Summary

Over the past few years, TOC came to the conclusion that the TPM was in need of a significant overhaul in order to ensure consistency throughout the manual and with ICAO. Every year, several slight changes are made to individual policies, but there is a need to look at the entire TPM in a holistic way.

Introduction

1.1. The Technical Professional Manual (TPM) requires continuous updates due to changes in technology and the Federation’s needs. The Advanced Avionics Systems (AAS) section is especially prone to changing times and advancements.  Several policies require amendments ranging from minor ICAO phraseology adoption to major overhauls.

Discussion

2.1. The AAS section of the manual requires a series of updates to reflect changing technology, ICAO publications, and overall clarity. The changes range from minor grammar to suggested full policy reviews.

2.2. AAS 1.2 – Automatic Dependent Surveillance (ADS).

2.2.1. The existing policy fails to address major developments such as ADS-B and ADS-C. There are other issues that need to be addressed such as whether ICAO risk analysis is within the IFATCA spectrum, the use of a non-ICAO definition of ADS, among others. This policy requires some amendments to achieve some immediate repairs. Additionally, it is recommended to add this policy to a future working programme for a full policy review.

2.2.2. In the first paragraph, the phrase “control team” is utilized, in an effort to harmonize the policy with ICAO documents it is proposed to change this phrase to “ATCOs”. The revised policy would read:

2.2.3. The second section of the policy was added in 1995 to reflect the current surveillance and technology available at that time. Shortly thereafter (in 1998) ICAO published the Manual on Airspace Planning Methodology for the Determination of Separation Minima which states:

1.11 The introduction of ADS into the procedural ATC environment offers the potential for more frequent position updates as well as information on the future intent of the aircraft. In an ADS environment where position reports are communicated directly from the aircraft to ATC, and where ATC is automatically kept up to date on the intentions of the aircraft, significant reductions in separation minima should be possible. The extent of separation reductions need to be determined by either collision risk modelling or the other techniques detailed in the methodology in this manual.

Document 9689 – First Edition

As there is existing ICAO text regarding the matter it is proposed to delete this section of the policy from the TPM:

2.2.4. The third paragraph of policy requires rephrasing for both strength and harmonization, revised wording would read as follows:

2.2.5. In the sixth paragraph of the policy, the utilization of the phrase “radar surveillance” is changed to read simply “surveillance”. When something is being monitored the radar is only one method of surveillance, therefore not needed in the phrasing:

2.2.6. The final line of the policy features the definition of ADS. Being that this section contains only a definition it should be moved to the Acronym and Terms section of the TPM:

2.2.7. In addition to the proposed edits, this policy needs a more in-depth analysis and update. To accomplish this, it is proposed to add this policy to the TOC working programme for a full policy review.

2.3. AAS 1.3 – Mode S Development.

2.3.1. One minor modification that needs to happen in terms of housekeeping within the second paragraph is moving the final line which defines Flight ID to the Acronyms and Terms section of the TPM. The amended paragraph would read as follows:

2.3.2. In the current policy, the last paragraph urges the IFATCA Executive Board to take action. Tasking the IFATCA Executive Board with an action in policy does not seem the most effective way to initiate change. This is a matter that is undertaken on an ongoing basis by our representative and member of the Surveillance Panel at ICAO. Therefore, it is suggested this section of policy is deleted from the manual:

2.4. AAS 1.4 – Required Navigation Performance (RNP) and Area Navigation (RNAV).

2.4.1. The policy as it stands is very wordy and can use some modification to aid in clarity.

2.4.2. The first paragraph of the current policy currently states:

Controllers should be presented with information, by any suitable means, concerning navigational capability of aircraft under their control.

