• The following are a collection of questions and answers which you may find useful when designing a new IFP or changing an existing one:

  • What speed should Instrument Flight Procedures be designed to?

    Designs will be to PANS-OPS standard speeds as stated in ICAO Doc 8168 Part 1, Section 4, Chapter 1 Table I-4-1-2, where this cannot be achieved the restricted speed is to be annotated on the AIP chart for the appropriate segment or entire procedure.

     

    What values are used in the UK for wind?

    Use ICAO Doc 8168, Part 1, Section 2, Chapter 3, Table I-2-3-1, substituting UK Wind (40kts + height in thousands of feet) for ICAO standard wind for designs up to and including 10000ft.

     

    Charting - Do draft charts need to be to an 'AIP ready' standard?

    It is not necessary to have an AIP ready chart for approval submission. It does though, greatly aid cartography if the draft is of similar layout to the UK AIP format.

     

    What Magnetic Variation value should be used for UK projects?

    US National Oceanic & Atmospheric Administration (NOAA) value specific to the aerodrome lat/long for the time of design or forecast promulgation date. Alternatively, the magnetic variation value can be confirmed with NATS AIS.

     

    What is the maximum e-mail size that can be delivered to the CAA mailbox?

    Maximum file size from an external organisation is 10Mb

     

    In what format do the CAA prefer design packages?

    The design package for IFP approvals is dependent on the APD QMS. However, where an AutoCad drawing is submitted then for the moment a 2010 format DWG file is required.

     

    How should an IAP RCF be depicted on an IAC?

    The RCF procedure where provided will be in textual form only. For RNAV procedures the RCF is not coded into the navigational database.

     

    When conducting 5-yearly reviews of IFPs is a flight validation required?

    A 5-yearly periodic review of IAPs would not normally necessitate a flight validation. However, if significant changes are introduced into the IAPs during the review process then this requirement will be assessed on a case by case basis by the CAA IFP Section.

     

    What is the range datum for Surveillance Radar Approaches (SRAs)?

    SRAs shall be designed to a minimum of 3° with ranges published relative to touchdown assuming a 15m (50ft) height at the runway threshold. Exceptionally, where local constraints dictate, ranges will be notified as being published from threshold.

     

     

     

    Where can I find UK allowances for 'high resolution' SRE equipment?

    AIP GEN 1-7 Doc 8168 UK Addition 6.6 refers.

     

     

     

    How should RTR to MAPt be constructed?

    The Final Approach Segment splays at 15° from the earliest fix tolerance of the RTR as this is the point where course guidance stops.

     

     

     

    What minimum safe altitude (MSA) values are published when multiple Navaids are available at an aerodrome?

    Derive the MSA for each facility used and then combine each specific sector using the highest calculated value. On the individual chart use the combined values but reference the MSA to the primary facility used for that individual instrument flight procedure

     

     

     

    How should advisory altitudes be calculated?

    Calculate the exact altitude then round to the nearest 10ft. To calculate the height, subtract THR elevation from the rounded altitude. This height figure is not rounded.

     

     

     

    What vertical datum should be used for non-precision approaches?

    Non-precision approach vertical datum is always THR elevation.

     

     

     

    In the initial MAP, can secondary assessment be used in conjunction with extension of the MAP surface for reduced MOC?

    It is the CAA's opinion that 'SOC refinement' and secondary dispensation cannot be both applied at the same time.

     

     

     

    Are there any restrictions on the use of a step-down fix in Instrument flight procedures?

    A step-down fix should only be included in an instrument flight procedure when a minimum of 50ft benefit can be achieved in the calculated OCA/H

     

     

     

    What altitude is published at the SDF?

    The actual MOCA is published on the profile in the grey box prior to the SDF. In addition the recommended altitude at the SDF is published in the Recommended Profile boxes.

     

     

     

    Do protection areas need to be constructed if Z+MOC is proven to be safely below the procedure altitude i.e. base turns/hold etc?

    The protection areas should always constructed to ensure that there is always something to base future enquiries on. Whilst it may not be necessary to conduct an obstacle analysis in this situation issues of airspace containment and future safeguarding questions can only be accurately assessed if the protection areas are constructed accurately.

     

     

     

    What secondary area criteria should be used for an extended hold procedure?

