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EUROCONTROL

GUIDANCE MATERIAL FOR

TRANSITION ALTITUDE CHANGE

First Edition

September 2004

EUROCONTROL Guidance Material for Transition Altitude Change

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RECORD OF AMENDMENTS

Version/ Amendment

Number

Date Amended by Comments


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Guidance Material

For Transition Altitude Change

Table of Contents Abbreviations………………………………………………………………… 5 Executive Summary……………………………………………………………. 6

Introduction………………………………………………………………….. 7 Part I - Airspace Design…………………………………………………. 8

1- TA Concept…………………………………………………. 8 2 - ICAO References…………………………………………… 9-11 2- Division Level……………………………………………….. 12 3- SID/STAR…………………………………………………….. 12 4- Holding Areas………………………………………………. 13 5- Sectorization………………………………………………… 14 6- Coordination/Transfer of Control points & Level………14 7- ICAO SARPS Compliance………………………………… 14

Part II - ATM Procedures………………………………………………… 15 1- Selection of QNH Sources……………………………….. 15 2- Access & Display of QNH Data…………………………. 16 3- Communications & Coordination………………………. 17-18 4- Letters of Agreement……………………………………… 19 5- Design, Development & Validation…………………….. 20 6- Flight Information services……………………………… 20 7- Equipment & Software Changes……………………….. 20 8- ICAO Compliance…………………………………………. 21 9- Publication and Distribution…………………………….. 21 10- Monitoring & Review………………………………………. 21 Part III – Safety …………………………………………………………….. 22

1- Safety Assessment………………………………………… 22 2 - Safety Considerations…………………………………….. 22-23


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Part IV - Equipment ……………………………………………………… 24 1- Operations Co-ordination………………………………… 24 Part V- Regulatory………………………………………………………. 25 1- Air Regulations Changes/AIP…………………………… 25 Part VI- Publications…………………………………………………….. 25 1- AIC/Notam Issuance………………………………………………. 25 2- Charts…………………………………………………………25 Part VII- Training…………………………………………………………… 26 1- Analysis, Design and Delivery………………………….. 26


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ABBREVIATIONS

AIC Aeronautical Information Circular AIP Aeronautical Information Publication

AIRAC Aeronautical Information Regulation and Control ANS Air Navigation Services

ANSP Air Navigation Service Provider ATC Air traffic Control ATM Air traffic Management ATS Air Traffic Services CDA Continuous Descent Approach

ECAC European Civil Aviation Conference ESARR EUROCONTROL Safety Regulatory Requirement

FDPS Flight Data Processing System FIC Flight Information centre FIR Flight Information Region FIS Flight Information Service FL Flight Level

hPA HectoPascal ICAO International Civil Aviation Organization

IFR Instrument Flight Rules ISA International Standard Atmosphere LoA Letter of Agreement

Mode C Transponder signal of encoded altitude Notam Notice to Airmen

QFE Atmospheric pressure at aerodrome elevation (or at runway threshold) QNE In the context of the document -Altimeter setting at ISA giving flight level reference QNH Altimeter setting giving altitude above sea level reference

RDPS Radar Data Processing System SARPS Standards and Recommended Practices

SID Standard Instrument Departure STAR Standard Instrument Arrival

TA Transition Altitude TL Transition Level

TMA Terminal Control Area VFR Visual Flight Rules


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Executive Summary

This guidance material was developed to assist airspace and air traffic services planners in implementing contemplated or intended changes to transition altitudes. The desirable result of any review or proposed changes to transition altitudes would be the harmonization of the concept of application as well as the selected altitude. Ideally, this would done by ECAC wide regional agreement. Alternatively, sub-regional agreements on a common transition altitude would be a partial but nevertheless positive step. Since no two changes of this nature are likely to be identical, not all elements in this guidance material will apply in all cases. There are, however, a number of generic factors which need to be considered when implementing TA changes. The intent of this document is to identify those major factors. Others which may be site specific to some ATM environments may also need to be considered. The site specific items and those that are not applicable to the particular circumstance will need to be identified during the planning and review process by those responsible for implementing the change.


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Introduction 1 The Transition Altitude (TA) is an integral part of airspace design and operational

procedures. It therefore follows that a change to the TA may necessitate changes to the airspace structure, the operational ATC procedures used in that airspace and the flight procedures.

2 The degree and complexity of change will be dictated, in part, by the magnitude

of the change of the TA value. An equally, and perhaps larger factor for the ANSP agencies will be a change in the TA application concept. For example, where the application of TA is changed from a runway or aerodrome application to an FIR/airspace wide application, the changes will be more pronounced and numerous to accomplish the transition to the new concept than will be the case for only a change in the altitude. That is not to say that a change in application concept is necessary with a change in the altitude. The two can be made independently if only one change is contemplated. It will be up to the agencies and regulators involved to decide which changes they wish to make based on their analysis and judgment.