This issue is presented as a blanket issue, whereas it is only applicable in some scenarios, the words “when necessary” should be added:

2.4.3. The opening and closing of the second paragraph restate the same thing “airspace where dynamic and flexible ATS routes are permitted”. The indication in the opening would be that within the described airspace the two listed conditions be met. Therefore, it is suggested to rewrite the paragraph in a bullet point format as follows:

2.4.4. The opening line of the 5th paragraph states that IFATCA should ensure the controllers’ input, but that is not IFATCA’s role; the ANSP or MA should be the one to ensure this input. The remainder of the changes would be small grammatical ones, and the revised policy would read as follows:

2.5. AAS 1.5 – Air-Ground Datalink.

2.5.1. This policy requires many small edits throughout as well as a few more significant modifications. The bulk of this paper originated in the mid 1990’s; since that time the application and perspective of Datalink use has had some shift and update accordingly.

2.5.2. The opening line of the policy appears to have a word omitted which makes the sentence unreadable. The sentence is missing the word “shall”; which would amend the policy to read:

2.5.3. The second paragraph of the policy has a similar issue of modifications for clarity and readability. The opening wording would have “That” removed and the word “are” would be replaced with “should be”. Revised wording of the Policy would state:

2.5.4. The third paragraph of the policy requires an edit much as the previous. The revised policy would alter the word “are” to shall be to better harmonize and clarify intent, thus the new policy would read:

2.5.5. In the original paper there is very limited information to back up the policy below. Within the policy itself the first line states that voice communications be maintained in all circumstances. Since the dual modes of communications would remain in place the necessity for an alerting device is redundant and thus this section of the policy should be removed:

2.5.6. In order continue harmonization with ICAO documents the word “must” is replaced by the word “shall” in the following paragraph:

2.5.7. Within the originating paper the following policy was generated. The paper states that in the event of an aircraft shifting to standby power they would still need to be able to access their Datalink capabilities. It seems to neglect the ability of a flight crew, even one which had been previously communicating via Datalink to revert to voice communications. Further this policy delves into being able to regulate aircraft equipage, which is outside the scope of IFATCA. As such, it is suggested this paragraph is removed:

2.5.8. A quite simple edit is needed for clarity within the policy segment below, following Datalink the word “is” was utilized but “shall” would allow for added strength and harmonization:

2.6. AAS 1.6 – Datalink Applications – The Use of Logical Acknowledgement (LACK).

2.6.1. This Policy was generated in 2001 and may need some updating and clarification. In 2018 it was suggested that this policy may need an update as well within the Future of CPDLC paper.

2.6.2. At the time this policy was created prevailing thoughts were that ATN would be the primary system of the future leaving FANS behind; this did not happen. Seeing as both FANS and ATN are accepted systems of CPDLC provision currently there is a need to update to policy to reflect this.

2.6.3. For aircraft utilizing ATN, per the current policy, there is policy within ICAO Document 10037 detailing some of how LACK is utilized.

B.2.1.5 Lack timer

Logical acknowledgement (LACK) messages (downlink message element DM 100 and uplink message element UM227) are used in ATN B1-based ACL and ACM message exchanges.

Document 10037

2.6.4. FANS aircraft do not possess a LACK timer, but that does not mean that there is not method to determine that messages are received in a timely manner. Ground timers, which per Document 10037, have a requirement of 120 seconds to be set or to alert the controller of the deficiency.

B.2.2.4.1 Controller-initiated dialogue

B.2.2.4.1.1 When the controller sends a CPDLC message, requiring an operational response, the ground system starts the ground-timer tts which value is set at 120 seconds.

a) When this timer expires (i.e. non receipt of operational closure response within tts, the controller is notified and reverts to voice to resolve the situation (refer to B.2.2.1).

Note 1.— ATN B1 aircraft systems also have implemented an aircraft-timer ttr, which is set at 100 seconds. In normal circumstances, the aircraft-timer ttr expires before the ground-timer tts expires and, consequently, follows the procedure indicated in B.2.2.4.1.

Note 2.— FANS 1/A aircraft do not have ttr timer.

b) The dialogue is closed locally by the ground system, ensuring that the dialogue does not remain open at the ground side.

Document 10037

2.6.5. One additional factor to consider is that ACARS features the ability for ATS units to receive message assurance (MAS).

