Kiri

Tel.: +1 514 315 2005 17 April 2025

Ref.: AN 4/27-25/29

Subject: Approval of Amendment 5 to the

PANS-Aerodromes

Action required: a) Implementation of the amendment

on 27 November 20251; and b) Publication of any

differences as of 27 November 20251

Sir/Madam,

I have the honour to inform you that the Air Navigation Commission, acting under

delegated authority, on 7 February 2025, approved Amendment 5 to the Procedures for Air Navigation

Services (PANS) — Aerodromes (Doc 9981), for applicability on 27 November 2025 except for

amendments related to obstacle limitation surfaces which should be indicated as 21 November 2030. The

amendment was approved on 4 April 2025 by the President of the Council on behalf of the Council in

accordance with established procedure. Copies of the amendment are available as attachments to the

electronic version of this State letter on the ICAO-NET (http://portal.icao.int) where you can access all

other relevant documentation.

Amendment 5 relates to visual aids and obstacle limitation surfaces. It arises from the

fourth meeting of the Aerodrome Design and Operations Panel (ADOP/4).

An implementation task list, including an outline of guidance material and an impact

assessment for the amendment are presented in Attachments B and C, respectively. An overview of the

approval process for Amendment 5 to the PANS-Aerodromes is also included for your information in

Attachment D.

Your Government is invited by the Council to implement the provisions of the

PANS-Aerodromes as amended. In this connection, I draw your attention to the decision taken by the

Council, on 1 October 1973, to discontinue the publication of differences in Supplements to the PANS

1 21 November 2030 for provisions related to obstacle limitation surfaces

999 Robert-Bourassa Boulevard

Montréal, Quebec

Canada H3C 5H7

Tel.: +1 514 954-8219-

Fax: +1 514 954-6077-

Email: [email protected]

www.icao.int

International

Civil Aviation

Organization

Organisation

de l’aviation civile

internationale

Organización

de Aviación Civil

Internacional

Международная

организация

гражданской

авиации

- 2 -

documents and, instead, to request States to publish up-to-date lists of significant differences from PANS

documents in their Aeronautical Information Publications (AIPs).

May I, therefore, invite your Government to publish in your Aeronautical Information

Publication a list of any significant differences which will exist on 27 November 2025 for provisions related

to visual aids and 21 November 2030 for provisions related to obstacle limitation surfaces between the

amended provisions of the PANS-Aerodromes and your national regulations and practices.

Accept, Sir/Madam, the assurances of my highest consideration.

Juan Carlos Salazar

Secretary General

Enclosures:

A — Amendment to the Foreword of the PANS-Aerodromes

B — Implementation task list and outline of guidance

material in relation to Amendment 5 to the

PANS-Aerodromes

C — Impact assessment in relation to Amendment 5 to the

PANS-Aerodromes

D — Overview of approval process for Amendment 5 to

PANS-Aerodromes

ATTACHMENT A to State letter AN 4/27-25/29

AMENDMENT TO THE FOREWORD OF THE

PANS-AERODROMES (DOC 9981)

Add the following element at the end of Table A:

Amendment Source(s) Subject Approved

Applicable 5 Fourth meeting of the Aerodrome

Design and Operations Panel

(ADOP/4)

a) visual aids; and

b) obstacle limitation

surfaces as of

21 November 2030.

4 April 2025

27 November 2025

21 November 2030

— — — — — — — —

ATTACHMENT B to State letter AN 4/27-25/29

IMPLEMENTATION TASK LIST AND OUTLINE OF GUIDANCE MATERIAL IN RELATION

TO AMENDMENT 5 TO PANS-AERODROMES (DOC 9981)

1. IMPLEMENTATION TASK LIST

1.1 Essential steps to be followed by a State in order to implement the amendment to

PANS-Aerodromes:

a) conduct a gap analysis between the new and modified ICAO provisions and national

regulatory framework;

b) identify the rule-making process necessary to transpose the new and modified ICAO

provisions into national regulations, where necessary;

c) draft the necessary modifications to the national regulations and means of compliance;

d) officially adopt the national regulations and means of compliance;

e) establish a national implementation plan that takes into account the new and modified

ICAO provisions;

f) train relevant personnel prior to implementation of the new and modified provisions;

g) communicate the change to impacted industry stakeholders and airspace users;

h) implement the new and modified national regulations by the relevant stakeholders;

i) modify the oversight framework according to the new and modified national

regulations;

j) oversight by the State of the implementation of the regulations; and

k) publish significant differences, if any, in the State’s AIP.

2. STANDARDIZATION PROCESS

2.1 Approval date: 4 April 2025

2.2 Applicability date: 27 November 2025 for provisions related to visual aids and

21 November 2030 for provisions related to obstacle limitation surfaces.

2.3 Embedded dates: N/A.

B-2

3. SUPPORTING DOCUMENTATION

3.1 ICAO documentation

Title Type (PANS/TI/Manual/Circ)

Planned

publication date

Procedures for Air Navigation Services —

Aircraft Operations, Procedures for Air

Navigation Services — Aircraft Operations,

Volume II — Construction of Visual and

Instrument Flight Procedures (Doc 8168)

PANS Published

Airport Services Manual, Part 6 — Control of

Obstacles (Doc 9137) Manual July 2025

Aerodrome Design Manual, Part 4 – Visual Aids (Doc

9157) Manual July 2025

3.2 External documentation

Title

External

Organization Publication date

None.

4. IMPLEMENTATION ASSISTANCE TASKS

Type Global Regional

Promote awareness and

roll-out

Workshops, training courses,

webinars

5. UNIVERSAL SAFETY OVERSIGHT AUDIT PROGRAMME (USOAP)

5.1 Certain Protocol Questions (PQs) relating to OLS and visual aids should be reviewed and

modified as necessary.

