Priority of Radio Instructions over Light Signals (ICAO Annex 2)?

[hvogt]

In Germany instructions given by radio have priority over light and ground signals as well as over signs. However, this does not seem to correspond with ICAO Annex 2. In fact I could not find any provision in Annex 2 that gave such priority to either kind of instructions.

If I am correct, this would mean that according to Annex 2 instructions given by radio had the same priority as light signals etc., which I find hard to believe. Could somebody enlighten me?

[niknak]

Under normal circumstances, no one has priority over anyone else unless it's an emergency.
If you are using an aerodrome which uses radio services (or ATC) and the radio is serviceable you wouldn't need to use light signals.
If you are flying into that aerodrome by prior agreement on a non radio basis, you would follow the pre briefed procedure and the consequent light signals, you don't deviate from that procedure.

In my experience, in the above circumstances, only one non radio aircraft is accepted at any one time and the aerodrome authority are responsible for ensuring that a robust system exists to ensure that happens, consequently the radio equipped aircraft communicate accordingly and non radio aircraft follow the light signals.

[VoxPopuli]

Are you refering to stopbars and the like?

[hvogt]

Thanks for your answer, niknak.

VoxPopuli, I was thinking of light signals transmitted with an aldis lamp, ground signals and signs. However, with stop bars my question would still be the same.

[Spitoon]

To get a proper answer to your question you probably need a lawyer. But here's a personal, and layman's view of how it all works.

In general, ICAO sets Standards which signatory States agree to implement - this usually requires the provisions of the Standards to be transposed into national law. ICAO Standards have evolved over time and sometimes represent an eclectic mix of the old - minimum standards, effectively a lowest common denominator that you can expect everywhere - and the new, such as detailed references to the use of datalink.

Each State has to decide whether it wants its national law to go beyond the ICAO provisions in order to support its own policies. In most cases, going beyond what ICAO says does not cuase any difficulties but, occasionally it can. This is one of the reasons that ICAO now seeks differences to be filed by States if they demand more than the SARPs locally.

As to Annex 2, remember that it originated when radios were not exactly a novelty but many flights were carried out without one - and, of course, failures were common. Hence light signals and signals squares. Over the years things have changed - it has been added to, there's now a reference to red stopbars which I'm sure was not there when it was first published in 1948, and the concept of ATC clearances and the way that the ATC system works in practice, certainly in Europe, is rather different to that on which much of the content of Annex 2 is based. Annex 2 does seem to have a few gaps and, perhaps, even inconsistencies - one of which you have identified; it doesn't appear to indicate a hierarchy of communications channels/signals.

So in Germany, you have taked the decision to remedy this by including a priority in your legislative framework. In the UK I don't think this has been done explicitly (although the rules do say that pilots must follow ATC instruction, or something along those lines).

niknak has given you a very practical answer which reflects the way things happen in the UK but if things ever go wrong and lawyers get involved I suspect that what the law says (or doesn't say) would take on a far greater significance!

[hvogt]

Thank you very much for your answer, Spitoon. I am glad you agree that there is an inconsistency in Annex 2. Having studied laws I must say that your "layman's view" is in fact very professional.

Since there is little secondary literature on the ICAO annexes it is always difficult to interpret them. Hence a view from the pilot's side is always great help to me (that goes for you too, niknak).

By the way - as for the stop bars, Annex 2, no 3.2.2.7.3 applies:
3.2.2.7.3 An aircraft taxiing on the manoeuvring area shall stop and hold at all lighted stop bars and may proceed further when the lights are switched off.
Cheers,

hvogt