has the property of gravitational equipotential and is used as the reference for the Mean Sea Level datum Thus, all IFR VNAV uses barometric altimetry, not GPS altimetry Example, from the Garmin GNS530W Pilot’s Guide • The distinction between the geoid and the ellipsoid model of the earth is a significant one – MSL across the world can vary by 100m from the WGS84 ellipsoid. • The geoid used in WGS84 is called EGM96 (Earth Geodetic Model 96), most aviation GPS receivers use this model to transform the Ellipsoid Terrain warning systems also use Radar and GPS altitude inputs to most aviation GPS receivers use this model to transform the Ellipsoid height coordinate into an altitude above MSL • Terrain warning systems also use Radar and GPS altitude inputs to avoid depending on the manual setting of QNH 52 GPS System Performance 1. A model of GPS performance measures and factors affecting them P A Accuracy Integrity Availability Continuity Vulnerability Definition the difference between true and indicated position the ability to provide timely failure warnings the ability to perform at the initiation of use the ability to perform without interruption susceptibility to unintentional or deliberate interference GPS System and Satellite • Ephemeris error • SV clock error • Ionospheric error • Tropospheric error • Ground monitoring of the Space segment and provision of RAIM • Satellite coverage • Satellite reliability • Terrain masking situation where terrain creates a mask angle greater than the 7 5 degrees the GPS constellation model is designed • Spoofing potential – Civilian GPS is vulnerable to ‘fake’ transmissions from ‘spoofing’ equipment Signal • Multipath error • Dilution of Precision • Signal noise data in the Almanac the 7.5 degrees the GPS constellation model is designed to provide coverage for • System is unaffected by number of users p g q p • Receiver noise • Receiver RAIM • Reliability of receiver • Receiver FDE • Installation GPS Receiver • Receiver processing error • Receiver display error prediction and monitoring (see Section 2d on RAIM and FDE) • Other receiver alarms and alerts hardware, software and antenna • Quality of installation and power supply • Reliability of receiver hardware, software and antenna • Quality of installation and power supply vulnerability to RF interference alarms and alerts • Dynamic masking GPS Database • Coding error • Quality assurance by database supplier • Completeness of database • Delivery method for updates masking or attenuation of a satellite signal through aircraft motion (eg. wing blocks the signal path in a bank) updates Pilot input and interpretation • Flight Technical Error • User “conceptual” error • Use of RAIM tools • Database updating • Inadvertent mis- operation interpretation 53 GPS System Performance 2. Sources of accuracy error in GPS P A Accuracy Nature of error Size of error • Ephemeris error • Satellite orbits, although precisely positioned, can deviate from the ephemeris model data transmitted in the Navigation Message 2.5m • SV clock error • Satellite clock errors are monitored by the Ground Segment and corrections are included in the Navigation message. These aren’t “real-time” and a small residual error can develop 2m GPS S t • Ionospheric error • Inconsistencies in how the ionosphere disperses radio signals can only be partially compensated for by the model data in the Almanac – this is the largest single source of error in civilian GPS 5m Tropospheric error • Different concentrations of water vapour in the atmosphere cause an inconsistency in how radio System and Satellite Signal • Tropospheric error • Different concentrations of water vapour in the atmosphere cause an inconsistency in how radio waves are refracted. This error is small, but can not be easily corrected by modelling or calculation 0.5m • Multipath error • In ground-based applications, a satellite signal may arrive at a receiver via a reflection from a building or terrain. This type of error is inherently less present in most phases of flight, although it is an issue - for future precision approach systems • Dilution of Precision • Like any position line fix, GPS accuracy is reduced if satellites are close together or very far apart. The total effect is called “Geometric Dilution of Precision” (GDOP). It is also expressed as Horizontal, Vertical, ‘Position’ (horizontal and vertical) and Time dilution: HDOP, VDOP, PDOP and TDOP • Dilution of Precision multiplies errors from the other sources - Dilution of Precision multiplies errors from the other sources • Signal noise • The result of signal noise compromising the accuracy of the PRN code received 1m GPS • Receiver noise • The result of noise in the receiver further compromising the accuracy of the decoded PRN 1m GPS Receiver • Receiver processing error and display error • Not operationally significant, unless there is a failure or software bug. Unlike an Inertial system, whose estimated position drifts away from true position over time, GPS