— — — — — — — —

ATTACHMENT C to State letter AN 4/27-25/29

IMPACT ASSESSMENT IN RELATION TO

AMENDMENT 5 TO THE PANS-AERODROMES (DOC 9981)

1. INTRODUCTION

1.1 Amendment 5 to the Procedures for Air Navigation Services (PANS) – Aerodromes

(Doc 9981) is intended to:

a) provide better situational awareness to pilots through enhanced visual aids; and

b) ensure that a holistic safeguarding of the airspace against obstacles is provided through

a set or sets of surfaces with clear purposes and characteristics that are performance

based and are adaptable to the type of operations conducted at the aerodrome.

2. IMPACT ASSESSMENT

2.1 Amendment concerning visual aids

2.1.1 Safety impact: Positive. The amendment will improve aerodrome safety as the pilots will

have enhanced visual aids to denote restricted use area or any temporary changes to the movement area due

to aerodrome maintenance activities.

2.1.2 Financial impact: The financial impact may vary based on the need to install additional

visual aids to indicate restricted areas at an aerodrome due to maintenance activities.

2.1.3 Security impact: No impact on aviation security is envisaged with the implementation of

this amendment.

2.1.4 Environmental impact: Nil.

2.1.5 Efficiency impact: Nil.

2.1.5 Expected implementation time: 1 to 2 years. This depends on whether aerodromes are

already compliant or if they must apply additional visual aids to indicate restricted areas due to maintenance

activities.

2.2 Amendment concerning obstacle limitation surfaces

2.2.1 Safety impact: Positive. The surfaces provide a holistic safeguarding of the airspace against

obstacles. Through obstacle free surfaces (OFS) and obstacle evaluation surfaces (OES), the entire airspace

is protected to ensure no obstacles will be left unnoticed or unaccounted for. The OFS will be steeper and

for some, it will be narrower and shorter. However, there will be additional surfaces, the OES, which

C-2

extends below and beyond the OFS. The entire airspace of concern to operations will be covered by one

surface or the other.

2.2.2 Financial impact: Depending on the State and their existing practices, there may be a need

to invest in additional resources (human and technological) to help States transition to this new

methodology of airspace safeguarding. However, these costs can be minimized by adapting certain

prescribed surfaces. For the industry survey may be initiated prior to the implementation of the new

surfaces, and there could be buildings or structures that may penetrate the new surfaces requiring

aeronautical studies.

2.2.3 Security impact: No security impact is envisaged with the implementation of this

amendment.

2.2.4 Environmental impact: Positive. With aerodromes being more accessible, the likelihood of

a go-around or missed approach due to obstacles will be greatly reduced. More efficient landings and

departures reduce unnecessary fuel burn, since extra fuel is consumed during a missed approach and

subsequent approach manoeuvres.

2.2.5 Efficiency impact: Positive. Increased accessibility to the runway reduces the likelihood of

go-around procedures due to obstacles. This will contribute to increased capacity and more efficient traffic

flow at the aerodrome. Unlike the current obstacle limitation surface (OLS) which is prescriptive, States

will have the flexibility to adopt or adapt surfaces that are needed to support the type of operations

conducted at the aerodrome. Surfaces that are not required need not be safeguarded and areas which would

otherwise be affected by the surfaces can then be released for development. This is an efficient way of

ensuring a good balance between aviation and land use needs.

2.2.6 Expected implementation time: For States, 3 to 4 years. While transposing the new

provisions into national regulations may require between 1 to 2 years, establishing the new surfaces and

incorporating amendments to zoning laws may take an additional 1 to 2 years. The industry may need 1 to

2 years to implement the surfaces and to acquire additional resources for the conduct of aeronautical studies,

where required.

— — — — — — — —

ATTACHMENT D to State letter AN 4/27-25/29

OVERVIEW OF APPROVAL PROCESS FOR

AMENDMENT 5 TO PANS-AERODROMES

Amendment

concerning Source(s)

Preliminary

review by

the ANC

State letter

and date

Final review

by the ANC

No. of replies at

final review

Approved

Applicable

Visual aids and

obstacle

limitation

surfaces

Fourth meeting of the

Aerodrome Design

and Operations Panel

(ADOP/4)

23 March 2023

(ANC 222-7)

AN 4/1.1.58-23/33

30 May 2023

Corr. No.1

26 March 2024,

28 March 2024

(ANC 225-10,

ANC 225-13)

73 Contracting

States

7 international

organizations

Total: 80 replies

4 April 2025

27 November 2025

21 November 2030

— END —

AMENDMENT No. 5

TO THE

PROCEDURES

FOR

AIR NAVIGATION SERVICES

AERODROMES

(Doc 9981)

INTERIM EDITION

The text of Amendment No. 5 to the PANS-Aerodromes (Doc 9981) was

approved by the President of the Council of ICAO on behalf of the Council on

4 April 2025 for applicability on 27 November 2025 for provisions related to

visual aids and 21 November 2030 for provisions related to obstacle limitation

surfaces. This interim edition is distributed to facilitate implementation of the

amendment by States. Replacement pages incorporating Amendment No. 5 are

expected to be distributed in October 2025. (State letter AN 4/27-25/29 refers.)

APRIL 2025

INTERNATIONAL CIVIL AVIATION ORGANIZATION

NOTES ON THE EDITORIAL PRESENTATION

OF THE AMENDMENT TO THE PANS-AERODROMES

The text of the amendment is arranged to show deleted text with a line through it and new text

highlighted with grey shading, as shown below:

1. Text to be deleted is shown with a line through it. text to be deleted

2. New text to be inserted is highlighted with grey shading. new text to be inserted

3. Text to be deleted is shown with a line through it followed

by the replacement text which is highlighted with grey

shading.

new text to replace existing text

2

TEXT OF AMENDMENT 5

TO THE

PROCEDURES FOR AIR NAVIGATION SERVICES

AERODROMES (DOC 9981)

TABLE OF CONTENTS

. . .