3 Where sub-regional groups of States are considering collective changes to TA(s) for operational reasons or harmonization, it is essential for the responsible agencies to coordinate not only the altitude(s) to be implemented but also the concept of applicability. It is therefore self evident that changes in altitude and concept, as may be agreed collectively, would be less disruptive to the overall operating environment and no doubt more economical to implement, in the longer term, if both are done simultaneously rather than in a two step process.

4 It is also important for the involved agencies to not only consider the current

operational environment but also how planned or forecast developments in technology and associated procedures, airspace design, traffic forecasts and regulatory mandates, may affect the future ATM environment.

Again, the economies of a concurrent change of the value and applicability compared to additional future changes will have to be weighed as an integral part of the process.


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PART I AIRSPACE DESIGN

1- Transition Altitude Concept 1.1 The first parameter planners must decide is what type of TA structure is to be

implemented since that decision will influence a number of subsequent factors.

1.2 There are a number of TA concepts in use within ECAC airspace. In some jurisdictions the TA is based on the individual runway elevation resulting in a number of TAs for the same airport. Other TAs are structured based on the surrounding airport and approach areas elevation; some are applied in individual TMA areas, others are common to all TMAs in a given FIR or State, some in all controlled airspace and yet others are applied in all State airspace.

The selection of a particular structure may have been based on the particular needs at the time of implementation or various interpretations of the applicable ICAO provisions.

1.3 Clearly, the runway based concept for TA is falling into disuse. Some are still

retaining it but a number of States that formerly used it have changed to either the aerodrome or TMA concept of applicability or to airspace wide application. The latter seems to be gaining more acceptance.

1.4 There are two distinct advantages to the airspace- wide application of TAs. The

first is the harmonized application for all flights regardless of location or type (VFR/IFR) and the second is added flexibility for adaptation of future route flexibility.

1.5 Regardless of the concept contemplated, planners involved should carefully

weigh all the factors in their proposed change and consider the impact on the neighbouring airspace through coordination and consultation with all adjacent jurisdictions and with the user community.

1.6 The ICAO references for TA selection are noted below.

Importantly, it should be kept in mind in the decision process that the ICAO provisions are published for global application and consequently are aimed at the lowest common denominator in terms of the minimum facilities required for their application. Accordingly, areas such as the ECAC States where numerous and advanced ANS facilities are available should be more easily adaptable to regional agreements on the applicability and selection of TAs.


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PANS – OPS, Doc 8168, Part VI, Chapter I

1.1.2 Transition Altitude 1.1.2.1 A transition altitude shall normally be specified for each aerodrome by the

State in which the aerodrome is located. 1.1.2.1.1 Where two or more closely spaced aerodromes are so located as to require

co-ordinated procedures, a common transition altitude shall be established. This common transition altitude shall be the highest of the transition altitudes that would result for the aerodromes if separately considered.

1.1.2.1.2 As far as possible a common transition altitude should be established:

a) for groups of aerodromes of a State or all aerodromes of that state; b) on the basis of an agreement, for aerodromes of adjacent States, States

of the same flight information region, of two or more adjacent flight information regions or one ICAO region; and

c) for aerodromes of two or more ICAO regions when agreement can be obtained between these regions.

1.1.2.1.3 The height above the aerodrome of the transition altitude shall be as low as

possible but normally not less than 900 m (3000 ft). 1.1.2.1.4 The calculated height of the transition altitude shall be rounded up to the next

full 300 m (1000 ft). 1.1.2.2 Notwithstanding the provisions of 1.1.2.1 a transition altitude may be

established for a specific area, when so determined on the basis of regional air navigation agreements. (emphasis not in original text)

1.1.2.3 Transition altitudes shall be published in aeronautical information publications

and shown on the appropriate charts.


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ICAO Air Traffic Services Planning Manual - Doc 9426

Part II, Section 5, Chapter 1

Altimeter Setting Procedures

1.1 INTRODUCTION

1.1.1 Altimeter setting procedures are contained in the Procedures for Air Navigation Services - Aircraft Operations (Doc 8168, Volume I) and the Regional Supplementary Procedures (Doc 7030). These documents should be used by States when specifying their altimeter setting procedures including the establishment of minimum flight levels, transition altitudes and methods for the determination of transition levels.