1.2.1.1.4 While there are no technical provisions to indicate to the ATS unit that an uplink message is available for display to the flight crew, the ACARS network allows the ATS unit to receive a message assurance (MAS) indicating that an uplink message has been delivered to the aircraft, as shown in Figure 1-3.

Note.— It is possible that after successful delivery of an uplink message to the aircraft, the delivery of the associated MAS success response to the ATS unit fails. Therefore, non reception of a MAS success response by the ATS unit is not necessarily a confirmation that the uplink was not delivered to the aircraft.

Document 10037

2.6.6. Moving forward, the existing policy must be altered to include not only ATN but FANS as well as it seems they will be running concurrently for the foreseeable future. The concepts at the heart of the policy still have some valuable aspects to retain – such as the use of timers and importance of knowing the data received is timely. Goals with the update of the policy include more general terms as opposed to specific technologies which can become rapidly outdated as equipment becomes obsolete.

2.6.7. It is suggested revised IFATCA policy is:

2.7. AAS 1.7 – Display of GNSS Status to ATC.

2.7.1. The second paragraph of the policy needs a minor change. All of the adjustments within this policy can be found in the last three words. “Must” requires a change to “shall” to continue ICAO harmonization. The final words ”should be declared” should be changed to “shall be activated”. The difference is that a procedure is implemented when it becomes valid. In this case the procedure is already in place and implemented. Changing to an alternative is therefore not an implementation, but rather an activation. This is why the new wording is proposed. The new policy would read:

2.8. AAS 1.8 – 4D Trajectory Concepts/Management.

2.8.1. This policy originated in 2008 and was amended during the 2017 conference whilst remaining provisional policy. The revised wording of the policy makes more sense because only airspace utilizing 4D trajectory would be required to be designed to accommodate it. This concept remains strong and valid. It is therefore proposed the existing policy be promoted from provisional to permanent. The introductory paragraph is an excerpt from the working paper when the policy was voted in. It is no longer relevant and should be deleted.

2.9. AAS 1.9 – Removal of Ground Based Aids.

2.9.1. The paper which the policy originates from dates back to 1999. Since this time there has been a great deal of improvement in navigation. In recent year there has been decreasing utilization of the terrestrial based NAVAIDs, especially with increased use of RNAV and RNP. The availability of the NAVAIDs allows for an extra layer of protection in atypical operations such as solar flares. The following section is from the Global Air Navigation Plan 2016-2030:

Future terrestrial infrastructure requirements The GANP has the objective of a future harmonized global navigation capability based on area navigation (RNAV) and performance-based navigation (PBN) supported by the global navigation satellite system (GNSS).

The optimistic planning that was considered at the time of the Eleventh Air Navigation Conference for all aircraft to be equipped with GNSS capability and for other GNSS constellations to be available, together with dual frequency and multi-constellation avionics capability being carried by aircraft have not been realized.

The current single frequency GNSS capability provides the most accurate source of positioning that is available on a global basis. With suitable augmentation as standardized within Annexes, single frequency GNSS has the capability to support all phases of flight. The current GNSS has an extremely high availability, although it does not have adequate resilience to a number of vulnerabilities, most notably radio frequency interference and solar events causing ionospheric disturbances.

Until a solution to this adequate resilience problem is available, it is essential that a terrestrial navigation infrastructure, suitably dimensioned to be capable of maintaining safety and continuity of aircraft operations, be provided.

ICAO GANP 2016-2030

2.9.2. Several concerns still remain in the matter including the concept of “failsafe procedures” as a whole in this concept. Issues still persist such as vulnerabilities from within the systems and from external impacts, such as solar flares and space weather, which must be considered.

2.9.3. There are several edits that need to be made. The first is changing the first word “Until” to “Unless”. This reflects the necessity and the gravity of the failsafe procedures. The next alteration is the replacement of “have been proven and installed” to “are in place”, not all projects need to be installed and while the end is a requirement the means to compliance are not specific:

2.10. AAS 1.11 – “Fly By” and “Fly Over” Waypoints.

2.10.1. Since the creation of this paper in 2011 there have been updates to the PANS-ATM, notably the 8th change to the 2016 edition, which states:

5.4.1.1.4 Where a route flown by an aircraft involves a specified turn which will result in the minimum lateral separation being infringed, another type of separation or another minimum shall be established prior to the aircraft commencing the turn (see Figures 5-1 and 5-2).