PART II — AERODROME OPERATIONAL MANAGEMENT

. . .

Chapter 10. Obstacle Evaluation and Control (Applicable as of 21 November 2030) .............. II-10-X

10.1 General .............................................................................................................................. II-10-X

10.2 Objectives .......................................................................................................................... II-10-X

10.3 Operational practices ........................................................................................................ II-10-X

Appendix to Chapter 10. Aeronautical study process

(Applicable as of 21 November 2030) ...................................... II-10-App-1

Attachment to Chapter 10. Aeronautical study flowchart

(Applicable as of 21 November 2030) .................................... II-10-Att A-1

FOREWORD

. . .

6. CONTENTS OF THE DOCUMENT

. . .

PART II — AERODROME OPERATIONAL MANAGEMENT

. . .

6.19 Part II, Chapter 10 — Obstacle Evaluation and Control

(Applicable as of 21 November 2030)

6.19.1 This chapter contains provisions pertaining to obstacle limitation surfaces and aeronautical

study. It deals with topics on selection of required obstacle limitation surfaces, comprising obstacle free

surfaces and obstacle evaluation surfaces, and how these surfaces can be adjusted to match the type of

operations provided at an aerodrome. In addition, the chapter provides guidance on how to conduct

aeronautical study.

3

. . .

ACRONYMS AND ABBREVIATIONS

. . .

ADG Aeroplane design group†

. . .

AT-VASIS Abbreviated T visual approach slope indicator system†

. . .

CNS Communications, navigation, and surveillance

OES Obstacle evaluation surface†

OFS Obstacle free surface†

. . .

LNAV Lateral navigation†

MLS Microwave landing system

NPA Non-precision approach procedures OCA/H Obstacle clearance altitude/height RNP Required navigation performance†

SBAS Satellite-based augmentation system SDF Step-down fixes†

. . .

TOD Terrain obstacle datasets† T-VASIS T visual approach slope indicator system†

. . .

VNAV Vertical navigation†

. . .

† Applicable as of 21 November 2030

2 Chapter 4

WORK IN PROGRESS (WIP)

. . .

4.3 OPERATIONAL PRACTICES . . .

4.3.3 A safety risk assessment of all planned works should be completed beforehand in order to ensure

the risks hazards to the safe operation of aircraft have been identified by the aerodrome operator in coordination with interested parties, and appropriate mitigation measures introduced to keep risks to an acceptable level. Risk mitigation actions include, inter alia, the use of visual aids to denote restricted use area.

. . .

4.3.8 The following actions should be taken when establishing the worksite, as well as throughout the duration of works, when necessary:

a) a safety risk assessment should be conducted to determine the need for visual aids to indicate

temporary changes to the movement area; ab) unserviceability markers are displayed when any portion of a taxiway, apron, or holding bay is unfit

for the movement of aircraft, but it is still possible for aircraft to bypass the area safely; bc) existing markings leading into a worksite should be masked or the route closed;

Editorial Note.— Renumber subsequent paragraphs accordingly.

. . .

Note 1.— Unserviceability relates to areas temporarily not available for operational use. . . .

Note 5.— Temporary changes to the movement area may include, inter alia, reduction in the runway length, reduction in the maximum allowable wingspan, taxiway closure or any other closure to the movement area. Certain visual aids such as closed runway lighting could be used for a temporary period varying from a few hours to several weeks or longer, depending on the works in progress or other closure reasons. . . .

Insert new text as follows:

Chapter 10

OBSTACLE EVALUATION AND CONTROL

(Applicable as of 21 November 2030)

10.1 GENERAL

3

10.1.1 The airspace around aerodromes is critical to the safety and regularity of operations. These

areas are often congested with aircraft that are performing landing and take-off operations. It is critical that this area be maintained free from obstacles that could adversely impact the safety and accessibility of intended aircraft operations at aerodromes. To meet this purpose, sets of obstacle limitation surfaces (OLS) were established to be introduced at aerodromes to prevent the aerodromes from being unusable due to uncontrolled growth of obstacle around aerodrome.

10.1.2 A new obstacle or the extension of an existing obstacle can adversely affect the safety and

regularity of aircraft operations; it may result in increased operating minima, changes in ANSP procedures, reduced capacity or operational restrictions on departures. It is therefore necessary to introduce OLS at and in the vicinity of aerodromes to effectively control the growth of obstacles and the possible turbulences that may be generated by these obstacles.

10.1.3 The existence of construction activities, buildings, structures, facilities, plantations, landfills

or activities of any nature that interfere with the OLS may impose limitations on the effective utilization of an aerodrome or a portion of the airspace. It is therefore important for coordination to exist between civil aviation authorities and aerodrome operators in managing the OLS.

10.1.4 The OLS defines the limits to which objects may project into the airspace and imposes

restrictions on any public or private property, making them an effective method in controlling land use in the vicinity of aerodromes.

10.1.5 The OLS comprises two sets of surfaces: obstacle free surfaces (OFS) and obstacle evaluation

surfaces (OES). The OFS and OES have distinct purposes and are applied based on the type of runway, aeroplane design group (ADG) and the flight procedures available for that runway.

10.1.6 The objectives and operational practices described in this chapter are intended to provide the

information needed to apply the surfaces defined in Annex 14 – Aerodromes, Volume I – Aerodrome Design and Operations.

