Contents and reading order#

Source basis#

Primary sources used in this folder:

• Doc 8168 Vol I (6th Edition, 2018) — Flight Procedures; crew use provisions.
• Doc 8168 Vol II (7th Edition, 2020) — Construction of Visual and Instrument Flight Procedures; the designer's technical reference. Local library copy at mds/PANS/8168_v2_cons_en.md.
• Doc 8168 Vol III (1st Edition, 2018) — Aircraft Operating Procedures. Local library copy at mds/PANS/8168_v3_cons_en.md.
• Doc 9613 (PBN Manual, 5th Edition, 2023) — Navigation specifications; procedure designer interface. Local library at mds/Documents/9613_cons_en.md.
• Doc 9905 (RNP AR Procedure Design Manual) — RNP AR APCH/DP criteria. Not in local library; cited per Doc 8168 Vol II amendment notes.
• Doc 9906 (Quality Assurance Manual for Flight Procedure Design) — 6-volume QA guidance. Not in local library; cited per Doc 8168 Vol II §4.1.1, §4.2, §4.3.
• Doc 10068 (Manual on the Development of a Regulatory Framework for IFP Design Service) — State regulatory framework guidance. Not in local library.
• Annex 4 (Aeronautical Charts), Annex 11 (ATS), Annex 14 (Aerodromes), Annex 15 (AIS) — supporting normative references.

What flight procedure design is#

Flight procedure design is the technical engineering discipline of constructing instrument flight procedures (IFPs) for use by IFR aircraft. An IFP is a series of predetermined manoeuvres, defined by fixes and tracks, that allows an aircraft to navigate safely in instrument meteorological conditions (IMC) while maintaining prescribed clearance above terrain and obstacles.

PANS-OPS — Doc 8168, Procedures for Air Navigation Services, Aircraft Operations — is the ICAO PANS that governs this discipline. It is published in three volumes:

• Volume I (6th Edition, 2018): Flight Procedures — the flight operations provisions used by flight crew and operators.
• Volume II (7th Edition, 2020): Construction of Visual and Instrument Flight Procedures — the designer's technical bible, containing obstacle clearance criteria and construction rules for every procedure type.
• Volume III (1st Edition, 2018): Aircraft Operating Procedures — separated from Volume I material in 2018.

The Instrument Flight Procedures Panel (IFPP) is the ICAO expert panel that maintains and develops the criteria in Doc 8168. It succeeded the Obstacle Clearance Panel (OCP), which first codified IFP criteria in the 1960s.

Where flight procedure design sits in the ICAO framework#

Flight procedure design is the point where three domains of the ICAO framework converge:

1. Navigation infrastructure (Annex 10, PBN Manual Doc 9613): the accuracy and integrity of the navigation signal available to the aircraft determines what tolerances the procedure can assume, which in turn determines how tightly the protection area can be drawn and how low the OCA/H can be set.

2. Terrain and obstacle data (Annex 14 OLS, Annex 15 eTOD): the quality of obstacle and terrain survey data is the primary input to the obstacle clearance calculation. A procedure cannot be safer than its input data.

3. Aeronautical information (Annex 15, Annex 4): the procedure designer's output — the OCA/H, waypoint coordinates, procedural constraints, charting data — must be published in the AIP and on instrument approach charts in a form that flight crew can use safely. The data integrity chain from designer to cockpit display is governed by Annex 15 and the AIM framework.

These three domains also situate procedure design inside the ASBU framework: the APTA thread (Optimization of Approach Procedures including Vertical Guidance) is essentially an ASBU wrapper for the global rollout of PBN approaches designed to PANS-OPS criteria, prioritizing LPV/Baro-VNAV APV approaches at airports currently served only by NDB or VOR approaches.

The safety purpose#

The fundamental safety purpose of PANS-OPS criteria is to guarantee that an aircraft navigating correctly in accordance with a published procedure will not strike terrain or an obstacle. The design criteria achieve this through three mechanisms:

• Protection areas: geometrically defined areas around the nominal flight track within which all obstacles must be identified and evaluated. No obstacle may penetrate the obstacle clearance surface.
• Minimum obstacle clearance (MOC): the vertical margin above the controlling obstacle within the protection area that the procedure must provide.
• Conservative assumptions: the criteria assume worst-case navigation system error, wind, temperature, and aircraft performance within the applicable aircraft category, so that the protection holds even under adverse conditions.

CFIT (controlled flight into terrain) prevention is the explicit motivation for the CDFA technique, the procedure altitude/height concept, and the flight validation requirement introduced in successive amendments to PANS-OPS.

Who uses flight procedure design output#

• Flight crew: read Volume I provisions and follow published procedure charts derived from Volume II designs.
• Operators: use OCA/H to determine DA/H or MDA/H; plan approach categories; assess fleet capability for RNP operations.
• Air traffic controllers: issue clearances for SIDs, STARs, and approach procedures; understand missed approach routing to provide separation.
• ANSPs / CAAs: commission, quality-assure, and periodically review published procedures; maintain the regulatory framework for IFP design services; exercise oversight per Doc 10068.
• States: hold responsibility under international law for all IFPs published in their airspace per Doc 8168 Vol II §4.1.2.
• Airspace planners: coordinate procedure design with ATC routes, sector boundaries, and noise abatement requirements.

References#

• Doc 8168 (PANS-OPS), Vol I, 6th Edition (2018), Foreword — Scope of the three volumes and their division of material.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Foreword §1.3 — Volume II intended for guidance of procedures specialists; provides essential obstacle clearance requirements.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part I, Section 2, Chapter 4, §4.1.2 — State responsibility for safety of all published IFPs; quality of process required.
• Doc 9613 (PBN Manual), 5th Edition (2023), Volume I, Chapter 3, §3.3 — Instrument flight procedure design as a stakeholder interface with the PBN concept.

The five approach segments#

An instrument approach procedure (IAP) consists of up to five sequential segments. Each segment has defined start and end fixes, a nominal track, and an associated protection area geometry.

Arrival route (en-route to IAF)#

The segment linking the en-route structure to the Initial Approach Fix (IAF). Protection uses en-route obstacle clearance criteria: MOC 300 m in non-mountainous areas, 600 m in mountainous areas. Area minimum altitudes (AMAs) are computed per Part I, Section 2, Chapter 1, §1.9.