1.1.2 The basic method used in providing adequate vertical separation between aircraft and adequate terrain clearance during all phases of flight is based on a number of basic principles. Those principles are outlined below:

a) during flight, when at or below a fixed altitude (called the transition altitude), an aircraft is flown at altitudes determined with the aid of an altimeter set to sea level pressure (QNH) and its vertical position is expressed in terms of altitude;

b) during flight above the transition altitude an aircraft is flown along surfaces of constant atmospheric pressure based on an altimeter setting of 1013.2 hPa (1013.2 mb). Throughout this phase of flight, the vertical position of an aircraft is expressed in terms of flight levels. Where no transition altitude has been established for the area, aircraft in the en-route phase shall be flown at a flight level;

c) when climbing, the change in reference from altitude to flight levels is made at

the transition altitude and when descending the change from flight level to altitude is made at the transition level;

d) during any phase of a flight adequate terrain clearance may be maintained in any of several ways, depending upon the facilities available in a particular area. The recommended methods in the order of preference are:

1) the use of current QNH reports from an adequate network of QNH reporting stations;

2) the use of such QNH reports as are available, combined with other meteorological information such as forecast lowest mean sea level pressure for the route or portions thereof;

3) where relevant current information is not available, the use of the lowest altitude values of flight levels which have been derived from climatological data;

e) during the approach to land, terrain clearance may be determined by using

the QNH altimeter setting (giving altitude) or, under specified circumstances a QFE setting (giving the height above the point to which the QFE is related, e.g. the runway threshold).


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1.1.3 The method provides sufficient flexibility to permit variation in detailed procedures which may be required to account for local conditions, without deviating from the basic procedures.

1.2 ESTABLISHMENT OF THE TRANSITION ALTITUDE

1.2.1 The basic principles for the establishment of the transition altitude are contained in Doc 8168, Volume I, Part VI. Preferably a common transition altitude should be established for groups of aerodromes, aerodromes in adjacent States or for a specified area when so determined on the basis of a regional air navigation agreement.

1.2.2 The selection of a transition altitude will be governed by the following factors: a) the amount of traffic operating in the lower airspace; b) the types and performance categories of aircraft; c) the ratio of level flights to those climbing and descending in the same

airspace; d) the terrain configuration; e) the departure and arrival procedures including noise abatement procedures;

f) variation in the route distances involved and thus variation in cruising levels required;

g) the rate of change in barometric pressures and the range of fluctuations along air traffic services (ATS) routes within certain areas;

h) the infrastructure for the provision of area QNH; and i) the existence of other aerodromes in the vicinity.


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2- Division Level 2.1 It is not imperative that a TA should be coincident, or nearly so, with a particular

division level but it would be desirable, if possible, since it adds an element of harmonization.

2.2 There are a number of division levels in use within ECAC airspace. Some States

have upper/lower airspace division levels set at FLs 285, 245, 195, 185. Airspace classification levels within ECAC now have been accepted at FL195 for Class C and FL 95 is the favoured lower division level for this airspace. There are also various divisions established for TMA cap levels.

It is unlikely that such current higher levels will be selected as a TA but any division level which exists within a particular jurisdiction, or a closely related altitude, should at least be reviewed and considered as a potential candidate for a TA by planners as long as it is meets the objective, is operationally suitable and complies with the ICAO provisions.

3- SID/STAR 3.1 Standard Instrument Departures (SID) are designated instrument flight rules (IFR)

departure routes linking the aerodrome or a specified runway of the aerodrome with a specified significant point, normally on a designated ATS route, at which the en-route phase of flight commences. They are published in graphic and textual form for most airports. They provide a standard predictable profile, normally including a vertical element, for departing aircraft to follow thus reducing the workload for both the controllers and pilots of suitably equipped aircraft.

SIDs will normally be composed of two segments:

a) an initial segment from the departure end of the runway to the position where the aircraft will first turn from the initial departure heading and

b) a second segment, either via radar vectors or by pilot navigation, from the first turning point to the SID termination point.

3.2 SID procedures may be used by ATC to provide segregation from other departure or arrival profiles for the same or adjacent airports or segregation from adjacent airspace. Noise abatement procedures are usually included in the SID. The vertical element of a SID does, in many cases, consist of a stop altitude or one or more step altitudes designed to provide the required obstruction clearances and/or ATC traffic management requirements.

To avoid the potential for error or level bust induced by a change of vertical reference and adjustment as well as reducing pilot workload during the work intensive departure phase, it is generally accepted that SID step and stop levels should be at an altitude and not a flight level. Most new SIDs now conform to this concept or have been modified accordingly. A minority still consist of a mixture of vertical reference requiring minimum altitudes to be observed, on some segments of the route, which are above the transition altitude.