The Surfaces

10.1.7 The OFS are surfaces that are applied within a defined airspace in the immediate vicinity of the aerodrome. The OFS are established to protect the existing and future operational capacity of the aerodrome by limiting obstacles. The OFS are intended to preserve accessibility of the aerodrome by containing standard operations (straight-in approaches) with a high level of probability. As such, they are to be kept free from obstacles except for existing obstacles and/or terrain which would have been assessed earlier.

10.1.8 The OES are surfaces that are applied in a defined airspace, in addition to the OFS, to be

evaluated against obstacles. They are used in determining the acceptability of obstacles in ensuring safety and regularity of operations at the aerodrome. The penetration of the OES by terrain or obstacles are to be evaluated as they may adversely affect the safety or accessibility of the intended aircraft operations.

10.1.9 The dimensions of OFS and OES are determined based on aeroplane design group (ADG)

categorization. The ADG utilizes two criteria, which are related to the aeroplane performance characteristics and dimensions. The first criterion is based on the aircraft’s indicated airspeed at threshold and the second criterion on the aeroplane wingspan.

10.1.10 In addition to existing operations, the OFS and OES selected for the aerodrome should

safeguard future planned aircraft operations.

4 Aeronautical study

10.1.11 Objects penetrating the OFS and OES may adversely impact flight operations. The impact of these penetrations to safety and regularity of aircraft operations must be examined through the conduct of an aeronautical study.

10.1.12 An aeronautical study is a process of examining an aeronautical concern by assessing its

impact on safety and regularity of aircraft operations and identifying, if need be, possible mitigation measures.

10.1.13 An aeronautical study may also be applied to examine the impact of obstacles at and in the

vicinity of new airports or renovated and expanded airports at the master planning stage. Note.— Further guidance on master planning can be found in the Airport Planning Manual, Part I –

Master Planning (Doc 9184). 10.1.14 In addition to flight operations, the aeronautical study must consider and address other

aeronautical concerns such as impact on communication facilities, navigational aids, aerodrome operations and air traffic control line of sight.

10.2 OBJECTIVES

10.2.1 States shall define the roles and responsibilities of stakeholder(s) and delegate them the appropriate authority in the identification of the OFS and required OES, the safeguarding of these surfaces, and the surveillance of the areas within these surfaces.

Note.— Stakeholder(s) include the aerodrome operator, local authority, ANSPs, land use agency,

military organization or any agency the State deems appropriate.

10.2.2 States shall establish a process for the identification of OFS and OES required to protect flight operations at an aerodrome.

10.2.3 Through the process, States or the appropriate authority shall:

a) determine the OFS and OES applicable based on ADG category; b) vary the OFS, when required, to account for changes in the approach angle to account for local

conditions and aeroplane characteristics; c) determine the OES required to protect the operations at the aerodrome; d) vary the OES based on the operational requirements of the aerodrome; e) ensure the safeguarding of the OFS and OES; and f) identify obstacles and terrain data penetrating the OFS and OES.

Note.— The data collected are to be in accordance with terrain and obstacle datasets (TOD) provisions

as stipulated in Annex 15 — Aeronautical Information Services and the Procedures for Air Navigation Services—Aeronautical Information Management (PANS-AIM, Doc 10066).

5

10.2.4 When instrument approaches are carried out on non-instrument runway(s), States or the

appropriate authority shall review the dimensions of the approach and transitional OFS for such runway(s). 10.2.5 States shall establish a process for conducting aeronautical study. 10.2.6 States shall define the party/parties responsible for conducting the aeronautical study. 10.2.7 The process to be established by States shall include the following details:

a) identify stakeholders involved in the aeronautical study process; b) define situations where an aeronautical study is required; c) define the data required to produce a complete description of the aerodrome, obstacle and its

environment; d) describe the methodology for the conduct of the impact assessment; e) identify appropriate mitigation measures to address any impact posed by an obstacle; f) define the acceptance criteria taking into consideration all studies and assessments submitted prior

to approving the proposed obstacle; and g) define documentation and promulgation procedures of the aeronautical study.

Note.— An aeronautical study may be conducted anytime when, in the opinion of the State or

appropriate authority, a proposed obstacle may adversely affect aircraft operations.

10.3 OPERATIONAL PRACTICES

10.3.1 Preventing the growth of obstacles

10.3.1.1 The primary responsibility to ensuring the aerodrome and its environment is and remains

free from obstacles should be shared between the State and the aerodrome operator. The responsibilities and interactions among other additional stakeholders such as the aircraft operator, ANSP, local authority, etc. should be established and coordinated by the appropriate authority.

10.3.1.2 States are responsible for establishing a process for the selection of OLS required to protect

the airspace against growth of obstacles and for evaluation of existing and potential obstacles and terrain. The process should include guidance on:

a) identifying the OLS needed to support the existing and/or planned operations at the aerodrome;

Note. — For OLS selection, refer to 10.3.1.5. b) establishing the mechanisms to protect the surfaces and empower the appropriate authority to deny

objects that may impact the safety and regularity of operations; and c) using OFS and OES for survey of the aerodrome and its surroundings and the collection of obstacle

6 data.

10.3.1.3 The ADG consists of two criteria, indicated air speed at threshold and wingspan. In choosing the applicable ADG, the appropriate authority should consider the critical aeroplane operating at the aerodrome based on these two criteria (see Annex 14, Volume I, Chapter 1, 1.8.1 and 1.8.2).