is continuously updated and does not suffer from systematic “map shift” error - Th “U E i l t R E ” (UERE) i i ili GPS i b tt th 35 h i t ll d 75 • The “User Equivalent Range Error” (UERE) in civilian GPS is better than 35m horizontally and 75m vertically 95% of the time. In practice, the accuracy is significantly better almost all of the time. 54 GPS System Performance 3. GPS performance model: a practical risk assessment from a pilot’s perspective P A (applies only to IFR-approved aircraft installations) Accuracy Integrity Availability Continuity Vulnerability GPS System and Satellite Very low risk of system or accuracy failures that are not identified by a Receiver RAIM At the system level, very low risk of a loss of service not predicted by RAIM tools At the local level terrain and satellite geometry surveying is Signal y or Loss of Integrity alert At the local level, terrain and satellite geometry surveying is part of the RNAV procedure design process and thus a very low risk of local availability or continuity problems GPS Receiver Very low risk of design problems with TSO/ETSO certified hardware and software Approved installations have proven highly reliable in millions of hours of service. Of course, like all radio aids, they depend on aircraft power GPS Database Generally highly reliable. However, in the current phase of rapid deployment of RNAV (both new procedures and approaches and new designs of procedure and approach) some extra caution is warranted in checking GPS nav data against paper charts. Use of d i d d t b t di ti t i k Note: these “green” risks are not zero, and regulations thus require alternative procedures and facilities to f G S unapproved or expired databases presents a distinct risk Pilot input and interpretation The major risk is pilot error in operating and interpreting GPS navigation equipment be available for many GPS applications interpretation • Just as in conventional IFR the human factor risks in using GPS equipment can be safely Just as in conventional IFR, the human factor risks in using GPS equipment can be safely managed through pilot training, currency and adherence to Standard Operating Procedures 55 Systems used to improve upon GPS accuracy and integrity Ground-based Augmentation Systems (GBAS) Satellite-based Augmentation Systems (SBAS) • The principle of GBAS is also called “Differential” GPS • SBAS uses the same principle as GBAS (differential corrections • The principle of GBAS is also called Differential GPS • Many of the most significant errors in basic civilian GPS are common to 2 receivers in the same geographical area (eg. Ephemeris, SV clock & Atmospheric errors, Signal noise and GDOP) • A reference GBAS ground station whose position is very accurately p p ( derived from ground-based stations) to achieve ~2m accuracy • The system is implemented by – a network of Reference Stations providing regional/continental coverage – a Master Station which collates their data, calculates a differential correction for each satellite in the GPS constellation being tracked and prepares a SBAS broadcast • A reference GBAS ground station, whose position is very accurately surveyed, can calculate a correction for such errors which can be broadcast to nearby stand-alone GPS receivers. • The resulting correction can improve the User Equivalent Range Error by a factor of 20x: from 35m horizontal and 75m vertical to 1m horizontal g p p – a Ground Earth Station that uplinks the broadcast to a geostationary satellite – the geostationary satellite broadcast of SV corrections as an additional C/A code on the L1 frequency – A SBAS-enabled GPS receiver which decodes the data and applies the corrections • There are a number of regional SBAS systems, two key ones are the FAA’ Wid A A t ti S t (WAAS) d th E and 2m vertical • Differential GPS (DGPS) systems originated in the time before “Selective Availability” was permanently switched off by the US DoD and civilian FAA’s Wide Area Augmentation System (WAAS) and the European Geostationary Navigation Overlay Service (EGNOS). These systems are compatible, so that current WAAS-enabled GPS receivers can work in Europe Differential GPS (DGPS) WAAS GPS accuracy was ~100m. This proved inadequate for safe marine navigation and, in the late 1990s, the US Coast Guard implemented a DGPS system in US waters. Similar systems were developed in Europe, partly also to replace the defunct Decca marine navigation system • 38 reference stations in the continental US, Canada, Alaska, Mexico and Hawaii • Commissioned in 2003 for aviation use. WAAS GPS is approved as a primary (sole) navigation aid for Enroute and Oceanic navigation, and L l A A t ti S t (LAAS) WAAS • An aviation application designed to provide precision approach capabilities to CAT III Autoland levels of accuracy and integrity • “Local” in the sense that reference receivers are around a single airport at precisely surveyed locations The system calculates a differential primary (sole) navigation aid for Enroute