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3.3 The implementation of continuous descent approaches (CDAs) for improved environmental sensitivity in the future may be more problematic for aerodromes with a low TA because such flight profiles may introduce a greater mix of flight level/altitude during approaches.

3.4 Likewise, a Standard Instrument Arrival (STAR) is an IFR arrival route linking a significant point, normally on an ATS route, with a point from which a published instrument approach procedure can be commenced.

These published procedures also normally contain a vertical profile by specifying levels to be observed at significant points along that route. As with SIDs these may be for adequate obstacle clearance and/or for ATC considerations.

Similarly to SIDs, most STARs are now designed so that the vertical reference is in altitudes from the initial approach fix inbound. A minority still do not conform to this norm requiring pilot conversions of flight levels to altitudes to ensure adequate obstacle clearance when the atmospheric pressure is lower than ISA.

3.5 Planners should therefore consider all these factors carefully in their selection of TAs so that, ideally, the vertical reference remains constant during the procedure to the greatest degree possible.

4. Holding Areas 4.1 Designated holding areas or fixes are normally used for traffic metering and may

also be used for other purposes such as awaiting weather improvement. Aircraft may receive a clearance to hold at an altitude or a flight level depending on the need.

Any change in TA should consider holding levels normally used. For safety reasons planners should avoid situations which would entail a mix of aircraft holding at a designated fix at both flight levels and altitudes. Transition from one vertical reference to another while stepping down in a holding stack should also be avoided for the same reason.

4.2 Environmental concerns will also be a more prominent element for planners to consider if holding area minimum altitudes need to be raised for that reason, which may in turn affect the choice of TA.


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5. Sectorization 5.1 Sectorization of airspace is commonly used for managing controller workload;

because of communications limitations, the segregation of general types of flight operations e.g. terminal and en-route, or for sovereignty or jurisdiction of airspace boundaries.

5.2 The sector boundaries may be geographical or vertical or combinations thereof.

Although a change in TA will not normally necessitate a change in sectorization it is nevertheless a consideration which planners should review, particularly where national or jurisdiction boundaries are involved. Obviously, changes of vertical reference within the same sector add a measure of complexity, both for pilots and controllers, which should be minimized or avoided where feasible.

6. Co-ordination Points 6.1 Intra and inter unit co-ordination/transfer of control points and the corresponding

level allocation will need to be reviewed if a TA is changed to ensure that they are still operationally valid. Depending on the magnitude of the change in the TA, the level reference of these designated points may need to be changed from a flight level to an altitude or adjusted to best suit the circumstance.

6.2 A significant change to a TA on one side of a national boundary could negate the practicality of previous transfer points.

7. ICAO SARPS Compliance 7.1 All airspace design changes contemplated and the corresponding ATC and flight

operations procedures must be vetted by the involved planners to ensure compliance with applicable ICAO SARPS.


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PART II ATM PROCEDURES

1. Selection of QNH Sources 1.1 As noted in the ICAO ATS Planning Manual reference in Part 1 of this document,

the recommended method for flights to maintain adequate terrain clearance is by “the use of current QNH reports from an adequate network of QNH reporting stations”.

The issue of terrain clearance is of course prominent in the choice of a TA, whether aerodrome/TMA based or applied over a wide area. The latter application of a TA does introduce the need for more QNH data availability than a localized TA and more so if the selected TA is in the middle altitude range (10,000 ft) or higher since the higher the TA the more ATC sectors and traffic will be involved. QNH data will need to be available for delivery to all aircraft needing it in all airspace below the transition level.

1.2 There are several methods already in place for the selection of QNH data. Some jurisdictions have divided the airspace into areas within which one specific QNH source is used for aircraft flying within that defined area which require a QNH altimeter setting. Some use the lowest QNH from a number of sites within an FIR as an area QNH.1 Other jurisdictions mandate that a QNH source closest to the route of flight is used. The latter has been accepted by most jurisdictions that use the area wide TA concept.

1.3 Planners must first determine what sources of QNH data are available within the airspace under review. As is the case in most of the ECAC area there are numerous sources available. From these it is recommended that planners chose those which are available on a 24 hr basis, whenever possible, in order to assure constant availability of the same sources.

Sites should be selected so as to provide enough data for the intended airspace coverage. It is generally accepted in some jurisdictions that use an area wide TA (e.g. Australia, Canada, U.S. and others) that enough sources of QNH are selected to provide data from a source for approximately each 100nm diameter block of airspace for en-route operations. The normal rate of pressure change from one sector to another in most areas is not large enough to affect vertical separation. Any minor variations in QNH within the 100nm distance will, in all but exceptional cases, result in minor altitude variations which are still well within the 300 ft ICAO Mode C tolerance or the lower 200 ft State tolerance where applied.

