Originally Posted by 177
I just finished reading the ICAO Doc 9432 which wasn't updated since 2007. How common are SRA and PAR approaches these days? Are they still practiced anywhere in Europe?
ICAO Doc 9432 was based on the first edition of the UK Radiotelephony Manual CAP 413 which is now in its 22nd edition.
In UK a PAR talkdown can be done at over 20 military aerodromes but it is unavailable to most civil pilots. Elsewhere in Europe, perhaps in Germany or Sweden, it may be possible at one of the joint civil–military aerodromes.
SRAs can still be done at about two dozen aerodromes in UK although only a handful offer half-milers. Details in AIP.
Originally Posted by 177
Why there are so many approach lighting systems? Why not just have only 2 or 3?
There are only about half a dozen different systems and they mainly categorised by the instrument approach procedures served. The choice of system depends on budget constraints, the type/volume of traffic intended, the need for reduced instrument landing minimums, the surrounding topography, and so on. Supplementary lighting such as bars for roll guidance near the threshold will be used for CAT III precision approaches, etc. Some history on the Calvert system is at
Calvert Cross Bar Lighting System
Originally Posted by 177
What's the PRACTICAL application of each lighting scheme? I mean, do they really help pilots in a different kind of way?
Visual identification of the intended landing surface during instrument conditions, indication of deviation from the extended runway centreline, roll guidance, and so on. The AVweb article Approach Light Secrets by Jeff Van West, Apr 2014, while intended for a US audience covers much common ground and addresses your questions:
https://www.avweb.com/news/features/...-221926-1.html
For a pertinent technical report from the FAA's Airport Technology Branch see Reduced Approach Lighting Systems (ALS) Configuration Simulation Testing (
DOT/FAA/AR-02/81; Gallagher, DW. Jul 2002). Here is the abstract:
Originally Posted by DOT/FAA/AR-02/81
The availability of Global Positioning System (GPS) approaches has already increased the number of runways capable of handling Instrument Flight Rule (IFR) approach operations. A major factor in upgrading the instrument capability of these runways is, and will remain, the need for installation of many new approach lighting systems (ALS). Therefore, it has become necessary to re-evaluate the present standard systems to identify possible means by which installation, operation, and maintenance costs can be reduced.
In an effort to reduce the overall length of ALS's, this report describes the methods, using simulation, by which the minimum visual cues with respect to length of an ALS is needed by pilots during an approach at Category I minimums. The current US standard is the 2400-foot-long Medium Intensity Approach Lighting System with Runway Alignment Indicator Lights (MALSR). Subject pilots evaluated ten different length configurations and were given questionnaires for each configuration flown.
The results indicate that shortening the system to a length of 1600 feet was not acceptable. Shortening the system to a length of 1800 or 2000 feet may be conceivable if enhancements to the visual segment portion of the system (i.e., additional steady burning barrettes at 1600,1800, and/or 2000 feet) would be considered. Shortening the system to a length of 2200 feet will only provide minimal reduction in ground area required and result in virtually no benefit in reduced equipment or power requirements.
Originally Posted by dook
The standard parallel separation quoted is the ideal separation for maximum accuracy of detail.
That depends on the spatial map extent and choice of distortion measure to be optimised among other factors, see eg first couple of sections in: Savric B, Jenny B. 2016. Automating the selection of standard parallels for conic map projections: Computers and Geosciences, 90, 202–212. (
PDF).
See also p 91 (and footnote 24 re the figure Alex mentions on scale error) in Deetz CH, and Adams OS. 1934. Elements of map projection with applications to map and chart construction (4th ed): U.S. Coast and Geodetic Survey Spec. Pub. 68. (
PDF):
Originally Posted by Deetz and Adams (1934, p 91)
In general, for equal distribution of scale error, the standard parallels are placed within the area represented at distances from its northern and southern limits each equal to one-sixth of the total meridional distance of the map. It may be advisable in some localities, or for special reasons, to bring them closer together in order to have greater accuracy in the center of the map at the expense of the upper and lower border areas.