and Oceanic navigation, and CAT I Precision Approaches (LPV) • Europe’s equivalent to WAAS Local Area Augmentation System (LAAS) EGNOS at precisely surveyed locations. The system calculates a differential correction which is transmitted via a VHF data link. The LAAS Receiver on board an aircraft can then create a ‘synthetic’ ILS display • First-generation LAAS proved more expensive and not significantly more accurate than WAAS. However, future versions will be used as CAT II • The system is fully deployed and undergoing certification trials • See the EGNOS section of the European Space Agency website http://www.esa.int/esaNA/egnos.html and III precision approach aids, to improve on the CAT I limit of WAAS 56 Course contents 1. RNAV and RNP theory 4. RNAV(GPS) Approach Procedures a. Introduction b. The Path-Terminator c. RNAV procedure design a. GPS procedure types b. GPS approach requirements and approvals d. RNP principles e. RNAV and RNP applications c. GPS approach operations 5. Avionics training 2. GPS Navigators and their application to RNAV a. The GPS system b. Databases and Coding 6. Simulator and/or Flight training c. Procedures d. Error detection and warnings 3. P-RNAV Terminal Procedures a. P-RNAV requirements and approvals b. P-RNAV training topics c. P-RNAV operations 57 Sources of navigation data 1. Concept of the “aeronautical data chain” P A Originators AIS Commercial providers Users (general aviation examples) Airports Example of a commercial provider of general aviation products: Jeppesen Individual States are responsible for providing Aeronautical Information Services (AIS) to ICAO standards Airways Manual Paper charts Airports Air Traffic service Aeronautical Information Publication (AIP) Electronic airways manual providers Communications AIP Supplements (SUP) service providers Procedure and Aeronautical Information Circulars (AIC) “The Jeppesen Aviation Database (JAD) is composed of over one million records. Each 28-day cycle, Flight planning software PCs, Electronic flight bags (EFBs) and some multifunction displays Airspace designers Other Notices to Airmen (NOTAM) y y the flight information analysts edit and verify an average 150,000 JAD transactions. Only original source documents are used; gathered from 220 separate agencies worldwide and then cross-checked using lti l ” “NavData” GPS database and some multifunction displays (MFDs) with the ‘Chartview’ feature government agencies multiple sources” Source: www.jeppesen.com G i H ll d th Also database of features specific to individual GPS models (eg terrain Garmin, Honeywell and other aviation GPS units individual GPS models (eg. terrain, obstacles, topographic maps) 58 Sources of navigation data 2. An overview of standards relevant to RNAV databases P A ICAO Annex 15 states that ‘Contracting States shall ensure that the integrity of aeronautical data is maintained throughout the data process from survey/origination to the next intended user’ Originators AIS Commercial providers Users • ICAO doc 8168 PANS OPS • RTCA Do 200A • FAA TSOs EASA ETSOs Data standards how is data originated to a consistent standard? how is quality assured in data processing? • FAA TERPS • ECAC Guidance Material • …etc – standards for the design of IFR facilities and procedures, and the format of AIS data • RTCA Do 201A • EUROCAE ED 77 – quality assurance for the supply of AIS data used in RNAV databases • RTCA Do 200A • EUROCAE ED 76 – data processing quality assurance for commercial providers that create RNAV databases from AIS data • EASA ETSOs – technical certification for IFR GPS equipment • FAA AC120-138, • EASA modification approval – airworthiness approval for IFR pp GPS units (or Type Certification for original equipment in newer aircraft) • FAA: 14CFR Part 91 or 135 • EASA: national laws (private) or JAR OPS Coding standards how are databases created from AIS data? • The ARINC 424 standard – standard for the structure of aviation navigation databases, including the type of data records (eg. Airports, VORs) and the coding of data fields (eg. runway elevation, VOR frequency) – includes standards for coding routes (airways) and procedures (terminal, approach) (private) or JAR-OPS (commercial) • Airplane Flight Manuals and AFM Supplements • P-RNAV: FAA AC90-96A, JAA TGL10 from AIS data? g ( y ) p ( , pp ) as well as individual facilities and waypoints Update standards • The AIRAC cycle ICAO standard for publishing additions and revisions to AIP data based on a schedule of calendar – operator requirement to use current data as a condition of approval for RNAV applications p how are databases kept current? – ICAO standard for publishing additions and revisions to AIP data based on a schedule of calendar dates and a process associated with those dates to ensure all users receive timely and “synchronised” updates • Navigation data management and quality assurance is a specialised topic, most of which is beyond the scope of this course • The focus in this section will be