Note 1.— For flyover waypoints aircraft are required to first fly over the waypoint before executing the turn. After the turn the aircraft may either navigate to join the route immediately after the turn or navigate to the next defined waypoint before re-joining the route. This will require additional lateral separation on the overflown side of the turn (refer to Figure 5-1).

Note 2.— An aircraft may commence a fly-by turn up to 37 km (20 NM) prior to the turn waypoint, and fly a path displaced from that waypoint by as much as 16.7 km (9.0 NM). The defined radius for the fixed radius transition (FRT) turn dictates how early the aircraft starts the turn and the displacement from the waypoint. Fly-by and FRT turns, therefore, have the possibility of affecting a restricted area or another route on the inside of the turn. For instrument flight procedures, the radius arc to a fix (RF) path terminator will provide consistent turn performance (refer to Figures 5-1 and 5-2). Further details on this issue can be found in the Manual on the Use of Performance-based Navigation (PBN) in Airspace Design (Doc 9992).

Note 3.— An example of a prescribed lateral separation minima based on a specific navigation performance can be found in 5.4.1.2.1.6.

An aircraft will calculate a turn radius and angle of bank (AOB) subject to performance characteristics, airspeed, altitude, angle of turn and wind conditions. The aircraft determine to initiate the turn, prior to the waypoint, based on the calculated radius — this may be up to 20 NM before the waypoint. There will be a variation in the paths because each aircraft calculates its own turn radius (indicated by the grey area in the figure within which the flight path of the aircraft will be located). This variation becomes more apparent at higher altitudes and greater turn angles. The controller can expect the aircraft track to be on the inside of the waypoint.

Figure 5-1. Turn over flyover waypoint and turn at fly-by waypoint (see 5.4.1.1.4)

An aircraft will come to the overhead of the waypoint before initiating the turn onto the next leg. Therefore, if the minimum prescribed lateral separation is applied, it will be infringed upon as the aircraft manoeuvres onto its next leg. The controller can expect the aircraft track to be on the outside of the waypoint.

Figure 5-1 (cont.d). Turn over flyover waypoint and turn at fly-by waypoint (see 5.4.1.1.4)

PANS-ATM 5.4.1.1.4

2.10.2. These updates do not include the table as suggested in the existing policy. The update details that if the use of a fly-by way point reduces separation to below allowable levels an alternative form of separation must be used. Whilst the sentiment of the original policy has good logic behind it this seems to be a case of prescribing a specific chart instead of describing the end goal of maintaining separation.

2.10.3. It is vital that fly-by transitions are accounted for when designing routes which are closely spaced, such as using minimum separation. The risks inherent to such design choices should be considered and the safety of it must be analysed.

2.10.4. The policy is in need of an update which takes into account the ends and not the means to achieve the goal:

Conclusions

3.1. The AAS section required amendments, both big and small, to bring the manual up to date and in harmonization with ICAO documents. While there is still more work to do, both to complete this task and to upkeep the manual, these amendments are a great step forward.

Recommendations

4.1. It is recommended that the abovementioned sections of the Technical and Professional Manual (TPM) be amended accordingly, as described in Section 2 of this working paper.

References

ICAO. (2016a). ICAO World Civil Aviation Report, 5^th ed. Montréal, Canada: International Civil Aviation Organization.

ICAO. (2016b). Procedures for Air Navigation Services – ATM (Doc 4444), 16^th ed., 8^th Amdt. Montreal, Canada: ICAO.

ICAO. (2017). Global Operational Data Link (GOLD) Manual. Montréal, Canada: International Civil Aviation Organization.

IFATCA. (2019). IFATCA Technical and Professional Manual (TPM). 2019 Ed. Montréal, Canada: International Federation of Air Traffic Controllers’ Associations.