53RD ANNUAL CONFERENCE, Gran Canaria, Spain, 5-9 May 2014
WP No. 93
Harmonised Transition Altitude
Presented by TOC
The harmonisation of transition altitude is a subject, which has already been discussed for a long time. More and more stakeholders and several new technologies are demanding a harmonised and raised transition altitude. The realization however is difficult, due to conflicting interests, sometimes out-dated ICAO provisions and a lack of clear image of the costs versus the benefits.
1.1. One of the provisions written by ICAO in the 1950’s was to set a transition altitude (TA) as low as possible (but not below 3000ft AAL).
1.2. With the beginning of ATC in the United States, the transition altitude was decided to be set at 18 000ft. Nowadays, a TA at or above 10,000ft is not only in use in the US and Canada, but also in states like Australia (10,000ft), New Zealand (11,000ft), Japan (14,000ft), Papua New Guinea (20,000ft), Philippines (11,000ft), Nepal (13,500ft) and Kuwait (13,000ft).
1.3. In Europe a wide variety of TAs is used. The area in which a certain QNH is used also differs. Some countries have several QNH regions, others use the QNH from the nearest large aerodrome till traffic is clear of conflicts to switch to a local QNH. QNH areas per TMA or even per runway are, although to a lesser extent, also used.
1.3.1. Since programs like Single European Sky are calling for a harmonised Air Traffic Management system, the need for a Harmonised European Transition Altitude (HETA) has increased.
1.4. On the 12th Air Navigation Conference (held in November 2012, Montréal) IFALPA – who strongly advocates a harmonised TA of 18000ft – presented a paper on the subject. IFATCA presented a second paper to support IFALPA on harmonisation according IFATCA policies.
1.4.1. In the paper States were invited to give full support to harmonisation of transition altitudes with the ultimate goal of obtaining a global transition altitude to create standard operating procedures and enhance safety.
1.4.2. The discussion on a harmonised European transition altitude started again but the European Member States could not come to an agreement. Eurocontrol is doing further research on the subject.
1.5. This paper gives an overview of the current situation and the biggest issues on implementing a harmonised transition altitude.
2.1 The harmonisation of transition altitude is a subject which has been globally discussed since a long time.
The rise in traffic and the advent of jet aircraft in the late 1950’s caused ICAO to come up with a policy on, for example, transition altitudes. At that time there were several reasons for this principle. One of the main reasons was the lack of air navigation service facilities. Some centres did not have the facilities to provide current pressure information to en route traffic. Therefore provisions such as the use of the standard QNH setting of 1013.25 hPa and a transition altitude were adopted worldwide, providing a common reference for vertical separation during the flight.
ICAO Doc 8168, Procedures for Air Navigation Services – Aircraft Operations, Volume I – Flight Procedures:
2.1.2 Transition altitude
188.8.131.52 A transition altitude shall normally be specified for each aerodrome by the State in which the aerodrome is located.
184.108.40.206 Where two or more closely spaced aerodromes are located so that coordinated procedures are required, a common transition altitude shall be established. This common transition altitude shall be the highest that would be required if the aerodromes were considered separately.
220.127.116.11 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:
1) aerodromes of adjacent States;
2) States of the same flight information region; and
3) States 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.
18.104.22.168 The height above the aerodrome of the transition altitude shall be as low as possible but normally not less than 900 m (3 000 ft).
22.214.171.124 Despite the provisions in 2.1.2, “Transition altitude”, a transition altitude may be established for a specified area on the basis of regional air navigation agreements.
2.1.2 With the introduction of high-performance aircraft, the ATC operational environment changed significantly. The performance characteristics of modern aircraft are completely different and result in the requirement to change altimeter settings during phases of flight were the flight crew workload is at its highest.
2.2.1 In order to determine the cockpit workload a survey was conducted by Eurocontrol. During the survey a limited number (10) of flights was monitored. All actions of the captain and co-pilot were registered. Similar actions were divided in groups and a weight was allocated to each specific group of actions. Afterwards the total weight of each group was calculated per altitude band (2000ft each). A mean value was calculated for the flights during climb and descent. These values, in relation to the altitude bands, were plotted in the graphics below.