Aeroplane

design group Indicated airspeed at threshold Wingspan

I Less than 169 km/h (91 kt) and Up to but not including 24 m

IIA Less than 169 km/h (91 kt) and 24 m up to but not including 36 m

IIB 169 km/h (91 kt) up to but not including 224 km/h (121 kt) and Up to but not including 36 m

IIC 224 km/h (121 kt) up to but not including 307 km/h (166 kt) and Up to but not including 36 m

III Less than 307 km/h (166 kt) and 36 m up to but not including 52 m

IV Less than 307 km/h (166 kt) and 52 m up to but not including 65 m

V Less than 307 km/h (166 kt) and 65 m up to but not including 80 m

10.3.1.4 In aerodromes with more than one runway, the appropriate authority can define different

ADG for each runway and in areas where the surfaces overlap, the more stringent surface will apply. Note.— Guidance on the application of ADG can be found in the Airport Services Manual, Part 6 –

Control of Obstacles (Doc 9137).

10.3.1.5 The OLS to be adopted are dependent on: a) the type of runway – precision, non-precision and non-instrument; b) the ADG applicable for the runway; and c) existing and/or planned flight operations at an aerodrome and the corresponding OES(s) needed to

protect the flight procedures. When selecting OES, the appropriate authority can adopt the OES defined in Annex 14, Volume I, Chapter 4, or design OES specific to the procedures conducted at the aerodrome.

10.3.1.6 States may delegate the responsibility for the safeguarding and surveying of areas within

these surfaces to other appropriate authority. 10.3.1.7 The protection of these surfaces can be enhanced by incorporating them into the zoning laws.

In lieu of zoning laws, authority may also consider having the necessary coordination process with the land use agencies to ensure aviation requirements are factored into land use planning and airport master planning. The aviation requirements are not limited to OLS only but may include other requirements relating to disturbance to communications, navigation, and surveillance (CNS) facilities, glare or glint issues, wildlife management considerations and other potential hazards.

Note.— Further guidance can be found in the Airport Services Manual, Part 6 – Control of Obstacles

(Doc 9137). 10.3.1.8 The surveying of aerodromes and their vicinity is key to ensuring safety of flight operations.

The establishment of OFS and OES help in ensuring the obstacle database remains updated. Objects that penetrate these surfaces are to be assessed and their information captured in the database.

10.3.1.9 A process shall be established to share the obstacle data with AIS.

7

10.3.1.10 The data collected, specifically the geographical coordinates of obstacles in TOD Area 2

and Area 3, should be measured and reported in degrees, minutes, seconds and tenths of seconds. In addition, the top elevation, obstacle type, marking and lighting (if any) of obstacles should be reported.

Note.— The TOD requirements including specifications on data quality can be found in Annex 15 and

PANS-AIM, (Doc 10066), Table A1-6.

10.3.2 Adapting OFS and OES to operational needs

Adjusting obstacle free surfaces

10.3.2.1 The OFS are designed based on the nominal approach angle of 3.0°. There are aerodromes where the approach angle can either be lower or higher.

10.3.2.2 The slope of the approach surface is intended to adapt to approach operations that have an

approach angle of 3.0° or higher. The slope of the approach surface may be raised if approach procedures with an approach angle of more than 3.0° are implemented. However, the approach angle should not be increased to enable the growth of obstacles.

10.3.2.3 Where the approach angle is less than 3.0° the slope of the approach surface must be lowered

to protect the operations. 10.3.2.4 In certain circumstances, due to alignment of visual slope indicator systems with instrument

landings aids, the slope of the approach surface must be lowered, too, to align the surface with the requirements of the Procedures for Air Navigation Services — Aircraft Operations (Doc 8168).

Adjustments of the Approach OFS 10.3.2.5 The approach OFS has been designed based on the approach angle of 3.0° and runway type.

Any changes to these parameters will require changes to the dimensions of the OFS. 10.3.2.6 Changes to the approach angle will affect the slope and length of the approach OFS. As the

OFS for instrument runway is designed to reach a height of 150 m (500 ft) or up to the obstacle clearance altitude/height (OCA/H), an increase or decrease in the slope will change the length of the surface.

Note.— Further guidance on changing the slope of OFS is given in the Airport Services Manual, Part 6

– Control of Obstacles (Doc 9137). 10.3.2.7 The slope of the approach OFS is associated with:

a) the visual segment surface (see PANS-OPS (Doc 8168), Volume II, Part I, Section 4, Chapter 5,

paragraph 5.4.6.2) which protects the visual phase of an instrument approach procedures; and b) the obstacle protection surface of a PAPI for both instrument and non-instrument approach

procedures. 10.3.2.8 To calculate the slope when there are changes to the approach angle, the following steps

should be taken: a) for runways served with instrument approaches:

8 i) subtract the standard angular margin from the promulgated approach angle. The standard

angular margin equals the difference between the standard approach angle of 3.0° and the standard approach surface's gradient of 3.33 per cent which is approximately 1.91 per cent (3.0° - 3.33 per cent);

Note.— Further guidance on the calculation of slope and their precalculated values is provided

in Doc 9137, Part 6.

ii) identify the slope associated with the obstacle protection surface. e.g. The harmonization between a 3.0° ILS and the PAPI will result in the obstacle protection surface of the PAPI to be at 3.22 per cent to align with the signal of the ILS. (see Annex 14, Volume 1, Chapter 5, Figure 5-21 and Table 5-3). The slope of the approach surface shall be reduced accordingly; and

iii) the lower slope between the two calculated in (i) and (ii) will be adopted for the approach OFS;

b) for runways intended for visual approach operations only:

i) when T visual approach slope indicator system (T-VASIS), abbreviated T visual approach slope indicator system (AT-VASIS), PAPI and APAPI are provided, the obstacle protection surface will be used to determine the slope.

10.3.2.9 The length of the approach OFS is calculated to ensure the surface reaches a height of

150 m (500 ft.). e.g. For approach OFS slope of 4.1 per cent, the length is 500 ft/0.041 = 12 195 ft or 3.7 km. For instrument approaches, the length may need to be extended to reach the applicable OCA/H.