ATC Procedures for QNH delivery to aircraft need to include consideration for exceptional circumstances when steep pressure gradients occur and therefore more frequent QNH updates along a given route of flight across such gradients may be needed.

Local QNH should of course continue to be used for arrival/departure operations.

1 This method may not provide a true altitude indication except within an acceptable distance from the source but, by using the lowest QNH, does provide a safety margin for terrain clearance.


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1.4 Once the QNH sources have been determined, each en-route ATC sector should be allocated a primary source and one alternate source within the 100nm parameter.

Depending on the sector size, one source may serve several. This serves the dual purpose of fewer QNH updates and reduced communications. Allocating the same QNH sources to adjacent sectors also eliminates any concerns which might arise regarding what altimeter setting is being used by aircraft entering the sector.

1.5 The selected TA concept proposed and the altitude selected will determine to what degree planners need to examine the QNH issue. If a local/TMA based TA concept is being retained or proposed, en-route QNH is not an issue. If the TA concept is being changed to an area/airspace wide concept, the planners should carefully study the issue to determine the best selection and allocation of QNH sources to suit their particular need.

2. Access and Display of QNH Data 2.1 There are various methods in use to display QNH data to controllers. These may

range from simple hand written entries updated from the meteorological services data available, to sophisticated electronic displays with automatic updates.

One principle which should be observed is to keep the method as simple as possible to meet the operational requirement in order to minimize search and access time for controllers. Accepted human factors elements should be observed.

Among many other sources, ICAO Doc 9758-AN/966, Human Factors Guidelines for ATM Systems, Chapter 4 Attachment provides some information.

2.2 The requirement will of course vary depending on the TA concept adopted. For en-route sectors, the QNH data presented to the controller should be limited to the dedicated sector source, the alternate one and the source(s) for the adjacent sectors, where those differ.

The data should be prominently displayed and readily accessible to the controller to limit search and access time.

2.3 Since an ICAO requirement already exists2 an adequate system may already be in place but planners should nevertheless review the issue to ensure any impact a proposed change in TA may have is adequately considered.

2 PANS-ATM Doc 4444,Chapter 4, 4.10.4.2 Flight information centres and ACCs shall have available for transmission to aircraft on request an appropriate number of QNH reports for forecast pressures for FIRs and control areas for which they are responsible, and for those adjacent.


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3. Communications and Co-ordination 3.1 The nature and degree of change proposed for TAs will dictate what changes need

to be planned and implemented. For example, the change proposal might involve en-route controllers who may have had no practical experience or particular training on providing en-route QNH as part of the normal sector duties.

Although it may seem somewhat simplistic and redundant, planners should nevertheless ensure that the procedures developed for the change include this new element for such controllers.

The phraseologies for transmission and read-back requirements are contained in ICAO PANS-ATM Doc 4444, Chapter 12; ICAO Manual of Radio Telephony, Doc 9432 and ICAO PANS–OPS Doc 8168.

3.2 Existing transfer of communications and control procedures should not be affected by a change of TA except for the additional element of the altimeter setting where the new TA will involve en-route ATC. Where this is the case, planners need to decide who will issue such altimeter settings to pilots and when.

One option is to issue a QNH altimeter setting update (for en-route aircraft transiting at or below the TA) to such aircraft on initial contact. Another is to issue the QNH for the next sector in conjunction with the transfer of communications to that sector. Some jurisdictions have rules which dictate that an altimeter setting must be issued once in each sector. This last procedure may be necessary where sectors are relatively large e.g. 100 nm or more. This would be redundant in small sectors where the pressure differential from one to another would be very small in all but exceptional circumstances and therefore would not exceed the vertical Mode C tolerance. For reference, a pressure differential of approximately 7 hPA results in a 200 ft variation.

Planners should review the airspace in detail and determine the minimum QNH update requirements for en-route flights (if the proposed TA will affect such flights) in order to avoid needless duplication of effort and minimize the associated communications.

For example, where one QNH setting is determined to be sufficient for a group of sectors, planners may want to assign the QNH delivery to only a specific sector or distribute this task as best suits their airspace environment.


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3.3 Planners also need to consider contingencies for when steep pressure gradients occur within the airspace. In such circumstances the QNH will require more frequent updates over time and/or distance. ICAO Annex 33 recommends a new QNH issue when an agreed magnitude of change occurs. Planners should refer to their State meteorological authorities to determine what parameters exist, if any. Where none are stated, planners should implement a method to alert controllers to rapid changes of pressure and consequent actions required of controllers. Some electronic sensing and display systems already have such features to alert controllers of pressure drops/increases at set parameters. Others may be adaptable to the inclusion of this feature.

