Conditional Clearances

Conditional Clearances

42ND ANNUAL CONFERENCE, Buenos Aires, Argentina, 17-21 March 2003

WP No. 90

Conditional Clearances

Presented by SC1

Introduction

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.

Discussion

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.”

2.6 In the EUROCONTROL ATM Procedures Development Sub-Group (APDSG), this fact was accepted and a proposal was made on changes to ICAO PANS ATM Doc. 4444 regarding the use of conditional clearances. Currently, the procedure detail is located within Section XII (Phraseologies). It is more appropriate that where such procedures are being applied to the aerodrome environment, that they should be located in Section VII (Aerodrome) of this document.

The final proposal reads :

PANS-ATM Chapter 7, Aerodrome Control Service

7.10 Procedures for the use of conditional clearances affecting movements on runway(s)

7.10.1  Conditional phrases, such as “behind landing aircraft” or “after departing aircraft” shall not be used for movements affecting runway(s), except when the aircraft or vehicles concerned are visually and unambiguously identified by the appropriate controller and pilot.

7.10.2  Each clearance containing a conditional phrase shall relate to one subject only.

7.10.3  The subject of the condition (aircraft or vehicle) shall be the next movement along the runway that passes in front of the aircraft receiving the conditional clearance.

7.10.4  When a runway is used exclusively for departures, and in the case of multiple departures using the same runway access point, a conditional clearance instructing aircraft to line up behind preceding shall be issued only when the subject of the condition is ahead of and visible to the aircraft receiving the conditional clearance.

7.10.5  The runway (number), and, where applicable, the intersection (name of the intersection) shall be specified in the clearance.

7.10.6  Conditional clearances shall be given in the following order and consist of:

i)  identification

ii)  the condition

iii)  description and position of the subject of the condition (aircraft or vehicle)

iv)  the clearance, and

v)  brief reiteration of the condition

7.10.7  Conditional clearances shall be read back in a manner to clearly indicate that they have been understood and will be complied with.

7.10.8  Flight crew unable to make an unambiguous identification of the subject of the condition (aircraft or vehicle), and therefore unable to comply with the conditional clearance, shall inform ATC.

2.7 In addition on 2.6, above changes are proposed on PANS-ATM 12, section Phraseologies to read:

12.2.4 Conditional clearances shall be given in the following order and consist of:

  • identification
  • the condition
  • description and position of the subject of the condition (aircraft or vehicle)
  • the clearance, and
  • brief reiteration of the condition.

For example:

ATC : “ KLM 313, BEHIND DC9 ON ONE MILE FINAL, LINE UP RUNWAY (number), (INTERSECTION (name of intersection)), BEHIND “.

PILOT : “ BEHIND DC9 ON ONE MILE FINAL, LINING UP RUNWAY (number), (INTERSECTION (NAME OF INTERSECTION)), KLM 313 “.

Note 1. – This implies the need for the flight crew receiving the conditional clearance to identify the subject of the condition (aircraft or vehicle).

Note 2. – The provisions applying to the use of conditional clearances when associated with aerodrome control service, are specified in Chapter 7, Section 7.10.

12.3.4.10

j) (condition) LINE UP RUNWAY (number) [INTERSECTION (name of intersection)]

k) (condition) LINING UP RUNWAY (number) [ INTERSECTION (name of intersection)] (condition)

Conclusions

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.

Recommendations

It is recommended that;

4.1 This paper be accepted as information material.

References

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.

Last Update: September 29, 2020  

March 22, 2020   290   Jean-Francois Lepage    2003    

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