Initial approach segment (IAF to IF)#

Begins at the IAF and ends at the intermediate fix (IF). The aircraft transitions from en-route altitude to an altitude suitable for the intermediate segment. Protection area geometry depends on the track alignment and the navigation specification in use.

MOC: 300 m (primary area). Secondary areas reduce from 300 m to 0 m linearly across the secondary area half-width.

Intermediate approach segment (IF to FAF/FAP)#

Begins at the IF (or start of the intermediate fix area) and ends at the final approach fix (FAF) or final approach point (FAP). Purpose: stabilize the aircraft on the final approach configuration before commencing descent.

MOC: 150 m. The intermediate segment width narrows from the initial approach width to the final approach width.

Final approach segment (FAF to MAPt)#

The operationally critical segment where the aircraft descends toward the runway. OCA/H is calculated by finding the highest obstacle within the final approach protection area and adding the appropriate MOC.

MOC values vary by approach type:

• NPA (non-precision): 75 m straight-in; 90 m circling approach.
• APV/Baro-VNAV: the vertical guidance eliminates step-down uncertainty; MOC for the APV segment is specified in PANS-OPS Vol II Part III.
• RNP APCH (LNAV, LNAV/VNAV, LP, LPV): criteria per PANS-OPS Vol II Part III, Sections 3 and 4.
• ILS/MLS/GLS precision approach: Obstacle Assessment Surface (OAS) or Collision Risk Model (CRM) method per PANS-OPS Vol II Part II.
• RNP AR APCH: criteria per Doc 9905; tighter tolerances permit lower OCA/H in terrain-constrained environments.

Missed approach segment (MAPt onward)#

Begins at the missed approach point (MAPt), the fix or point at which a missed approach must be initiated if the visual reference to continue has not been established. The missed approach must return the aircraft to a safe altitude (en-route or holding MOC).

MOC rises from 0 m at the MAPt to 50 m in the straight missed approach area. Turning missed approaches require additional area construction. The missed approach holding fix (MAHF) defines the end of the missed approach.

Departure design#

Departure procedures (DPs) apply from the departure end of the runway (DER) through climb to the IFR en-route structure.

Key design parameters:

• MOC in the departure protection area: 90 m.
• Procedure Design Gradient (PDG): the minimum required climb gradient, defaulting to 3.3% (200 ft/NM). If a higher PDG is needed to clear obstacles, it must be published.
• The obstacle identification surface (OIS) is evaluated to identify controlling obstacles; any obstacle above the OIS drives the PDG requirement.

Omnidirectional departures cover all directions from the aerodrome; directional departures restrict the departure track to a specified corridor. PBN departures (SIDs using RNAV or RNP specifications) use the same MOC but apply the navigation specification accuracy to narrow the protection area, potentially permitting lower PDG requirements.

Protection area geometry#

Every segment area is normally symmetric about the nominal flight track and subdivided into a primary area and secondary areas.

Primary area#

A defined area symmetrically disposed about the nominal flight track in which full MOC is provided. No obstacle within the primary area may penetrate the obstacle clearance surface. (Doc 8168 Vol II §1.2.1 and the definition in the Definitions chapter.)

Secondary areas#

Defined areas on each side of the primary area in which MOC reduces linearly from the full MOC value at the inner edge (primary boundary) to zero at the outer edge. When secondary areas are permitted, the outer half of each side of the total area width is designated as secondary. The MOC in a secondary area at distance Y from the outer edge of the primary is:

MOCsy = MOCp * (1 - Y/Ws)

where Ws is the secondary area width and MOCp is the primary MOC.

An obstacle in the secondary area that penetrates above the secondary surface does not necessarily prevent publication; it may instead raise the OCA/H from the controlling primary obstacle level.

Area widths and splay angles#

Area widths depend on the navigation specification in use. Conventional (VOR, NDB, ILS, VOR/DME) areas splay outward with distance using angular tolerances based on the equipment tolerance (for example, VOR bearing error, DME distance error). PBN areas use the Total System Error (TSE) budget of the navigation specification to define the cross-track protection half-width.

For conventional non-precision approaches, areas are typically wider than for RNAV/RNP approaches, which is why PBN approaches generally achieve lower OCA/H values in terrain-constrained environments.

The obstacle clearance model#

Defining OCA/H#

OCA/H (Obstacle Clearance Altitude/Height) is defined as the lowest altitude (OCA) or height above the reference elevation (OCH) at which the applicable MOC constraints are satisfied. It is the key output of the procedure designer's calculation.

• OCA is referenced to mean sea level.
• OCH for non-precision approaches is referenced to aerodrome elevation (or threshold elevation if the threshold is more than 2 m below aerodrome elevation).
• OCH for precision approaches and APV is referenced to the threshold elevation.

From OCA/H to operating minima#

The procedure designer publishes OCA/H. The operator and regulatory authority then add:

• Meteorological minima (visibility, cloud base).
• Aircraft category-specific factors (go-around climb capability, decision height additions).
• Radio altimeter versus barometric altimeter correction where relevant.

The result is the DA/H (for 3D approaches) or MDA/H (for NPA) that appears in the operator's operations manual and on the chart.

Design inputs#

A procedure designer requires the following categories of input before beginning design:

• Terrain and obstacle data: State survey data, Annex 15 eTOD (electronic Terrain and Obstacle Data), or equivalent verified obstacle database. WGS-84 coordinates. Accuracy and integrity must meet the requirements of Annexes 4, 11, 14, and 15 for the position critical area.
• Navaid / GNSS performance data: ILS localizer and glide path alignment and performance data (including GP angle, RDH, FPAP for GLS); or the applicable navigation specification accuracy for PBN (e.g., RNP 0.1 for RNP AR APCH).
• Aircraft performance data: aircraft category (based on threshold speed Vat), applicable for protection area widths and speed limits.
• Airspace structure: sector boundaries, restricted areas, airspace class constraints, military training areas, noise abatement requirements.
• ATC operational requirements: runway in use, approach type, missed approach routing to fit the ATC environment.