As a basic principle the trigger parameters should be selected so that the vertical Mode C tolerance (300 ft or 200ft depending on the State) is not exceeded.

3.4 QFE settings do not involve en-route controllers regardless of the TA selected since its use is restricted to the approach and landing phases of flight. Nor should any changes be necessary to QNH delivery procedures by local controllers (tower or approach) for arriving and departing flights.

3.5 In the case where the accepted or proposed TA concept is airspace wide the selected QNH sources for en-route use must be co-ordinated with flight information services so that both ATC and FIS personnel use a common base for a given airspace.

3 4.11.2 Recommendation.- For local air traffic services units QNH and, if required, QFE should be kept current by routine issues, supplemented by the issue of new data whenever changes occur which exceed an agreed magnitude.


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4. Letters of Agreement 4.1 When a proposed TA change will have an impact on adjacent units, the procedures

adopted must be co-ordinated between the affected units and included in letters of agreement (LoA).

4.2 Where LoAs already exist, new procedural agreements regarding when and how QNH related actions will take place and who will initiate them must be included. These can be included in the appropriate Annex to the common format LoA in use by EUROCONTROL member States or in whatever format is otherwise agreed.

ICAO Air Traffic Services Planning Manual, Part II, Section 1, Chapter 2 provides guidance for co-ordination.

4.3 The most problematic issue to resolve is where adjoining States have selected different TA concepts or where selected TAs vary significantly.

At boundaries where the TA is significantly different from one State to another, (e.g. 3000 ft in one and 10000 in the other or one State applies an airspace concept and the other only a local aerodrome TA) an agreed method must be implemented to ensure vertical separation will not be compromised for transiting flights. Loss of vertical separation could occur between aircraft operating on significantly different altimeter settings.

4.4 There are a number of methods which can be used to resolve such potential conflicts:

1- If the airspace is within adequate radar coverage the transition of altimeter settings QNE4/QNH and the resultant vertical adjustments may be accomplished under radar monitoring or radar vectors if required.

The degree of vertical change will of course vary depending on the pressure differential.

This method may be feasible for normally low traffic areas but too work intensive in others since it requires close monitoring, co-ordination and possible tactical intervention by controllers.

2- Segregated or uni-directional routes may be established across boundaries of TA structures to facilitate the vertical transition on these routes or segments thereof.

This method may be overly complex and costly to implement and could also be work intensive to apply.

3- Where the TA difference is minimal it may be acceptable and operationally feasible to sterilize one or more flight level(s)/altitude(s) for a segment across the boundary. This may be unduly restrictive and may also be impractical where few available levels exist.

4- A transition area may be designated within which transition to/from flight level/altitude may be made. This naturally is best handled within only one side of the boundary so that co-ordination and communications can be minimized. Such a concept requires the willingness of one jurisdiction to accept the associated workload.

4 In the context of the document, the terms QNE/QNH/QFE are used for expediency to indicate various altimeter settings.


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4.5 Planners first need to analyze the level of activity across the transition zones before deciding on which method best suits their situation. Whichever method(s) is selected and agreed upon must be clearly defined in the applicable agreement.

The issue of VFR traffic across these zones also needs to be addressed to determine if there is a need for any State regulatory involvement.

4.6 Where regional agreements are being considered, common procedures should be negotiated and co-ordinated as part of any change proposal and any State differences which cannot be resolved should be clearly identified.

5. Design, Development and Validation 5.1 As for all ATM procedures, development should follow established processes to

ensure that the end result is well conceptualized and operationally robust.

The first step is to ensure the operational requirements are well defined so that the procedures can clearly address them.

Draft procedures should be reviewed by appropriate experts contributing to their refinement. All stakeholders should be consulted and given the opportunity for review and comment.

An important part of the development is the validation process intended as a means of ensuring that the procedure can meet the operational requirement with agreed levels of safety. This can be done through simulation studies, as judged to be needed, and the application of safety assessment methodologies.

If considered necessary, a controlled and limited trial application may be considered as a further validation tool.

6. Flight Information Services 6.1 All new procedures derived from a change of TA must be co-ordinated with the

FIS element to ensure that any new concepts are understood and uniformly applied, particularly the allocation of en-route QNH sources if applicable.

Where FIS facilities are used for pre-flight briefings this also provides an opportunity for a structured pilot awareness program to be put in place if changes are substantial enough to warrant such action. Self briefing terminals could also be used for this purpose.

