Synopsis

In the United States (US), the meaning of ‘AT PILOTS DISCRETION’ in radio telephony voice communications related to climb/descent clearances is promulgated to include the option for pilots to level off at intermediate levels. However, the meaning of this phrase in this sense is not understood globally and there is a risk that its use outside the US could lead to adverse safety outcomes if non US-based controllers unwittingly approve pilot requests to climb/descend at their own discretion.

ICAO Provisions

ICAO Doc 4444, PANS ATM, Chapter 12, Phraseologies:

• The verbal use of the word ‘discretion’ is referred to in several places mainly in association with ‘push’ and ‘start’ clearances,
• The phrase ‘WHEN READY’ is included, variously, in the context of departure, changing frequency and climb/descent, meaning that these actions may take place at a time when convenient to the pilot.

Notes:

1. The phrases ‘AT PILOTS DISCRETION’ and ‘WHEN READY’ are also included in PANS ATM Appendix 5 – Controller-Pilot Datalink Communications (CPDLC) message set. The meanings in CPDLC are synonymous in that they are both used to indicate execution when the pilot is prepared to do so.
2. ICAO Doc 9931 (Continuous Descent Operations (CDO) Manual) includes the use of either ‘DESCEND AT PILOT DISCRETION’ or ‘DESCEND WHEN READY’ for some CDO clearances. Both of these phrases mean that the pilot may adjust the rate of descent as required although by their very nature these types of operation imply that pilots would not execute a level off.

Analysis

The meaning and use of ‘AT PILOTS DISCRETION’, in voice communications, including the option for intermediate level offs, applies only in US airspace where it provides some operational flexibility. However, outside the US, cases have been reported where the understanding of ‘AT PILOTS DISCRETION’ in the operational context described is not the same; controllers expect pilots to make a continuous climb/descent to the level cleared. The unsuspecting use of ‘AT PILOTS DISCRETION’ by non US-based controllers in response to US-based pilot verbal requests could therefore lead to a situation where they approve the request for ‘own discretion’ (to climb/descend) without recognising the potential of an unexpected outcome i.e. a possible intermediate level off. The use of the voice message, ‘WHEN READY’ as per PANS ATM Chapter 12.3.1.2g, namely “WHEN READY CLIMB (or DESCEND) TO (level)” prevents any possible misunderstanding outside the US and does not imply any intermediate level off.

Your Attention is Required

• Aircraft operators are reminded that the option for an intermediate level off following an ‘AT PILOTS DISCRETION’ request to climb/descend applies only in US airspace and are invited to review SOPs and note the subject for consideration and awareness.
• Non-US air navigation service providers are also invited to:
  • Note the subject and share any relevant operational experiences concerning the issues described.
  • Note the availability of both ‘AT PILOTS DISCRETION’ and/or ‘WHEN READY’ type phrases for specific CPDLC messages and CDO operations.
  • Consider using the voice phrase ‘WHEN READY’, as per PANS ATM Chapter 12 Phraseologies, rather than ‘AT PILOTS DISCRETION’ when it is appropriate to do so.
  • Exercise caution in approving verbal requests from pilots to climb/descend ‘AT OWN DISCRETION’.

Further Information

• ICAO PANS ATM, Chapter 12.
• IFALPA Briefing Note, 15ATSBL01, “When Ready” vs “At Pilot’s Discretion”, 15 April 2014.

Disclaimer

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