References#

• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part I, Section 2, Chapter 1, §1.2.1 — Primary and secondary area definition.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part I, Section 2, Chapter 1, §1.2.2 — Secondary area width formula.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part I, Section 2, Chapter 1, §1.3 — MOC formula for secondary areas.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part I, Section 3, Chapter 2, §2.5–§2.7 — Departure MOC, OIS, and PDG.
• Doc 8168 (PANS-OPS), Vol I, 6th Edition (2018), Part II, Section 5, Chapter 1, §§1.2–1.4 — Approach segment definitions and OCA/H.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Definitions — Formal definitions: primary area, secondary area, OCA/H, MOCA, MAPt, PDG, MOC.
• Doc 9613 (PBN Manual), 5th Edition (2023), Volume I — Navigation specification accuracy as input to PBN procedure protection area width.

Mapping ASBU blocks to procedure types#

In flight procedure design, the analogue of ASBU blocks is the procedure family — the axis of maturity from conventional ground-based procedures through RNAV and RNP, to Authorization Required PBN with radius-to-fix legs. Each generation builds on the preceding one, and each requires additional infrastructure, aircraft capability, and designer competency.

Block 1: Conventional ground-based procedures#

ILS (Instrument Landing System)#

Precision approach using localizer (lateral) and glide path (vertical) guidance. Three categories:

• Cat I: OCA/H down to 60 m / decision height 200 ft. Visibility 550 m.
• Cat II: OCA/H down to 30 m / decision height 100 ft. Visibility 300 m.
• Cat III: decision height below 100 ft or zero; visibility below 200 m.

Design criteria use the Obstacle Assessment Surface (OAS) method for Cat I and the Collision Risk Model (CRM) for Cat II/III.

NDB and VOR approach procedures#

Non-precision approaches using NDB (non-directional beacon) or VOR (VHF omni-range) radio navigation. Wide protection areas (large bearing errors) result in high OCA/H values. Subject to progressive replacement by RNP APCH under ICAO PBN transition plans.

NDB/DME and VOR/DME#

Adding DME distance measurement to the bearing fix narrows the fix tolerance area, permitting tighter protection and lower OCA/H compared to NDB or VOR alone. Step-down fix techniques apply.

Standard Instrument Departures (SIDs) and Arrivals (STARs)#

Conventional SIDs and STARs route aircraft using ground-based navaid fix sequences. Wide area tolerances produce airways-style protection areas. PANS-OPS Vol II Part III Sections 1 and 2 cover arrival and departure construction criteria.

Holding patterns#

Designed per PANS-OPS Vol II Part IV. Protection area is an oval (racetrack) that accounts for aircraft banking, wind, and speed at the holding level. MOC: 300 m (non-mountainous) or 600 m (mountainous).

Block 2: RNAV / Basic PBN#

En-route and terminal area navigation using multi-sensor RNAV systems (GNSS, VOR/DME, DME/DME). Protection areas are based on navigation specification accuracy (Total System Error budget).

RNAV SIDs and STARs provide more efficient routing than conventional procedures because the aircraft is not constrained to overfly a ground navaid. Curved tracks, T/Y bar approach layouts, and Terminal Arrival Altitudes (TAAs) are design features specific to RNAV procedures.

Block 3: RNP APCH — PBN approach procedures#

RNP APCH is the primary ICAO PBN procedure for approach to landing below 5 NM from the airport. It is designed per PANS-OPS Vol II Part III, Sections 3–5 and provides multiple optionally publishable minima on a single procedure:

LPV approaches can achieve OCA/H values comparable to ILS Cat I (approximately 60–75 m OCH) at aerodromes with no ILS infrastructure. This is the main ASBU APTA-B0 target: instrument access with vertical guidance at all aerodromes.

RNP APCH can also use the Radius-to-Fix (RF) path terminator as an optional capability (not authorization required) to allow curved track segments, improving routing in terrain-constrained terminal environments.

Baro-VNAV (APV/Baro-VNAV): an instrument approach using barometric altimetry to provide vertical navigation guidance without SBAS. Designed per PANS-OPS Vol II Part III, Chapter 4. Subject to temperature correction at cold aerodromes. Widely deployed because it requires no additional ground infrastructure.

Block 4: RNP AR APCH — Authorization Required#

RNP AR APCH (Required Navigation Performance Authorization Required Approach) provides the highest performance PBN approach capability. Criteria are in Doc 9905 (RNP AR Procedure Design Manual), not in PANS-OPS Vol II directly, though Vol II references Doc 9905.

Key characteristics:

• RNP value as low as 0.1 NM on the final approach (vs 0.3 NM for standard RNP APCH).
• Mandatory RF leg capability on final approach for curved approach paths.
• On-Board Performance Monitoring and Alerting (OBPMA) required.
• Specific State authorization for both operator and aircraft.
• Enables approach to aerodromes in severe terrain (mountain valleys, island approaches) where no straight-in approach geometry is achievable.

RNP AR Departure Procedures (RNP AR DP): introduced alongside RNP AR APCH. Uses RF legs on departure to navigate terrain-constrained departure corridors.

Approach classification summary#

The 2013 approach classification (ACTF/IFPP) aligned ICAO procedure types with operational categories:

References#

• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part II — Precision approach criteria (ILS, MLS, GLS); OAS and CRM methods.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part III, Sections 3–5 — RNP APCH (LNAV, LNAV/VNAV, LPV, Baro-VNAV, SBAS) criteria; T/Y bar layout and TAA concept.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part I, Section 3 — Conventional and PBN departure procedures.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part I, Section 4 — Conventional arrival, initial, intermediate, final, and missed approach.
• Doc 8168 (PANS-OPS), Vol I, 6th Edition (2018), Part II, Section 5, Chapter 1, §1.2–§1.4 — Approach classification: NPA, APV, PA.
• Doc 9905 (RNP AR Procedure Design Manual) — RNP AR APCH and RNP AR DP criteria; RF leg mandatory use (authoritative source — not in local library).
• Doc 9613 (PBN Manual), 5th Edition (2023), Volume II — Navigation specifications for all RNAV/RNP applications; procedure design application guidance.

The six functional axes#

Flight procedure design work is organized along six functional axes (threads), each with its own tools, standards, and competency requirements. In practice all six must be active for a single procedure to be published safely.