126.96.36.199 It is important to note that actions were registered instead of workload. In order to reach a complete workload overview other functions, such as mental actions, should be added. The overall quantity of actions for departure is lower than for arrival because of the preparation prior to a departure.
Below 10 000ft (or FL100 where applicable) most companies apply the “sterile cockpit” concept where only primary tasks (flying the aircraft, communication with ATC and doing the appropriate checklists) are performed. After passing 10 000ft (in climb), less critical actions, so called “associated actions” (such as turning off the seat belt sign and filling out the Operational Flight Plan Copy) are being performed. In descent these associated actions are performed between 10 000 and 8 000ft, causing a higher action quantity in the graphics.
Because the associated actions are all grouped actions, the actual workload is – though action quantity is higher – not as high as in the sterile cockpit phase. The research concluded a change in transition altitude would most preferably be above 10 000ft, so the critical actions in the sterile cockpit-phase are free from any interference. This would reduce the risk of pilots omitting to change the altimeter setting, which would result in increased safety.
2.2.2 Several researches on level busts have been performed to identify whether or not altimeter-setting procedures have been a contributing factor.
188.8.131.52 Between 1998 and 1999 the UK CAA conducted a study (CAP710 “On the level”) to:
“identify, monitor and analyse common causal and circumstantial factors for level busts in the UK and to make appropriate recommendations for safety improvements”. The research concluded that almost two-thirds of the erroneous altimeter settings involved aircraft climbing to a flight level with QNH still set and recommended: “the transition altitude should be raised to a significantly higher value (e.g. 18,000ft) and ultimately this should be common throughout Europe”.
184.108.40.206 In 2004 Eurocontrol published the European Action Plan for Level Bust, which recommended adopting best practices (such as Standard Operating Procedures) to reduce the chance of level busts. According to the action plan a future consideration should be to consider the establishment of a common European transition altitude.
220.127.116.11 A European State did the same detailed analysis and reported that almost 13% of the level busts in the years 2007-2009 were related to altimeter setting errors. The main cause of the 163 level busts was the pilot forgetting to change the altimeter setting at transition altitude. Thirty-six of these level busts were classified as a Safety Significant Event, often resulting in a loss of separation.
18.104.22.168 Around 2010 the ‘Feasibilty Study for Transition Altitude Change in Northern Europe’ was published. Finland, Norway and Sweden carried out a detailed analysis of safety occurrences and found that in the period of 2006 to 2008 a total of 61 incidents involving altimeter settings occurred. Thirty-five of these altitude deviations involved a failure to adjust the altimeter settings to standard QNH after departure, while twenty-six deviations were listed in the approach phase.
2.2.3 In 2011 Eurocontrol launched the Harmonised European Transition Altitude Task Force (HETA TF), which was initially tasked to develop a Preliminary Impact Assessment. The results were published in December 2011. After the 12th Air Navigation Conference the HETA TF was tasked to perform a costs-benefit analysis of which the results are expected around May 2014.
2.3.1 IFALPA strongly supports the introduction of a common TA at or above 10 000ft. The IFALPA policy below relates to the applicable ICAO PAN-OPS, Volume I, Part VI, Chapter 1, Basic requirements:
IFALPA is in agreement with the evident underlying intent throughout section 1.1.2 to eventually establish common transition altitudes over wide areas of the world. However, IFALPA also finds that the language of many of the subsections of 1.1.2 has an effect counter to the underlying intent, in that it supports the wide diversity of transition altitudes around the world. This diversity is operationally unsatisfactory for IFALPA as it gives rise to serious flight operational problems and even airmisses.
IFALPA also believes that the ICAO provision in para. 22.214.171.124, stating that the transition altitude shall be as low as possible, is obsolete. It increases workload in a critical phase of flight and fails to reflect the performance and navigational capabilities of current aircraft.
IFALPA recommends the establishment of a common transition altitude within each State and, where possible, within each ICAO region. Given that standardisation is an essential goal in itself and having regard to the basic requirement to apply the standard altimeter setting of 1013,2 hPa in the maximum possible airspace, a standard transition altitude must, of necessity, take account of the appropriate terrain configuration, availability of reliable area QNH, character of air traffic and performance characteristic of modern aircraft. To reduce diversity and introduce a rational system that respects of the performance and modes of operation of present aircraft equipment, the choice of transition altitudes should be limited to 10.000 or 18.000 feet.
