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.