Thread 1: Criteria and obstacle clearance#

This is the core technical thread. It covers the application of PANS-OPS Vol II criteria to real terrain and obstacle data to compute OCA/H for each procedure type and phase.

Key activities:

• Identify the controlling obstacle in each segment protection area.
• Apply the correct MOC for the segment (300/150/75 m per segment type) and the aircraft category.
• Handle mountainous area increased MOC (up to 100% increase where wind- induced altimetry errors are expected).
• Apply the secondary area formula where secondary areas are permitted.
• Compute area minimum altitudes (AMAs) for the terminal area.
• For precision approaches: apply the OAS or CRM method per PANS-OPS Vol II Part II.

The criteria are revised edition-by-edition by the IFPP. Designers must track amendments: the 7th Edition (2020) included updated GBAS Cat II/III criteria, PBN to xLS (RF leg to ILS final) criteria, and charting navigation specification identification.

Thread 2: PBN procedure design#

PBN procedure design applies the navigation specification accuracy to narrow protection areas compared to conventional procedures. It requires additional knowledge of:

• Navigation specifications: which specification (RNP APCH, RNAV 1, RNP 1, Advanced RNP) applies to the operation, and what accuracy, integrity, continuity, and functional requirements it places on the aircraft and the procedure.
• Path terminators: ARINC 424 leg types (TF, CF, DF, RF, FA, CA, VA, etc.) used to encode the procedure into the navigation database. The RF (Radius to Fix) path terminator is required for RNP AR APCH final approach turns and is an optional capability for RNP APCH and RNAV 1.
• T/Y bar approach layout: the standard RNAV approach layout with one or two IAFs connected via a racetrack or T/Y-shaped initial approach route.
• Terminal Arrival Altitude (TAA): an altitude associated with the TAA sectors centered on the IAF/IF, providing an MSA substitute for RNAV procedures without ARC/sector MSA.
• Database coding: PBN procedure designers must provide the encoded waypoint coordinates, leg types, altitudes, and speeds in a format suitable for ARINC 424 database coding; errors in coding are a known CFIT source.

Doc 9613 Chapter 3 explicitly addresses the procedure designer's use of the PBN concept, including how navigation specification requirements constrain design choices.

Thread 3: Charting and database coding#

The charting thread converts the procedure design output into instrument approach charts (Annex 4 format) and navigation database entries (ARINC 424 coding). Both representations must faithfully reflect the designed procedure.

Key elements:

• IAP chart (instrument approach chart): depicts the plan view (overhead view of the procedure), elevation profile (side view showing altitudes and obstacles), minimums section (OCA/H by category, DA/H or MDA/H space for operator minima), and information box (navaid frequencies, transition altitudes, chart effective date).
• PBN identification box: for RNP and RNAV approach charts, a box identifying the navigation specification and any optional capability required (e.g., RF, BARO-VNAV).
• Database coding review: the procedure designer provides a coding worksheet specifying waypoints (name, coordinates, code, altitude), leg types, speed limits, and altitudes. An independent coder enters this data; an independent reviewer checks the coded database entry against the design documentation.
• Obstacle depiction: significant obstacles within the chart area must be depicted in accordance with Annex 4 requirements.

The data transfer between designer and database coder is a known error point. The 6th Edition amendment introduced definitions to "avoid misunderstanding on data transfer between the procedure designer and the database coder" (amendment note).

Thread 4: Validation (ground and flight)#

Validation is the final quality assurance gate before publication. Doc 8168 Vol II §4.3.5.1 defines it as verification of obstacle and navigation data, assessment of flyability, assessment of crew workload and human factors, and confirmation of correct database coding and avionics behaviour for PBN procedures.

Ground validation#

Ground validation uses flight simulation (FSTD) or desktop simulation tools to:

• Verify that the procedure as coded in the navigation database matches the design.
• Assess flyability: track capture, leg sequencing, display behaviour, autopilot coupling.
• Identify any crew workload issues (excessive intercept angles, ambiguous transitions, non-intuitive procedures).

Ground validation is conducted by a qualified flight validation pilot (or a team including one) before flight validation is authorised.

Flight validation#

Flight validation is conducted by a State-approved flight validation pilot in a suitably equipped aircraft (or FSTD where sufficient for the scope). It achieves the final verification that:

• Navigation tracks as designed, fix sequencing is correct.
• Obstacle clearance is maintained throughout the procedure.
• OCA/H as published is appropriate and crew workload is acceptable.
• CFIT risk from terrain environment is properly assessed from the cockpit perspective.

Flight validation is mandatory for new procedures and for existing procedures undergoing significant changes. Doc 9906 Vol 5 is the reference for flight validation scope and methodology. Doc 9906 Vol 6 covers flight validation pilot training and evaluation.

Thread 5: QA and data integrity#

The QA thread covers the entire IFP process as a managed quality system, not just individual validation steps. It corresponds to the ISO 9001- style process management approach described in Doc 9906 Vol 1.

Key elements:

• Process documentation: each step of the IFP process (data collection, design, review, validation, publication) must be documented with traceable records. Doc 8168 Vol II §4.3.4 sets minimum documentation.
• Data integrity from source to publication: the quality and integrity requirements of Annex 15 apply to aeronautical data throughout the pipeline: original survey, terrain/obstacle database, design inputs, AIP publication. CRC checking for electronic data.
• Periodic review: Annex 11 Appendix 7 mandates a maximum five-year review cycle for all published procedures. On review, the procedure must be checked against current criteria and current obstacle data.
• Independent review: §4.3.3.2 requires that each new or revised procedure is verified by a qualified designer who was not involved in the original design.
• Regulatory oversight: the State must exercise oversight over the IFP design service, which may be provided by the ANSP, a contracted specialist, or another State. Doc 10068 addresses the regulatory framework. Doc 8168 Vol II §4.6 covers regulatory oversight.

Thread 6: Designer competency#

PANS-OPS Vol II §4.2 places the competency of the flight procedure designer at the centre of quality assurance. The State shall establish required competencies in its regulatory framework; designers must meet these through initial training and supervised on-the-job training (OJT), then maintain competency through recurrent training at State-defined intervals.