    When the hold is being used as a hold the areas will be calculated by using the hold criteria with buffers, when the hold is extended, the racetrack criteria should be used with the use of primary and secondary areas.

     

     

     

    Can radar ranges to threshold be used in lieu of Distance Measuring Equipment (DME) for Instrument Landing System (ILS) approaches?

    To facilitate continued use of the ILS/DME procedure when the DME fails, practice has evolved in which the local Air Traffic Services Unit (ATSU) passes an equivalent radar range to threshold to the pilot. This can only be done where the local ATSU has formally agreed and is able to pass such ranges. 

    This will be notified on the appropriate IAP chart in the following format: 

    AIRCRAFT UNABLE TO RECEIVE DME I-XX: Advise ATC. ATC will pass an equivalent position at X.X and Y.Y NM outbound and 4NM inbound.

     

     

     

    Is it still necessary to include conventional ground based navigation aid bearing and distance information as a positional cross check of the IAF Waypoints on RNAV charts?

    When RNAV IAPs were first introduced in the UK it was felt that the inclusion of the above data was a useful gross error check for pilots before commencing the procedure. Now with the programmed removal of many conventional navigation aids and the demonstrated accuracy and integrity of the GNSS system the CAA feels that it is appropriate that the requirement for the extra data should now be removed.

    This also allows for the removal of all conventional navaid data from the RNAV charts unless there is an on-going requirement for a conventional Missed Approach Procedure. 

     

    For the FAS DB, what should be used for the FPAP Orthometric Height (metres)?

    Where the FPAP is a surveyed location (e.g. LOC or ASDA_END) then the elevation from the survey in metres rounded to the nearest 0.1m. Where it is calculated then the closest surveyed ground point elevation should be used.

     

     

     

    RNAV APCH-LPV: Do I need to save the FAS DB html page and if so how should it be presented?

    The EUROCONTROL SBAS FAS Data Block Tool now provides the facility to output a pdf page of results which can be supplied to AIS along with the draft chart and coding tables for the procedure.

     

     

     

    For RNAV initial and intermediate approaches do the segment lengths need to be divisible by 0.1NM?

    The length used should be consistent with the procedure altitude and profile required. In many cases the WP can be placed to facilitate the exact distance required. The lengths of the segments do not need to be divisible by 0.1nm in the design process but should be charted with lengths rounded to the nearest 0.1nm

     

     

     

    SBAS - Where should the GARP be placed when the GARP-LTP distance is <2000m?

    The position of the FPAP should be such that the LTP/GARP distance is at least 2000m. On short runways the FPAP needs to be situated beyond the end of the runway to maintain the relationship of 105m course width at LTP with the max angle of full scale deflection of 3° (see Doc 8168 III-2-6-App A-4 Explanation of FAS Data Block Entries paras 3I and m). When this methodology is used there will be a “D length offset” that has to be completed in the FAS Data Block fields. See also Annex 10, Vol 1, ATT d-62, Fig D-6.

     

     

     

    RNP APCH - Is it acceptable to use large track-angle changes with a DF (e.g. for a turning missed approach) due to current IFPP concerns that an aircraft may turn in the wrong direction?

    There is a known issue with RNAV coding whereby if a direct to fix path terminator is used to define a free turn back through 180° some aircraft systems will turn the shortest way irrespective of which direction is specified. In crosswind situations the shortest way may be the wrong way. Therefore a Missed Approach design utilising at least two waypoints is required.

     

     

     

    Which method of classification of approach/missed approach obstacles must be used for LPV?

    The 'range method' classification from ICAO PANS-OPS III-3-5.4.5.9.2 is the only option currently approved by the UK CAA.

     

     

     

    For LPV approaches, where a LOC already exists, should the course width from the calibration reports be used for the LPV?

    In most cases the answer will be yes. However, in the case of a short runway this will need to be discussed as the FPAP will be placed such that the LTP to GARP distance is at least 2000m.

     

     

     

    When is an initial CA leg required to prevent turns below 500ft?

    In the UK for all SIDs there is a requirement for “No turns below 500ft QFE”. In general if the early turn point for the first waypoint is before the point at which an aircraft would reach 500ft AAL following a 3.3% climb gradient from 5m above DER then a CA leg would be required.