7. Equipment and Software Changes 7.1 Significant changes to the TA may well require changes to data access and

display equipment. Airspace and procedures planners should therefore co-ordinate their efforts with their colleagues responsible for equipment acquisition or modification to ensure that they understand the operational requirements and have the means to deliver the desired outcome. Equipment readiness will also affect the timing and cost of implementations plans.

7.2 The main system normally requiring modification because of a change in TA is the Radar Data Processing System (RDPS) which provides the controller with the automated vertical data. The QNH inputs to the RDPS used for the conversion of Mode C data (always transmitted based on ISA) to altitude needs to be compatible with the QHN sources selected for sector delivery.

Where the RDPS and the Flight Data Processing System (FDPS) are highly integrated the latter may also require corollary modifications.


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8. ICAO Compliance 8.1 Throughout the planning process for a TA change and associated changes to

procedures methods and systems, adherence to ICAO provisions or as amended by State authorities should be confirmed.

Where regional or sub-regional TA agreements are considered, planners should bear in mind that not all States may have identical requirements.

9. Publication and Distribution of Procedures 9.1 Normal processes should be used for the publication and distribution of new or

amended procedures. One essential factor for planners is to ensure that all the co-ordination required with the internal and external stakeholders has been done in preparation for implementing the change.

Obviously, the greater the change of the area of applicability in the case of regional or sub-regional area, the more co-ordination channels will be needed and these should be tracked during the planning process so as not to overlook any.

9.2 The selection of an implementation date for the change(s) needs to be co-ordinated with AIS requirements and in parallel with any required training activities.

9.3 Controller certification and briefings as may be required for new procedures also need to be documented in accordance with unit or State policies.

10. Monitoring and Review 10.1 As with all new or amended ATM procedure implementation, operations

management should have a monitoring and review process in place to ensure that the expectations have been achieved and that there are no undesirable effects.

Any problems that do arise from the new procedure should be fully analysed and the procedure amended accordingly.


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PART III

SAFETY

1. Safety Assessment 1.1 For EUROCONTROL member States the process for safety assessment is

governed by the Eurocontrol Safety Regulatory Requirement (ESARR).

ESARR 4 concerns the use of risk assessment and mitigation, including hazard identification, in Air Traffic management when introducing and/or planning changes to the ATM system. This requirement applies to all providers of ATM services in respect to those parts of the ATM/CNS System and supporting services for which they have managerial control. As such, any change proposal to a TA will need to undergo this process.

1.2 ESARR 6 governs safety requirements for software in ATM.

1.3 In addition to, or in lieu of the above, States may have supplementary requirements governing safety assessment. Planners should therefore research the issue thoroughly.

1.4 The depth and effort this process requires will of course depend on the nature and magnitude of the change proposed. No changes should be contemplated unless, and until, the risk assessment and mitigation concludes that acceptable safety levels can be met.

1.5 All documentation of the risk assessment process(s) should be permanently retained as confirmation that the mandated process has been conducted.

2. Safety Considerations 2.1 EUROCONTROL commissioned two studies on TAs; “Common European

Transition Altitude – A flight Deck Perspective” and “Common European Transition Altitude – An ATC Perspective” published in Sept 2002.

These studies detail some of the safety issues which should be considered in the selection and implementation of a TA. Planners should avail themselves of these documents, as well as others referred to therein, which they may find useful in their analysis.

2.2 It is accepted, without exception, that standardization of procedures is a proven method of reducing the risk of error and therefore the potential for accidents. To that end, standard operating procedures on the flight deck are an essential element. The multiplicity of TAs currently in use within ECAC airspace is an impediment to standardization and therefore increases the potential for latent errors which can develop into unsafe situations.


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2.3 Flight crews who operate on inter-state route segments, or intra-state routes where TAs are aerodrome or TMA based, must constantly adjust their altimetry related procedures and altitude awareness processes to adapt to the TA in each different airspace environment. This is clearly a risk which airspace planners can reduce by harmonizing TA structures over as wide an airspace area as possible, by striving for regional or sub-regional TA agreements.

2.4 The overriding safety consideration in the selection of the TA is of course the surrounding terrain/obstacle clearance requirements.

Obstacle elevations are charted as altitude above MSL. Flight crews must therefore ensure that the appropriate minimum safe altitudes are met when operating at the flight level mode by determining the corresponding true altitude which is dependant on the surrounding QNH. The flight crew is always responsible for terrain/obstacle clearance except when being radar vectored. It is therefore incumbent on the flight crew to constantly be aware of the minimum safe altitude and do the necessary altitude conversions necessary. Such potential for errors in conversion or errors of omission are always present.