Initial training must cover at minimum:

• PANS-OPS criteria theory and application.
• Terrain and obstacle data management.
• Airspace and ATC coordination.
• PBN navigation specifications and database coding.
• Quality assurance processes.

Recurrent training ensures maintenance and improvement of knowledge and skills. Doc 9906 Vol 2 provides guidance for planning and evaluating a flight procedure designer training programme.

Designer competency verification is required at regular intervals per §4.2.6. The designer role in flight validation is to brief the flight validation crew and to participate in the validation to obtain direct knowledge of operational issues (§4.3.5.6).

References#

• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part I, Section 2, Chapter 4, §4.2 — Procedure designer qualifications and training.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), §4.2.1 — State obligation; competency through training and supervised OJT.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), §4.3 — IFP process; seven sub-steps from data collection to periodic review.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), §4.3.3.2 — Independent review requirement.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), §4.3.3.3 — Periodic review; five-year maximum interval; reference to Annex 11 Appendix 7.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), §4.3.5.1 — Validation definition; purpose; reference to Doc 9906 Vol 5.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), §4.3.5.4 — Flight validation; State-approved flight validation pilot.
• Doc 9906 (Quality Assurance Manual for Flight Procedure Design) — Vols 1–6 covering QA System, Designer Training, Software Validation, Validation of IFPs, Flight Validation Pilot Training (authoritative source — not in local library).
• Doc 9613 (PBN Manual), 5th Edition (2023), Volume I, Chapter 3, §3.3 — Procedure designer interface with PBN concept.

Worked example: designing an RNP APCH to LPV minima#

This module walks through the complete design of a single RNP APCH procedure with LPV (Localizer Performance with Vertical Guidance) minima at a hypothetical mountainous aerodrome (ZXYZ, elevation 1 450 m MSL, single runway 18/36, no existing ILS). The purpose is to illustrate how each thread of the discipline (criteria, PBN design, charting, validation, QA) interacts in practice.

Step 1: Data collection and validation#

The designer assembles four data packages:

1. Obstacle and terrain data: the State terrain and obstacle survey for the terminal area (5 NM radius around the aerodrome) in WGS-84, with accuracy and integrity meeting Annex 15 requirements for Category 1 data (obstacle within the inner approach surface and take-off/climb surface). Any suspect data point is queried and the source resurveyed before design commences.

2. GNSS/SBAS coverage: SBAS service provider (e.g., GAGAN, MSAS, EGNOS, WAAS) confirms LPV service availability and the applicable protection levels at the aerodrome location. Without confirmed LPV vertical service, only LNAV or LNAV/VNAV minima can be published.

3. Aircraft database: design assumes categories A, B, and C aircraft (Vat up to 165 kt). Category D capability may be added later.

4. Airspace and ATC constraints: the ATC unit identifies the missed approach routing requirement — the aircraft must be clear of restricted area R-47 by the time it passes 10 NM from the runway on the missed approach track. This constraint will drive the missed approach turn and the MAHF location.

Step 2: IAF/IF/FAF placement — T-bar layout#

The designer selects the T-bar layout (standard RNAV approach) with two IAFs flanking the runway axis, an IF aligned on the extended runway centreline approximately 8 NM from the threshold, and a FAF at 5 NM.

• IAF1 (ZXYZ3): 10 NM from threshold on the runway extended centreline (for straight-in arrivals from the north).
• IAF2 (ZXYZL): 10 NM off to the left of the centreline at a 45-degree intercept angle.
• IF (ZXYZF): 8 NM from threshold, on centreline.
• FAF (ZXYZD): 5 NM from threshold.
• MAPt (ZXYZM): defined by the SBAS final approach segment data; nominally at the runway threshold.

All waypoint positions are calculated in WGS-84 and rounded to the nearest 0.01 arc-minute. The designer documents the calculation in the design worksheet.

Step 3: Final approach segment (FAS data block)#

For LPV, the final approach is defined by the Final Approach Segment (FAS) data block — an SBAS concept defined in PANS-OPS Vol II Part III, Chapter 5. The FAS data block parameters include:

• Landing Threshold Point (LTP): WGS-84 coordinates of the runway threshold (Runway 18, surveyed to 0.3 m accuracy).
• Flight Path Alignment Point (FPAP): located at or beyond the far threshold, aligned with the runway centreline.
• Threshold Crossing Height (TCH): 15 m (50 ft) standard.
• Glide Path Angle (GPA): 3.00 degrees (standard; increased to 3.5 degrees if obstacle analysis requires it).
• Reference Datum Height (RDH): derived from GPA and TCH.

The designer sets the GPA and checks that the resulting OCA/H for the APV segment clears all obstacles within the SBAS approach protection area by the required MOC. For LPV, the criteria are in PANS-OPS Vol II Part III, Chapter 5. The controlling obstacle is found 2.3 NM from the threshold on the extended centreline at 1 620 m MSL. The designer calculates the OCA for this obstacle type and confirms the LPV OCH remains above the required minimum.

Step 4: Missed approach design#

The missed approach from MAPt involves:

• Straight phase: climb at or above PDG from MAPt to a turn altitude.
• Turn phase: left turn (to avoid R-47 to the east) at the MATF (Missed Approach Turning Fix) to a track of 270 degrees.
• End: MAHF at 15 NM west of the aerodrome at 4 500 m MSL.

The designer evaluates all obstacles within the turning missed approach protection area. The controlling obstacle requires a PDG of 5.0% on the initial climb to ensure adequate MOC before the turn. This PDG is published on the chart as a minimum climb gradient constraint.

Step 5: Departure and SID coordination#

If the aerodrome is adding a PBN SID on Runway 18 simultaneously, the SID and approach missed approach tracks are coordinated to avoid conflict in the terminal area. The SID initial departure segment protection area is evaluated against the same obstacle dataset. A PDG of 3.3% clears all obstacles on the SID track; no increased PDG is needed for departure.

Step 6: Independent design review#

A second qualified designer reviews all calculations, checks the protection area geometry against the obstacles (confirming the controlling obstacle identification), checks waypoint coordinates, and reviews the FAS data block. Three minor corrections are identified and incorporated: a waypoint name conflict with an existing fix in the AIRAC database, a rounding error in one waypoint latitude, and an incorrect altitude constraint on one leg of the STAR connection.