IFALPA recommends the following revision to Section 1.1.2 as indicated below.
126.96.36.199 Each State shall specify a single common transition altitude for the airspace over which the State exercises jurisdiction.
188.8.131.52.2 The height of the transition altitude shall be above the minimum safe altitude, taking into account cold temperatures.
184.108.40.206.3 The common transition altitude shall be either 10,000 feet (3,050 metres), or 18,000 feet (5,490 metres).
220.127.116.11.4 The height of the transition altitude shall be above all altitudes in the approach procedures within the area concerned.
2.3.2 At the ICAO ANC 2012 IFALPA presented a working paper regarding the Harmonised Transition Altitude in the ECAC airspace. The European States were encouraged to implement a harmonised transition altitude of 18 000ft. IFALPA considers this to be a major step towards globally harmonised procedures.
2.4.1 Following IFALPAs paper, IFATCA presented a second working paper at the ANC2012 encouraging both European and other States to implement a harmonised transition altitude. Standardised and harmonised procedures are seen as a key enabler for future ATM procedures and postponing the introduction may have adverse effects on future developments like SESAR and NextGen.
18.104.22.168 Furthermore IFATCA stated that synchronization of a common implementation date, workload issues, best practice and impact on capacity should be taken into account when determining a common transition altitude.
IFATCA emphasized that harmonization should be considered as one of the factors in determining what is meant by “as low as possible” als stated in ICAO PANS-OPS volume 1, paragraph 22.214.171.124 .
2.4.2 IFATCA Policy is:
|Standardisation of Transition Altitudes on a region wide basis be implemented where applicable.
WP 35, Nairobi, 1987.
126.96.36.199 TOC considers the current IFATCA policy to still be valid.
2.4.3 In recent studies, several options (see 2.10.2) to raise the European transition altitude have been discussed. In TOCs opinion the option to raise the transition altitude to any altitude at or above 10’000ft, but only by defining common criteria and without specifying a fixed altitude may again result in various different Transition Altitudes from country to country and is a highly unwanted, intermediate, solution.
2.5 In the TMA
2.5.1 In an environment where both a transition altitude and a transition level are used, a level is lost when the QNH is lower than the standard setting, regardless of the height of the transition altitude. However, such loss has a bigger impact in a TMA environment at low altitudes. Consequently, a higher transition altitude might result in capacity improvement in the TMA.
188.8.131.52 In high pressure, FL080 and 7000ft can both be used while separation is guaranteed. However, at low pressure FL080 might not provide enough separation from 7000ft. In extreme case (a QNH lower than 979hPa) even 2 levels could be lost in the transition layer to provide the necessary separation.
2.5.2 The published SIDs and STARs were developed to take advantage of the capabilities of advanced airborne navigation systems. They provide a predictable track and allow a more efficient use of terminal airspace and ATC capacity by reducing communications and streamlining flight profiles.
184.108.40.206 The SIDs and STARs usually contain vertical constraints to be observed along the route. These may be due to obstacle clearance, ATC considerations or any other reason. Most of the SIDs and STARs are designated so that the vertical reference is in altitude instead of flight levels. The change of altitude reference to flight level reference during either procedure introduces complexity at a point where workload in the cockpit is very high, which could induce errors.
220.127.116.11 Cold temperatures could lead to a correction on the lowest available flight level in mountainous terrain. In this case 1000ft or 2000ft has to be added to the published SIDs and STARs. If the transition altitude is above a SID or STAR, the problem of confusion and possible safety issues about these corrections could be solved.
2.5.3 In case of a missed approach a low transition altitude could, in combination with the high workload in the cockpit, lead to potential errors and separation loss.
18.104.22.168 In April 2007 the Norwegian Accident Investigation Board (Statens Havarikommisjon for Transport) published their report on an incident, which happened after a missed approach (Report SL2007/16). The aircraft performing a missed approach procedure was cleared to FL080 but instead climbed to 8 000ft on the aerodrome QNH. Because of this, the separation to an aircraft holding was reduced to less than half of the applicable minimum. The board recommended that:
“From a flight operational point of view, a standardised transition altitude for an as large as possible geographical area is desired.”