10.3.2.10 Where the final approach track is offset and intersects the extended runway centre line, the

splay on the side closest to the final approach track should be increased by the offset angle. Where the final approach track is offset but does not intersect the extended runway centre line, the splay closest to the final approach track should be increased by an amount equal to the final approach course offset at 1 400 m from the runway threshold.

Offset angle α

α = Offset

α

α Splay increased by

offset “ valueα ?

1 400 m

Min 1 400 m

9

Figure 10-1. Plan view visual segment surface offset final approach with runway centre line

crossing

Adjustment of the inner approach OFS

10.3.2.11 The inner approach OFS is part of the approach OFS. The surface will have the same slope

as the approach OFS. Any adjustment to the slope of the approach OFS will bring about a corresponding

change in the slope of the inner approach OFS. As the length of the inner approach extends to a height of

45 m, any variation to the slope will require adjustment to the length. The length of the inner approach can

be calculated using the following formula:

Length of inner approach = 45 m/slope. For example, an aerodrome with inner approach slope

of 3.33 per cent, the required length is: 45 m/0.0333=1 350 m.

Runway holding position and penetration of the approach OFS

10.3.2.12 The runway holding position can be established at the runway end or at the location prior

to the landing threshold to reduce runway occupancy and increase runway capacity. This position is in

accordance with the dimension stated in Table 3-2 of Annex 14 – Aerodromes, Volume 1 – Aerodrome

Design and Operations. In any case, the following surfaces should not be penetrated:

a) inner approach, inner transitional and balked landing surfaces (OFS):

the inner approach, inner transitional and balked landing surfaces establish airspace for the

protection of aeroplanes during balked landings and late go-arounds against fixed and mobile

objects and

b) obstacle clearance surface:

the OCS are introduced in PANS-OPS (Doc 8168) to deal with penetrations of the visual segment

surface (VSS). Obstacles shall not require the pilot to destabilize the approach to avoid them. For

this purpose, no obstacle shall penetrate an obstacle clearance surface (OCS).

Adjusting obstacle evaluation surfaces

10.3.2.13 The OES selected by the State or the appropriate authority should reflect the type of

operations conducted/planned at the aerodrome. In selecting the OES, the appropriate authority should

consider both existing and planned operations.

10.3.2.14 The appropriate authority can either:

a) modify the OES to suit the existing and planned operational needs of the aerodrome;

b) design an OES specific to the flight procedures conducted at the aerodrome; or

c) declare an OES as an obstacle free surface.

10

Adjustment of the take-off climb surface

10.3.2.15 Aircraft during take-off may have different climb performances and therefore would be

variably affected by an obstacle. At take-off, not all aircraft lift off the runway from the same point nor do

they follow the same climb rates. Hence, an object may be an obstacle for an aircraft with low performances

on take-off but not to another aircraft with higher performance.

10.3.2.16 The slope of the take-off climb surface can be reviewed if the local conditions and the operational characteristics of aeroplanes of ADG IIC, III, IV and V operating at the runway support a slope higher than 2 per cent. Such review should be done in consultation with the aircraft operator as any increase to the slope may impact take-off performances and reduces payload.

10.3.2.17 A balanced approach to the selection of the gradient for the take-off climb surface is

recommended. Local considerations need to be accounted for, as well as aircraft operator’s requirements

for efficient operations.

10.3.2.18 For typical aircraft operations with take-off masses not at maximum, the slope of the

take-off climb surface may be increased to match the slope of the approach OFS in the opposite runway

direction when no significant limitations are to be expected, e.g. for narrow-body aircraft at low elevation

aerodromes with longer runways.

10.3.2.19 In contrast, some aerodromes at higher elevations and/or in hot environments may require

a slope of the take-off climb surface of less than 2.0 per cent.

Modifying horizontal OES

10.3.2.20 In situations where there are no circling or visual circuits, there is no need to establish the

entire extent of horizontal OES. When a circling approach or visual circuit is not allowed on one side of the

runway, the extent of horizontal OES may be reduced in order not to limit new constructions in that area.

10.3.2.21 Often, circling minima are not at the minimum due to the terrain and obstacle environment.

In such cases, the height of the horizontal OES may be raised to match the obstacle clearance altitude (OCA)

of the circling approach, considering the applicable minimum obstacle clearance requirements.

Note 1.— A single or a combination of horizontal OES is to be adopted at aerodromes where there are

circling operations.

Note.2.— It must be ensured that the modification of the horizontal OES will not impact the safety of

visual procedures and aerodrome circuits, nor significantly affect the regularity of other flight procedures

including instrument approach and departures procedures.

11

Figure 10-2. Modifying horizontal OES on a non-circling area

Declaring an OES as a surface that is free of obstacles 10.3.2.22 States or the appropriate authority may decide to declare an OES as a surface that should

be free of obstacles. This may be done to protect the airspace in the vicinity of the aerodrome by restricting growth of obstacles that may undermine future aerodrome needs and flight operations. By not allowing penetration of the OES, it would simplify the process for approving obstacles, reducing the number of aeronautical studies required and reduce the likelihood of the flight procedures being amended.

10.3.2.23 When declaring an OES as a surface that should be maintained free of obstacles,

amendments are necessary to the local zoning laws, aerodrome standards, etc. Specific obstacle evaluation surfaces 10.3.2.24 In cases where existing and/or planned flight procedures cannot be safeguarded by the OES

specified in Annex 14, Volume 1, Chapter 4, specific OES should be established to account for the local flight procedures.

