WP-WGB1707

Agenda item 9. ICAO guidance material on radio frequency interference

Radio interferences

(Presented by A.Dedryvere)

Introduction :

The report of the 11th ANC recommends (Rec 5/2) that ICAO :

a) intensifies its activities to secure protection of aeronautical CNS systems from the adverse effects of electromagnetic interference and develops guidance material as necessary

b) develops material to assist States in assessing interference from FM broadcasting stations

c) supports the relevant activities of the ITU ………

d) develops guidance material on the control and removal of interference to aeronautical systems

One project, also commented in the group F, is to create a common interference declaration model to feed an international database.

NB: The Paris ICAO bureau sent in august 03 to the EurNat States a proposal of interference declaration model for comments. The discussion held in Tokyo showed that this model had already been adopted in other regions. As some dispersion between regions was not desirable, only significant comments would be welcome, France resigned to modify the text and the project seems adopted. Nevertheless the suggestions stay for the future database:

-All frequency bands should be concerned including radar, ILS, DME and GNSS

-The type of perturbation (aeronautical, non aeronautical, intentional) should be quoted .

The goal of this paper is to help writing guidance material for the States on the subject.

General description.
A general description of what is currently done in France was explained in WgB 16/WP07

and annexes. Some more explanations were asked.

1-The pilots are encouraged to report radio interferences by a formatted form, published in AIC France A (20/2001), and to send it by Fax directly to the SCTA (see I was informed that the pilots use less than previously this procedure, therefore most of the reports are made by controllers (it includes the cases when the pilot complaints can pass thru the VHF and are collected by the controller). An e-mail collection of the pilot complaints would be an improvement on the present procedure.

2-The chart attached to WP07 (Interferences in France VHF/Aeroband 2000) raised some questions. It is reproduced in appendix2 (pie chart ppt) with the 2001 figures.

“Permanent transmission” (# 7%) means stuck microphone , “carrier” (1 to 3.5%) means the same type of perturbation but generally originating from ground transmitters and only perceived by pilots (harmonic of, or intermodulation with broadcasting stations)

3-The biggest part (other items #66%) is sporadic and unknown, therefore difficult to process.

WP07 did not highlight that interferences may cause ATC limitations, delays and even airproxes. A new presentation of the ATC frequencies interferences (2001/02/03) is presented in annex1 thereafter.

The majority (97%) of ATC delays in 2001 were caused by unidentified perturbations on the primary approach radar (21 cm band) of Nice. These perturbations disappeared without explication in autumn 2001.
The radar of Bale-Mulhouse (near Switzerland and Germany, also 21 cm) suffers from time to time from radio amateurs transmissions in Germany. There is a threat on S band (10 cm) radars from mobile reporting cameras and the aeronautical world should be vigilant.

En route ATC regulation:

In 2002 and 2003 the ACC of Bordeaux introduced delays due to VHF interference (once for stuck microphone)

Upper aero communication band:

Frequencies above 130 MHz are frequently troubled by unlawfull transceivers used by farmers or fishers. Ex: 133,875 MHz in the mediterranean sea in 2001, 2002 and less in 2003. (Seems to disappear in 2004)

Technical and legal organisation against interferences

The French civil aviation will soon be coherent with the European Union's "Single Sky" framework . Under this organisation spectrum issues problems will be considered « regulatory » and frequency management « operational ». Nevertheless the description and processing of interference problems already described should remain almost unchanged.

The names of the main ATC operator (SCTA) and central technical service (STNA) may change but are still used in the present text or annexes.

The ANFR ( Agence Nationale des Fréquences) is the national regulator overseeing frequency management and spectrum allocations in France.

Confronted with an interference situation, the controller is instructed to call the local technical service which in its turn fills in an interference finding sheet and transmits it to SCTA, even if the problem is by that time resolved, and this with the view of gaining experience. In case a reported interference is not solved at the local technical service level it will then be processed by the central office of SCTA.

New equipments for the central (STNA) and local technical services, including one aircraft (2002), helped to localize and identify the cause of interferences. The case is sometimes hard to identify between harmonics (or intermodulation) of broadcasters and extra causes: 15 french and 2 spanish FM stations are currently suspected in SW of France.

If the interferer is a foreign aeronautical user, we try to solve the interference issue using ICAO channels.

If the interferer does not belong to the aeronautical community, as resulting for instance from FM broadcasting the procedure may involve the ANFR or the CSA ( Conseil Supérieur de l'Audiovisuel which is the regulatory body overseeing public broadcasting at the national level).

Both may initiate a formal investigation by police and consequential prosecution in court of justice, if the interfering source is within France's borders , or an enquiry by their international counterparts otherwise.

As civil aviation “owns its aeroband” there is sometimes a lack of legal registration to the official frequency agency (ANFR in France) which manages the use of the full spectrum.

As a consequence the official public data bases may be out of date. We suspect than this situation also occurs outside of France.

The current data bases used by Eurocontrol (operational, non “legal” data) are also full of omissions and errors.

Aeronautical interference may be solved, sometimes hardly, by the common ICAO procedure.

Of course the non aeronautical interferers should not be present, but they are and the procedure to push them out may slow down by this lack of legal registration especially if justice is needed.

The problem of foreign interference is obviously harder to solve.

The management of legal registration and database updating costs money.
For the first time the French DGAC decided to introduce fees for AOC, AAC etc

This is concerning airlines, aeroclubs, private owners, telecom operators like SITA or ARINC.

Conclusion

The group is invited to consider these elements when writing guidance material according to the 11th ANC recommendations

- Annex1: Interferences on ATC frequencies in France 2001/2002/2003 Values

- Annex2: Pie charts 2001/2002 separate text PPT

INTERFERENCES ON ATC FREQUENCIES IN FRANCE

2001/2002/2003 VALUES

ITEMS / RESULTS / OBJECTIVES
2001 / 2002 / 2003
Nb of AIRPROX / 0 / 0 / 0 / 0
ATC delays due to interferences (including radars) / 63124 mn / 459 mn / 1450 mn
Stuck microphone (from aircrafts, sometimes on ground) / 59 / 40 / 76
Total reported interferences / 773 / 1099 / 1014
Classified interferences, other than”various” and classified in cases / 397 / 348 / 487
Cases of interference / 48 / 63 / 43
Cases resolved after action / 32 / 30 / 27
Cases resolved spontaneously / 14 / 29 / 13
Non resolved cases / 2 / 4 / 3
Resolved cases analysis / On time / Out of time / Ratio / On time / Out of time / Ratio / On time / Out of time / ratio
Interferences type MP* / 15 / 4 / 79% / 9 / 2 / 82% / 4 / 100% / 75%
Interferences type MI* / 8 / 4 / 66% / 12 / 4 / 75% / 14 / 6 / 70% / 75%
Interferences type HM* / 1 / 0% / 3 / 0% / 3 / 0% / 75%

*:

Type MP : Permanent interference with cause on french territory / On time = / 5 days max
Type MI : Intermittent interference- with cause on french territory / 30 days max
Type HM :Interference with foreign cause / 30 days max