Step 7: Flight operational review#

A rated instrument-rated pilot (not involved in design) reviews the procedure from the flight deck perspective:

• Track geometry is flyable; intercept angles are within limits.
• Altitude constraints are achievable at expected aircraft performance.
• The missed approach turn direction and height constraint are clear and unambiguous.
• The procedure identification naming ("RNAV (GNSS) Y RWY 18") is correct per the naming convention; the PBN box lists "RNP APCH; BARO- VNAV NA below -15 deg C".

One comment: the IF to FAF leg is slightly short (3.4 NM), which is below the recommended minimum for aircraft transitioning from a high altitude IAF. The designer re-examines the geometry and adds a speed constraint on the IF to address this concern.

Step 8: Ground validation (FSTD)#

The coded procedure is loaded into an FMS/FSTD. The flight validation pilot flies the procedure in the simulator:

• All waypoints sequence correctly.
• The FAS captures on time; vertical path tracks as designed.
• Missed approach turn triggers at the correct point.
• LPV annunciation behaviour at downgrade to LNAV/VNAV (when SBAS unavailable) is verified.
• No unusual FMS behaviour is observed on approach with crosswind.

Three database coding errors are identified: one incorrect altitude constraint, one waypoint coded with wrong magnetic bearing, and one wrong waypoint sequence in the STAR feed. All three are corrected and the procedure is re-coded and re-validated on desktop before flight.

Step 9: Flight validation#

The State-approved flight validation pilot flies the procedure in the actual aircraft (or an approved FSTD where permitted by the State). Objectives per §4.3.5.4:

• Confirm the procedure can be flown safely at the published OCA/H.
• Verify obstacle clearance is not compromised during normal operations.
• Confirm crew workload is acceptable.
• Sign the flight validation report.

The flight validation report becomes part of the procedure documentation package submitted for regulatory approval.

Step 10: Regulatory approval and AIP publication#

The documentation package (design worksheets, independent review record, FAS data block, flight validation report) is submitted to the State authority. Following regulatory approval, the procedure is assigned an AIRAC cycle effective date (minimum 28 days before effective date) and published in the State AIP and forwarded to chart publishers.

Key lessons from this example#

• Data integrity is the first constraint: the controlling obstacle identified at Step 3 would have been missed with the aerodrome's older obstacle database, which did not include a new communications tower built 2 years earlier.
• FAS data block accuracy is critical: the SBAS final approach is defined entirely by this data; an error in coordinates shifts the guidance and invalidates the OCA/H.
• Ground validation catches most coding errors before flight validation, making flight validation more efficient and safer.
• The design process is iterative: the Step 7 comment required a design change that in turn required re-verification of the affected segment.

References#

• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part III, Chapter 5, §5.1–§5.8 — SBAS NPA, APV I, and Cat I criteria; FAS data block structure and parameters.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part I, Section 2, Chapter 4, §4.3 — IFP process steps; independent review; validation.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), §4.3.5.4 — Flight validation objectives; flight validation pilot qualification.
• Doc 9906 (Quality Assurance Manual for Flight Procedure Design), Vol 5 — Validation of Instrument Flight Procedures; methodology for ground and flight validation (authoritative source — not in local library).

CNS enablers#

GNSS and augmentation systems#

Satellite navigation is the primary sensor for all PBN procedures. GNSS (primarily GPS, plus GLONASS, Galileo, BeiDou as multi- constellation) provides the core position fix. Augmentation systems improve accuracy and integrity for approach operations:

• SBAS (Satellite-Based Augmentation System): EGNOS (Europe), WAAS (North America), GAGAN (India), MSAS (Japan), SDCM (Russia). SBAS enables LPV minima (down to ILS Cat I equivalent OCA/H) without ground infrastructure. Required for LPV approaches. Also enables LP (localizer performance, lateral only) and SBAS Cat I.
• GBAS (Ground-Based Augmentation System): a ground station at the aerodrome broadcasts corrections and integrity information on VHF data link. Enables GLS (GBAS Landing System) Cat I, and with upgraded standards (GAST D) Cat III. GBAS is site-specific and requires capital investment per aerodrome.
• Multi-constellation GNSS: reduces availability and continuity outage risk; enables approach operations at high latitudes and terrain- constrained sites. An enabler for the ASBU NAVS thread.

Without confirmed SBAS/GBAS service, procedure design is constrained to LNAV (basic GNSS lateral only) or Baro-VNAV (advisory vertical guidance without SBAS accuracy).

Ground-based navaids#

VOR, NDB, ILS, and DME remain the infrastructure for conventional procedures. The global PBN transition (ICAO PBN Manual, Doc 9613) envisages rationalization of the VOR/NDB network as PBN procedures replace conventional ones, but ILS remains essential for Cat II/III precision approach where low visibility operations are required.

Surveillance#

Procedure designers do not directly use surveillance, but ATC's surveillance capability affects how close an IFR aircraft can be vectored to an approach before transferring to the published procedure. Radar vectoring procedures (PANS-OPS Vol II Part I, Section 4, Chapter 8 equivalent) allow the controller to issue vectors to position the aircraft on the final approach track, reducing the reliance on published transition fixes.

Survey and terrain/obstacle data#

The quality of terrain and obstacle data is the single most consequential non-navigation enabler for procedure design. A procedure cannot be safer than its input data.

eTOD (electronic Terrain and Obstacle Data)#

Annex 15 requires States to provide terrain and obstacle data for the operational data areas (Area 1: worldwide; Area 2: aerodrome vicinity; Area 3: runway; Area 4: category II/III operations area). ICAO Doc 9881 (Guidelines for Electronic Terrain, Obstacle and Aerodrome Mapping Information) addresses the data collection methodology.

For procedure design, the critical data is Area 2 (within at least 10 km of an aerodrome reference point) — the area within which the approach and missed approach protection areas lie. Obstacle height, position, and type must meet the accuracy and integrity requirements of Annex 15.

Aerodrome survey#

For RNP APCH LPV/SBAS Cat I, the Landing Threshold Point (LTP) and Flight Path Alignment Point (FPAP) must be surveyed to sub-metric accuracy in WGS-84. Any error in these coordinates translates directly into guidance error at the runway threshold and invalidates the FAS data block. ICAO Doc 9764 (Preparation of an Aerodrome Manual) and Doc 9368 (Instrument Flight Procedures Construction Manual, Attachment C) address the FAS data block survey and computation.