22.214.171.124 A similar incident happened in the United Kingdom in October 2013. Strong winds forced several aircraft into missed approach procedures after which they had to be vectored back to the holding fixes. An aircraft failed to change back from the low QNH into the standard 1013.2hPa, which made him cause a levelbust leaving only 100ft separation within 4NM from other traffic.
2.5.4 The implementation of continuous descent approaches (CDAs), continuous climb operations (CCOs), Performance Based Navigation (PBN) and merge-tools could be more problematic for aerodromes with a low transition altitude.
126.96.36.199 Continuous descent arrivals were developed to save fuel and reduce noise during the arrival phase of the fight. The on-board FMS is programmed to fly an optimised descent profile while the engines stay idle. Ideally, CDAs should be commenced as high as possible but this may not be feasible due to ATC constraints. To optimize the CDA, the use of one vertical reference during the procedure is advised. Therefore, it is preferable to have the QNH value set at the start of the continuous descent.
In practice this would mean that controllers vector from top-of-descent to the transition altitude to establish separation with other traffic. After the transition altitude has been passed there should be no ATC interference to maintain the optimised profile. Logically, a high transition altitude would enable a longer continuous descent and therefore be more effective.
188.8.131.52 ICAO Doc 9931 (Continuous Descent Operations (CDO) Manual) sets some additional requirements in case a CDO starts above the transition level and recommends that transition altitudes should be established as high as possible. ICAO Doc 9931, Continuous Descent Operations (CDO) Manual
2.2.4 Transition altitude-transition level
184.108.40.206 If a CDO starts above the transition level (TL), a buffer should be established by the procedure designer and added to the minimum levels along the path. This buffer will be calculated based upon the aerodrome historical pressure altitude range. The implications of TL for local CDO design should be collaboratively agreed and reviewed in the light of experience.
220.127.116.11 In order to optimize CDO performance, it is recommended that transition altitudes (TA) be established as high as possible, e.g. 10 000ft or higher.
2.5.5 During the Air Navigation Conference in 2012 the Committee recognized that the implementation of performance-based navigation (PBN) routes could have significant efficiency benefits on flight operations in the en-route environment. They recommended that:
“…states fully assess the operational, safety, performance and cost implications of a harmonization of transition altitude and, if the benefits are proven to be appropriate, undertake further action on a national and (sub)regional basis a first step towards a globally harmonized transition altitude…”
2.6 Holding situations
2.6.1 With any change in the transition altitudes, the holding levels normally used should be considered.
18.104.22.168 In states where the transition altitude is at such an altitude that it is in the middle of a holding, a mix of flightlevels and altitudes are used in a holding. Depending on the current pressure, the lowest available altitude is being calculated and it’s determined which flight levels above the transition level are available for holding. In the United States both altitudes and flight levels are used in one holding stack.
22.214.171.124 With the implementation of a transition altitude at 18 000ft in the United Kingdom, the transition would also be in the middle of a holding stack. The UK is planning to use a similar system; all levels currently available would be used, except for those, which fall within the new transition layer.
2.7 Terrain clearance
2.7.1 In airspace where transition altitudes have been established sufficiently high enough to assure adequate clearance from all possible obstacle conflicts, flying at the minimum flight level on the standard altimeter setting does not impose any safety risk. However, lower transition altitudes require specific procedures for mountainous areas.
126.96.36.199 Altimeters are subject to a number of systemic errors, which require correction factors to be applied to determine terrain clearance. These errors could lead to significant differences between the indicated- and actual altitude when flying at a flight level in an area of low pressure. For example a combination of the pressure error, mountain waves and low temperature could lead to an error up to 2000ft (A common European transition altitude – An ATC perspective” – Euroncontrol, 2002). The altimeter corrections can be complex and time-consuming which could lead to either loss of vertical separation or loss of pilot awareness resulting in a collision with terrain.
2.7.2 According to ICAO Annex 2 (chapter 5, 5.1.2):
“an IFR flight shall be flown over high terrain or in mountainous areas, at a level which is at least 600m (2 000ft) above the highest obstacle located within 8km of the estimated position of the aircraft”.