Planners should in all cases select TAs which are above all terrain/obstacle altitudes over a wide area around the aerodrome or, preferably, over all airspace for which they are responsible, or as may be agreed for a regional or sub-regional area.

2.5 TAs which are lower than some surrounding terrain/obstacle altitudes are clearly to be avoided.


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PART IV EQUIPMENT

1. Operations Co-ordination

1.1 Planners should consult with the appropriate technical experts once their operational requirements have been clearly defined. Of particular importance will be the selection of the QNH sources which have been determined for ATC operations as noted in PART II, 1 above.

It may be significant that the same or compatible sources be used for the automatic altitude conversion used in the RDPS. Of equal consideration is the co-ordination with other units or States whose radar sources form part of a mosaic system. The degree of co-ordination needed will naturally vary with the nature and magnitude of the change proposal.

1.2 Where TA changes involve several States or units, dedicated contacts should be nominated and established for this purpose.

1.3 Planners should develop a checklist for each operational requirement which denotes all the equipment involved so that the technical experts can determine all the equipment acquisitions or modifications necessary to meet those requirements. From this, they should develop a plan which will then form an integral part of the overall project plan, timelines and cost estimation.

1.4 Documentation of equipment changes should be retained in unit records as

directed by the appropriate authority. 1.5 Where equipment changes or modifications are required to implement a multi

unit or multi State group proposal, these should be referenced in letters of agreement to avoid any initial or subsequent misunderstandings or incompatible system capabilities.

1.6 All relative equipment changes or modifications made should then be

incorporated in the publication of new or amended ATC operational procedures or annexed thereto for information.


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PART V

REGULATORY

1. Air Regulations/AIP 1.1 Depending on the legal or institutional structure of the State, changes to the TA

may require a change to State regulations. Planners must review all applicable regulatory provisions to ensure that none are infringed by the change proposal. They should also be aware that such changes, where they involve national legislation, may entail a lengthy time period and factor this in their project plan.

1.2 State AIPs, (normally Section En-Route 1.7 but may differ) refer to altimeter

setting procedures, TAs and TLs. Any change proposal will therefore require a change to this publication to be approved by the State national aviation authority by whatever process is in place for that State.

Planners who intend such changes should present a detailed documentation substantiating the proposal and will normally need to include documented evidence that the required safety assessment has been done.

1.3 To avoid wasted effort and resources it is important for planners to secure the

legal approvals, at least in principle, at a very early stage and to keep the designated authorities informed.

Planners should also note the Aeronautical Information Regulation and Control (AIRAC) cycle which governs the timing of such changes to publications and plan implementations dates accordingly. This information is referred at ICAO Annex 15 Chapter 6.

PART VI

PUBLICATIONS 1. AIC/Notam 1.1 ICAO Annex 15, Aeronautical Information Services contains the standards and

recommended practices for the publication of aeronautical information. For major change proposals, planners may consider the issuance of an

Aeronautical Information Circular (AIC) to announce the intended changes well in advance of their final publication in an AIP amendment.

As a further measure for the safety net, consideration should also be given to the

issuance of a brief Notam of appropriate duration twenty four hours prior to the implementation of the change taking effect as a final reminder to flight planners and pilots. Planners may consider including a concise message on ATIS for a determinate period as another safety reminder for pilots when the TA changes affect flight operations.


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2. Aeronautical Charts 2.1 The standard processes and procedures for the publication of aeronautical charts

which are in place should be observed diligently. Planners should be keenly aware of the time requirements to effect such changes as may be required. These may be relatively simple for a local TA but much more complex and time consuming if the change involves a national or multi state group change of TA structure. The appropriate sources and personnel responsible for design and publication should be informed well in advance of the anticipated implementation.

PART VII

TRAINING

1. Analysis, Design and Delivery 1.1 The first step in the development of a training plan is to conduct a thorough

training needs analysis. This will identify the knowledge gap and this information will then be used by training personnel to develop the specific program to fill that gap. It can be reasonably expected that most experienced controllers will already be familiar with the subject. There may be some, however, who’s specialized ATC training and work experience has not afforded much exposure.

. 1.2 The design and validation of the training should follow the accepted training

practices and policies. Any new procedures developed for the proposed TA change will also need to be addressed as part of the planned training. Training specialist should therefore work closely with their procedures counterparts so as to fully understand the objectives.

1.3 It is an accepted best practice that any training should be delivered as closely as

possible to the time when the new information needs to be used. For this reason planners need to co-ordinate the project timing closely with the training element.

Training needs will vary depending on the controller population and the magnitude of the change.

1.4 Documentation of the training and any associated personnel certification should

be retained in accordance with unit or agency policies.

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