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Passing of level information when providing Traffic Information/Responses
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Summary of Responses
A total of 17 responses were received: 10 ANSPs, 4 National Authorities, 1 Association and 2 other independent professionals.
Use of Relative Vertical Position level information:
- Relative Vertical Position (RVP) is an option that is in use in 9 out of the 10 ANSPs who responded.
- For the majority of respondents, RVP and actual/indicated level are both acceptable methods of passing level information.
- However, the general consensus is that in most situations RVP is likely to give the pilot a more immediate clue as to the position of the other traffic in relation to their flight than the use of indicated/actual level information.
Policy/Authority for use
- The situation regarding a formal policy or authority to use RVP varies amongst States and ANSPs.
- Some States (3) either actively promote the use of RVP as an option or in some cases mandate that the actual level should not be passed in certain circumstances.
- In one state RVP is used/authorised as an option in specific circumstances e.g. when in the opinion of the controller the proximity between aircraft may diminish to less than the applicable separation minima. In another State, RVP is authorised when providing level information in the context of STCA communications.
- Of the 9 ANSPs where RVP is used, the practice is ‘authorised’ in 7 of them through the MATS (or equivalent). In the 2 ANSPs where RVP is used but not ‘authorised’, it is seen by ATCOs as a ‘best practice’ defensive controlling mechanism with safety benefits.
- Only 5 out of the 10 ANSPs who responded said that they provide some form of RVP training: ab initio (3); OJT/Unit (4); and recurrent/refresher training (2). Note: In some cases ANSPs provide more than one type of RVP training.
- In the States/ANSPs where RVP is used but where there is no formal RVP training, it is common for experienced controllers to promote its use as operational ‘best practice’.
- States do not promulgate the use of RVP in AIPs as an ICAO ‘difference’ because it is a PANS ATM provision and not an ICAO SARP.
- Some States have issued standards/guidance (e.g. UK CAP 413) which supports the use of RVP.
- Use of RVP, where authorised, is often published in the ANSP MATS (or equivalent).
- One ANSP specifically amended its MATS to include RVP as an option after publication of the RFS.
- The use of RVP is already widespread and appreciated by flight crews.
- RVP is generally the preferred option to receive level information – it helps visual acquisition and complements TCAS displayed information.
- The use of RVP needs to take into account the accuracy of the level information presented as 200 feet above could be at the same level.
- The use of RVP may be more or less beneficial depending on whether the receiving aircraft is in level flight or is manoeuvring. For instance, an aircraft subject to a clearance and therefore maintaining a level may be more likely to quickly assess the relevance to their flight of traffic information passed as an indicated level as opposed to manoeuvring traffic such as a VFR aircraft outside controlled airspace, were relative level may be more appropriate and quicker to assess.
- In situations where there are high closing vertical rates, the use of RVP can provided better awareness to pilots so they reduce the vertical rate as they approach a level thus further reducing the possibility of level busts.
- Many ANSPs include aircraft type (as per PANS ATM) when providing traffic information to help pilots identify the conflicting traffic and so reduce the possibility that they will take an incorrect action.
- ANSPs and States did not provide evidence of any safety reports to support the use of RVP. The rationale being that its widespread use is largely preventing the type of errors (i.e. pilots misinterpreting the information and then making incorrect manoeuvres) that led to its introduction in the first place.
- The overriding response of the SISG members to the question is that the matter should be taken forward for consideration by the EUROCONTROL ATM Procedures Development Sub Group (APDSG). The SISG’s strong view is that by embellishing current ICAO ‘level’ phraseology a known operational and safety consideration could be improved.
- The intention would be to propose the use of RVP as the preferred method to pass level information in certain conditions/contexts. This option could be an addition to, rather than be a replacement of, the existing PANS ATM phraseology which should be retained for the controller to use as deemed necessary.
- ICAO Doc 3492: Manual of Radio Telephony.