188.8.131.52 The Mont Blanc (or Monte Bianco) in the Alps is the highest obstacle in the ECAC (European Civil Aviation Conference) area. The mountain is 15 781ft high, so to comply to annex 2 it had to be overflown at at least 17 781ft.
This issue could be resolved for the ECAC region by raising the transition altitude to a minimum of 18 000ft.
184.108.40.206 A transition altitude of 18 000ft does not solve the problem with all the mountains globally. For example Mt. McKinley in Alaska. Alaska has a transition altitude at 18000ft but Mt. McKinley is 20 237ft. Because the terrain has to be overflown at least 2 000ft above, the lowest useable flight level in the area round the mountain is FL230, when the QNH is above 29.92inHg (1013.2hPa). This is adjusted accordingly when the QNH is below standard.
2.7.3 An issue to be resolved is how to handle large pressure gradients over short distances, particularly in mountainous areas. For instance during the “foehn” (A foehn wind is a type of dry, warm, down-slope wind that occurs in the downwind side of a mountain range. It causes a rapid change of temperature and pressure. Regionally these winds can be known by different names) weather phenomenon over the Alps, regular differences of 10hPa over 70NM can be observed, with a record of 25hPa and over 100kts wind in November 1982. This is a concern for both terrain clearance (1hPa equals 27ft and 80kts winds require a 812ft altimeter error adjustment) and separation between north and southbound traffic flying at altitudes (aircraft could possibly be on different QNH settings). Acceptable tolerances, operational procedures and definition of QNH regions will need better guidance material than is available today.
2.8.1 Raising the transition altitude requires a simplified structure of QNH regions. Ideally a QNH region would be as big as possible and, if necessary, without regards of a national boundary. ICAO does not set any requirements for the establishment of QNH regions, and at the moment different methods are being applied to determine the QNH in regions where the transition altitude is above 10 000ft.
220.127.116.11 Australia is divided into several smaller QNH regions (or Area QNH Zones – AQZ), which causes some sectors to have up to 15 different QNH-values. Each controller has a map at the console on which the latest QNH-values (calculated and updated every 3 hours) are displayed.
The AQZ are divided, and if necessary subdivided, to make sure that the area QNH forecasts are within 5hPa of the actual QNH at any low-level point (below 1000ft AMSL) within or on the boundary of the appropriate area during the period of validity of the forecasts. Also the area QNH must not differ from adjoining Area QNH by more than 5 hPa.
18.104.22.168 The United States has no specific QNH regions. Each sector has several QNH reporting stations, and aircraft are issued either the QNH for the destination aerodrome (if an arrival in that sector) or the one nearest to the aircraft route of flight through the sector. In the case of aircraft who will pass in close proximity to one another with minimum vertical separation, the controller would ensure each aircraft uses the same QNH. The QNH is issues to aircraft below the transition altitude on initial call, and to other aircraft when issuing a descent clearance below the transition altitude. A Mode C variance greater than 300 feet from the assigned flight level requires the controller to reissue the QNH and request the pilot to verify altitude.
In extreme cases, when the barometric pressure is greater than 31.00inHg (1049.7hPa) and the aircraft is below 18000ft, the altimeter should be set at 31.00inHg until reaching the final approach segment. This way the maximum thickness of the transition layer is limited. The local QNH is still mentioned in the initial call.
22.214.171.124 Canada is divided into an Altimeter Setting Region (ASR) and a Standard Pressure Region (SPR). During flight in the ASR the altimeter shall be set to the current altimeter setting of the nearest station along the route of flight or, where such stations are separated more than 150NM, the nearest station to the route of flight. In the SPR the switch from aerodrome altimeter settings to standard pressure will be made immediately prior to reaching the flight level at which the flight is conducted. Aircraft flying from one region to another shall, unless otherwise authorized by ATC, make the change in the altimeter setting while within the SPR prior to entering, or after leaving, the ASR.
2.8.2 An issue to be considered in the determination of AQZ and sectorization is the vertical separation between aircraft. A 5hPa difference in QNH equals a 135ft altitude difference. According to ICAO doc4444 the mode C read out can be ±300ft, or ±200ft in RVSM airspace, to be considered accurate. In Australia a 5hPa difference is considered to be safe, the US applies the ICAO standard of 300ft. Furthermore the maximum altimetry system error allowed is 245ft below fl290, the Minimum Aircraft System Performance Specifications allow a maximum error of 80ft within RVSM airspace.