10.3.2.25 Adjustments of the OES or specific OES may be required for, including but not limited to: a) instrument approach procedures based on NDB or radar; b) straight-in instrument approach procedures with low approach minima (OCA/H); c) offset instrument approach procedures, or d) curved instrument approach procedures (RNP AR). 10.3.2.26 While the Annex 14, Volume I, horizontal surface(s) and surface for straight-in instrument

approaches consider most common straight-in instrument approaches, the variety of all possible instrument approaches procedures cannot be addressed.

NO CIRCLING

Obstacle

Obstacle

Obstacle

OES of ADG III

OES of ADG I

OES of ADG II

260° 260°

105°

105°

12 10.3.2.27 Precision approaches as well as straight-in approaches with significant offsets or curved

approaches are not considered for the design of the surface for straight-in instrument approaches. Furthermore, low approach minima may not be fully addressed.

10.3.2.28 For non-precision approaches, approach minima of as low as 120 m (400 ft) may be

achieved. With a minimum obstacle clearance (MOC) of 75 m (250 ft) for the final approach, an obstacle as high as OES in the inner section (45 m or 150 ft) would result in approach minima of 120 m (400 ft). An obstacle as high as the OES in the outer section (60 m or 200 ft) would result in approach minima of 135 m (450 ft). An obstacle beyond the limits of the surfaces as high as 100 m (330 ft) would result in approach minima of 175m (580ft). In case the non-precision approach procedure supports step-down fixes (SDF), the approach minima of 175 m (580 ft) may be lowered to 135 m (450 ft) and to 120 m (400 ft).

10.3.2.29 For required navigation performance (RNP) approach procedures with lateral navigation

(LNAV)/vertical navigation (VNAV) minima or LPV minima (satellite-based augmentation system (SBAS) approach procedure with vertical guidance (APVI)), approach minima of approximately 85 m to 95 m (280 ft to 310 ft) (depending on the aircraft speed category) or 100 m to 110 m (330 ft to 360 ft) may be achieved, depending on the actual approach procedure design as well as altitude and temperature effects, assuming obstacles as high as the surface for non-precision approaches.

10.3.2.30 Low approach minima are considered by means of the Annex 14, Volume I surface for

precision approaches. This surface, however, is based on the basic ILS surfaces and are therefore considered precision approaches (using ILS, microwave landing system (MLS), GBAS, SBAS CAT I) only. For non- precision approach procedures (NPA) and APV with low approach minima (OCA/H), the dimensions of the Annex 14 surface for precision approaches is not sufficient and greater areas need to be considered.

10.3.2.31 The design of specific OES may be aligned with the protection areas specified for the

design of instrument flight procedures. The related criteria are contained in PANS-OPS (Doc 8168) and the Required Navigation Performance Authorization Required (RNP AR) Procedure Design Manual (Doc 9905).

10.3.2.32 Furthermore, specific OES may be established to account for the local visual flight

operations, including specified visual circuit patterns, VFR routes as well as VFR reporting points. Note.— Guidance material for the protection of visual flight operations is contained in the Airport

Services Manual, Part 6 – Control of Obstacles (Doc 9137).

10.3.3 Evaluating hazardous objects

10.3.3.1 Objects located beyond or below the OFS and OES may still be a concern to the safety and regularity of flight operations. These objects, due to their characteristics and purpose, may pose a hazard to air navigation. Such objects include wind turbines, chimneys, skeleton structures, transmission lines and power stations.

10.3.3.2 The orientation of buildings and their façades are known to cause turbulence, glare and

disturbance to CNS equipment. The appropriate authority should work with land planning agencies to manage these hazards for buildings that are in the immediate vicinity of the aerodrome.

10.3.3.3 An aeronautical study should be considered when examining the impact on safety and

regularity of flight operations due to these developments.

13

Note.— Details on the impact and references on possible assessment techniques to evaluate the risks

posed by these objects can be found in the Airport Services Manual, Part 6 – Control of Obstacles (Doc 9137).

Appendix to Chapter 10

AERONAUTICAL STUDY PROCESS

1. Aeronautical study

1.1 To investigate an aeronautical concern arising from the introduction of an obstacle, an aeronautical study is used to evaluate the impact of the obstacle on flight operations and identify possible measures that can mitigate these concerns.

1.2 The process of conducting an aeronautical study should include:

a) data gathering; b) stakeholder engagement and impact assessment; c) identifying mitigations (if applicable); and d) acceptance or rejection.

Note.— A flowchart showing the aeronautical study process is included as an Attachment to this Appendix.

2. Data gathering

2.1 Information collected should include but not be limited to: a) national regulations and procedures (zoning laws, land use policy); b) use of the aerodrome (day/night, IFR/VFR, public/private use, certified/uncertified); c) dimensions of approach lighting system; d) existing and future runway and taxiway characteristics; e) mix of aircraft operating at the aerodrome; f) number of regular flights (commercial air transport); g) procedures specific to the aerodrome; h) flight procedures (existing and future); i) contingency procedures; j) details on existing obstacles and mitigations;

14 k) existing/planned visual navigation aids/electronic navigation aids/surveillance aids/communication

aids etc.; and l) airspace structure and details of nearby aerodromes. Note.— For non-flight operations related aeronautical studies, other information may be required. 2.2 Details of the proposed obstacle or terrain should include but are not limited to: a) location; b) obstacle evaluation; c) classification (e.g., building, crane, tree(s), antenna(s), power lines); d) dimensions as well as height, top elevation including ground elevation; e) frangibility; f) permanence (permanent/temporary); g) presence (fixed/mobile); h) visibility (e.g., marking and lighting); and i) material (as it may interfere with electronic signals). 2.3 Aerodrome details (this list is not exhaustive and may include others): a) ICAO code; b) CNS facilities; c) procedures specific to the aerodrome; d) use of aerodrome (IFR/VFR day/low visibility operations) e) visual aids; f) type of aircraft; g) runway characteristics (number of runways, dimensions, type); h) airspace; i) nearby aerodromes; and j) aerodrome noise zones. 2.4 Affected surfaces:

