57TH ANNUAL CONFERENCE, Accra, Ghana, 19-23 March 2018
WP No. 91
Clearances vs Instructions
Presented by PLC and TOC
At the 2017 conference, some indistinctness was found in the difference between clearances and instructions. It was concluded that clearances are for aircraft, while instructions can also be provided to vehicles. There was no legal difference found between clearances and instructions.
1.1 At the IFATCA 2017 conference, a paper on conditional clearances to vehicles was presented by TOC in Committee B. During the discussion following the presentation, there appeared to be inconsistency on the meaning and usage of clearances and instructions.
1.2 The committee could not reach consensus on whether or not clearances are given to aircraft and instructions to vehicles, or if there was no difference.
1.3 TOC and PLC were tasked to study the subject to get clarity on what is what and how clearances and instructions are to be used.
2.1. The discussion from the committee in 2017 appears to have its origin in the inconsistency of usage of these terms in ICAO documents.
2.2. The first version of ICAO PANS-ATM, originating from 1944, only mentions clearances. It is likely that the greater possibility of a radio failure has to do with this. With increasing traffic volumes over the years, and the technical systems becoming more reliable, the need and possibility for instructions to guarantee an orderly and expeditious flow of traffic was born. In order to get clarity in this discussion, it is important to go back to the basics.
2.3 ICAO defines air traffic control clearances in both PANS-ATM Doc 4444, as well as in Annex 11.
|Air traffic control clearance – Authorization for an aircraft to proceed under conditions specified by an air traffic control unit.
Note 1.— For convenience, the term “air traffic control clearance” is frequently abbreviated to “clearance” when used in appropriate contexts.
Note 2.— The abbreviated term “clearance” may be prefixed by the words “taxi”, “takeoff”, “departure”, “en-route”, “approach” or “landing” to indicate the particular portion of flight to which the air traffic control clearance relates.
(Source: International Civil Aviation Organization (ICAO), Annex 11 Air Traffic Services, 14th Edition (July 2016), Chapter 1 – Definitions.)
2.3.1 According the ICAO definition, an air traffic control clearance is an authorization that allows a pilot to do something. Examples are: airway-, route- and approach clearances, but also clearances to enter, line up, land, take off backtrack, cross and hold short. A clearance will always require a read-back (International Civil Aviation Organization (ICAO), Manual of Radiotelephony [Doc 9432], 4th edition – 2007, chapter 22.214.171.124).
2.3.2 ICAO DOC4444 also specifies to whom clearances are to be given:
|126.96.36.199 Clearances are issued solely for expediting and separating air traffic and are based on known traffic conditions which affect safety in aircraft operation. Such traffic conditions include not only aircraft in the air and on the manoeuvring area over which control is being exercised, but also any vehicular traffic or other obstructions not permanently installed on the manoeuvring area in use.|
(Source: International Civil Aviation Organization (ICAO), Procedures for Air Navigation Services – Air Traffic Management (PANS-ATM) [Doc 4444] 16th edition (November 2016), Chapter 4.5 – Air traffic control clearances)
The manoeuvring area is defined as the part of an aerodrome to be used for the takeoff, landing and taxiing of aircraft, excluding aprons (International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I, 7th edition – 2016, chapter 1, page 1-7).
2.4 Air traffic control instructions are only defined in ICAO Doc 4444.
|Air traffic control instructions – Directions given by a person performing duty in air traffic control for an aircraft to conduct its flight in the manner specified in the directions.|
(Source: International Civil Aviation Organization (ICAO), Procedures for Air Navigation Services – Air Traffic Management (PANS-ATM) [Doc 4444] 14th edition (November 2016), Chapter 1- Definitions)
2.5 Whereas a clearance is defined as an authorization, an instruction is defined as an order; a specific action is required. The table below, composed of information from both Annex 11 and Doc 4444, as well as the ICAO Manual of Radiotelephony (Doc 9432), sums up the different elements once more.
For example, it is more important to follow the instruction to hold short of an active runway than complying with the “push back” clearance. The outcome of not following the instruction will be an incident in the best-case scenario or an accident in the worst case scenario. Whereas, not following the clearance, there will be no severe outcome.
2.7 From a legal aspect, no difference was found between clearances and instructions. It does not matter if the phrase ATCOs use is a clearance or instruction, both need to be complied with in order to keep the order, safety and flow of traffic. In ICAO documents, both terms are used interchangeably and after consulting with ICAO, it was learned that for ICAO there is also no significant difference. ATCOs should not be bothered during the routine actions/job if the phrase used is a clearance or an instruction. The ATCO should know that they are covered both legally and technically.
2.8 ICAO Doc 4444 gives controllers leeway to exercise their professional judgement during emergencies, thereby implying that procedures can be modified or interpreted as practicable if in the controller’s best judgement, it might increase the safety of the situation. It also states that all emergencies are different and therefore designing procedures to cover them all is impossible (IFATCA 17, Working Paper No.86 “Conditional clearances to rescue and firefighting vehicles”).
|188.8.131.52 The various circumstances surrounding each emergency situation preclude the establishment of exact detailed procedures to be followed. The procedures outlined herein are intended as a general guide to air traffic services personnel. Air traffic control units shall maintain full and complete coordination, and personnel shall use their best judgement in handling emergency situations.|
(Source: International Civil Aviation Organization (ICAO), Procedures for Air Navigation Services – Air Traffic Management (PANS-ATM) [Doc 4444] 14th edition (November 2016), Chapter 15- Procedures related to emergencies, communication failure and contingencies)
2.9 As TOC and PLC found no significant difference between clearances and instructions, it was found that the IFATCA Technical and Professional Manual does not need to be updated.
3.1 Even though there is a difference in definition, TOC and PLC found no significant legal or practical difference between clearances and instructions. Both are orders that have to be complied with, without one being stronger or more urgent than the other. This opinion is endorsed by ICAO.
3.2 TOC and PLC found no need to update the IFATCA Technical and Professional Manual.
It is recommended that this paper is accepted as information material.
International Civil Aviation Organization (ICAO), Annex 11 Air Traffic Services, 14th edition (July 2016).
International Civil Aviation Organization (ICAO), Procedures for Air Navigation Services — Air Traffic Management (PANS-ATM) [Doc 4444] 16th edition (November 2016).
International Civil Aviation Organization (ICAO) Annex 14 Aerodromes, Volume I, 7th edition (July 2016).
International Civil Aviation Organization (ICAO) [Doc9432].
Last Update: October 1, 2020