A maximum deviation, which is considered to be acceptable, needs to be determined per country or region.
2.9.1 The implementation of a harmonised or raised transition altitude will also affect systems and procedures, and will require modification of the aeronautical charts on both controllers and flight deck side. Several of the possible effects are listed below.
126.96.36.199 A change of transition altitude and/or QNH regions might cause a need for some system adjustments in the Human Machine Interface. Systems need to be able to handle several QNHs at the same time. Furthermore there needs to be a clear designation of the difference between flights on flightlevels and on altitudes, for example by a level menu or pop-up windows.
Proper tools need to be available for controllers to determine the applicable QNH and, for example, the lowest useable flightlevel in a holding situation or a mountainous terrain.
188.8.131.52 Since most area controllers are not or no longer used to working in a sector with a transition level, proper training is needed. A raise of the transition altitude will move some workload from the approach controller to the area controller, but should never lead to an unacceptable increase of workload.
184.108.40.206.1 The report of the “Initial Real-Time Simulation, in support of the implementation feasibility assessment of a European common Transition Altitude”, carried out in Riga, Latvia, in March 2003, concluded that “The simulation outcome indicated that there were some workload implications for ATS providers as the TA is raised but that such workload should be manageable with sound planning”.
220.127.116.11.2 In 2009 the Netherlands published a study on the safety, efficiency and environmental effects of a raised transition altitude. The results stated that the effects on workload are expected to be limited for Area Controllers once providing the QNH and having a mix of aircraft at altitudes and flightlevels has become routine.
2.9.2 Due to the extent of the changes and the international aspect, a harmonised TA needs to be implemented by all participating states at the same time and a step- by-step implementation needs to be avoided. A step-by-step implementation brings on significant issues related to boundary issues, which should be considered carefully.
2.9.3 Although several stakeholders and political organisations desire the harmonisation of the transition altitude, the implementation should never be hasted without considering all the consequences. Safety must always be guaranteed during the transition.
2.10.1 Within Europe the harmonisation of the transition altitude has been discussed since the end of the 90’s. In 2002 the Airspace and Navigation Team (ANT) tasked Eurocontrols ATM Procedures Development Sub Group (APDSG) to investigate the possibility to establish a ‘common transition altitude’. They published two studies to subscribe the need of a common European transition altitude, however in practice this appeared to be impossible due to major differences. In 2007 the ANT decided, after a long period of discussion, three possibilities for harmonisation should be considered:
1) National harmonisation of procedures
2) Sub-regional harmonisation of the transition altitude
3) a harmonised transition altitude in the entire ECAC area
2.10.2 In 2011 Eurocontrol finished the Preliminary Impact Assessment (PIA) to help policy-makers identify if, and to what extent, EU regulatory action is required. They evaluated three options:
- Option 1; Do nothing (no Regulatory Intervention)
- Option 2; Implementing Rule to implement a HETA at 18,000ft
- Option 3; Implementing Rule prescribing the common criteria for the determination of the TA at or above 10,000ft
18.104.22.168 Although the evaluation resulted in really close scores, there appeared to be a small preference for an ‘Implementing Rule prescribing common criteria for the determination of the ‘TA at or Above 10,000ft’. Following this PIA, the Eurocontrol Harmonised European Transition Altitude Task Force, is performing a costs-benefit analysis.
2.10.3 The Netherlands
22.214.171.124 In 2009 Air Traffic Control the Netherlands presented the ‘Concept of Operations, Raise of transition altitude’. Goal of the study was to determine the most optimal transition altitude for the Dutch ATM system in order to benefit developments like P-RNAV, CDAs, the Multi Airport System (Multi Airport System; “…the set of significant airports that serve commercial transport in a metropolitan region, without regard to ownership or political control of individual airports.” de Neufville & Odoni, 2003) and a raised interception of the ILS. The altitude chosen also had to be realistic and feasible for the use on a European level. Three basic principles were determined and used in the study:
1) The current 4 basic altitudes used for the separation to and from Schiphol airport have to be flown at QNH or Standard Pressure
2) Altitudes which are in use as the boundary of a sector or as a fixed altitude in a departure- or approach procedure should not be within the transition layer
3) Traffic switching between QNE and QNH need to be handled by the same controller
Furthermore, provisions from the Human Factor and the systems perspective were determined. Taking all these provisions into account, the study concluded that if harmonisation of the transition altitude with the surrounding countries were possible, a transition altitude at or above 15 000ft would be most feasible. Due to the fact that no harmonisation could be established at the time, no further actions to raise the transition altitude were taken.
