1.1  At the 41st annual Conference in Cancun 2002, SC1 accepted the request to investigate the use of conditional clearances.

1.2  Conditional clearances are used in all stages of flight. This paper will only address the use of conditional clearances during aerodrome operations.

2.1  Runways are often the bottleneck at airports, and soon (around 2005) they are expected to be the limiting factor in ATC capacity in Europe. Conditional clearances are often used as one of the methods to increase the runway capacity.

2.2  The use of conditional clearances in conjunction with other capacity enhancing procedures, such as intersection departures and multiple line ups, may contribute to a possible overly complex operational environment being created. This could result in a safety level below the levels accepted in normal aerodrome operations. Incidents in Paris Charles de Gaulle, Brussels International Airport and Los Angeles International Airport show that the use of conditional clearances can turn out extremely safety critical.

2.3  Now that the maximum runway capacity has to be used, conditional clearances give the controllers the additional 20 seconds to use that last bit of runway capacity. R/T phraseology, language proficiency, ATC experience, visibility for the controller and pilot, day or night, are, amongst the factors that can turn the use of conditional clearances into a safety critical procedure, if not used properly.

2.4  As conditional clearances are used more and more to make up for that last bit of capacity, the conditions under which these clearances could be applied, the procedures themselves and the phraseology, should be clearly defined.

2.5  The only information on the use of conditional clearances can be found in ICAO PANS ATM Doc. 4444, chapter 12 Phraseologies. Under 12.2.4 it states :

“Conditional phrases, such as “behind landing aircraft” or “after departing aircraft”, shall not be used for movements affecting the active runway(s), except when the aircraft or vehicles concerned are seen by the appropriate controller and pilot. In all cases a conditional clearance shall be given in the following order and consist of :

i)  identification

ii)  the condition

iii)  the clearance; and

iv)  brief reiteration of the condition

for example :

“SAS 941, BEHIND DC9 ON SHORT FINAL, LINE UP BEHIND”.

Note. – This implies the need for the aircraft receiving the conditional clearance to identify the aircraft or vehicle causing the conditional clearance.”

3.1  Conditional clearances are widely used in aerodrome operations. To avoid turning the use of this clearances into a safety critical procedure, the procedures to be followed and phraseology, should be clearly defined.

3.2  IFATCA agrees on the proposal to changes to ICAO PANS ATM Doc. 4444 made by APDSG. These changes consist of an addition on conditional clearances under Chapter 7, Aerodrome Control Service (see 2.6) and changes to Chapter 12, Phraseologies (see 2.7).

3.3  IFATCA should monitor developments on this issue closely.

It is recommended that;

4.1 This paper be accepted as information material.

Pans ATM, doc 4444, part XII (phraseologies).

ICAO doc 7030, EUR regional supplementary procedures.

APDSG/31.

Report of the AOT/9 meeting.

ANT/29 Agenda Item 3.2.2.