AOPA UK

NOTAM and AIS

For a number of years Michael Cross has represented AOPA UK on NOTAM and AIS matters. During this time NATS, who are contracted by the CAA to provide the service have delivered a steady flow of improvements.

The transition from a sheaf of paper NOTAM, several days old, hanging on the wall to a web-based briefing tool has resulted in a reduction in costs and head-count within NATS AIS, while the numbers of NOTAM in circulation has risen rapidly, as has the number of briefings being delivered. We are now on the second generation of Web-based delivery systems. The first system, introduced on 19 August 2002, involved UK AIS in maintaining a world-wide NOTAM database and delivering briefings from it via the Internet. In the current incarnation the database is maintained by Eurocontrol and shared among member states. This reduces costs by removing duplication of effort. Each European State now populates the European AIS Database (EAD) with its own NOTAM and the NOTAM of non-members are maintained centrally by Eurocontrol.

AOPA UK has been foremost among the GA community in driving improvements to the delivery system and Mike now also represents the BGA on these matters. The improvements include:-

  • Better presentation of data.
  • Error trapping to detect and highlight incorrect input.
  • Reduced numbers of PERM NOTAM (those that ought to be amendments ot the AIP rather than NOTAM)
  • Better education of users.
  • Accessible and relevant user guides
  • Improvements to NOTAM content.

Improvements to the delivery and presentation of data have resulted in a system that has much greater user acceptance and the focus of attention is now moving more to content rather than dellivery. Recent amendments to ICAO procedures have armed AIS with more power to instruct the originators of NOTAM, which should result in better content quality.

User Concerns

In no particular order here are some of the user concerns that have been put to Mike, together with his own commentary.

I want a graphical presentation of the data

The issue here is that the format of NOTAM is laid down by ICAO. That format is not designed to permit graphical presentation other than as a vertical cylinder defined by a centre and radius and a height band, all included in the Q line of the NOTAM in a defined sysntax. The E line, which contains textual data and frequently in the case of Nav Warnings contains co-ordinates is free-form text with no defined syntax. A number of gifted programmers have written applications to parse the E line and produce a graphical presentation but the lack of a defined syntax means that there is no reliable method of achieving it. An example may assist:- A NOTAM for a paramotor event said that the event would take place at one of five locations and would affect a radius of 15 nm from that location. The five locations were listed by their co-ordinates and the decision on which location to use was to be made on the day, based on prevailing weather. A program to parse this information would probably pick up the five co-ordinates and draw a closed polygon with them as its vertices. The correct plot would however have been tangents joining 15nm radius circles based on each location. The solution will come with the adoption of AIXM and xNOTAM, which are part of a joint Eurocontrol/FAA project. AIXM (Aeronautical Information Exchange Model) is an xml based language that will provide a standard format for describing geographic entities. This is important, not only for NOTAM presentation but also for charts and other data that has to be transferred into proprietary databases for GPS, FMS, Flight Planning tools, Flight Guides, the paper AIP and Electronic Flight Bags. Currently this is a hugely labour intensive operation involving re-keying and translation of data with many opportunities for error. AIXM will allow this process to be automated and human error to be eliminated from the process.

It remains to be seen what will happen to presentation once AIXM is adopted by ICAO and implemented. My guess is that briefings will continue to be presented in the current format and it will takes some time for a graphical presentation to be developed and brought into use. The current free NOTAM service is funded by en-route charges which most of GA does not pay. There is continual pressure from the airlines to end what they see as a cross-subsidy where GA benfits at their expense so funding a solution that benefits GA but is not needed by CAT could prove problematic and it may be that graphical presentation is initially taken up as a "value add" by commercial briefing services. EASA proposals for quality assurance of data provided to users may also affect the situation as they will inevitably impose obligations on people who provide or manipulate data.

I want clickable hyperlinks in NOTAM text

The difficulty in providing Hyperlinks is that NOTAM are required by ICAO to use the ITA-2 alphabet, which is based on a 5 bit teleprinter code rather than the 8 bit ASCII code used by the Internet. ITA-2 has only a small subset of the ASCII characters. with all of the lowr-case characters and many of the punctuation characters missing. This means that most Internet URL's cannot be written using the ITA-2 alphabet. Eurocontrol are exploring ways of getting round the restriction but the challenge is to find something that works and is not unduly labour-intensive. To fulfil these criteria it would have to involve data input as part of the origination process and is therefore likely, if adopted, to only function for European NOTAM.

There is too much irrelevant content in NOTAM briefs

I agree, and continie to exert pressure to reduce its quantity. There's an assumption by some that NOTAM are just for pilots, not so.They are also targetted at ATC staff, Operations Departments, and Air Navigation Service Providers. AIS also recognises the problem. The view I've expressed at meetings is that NOTAM targetted at pilots are there to influence the conduct of the flight. If they aren't going to alter behaviour then perhaps they should not be published.

NOTAM are difficult to read and interpret

The upper-case only format results from use of the ITA-2 alphabet referred to above, which is the standard for the Aeronautical Fixed Telecommunication Network (AFTN). Abbreviations used are those in the GEN section of the AIP. A direct link to the abbreviations glossary is being provided on the Website. Where textual descriptions are complex (e.g. the airspace restrictions for the Farnborough Air Display) an AIC containing charts is issued. The text still has to be in the NOTAM but the AIC is the best way to read the information. In the case of Nav Warnings, AUS (The Airspace Utilisation Section of the CAA) has improved readability with geographic identifiers (e.g. VCY SWINDON for "In the vicinity of Swindon") to supplement the raw geographic co-ordinates which is a welcome improvement.

Better access to AIP data improves safety

It is frustrating that we do not have simple programatic access to data. It ought to be possible to construct a link to display the current version of any piece of published AIP data. Unfortunately this is currently not the case. The obvious answer is for this to be provided by EAD, the European AIS Database, part of Eurocontrol.

UK Law requires the commander of the aircraft to "take all reasonable steps so as to be satisfied" that "the flight can safely be made, taking into account the latest information available as to the route and aerodrome to be used, the weather reports and forecasts available and any alternative course of action which can be adopted in case the flight cannot be completed as planned" (source UK Air Navigation Order)

This entails using a variety of sources, each with their own interfaces. Each State has its own way of making the data available and they all have their own (different) interfaces. The provision of a published standard for obtaining the data would mean that functionality could be built in to software to allow simple access. For example commercial flight planning software ought to be able to call up the relevant data for the flight or a user ought to be able to click on a map to activate a link to the official data.

This is not a difficult thing to implement. Quick and easy access to required data is a safety benefit. Ultimately it would reduce or do away with the need for States to devise and maintain their own interfaces. Eurocontrol have tried with EAD Basic but it is not user-friendly - exploring its functionality is difficult for the non-technical user. If they allowed others to develop data clients instead of forcing access through the "one-size fits all" EAD Basic interface they would quickly increase user take-up of EAD services.

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