126.96.36.199 The UK/Ireland FAB (Functional Airspace Block) is committed to implement a common 18000ft transition altitude. They will ensure that appropriate interface procedures are in place with neighbouring States regardless of whether they change at the same time or not.
188.8.131.52 QNH regions in the new UK design will be as large as possible to have as few changes as possible and to decrease RTF workload. The QNH used will be from a large regional aerodrome and will be calculated every half hour. Special weather updates will be ignored.
2.10.5 After the Twelfth Air Navigation Conference the Asia/Pacific Seamless ATM Planning Group (APSAPG) inserted the ANC 5/1 recommendation in the Asia/Pacific Seamless ATM Plan. This plan is used as a regional planning in order to define goals and means of meeting State planning objectives.
184.108.40.206 In the APSAPG/4 meeting in June 2013, the Islamic Republic of Pakistan presented a paper on the determination of transition altitudes. They stressed the fact that, while a harmonised transition altitude should be established according to ICAO Doc8168, the significant differences in the aerodrome elevations in the country make it impossible to also meet the provisions in the ICAO PANS-OPS to establish the transition altitude as low as possible.
220.127.116.11 Apart from the implementation in the ATM Plan, no further tangible actions were agreed on.
2.10.6 Most military organizations don’t have any direct advantage of the raise or harmonisation of the transition altitude. However, several organisations have already indicated that they are willing to adjust, if necessary.
3.1 Raising and harmonising the transition altitudes can be beneficial to safety in mountainous terrain. Furthermore a harmonised transition altitude can have a positive safety impact on cockpit operations. It could help to reduce the risk of level busts by the introduction of Standard Operating Procedures.
3.2 An increasing number of stakeholders and regions are demanding a raised and harmonised transition altitude. A final decision, without interim solutions, is strongly desired.
3.3 A harmonised transition altitude needs to be implemented by all participating states at the same time; a step-by-step implementation needs to be avoided.
3.4 TOC considers the current IFATCA policy to still be valid.
3.5 Workload, best practice and capacity impact should be taken into account when determining a transition altitude. Safety must always be guaranteed during the transition to raised and/or harmonised transition altitude.
It is recommended that;
4.1 This paper is accepted as information material.
Doc 4444 – ICAO.
Doc 8168 Aircraft Operations – ICAO.
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IFALPA Annex 9.
AIP America – Federal Aviation Administration.
JO7110.65 Air Traffic Control – Federal Aviation Administration.
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Towards a common Transition Altitude, a flight deck perspective – Eurocontrol, 2002.
Report of the Initial Real-Time Simulation, Riga – Eurocontrol and ANS centre, 2003.
European Action Plan for Level Busts – Eurocontrol, July 2004.
Guidance material for transition altitude change – Eurocontrol, September 2004.
Towards a common Transition Altitude- Instrument Pilot, journal of PPL/IR Europe. no.42, March/April 2004.
Workhop on Aviation Operational Measures for Fuel and Emissions Reductions – September 2006.
European Air Traffic Management-principles, practices and research – Dr. Andrew Cook, 2007.
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Concept of Operations Raise of transition altitude – Air Traffic Control the Netherlands, 2009.
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A-NPA 2012-01 – EASA, 2012.
ANC12 Report of the Committee to the conference on agenda item 5 – ICAO, 2012.
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Asia/Pacific Seamless ATM Plan – APSAPG, June 2013.
HETA CBA workshop – September 2013, Eurocontrol, Brussels.
Feasibility study for transition altitude change in Northern Europe.
Presentation Continuous Descent Arrivals – James Brooke (PARTNER), ICAO.
VFR Guide – Australia.
Article “Foehn wind” – Wikipedia.
Working group ‘Transition Altitude UK’.
Dutch Ministry of Infrastructure & Environment.
Last Update: October 1, 2020