15

a) surfaces penetrated; and b) extent of penetration. 2.5 Flight operations related to instrument flight procedures (this list is not exhaustive and may

include others): a) instrument approach procedures (initial, intermediate, final and missed approaches as well as visual

segment and circling); b) SIDs (standard instrument departure routes and/or omni-directional departures); c) standard arrival routes (STAR); d) minimum sector altitudes (MSA) and terminal arrival altitudes (TAA); e) holding patterns; f) ATC surveillance minimum altitudes; and g) en route ATS routes. 2.6 Flight operations (visual flight procedures and visual approaches): a) visual departures; b) traffic patterns (standard circuit patterns or other published patterns, incl. patterns for entry and exit

to/from circuit patterns); and c) VFR routes and VFR reporting points.

3. Stakeholder engagement and impact assessment

3.1 The proponent of the aeronautical study can either be an agency of the State, aerodrome operators or by any appropriate authority. In conducting the study, it is critical to have the participation of all relevant stakeholders. The stakeholders should include but are not limited to:

a) the civil aviation authority; b) proponent of the proposed construction/development;

c) the aerodrome operator;

d) air navigation services providers;

e) flight procedure designers;

f) aircraft operators (commercial aviation and the military); and

g) other appropriate authorities (e.g. land use planner, military etc.).

16 Note 1. — The level of stakeholders’ involvement may vary depending on the needs of the study. Note 2. — The design of procedures in accordance with PANS-OPS (Doc 8168) criteria assumes

normal operations. It is the responsibility of the operator to provide contingency procedures for abnormal and emergency operations. It might be necessary to involve aircraft operators in the aeronautical study process.

3.2 There could be a situation where more than one OES is penetrated. Due to different purposes each

OES serves, every surface needs to be evaluated individually to assess its impact. Note.— Explanations on how impact assessments are conducted can be found in the Airport Services

Manual, Part 6 – Control of Obstacles (Doc 9137).

4. Identifying mitigations

Note.— Identifying the mitigating measure and assessing their impact on stakeholders is a key task in

the aeronautical study process. Different measures are required to address OFS and OES penetrations. Certain mitigation measures, while acceptable, may not be desirable due to the penalty it imposes on aerodrome operations.

4.1 The mitigation measure identified should consider the OLS that is/are being penetrated. 4.2 Obstacles penetrating the OFS will impose an adverse effect on the safety of flight operations and

should be removed. Where removal is not practicable, the penetrations are to be mitigated by means of limiting operations at the aerodrome such as designating the runway for departure only or allowing only visual approaches to the runway, before considering other measures. Other measures include, but are not limited to:

a) displacing the threshold; and/or b) raising the glide slope and PAPI angle. 4.3 Obstacles penetrating the OES may have an adverse impact to the safety or accessibility of

intended aircraft operations. Mitigation measures may include, but are not limited to:

a) adjusting flight procedures (e.g., increased minimum obstacle clearance altitudes, increased minimum climb gradients, change of routing);

b) including the obstacles in the relevant ICAO charts; c) promulgating safety information to the users of the aerodrome (particularly concerning the change); d) increasing approach minima (OCA/H); e) increasing minimum climb gradient for departures (Procedure design gradient (PDG)); f) increasing descent gradients; g) increasing flight altitude; h) revising traffic/circuit patterns; i) revising VFR routes and/or reporting points; and j) adjusting/including marking and lighting.

17

4.4 Upon completion of the aeronautical study, it may be necessary to conduct a safety risk

assessment to quantify the risk probability and severity and the acceptability of any proposed mitigation measures in reducing the risk to an acceptable level.

Note. — Provisions on safety risk assessment are stipulated in Chapter 3 of this document and on the Safety Management Manual (Doc 9859).

5. Acceptance

5.1 The study may result in one of the following outcomes where the obstacle is: a) acceptable, because the risk is already mitigated; b) acceptable, only if the risk is mitigated; or

c) not acceptable, because the risk cannot be mitigated. 5.2 The State or the appropriate authority establishes the approval/acceptance criteria to be used in

evaluating the study. The study is to be submitted by the aerodrome operator or an appropriate authority prior to development or installation of the proposed obstacle.

5.3 The State or the appropriate authority should analyse the aeronautical study and verify that: a) appropriate coordination has been performed between the stakeholders; b) aeronautical concerns have been properly investigated and assessed, based on current and future

flight operations and procedures; c) proposed mitigation measures adequately address the impact posed by the obstacle; and d) the subsequent safety risk assessment, when required, has been conducted in accordance with

Chapter 3 of this document and meets the acceptability criteria specified in 3.5.1. Note. — It is preferable to have relevant experts from the State, as required, on the team that conducts

the aeronautical study. On completion of the analysis of the aeronautical study, the State or the appropriate authority:

a) gives formal approval or acceptance of the aeronautical study to the aerodrome operator or an

appropriate authority. If in the study some impacts to flight operations have been underestimated or have not been identified, coordinate with the aerodrome operator or an appropriate authority to reach an agreement on safety acceptance; or

b) if no agreement can be reached, rejects the proposal for possible resubmission by the aerodrome

operator or an appropriate authority; or c) may choose to impose conditional measures to ensure safety and regularity.

18

Attachment to Chapter 10

Aeronautical study flowchart

— END —

No

Yes

Aeronautical study triggered

Data gathering

Impact assessment

Impact?

Identify possible mitigation/s

Acceptance/rejection

End of study