IFP design software#

PANS-OPS calculations are geometrically intensive, especially for PBN protection areas with track-to-fix and radius-to-fix legs. Commercially validated software packages automate the area construction, obstacle evaluation, and OCA/H computation.

Doc 8168 Vol II §4.4 and Doc 9906 Vol 3 address software validation. States must ensure that software used for IFP design has been validated against the applicable PANS-OPS criteria to the State's regulatory framework. Software validation is not a one-time event; it must be revalidated when the software is updated or when criteria change.

Common software families include ISFD (Instrument Flight Procedure Designer), AirNav Pro, and in-house CAA tools. FAA, EUROCONTROL, and ICAO have each published software validation methodologies.

Regulatory and institutional enablers#

State regulatory framework#

Doc 10068 (Manual on the Development of a Regulatory Framework for Instrument Flight Procedure Design Service) provides the blueprint for States to establish:

• Authorization of IFP design service providers (State ANSP, contracted specialist, or foreign State).
• Competency and approval requirements for procedure designers and flight validation pilots.
• Acceptance and oversight of the IFP process outputs.
• Procedures for periodic review and amendment of published IFPs.

Without a functioning regulatory framework, States cannot meet the obligation in Doc 8168 Vol II §4.1.2 to ensure all published procedures can be flown safely.

Procedure designer training#

Doc 9906 Vol 2 provides guidance for developing a procedure designer training programme. There is no single ICAO-mandated certificate, but several bodies offer recognized training:

• ICAO Training and Operational Support Programme (TRAINAIR PLUS).
• EUROCONTROL Institute of Air Navigation Services.
• FAA Aeronautical Center Flight Procedure Design courses.
• IATA and CANSO member training programmes.

Training quality varies globally; a State's regulatory framework should define minimum competency standards rather than simply requiring attendance at a course.

Flight validation pilot approval#

Each State must approve flight validation pilots and/or organizations in accordance with its regulatory framework (§4.3.5.5). The qualifications include current instrument rating, familiarity with the procedure types being validated, knowledge of PANS-OPS criteria, and documented validation experience. Doc 9906 Vol 6 covers flight validation pilot training and evaluation in detail.

Environmental enablers#

CDO/CCO integration#

Procedure design increasingly considers continuous descent operations (CDO) and continuous climb operations (CCO) as environmental objectives alongside obstacle clearance:

• CDO (continuous descent operation): enabled by procedure design and ATC. An arriving aircraft descends continuously from a defined point to the final approach, using minimum thrust in low-drag configuration. The approach procedure design determines whether the altitude profile supports a continuous descent or forces level segments at intermediate altitude constraints. Designers minimize step-down constraints in the intermediate approach segment to facilitate CDO.
• CCO (continuous climb operation): the SID design targets continuous climb to cruise using optimum engine thrust and climb speeds. An SID that forces early level-off for noise or traffic management reasons adds fuel burn and emissions.

Both CDO and CCO are ASBU objectives (CDO-B0, CCO-B0 modules) and are mentioned explicitly in the definitions section of PANS-OPS Vol II.

Noise abatement#

Doc 8168 Vol II includes an appendix to the departure procedures chapter on environmental constraints in procedure design. While the obstacle clearance criterion takes precedence, designers consider noise- preferential routes (NPRs) and noise abatement departure procedures (NADPs) when configuring SIDs for major airports. NADP 1 (immediate close-in noise reduction) and NADP 2 (distant noise reduction) define the thrust and flap configuration profile; procedure designers ensure SID routing is compatible with both profiles.

References#

• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), §4.4 — Procedure design automation; software validation requirements.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), §4.1.1 — Reference to Doc 9906 and Doc 10068.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), §4.3.5.5 — Flight validation pilot qualification and training.
• Doc 9906 (Quality Assurance Manual for Flight Procedure Design), Vol 3 — Software Validation guidance (authoritative source — not in local library).
• Doc 9613 (PBN Manual), 5th Edition (2023) — Navigation specifications and SBAS/GBAS infrastructure requirements.
• Doc 10068 (Manual on the Development of a Regulatory Framework for IFP Design Service) — State regulatory framework blueprint (authoritative source — not in local library).
• Annex 15 (Aeronautical Information Services) — eTOD data quality and integrity requirements; Area 1–4 datasets.

The performance lens#

Flight procedure design is not an end in itself: procedures are tools to deliver operational performance. The ICAO performance framework (Doc 9854, Doc 9883) identifies eleven Key Performance Areas (KPAs). For IFP design, safety and access are the primary drivers, with efficiency and environment as growing secondary objectives.

Key Performance Areas and IFP design#

KPA contribution by procedure design maturity#

The table below scores each KPA by its principal benefit tier across the four procedure design maturity levels (1 = some benefit, 2 = clear benefit, 3 = primary driver). It mirrors the ASBU block contribution framework.

Performance objectives by procedure design function#

Safety: CFIT prevention#

Performance objective: each published procedure provides MOC at or above the PANS-OPS minimum for each segment at all times during normal operations.

KPIs:

• CFIT events per million approaches (global; tracked by CAST/ICAO CFIT reduction initiative).
• Serious incidents attributable to procedure design error (ground proximity in published procedure segment).
• Percentage of procedures reviewed within the five-year maximum cycle required by Annex 11 Appendix 7.

Access: instrument operations at under-served aerodromes#

Performance objective: increase the percentage of aerodromes worldwide served by an instrument approach with vertical guidance (APV or PA).

KPIs:

• Number of aerodromes with at least one APV or PA procedure (ICAO APTA monitoring; ASBU APTA-B0 module target).
• Number of approach procedures with LPV minima published globally (Jeppesen/Navdata catalogue).
• Number of aerodromes in mountainous regions served by RNP AR APCH enabling lower minima than achievable by conventional ILS geometry.

Efficiency and environment: CDO-compatible approaches#

Performance objective: published approach procedures enable CDO operations (no published step-down constraints in the intermediate approach segment that force early level-off).