on the basics of the Do200A/ED76 standards and the AIRAC cycle, and details of ARINC 424 relevant to users of RNAV GPS equipment details of ARINC 424 relevant to users of RNAV GPS equipment • Sections 3 and 4 will cover operational approval requirements for P-RNAV and GPS Approaches 59 What are the Do200A and ED76 standards? • RTCA (Radio Technical Commission for Aeronautics) is a US non profit organisation that develops standards RTCA and Do200A, EUROCAE and ED76 References • For the interested reader a source of further detail on the • RTCA (Radio Technical Commission for Aeronautics) is a US non-profit organisation that develops standards for communications, navigation, surveillance, and air traffic management (CNS/ATM) with the participation of government, academic and industry stakeholders. RTCA recommendations are used by the FAA as a basis for policy and regulatory decisions http://www.rtca.org • For the interested reader, a source of further detail on the methods of navigation data quality assurance is the Eurocontrol website, eg. the document “Integrity of Aeronautical Information - Data & Quality Management” (2003, AIM/AISD/DI/0007) http://www.ecacnav.com/downloads • EUROCAE (the European Organisation for Civil Aviation Equipment) is a non-profit organisation, formed in Switzerland in 1963 to provide a European forum for developing standards for electronic airborne and ground systems. Its recommendations are used by EASA for policy-making http://www.eurocae.eu • The full set of original sources for data standards are (from JAA TGL 9) – ICAO Annex 4, International Standards and Recommended Practices : Aeronautical Charts – ICAO Annex 11, International Standards and • RTCA Do200A and Eurocae ED76 are equivalent, they were developed in the late 1990s to regulate the quality assurance of navigation databases supplied by commercial providers (such as Jeppesen, EAG, Lufthansa Systems) to airline, commercial and private users. Recommended Practices: Air Traffic Services – ICAO Annex 14, International Standards and Recommended Practices: Aerodromes and Heliports – ICAO Annex 15, International Standards and Recommended Practices: Aeronautical Information • Do200A/ED76 were designed to meet the accuracy and integrity requirements of new RNAV RNP applications, such as P-RNAV • Airline and commercial operators are subject to quality management regulation (eg. JAR- OPS 1.035). The Do200A/ED76 standard may be used (eg. see JAA TGL 9) as a means Services – ICAO Document 8126, Aeronautical Information Services Manual AN/872 – ICAO Document 9613, Manual on Required Navigation Performance AN/937 of ensuring compliance for databases in Flight Management Systems (FMS) • For private GA operators, the requirements for a database are specific to the airworthiness approval of an IFR installation and the limitations imposed by the Flight Manual (eg. a GPS unit may only use an approved database and data card, they have part numbers like any other aviation component) – EUROCAE document ED-76; Standards for Processing Aeronautical Data. RTCA Inc. document DO-200A is technically equivalent to ED-76. A reference to one document, at the same revision level, may be interpreted to mean either document part numbers like any other aviation component) – for B-RNAV, a current database is not required, but paper charts must be used to verify data in an expired database – for GPS approaches, a current database will be a requirement specified in the approved Flight Manual GPS section or supplement a P-RNAV Letter of Authorisation will require use of both a current database and – EUROCAE document ED-77/RTCA DO-201A, Standards for Aeronautical Information – EUROCAE document ED-75A/RTCA DO-236A, Minimum Aviation System Performance Standards: Required Navigation Performance for Area Navigation. – a P-RNAV Letter of Authorisation will require use of both a current database and a supplier conforming to Do200A/ED76 (See next page and Section 3) 60 Database Supplier approvals relating to Do200A and ED76 The Type 1 and Type 2 Letters of Acceptance (LoA) P • The Do200A/ED76 standard was published in 1998 • As RNP RNAV procedures were being implemented circa 2003, many FMS and GPS systems were not available with conforming databases. It was the responsibility of AOC Operators to manually check such databases against co- ordinates on paper charts • International agreements were developed to reduce the burden of manual checks and to certify Database Suppliers g p y pp as conforming to Do200A/ED76 and other defined conditions. There are 2 kinds of certification: – the Type 1 LoA applies to databases that are not specific to any particular avionics system or aircraft, one can think of it as a “wholesaler” approval. The Type 1 LoA holder can not release databases directly to end users – the Type 2 LoA applies to databases compatible with specified avionics systems and may be released directly to end-users. The GA owner/operator is thus concerned with Type 2 LoA suppliers