KPIs:

• Percentage of approaches where a continuous descent is achievable from the FAF to the threshold without level-off.
• Excess fuel per arrival (CDO conformance KPI, tracked by IATA and CANSO).
• Noise contour area reduction at airports where noise abatement routing is embedded in SID and STAR design.

Quality: IFP process compliance#

Performance objective: all published procedures are designed, reviewed, validated, and periodically reviewed in full compliance with PANS-OPS Chapter 4 quality assurance requirements.

KPIs:

• Percentage of procedures with complete documentation (design worksheet, independent review record, flight validation report).
• Number of NOTAM-issued procedure withdrawals or suspensions due to design error discovered post-publication.
• Percentage of designer training programmes compliant with Doc 9906 Vol 2 guidance.

Performance reporting context#

Flight procedure design performance is not tracked as a single ICAO KPI stream. It is embedded in several overlapping frameworks:

• ASBU APTA thread: tracks APV/LPV approach coverage globally.
• ICAO Universal Safety Oversight Audit Programme (USOAP): assesses whether States have the regulatory and technical capability to design and maintain procedures to ICAO standards (Protocol Questions on Instrument Flight Procedures).
• Regional performance monitoring: EUROCONTROL Performance Review Commission tracks CDO conformance; APANPIRG and MIDANPIRG track PBN implementation coverage including approach procedures.
• Safety events reporting: ICAO ADREP and regional databases track CFIT events; the approach segment is disaggregated in the analysis.

References#

• Doc 9854 (Global ATM Operational Concept), Chapter 2 — KPA framework and their definitions (authoritative source — not in local library).
• Doc 9883 (Manual on Global Performance of the Air Navigation System) — KPA and KPI methodology (authoritative source — not in local library).
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Part I, Section 2, Chapter 4, §4.3.3.3 — Periodic review requirement; maximum five-year interval; reference to Annex 11 Appendix 7.
• Annex 11 (Air Traffic Services), Appendix 7 — Instrument flight procedure review obligation.

Evolution of PANS-OPS and instrument procedure design criteria#

Key panel transitions#

Edition history of Doc 8168#

References#

• Doc 8168 (PANS-OPS), Vol I, 6th Edition (2018), Foreword, Table A — Complete amendment history of PANS-OPS from 1951 to 2018.
• Doc 8168 (PANS-OPS), Vol II, 7th Edition (2020), Foreword, Table of Amendments — Complete amendment history of Vol II from 1961 to 2024.
• Doc 9613 (PBN Manual), 5th Edition (2023), Preface — History of the PBN concept from GNSS Panel through RNPSORSG to current edition.

Primary ICAO PANS and Docs#

• Doc 8168 (PANS-OPS), Vol I, Aircraft Operations — Flight Procedures, 6th Edition (2018), applicable 8 November 2018 — Flight operations provisions for crew and operators; definitions; approach segment descriptions; OCA/H and operating minima relationship.
• Doc 8168 (PANS-OPS), Vol II, Construction of Visual and Instrument Flight Procedures, 7th Edition (2020), applicable 5 November 2020 — Designer's technical reference; obstacle clearance criteria; protection area geometry; QA chapter; all procedure type construction rules.
• Doc 8168 (PANS-OPS), Vol III, Aircraft Operating Procedures, 1st Edition (2018), applicable 8 November 2018 — Aircraft operating procedures separated from Vol I; performance-based approach procedures.
• Doc 9906 (Quality Assurance Manual for Flight Procedure Design), 6 volumes — Vol 1: QA System; Vol 2: Designer Training; Vol 3: Software Validation; Vol 5: Validation of IFPs; Vol 6: Flight Validation Pilot Training (authoritative source — not in local library).
• Doc 9905 (Required Navigation Performance Authorization Required — RNP AR Procedure Design Manual) — Design criteria for RNP AR APCH and RNP AR Departure procedures; RF leg use; tighter tolerances permitting curved approach paths in mountainous terrain (authoritative source — not in local library).
• Doc 9613 (PBN Manual), 5th Edition (2023), Volumes I and II — PBN concept; navigation specifications (RNAV, RNP, RNP AR, Advanced RNP); procedure designer stakeholder interface; path terminators.
• Doc 10068 (Manual on the Development of a Regulatory Framework for Instrument Flight Procedure Design Service) — State regulatory framework blueprint; provider authorization; designer and flight validation pilot approval (authoritative source — not in local library).
• Doc 9854 (Global ATM Operational Concept) — CFIT and trajectory management context (authoritative source — not in local library).
• Doc 9883 (Manual on Global Performance of the Air Navigation System) — KPA and KPI methodology for ATM including procedure design performance (authoritative source — not in local library).

ICAO Annexes#

• Annex 4 (Aeronautical Charts) — Chart presentation requirements for instrument approach charts; PBN identification box; obstacle depiction.
• Annex 11 (Air Traffic Services), Appendix 7 — Five-year maximum interval for periodic review of published instrument flight procedures.
• Annex 14 (Aerodromes), Volume I — Obstacle limitation surfaces (OLS); aerodrome survey; relationship between OLS and departure protection areas.
• Annex 15 (Aeronautical Information Services) — eTOD (electronic Terrain and Obstacle Data) data quality and integrity requirements; Areas 1–4; AIP publication of procedure data; data integrity chain.

Authoritative external sources#

• https://www.icao.int/safety/airnavigation/AeronauticalInfrastructure/Pages/FlightProcedures.aspx - ICAO Flight Procedures Programme overview and resources
• https://www.icao.int/safety/pbn/Pages/default.aspx - ICAO PBN Programme; implementation guidance and State reporting
• https://store.icao.int/ - ICAO store: Doc 8168 (all three volumes), Doc 9905, Doc 9906, Doc 9613, Doc 10068
• https://www.eurocontrol.int/service/instrument-flight-procedures - EUROCONTROL IFP design services and flight validation capability (authoritative source — not in local library)
• https://www.faa.gov/air_traffic/flight_info/aeronav/procedures/ - FAA Flight Procedure Development programme; US procedure publication (authoritative source — not in local library)
• https://egnos-user-support.essp-sas.eu/new_egnos_ops/ - ESSP EGNOS Operations; LPV service availability for European procedure designers (authoritative source — not in local library)