Page 16 - 2017-Issue2

GETTING CLOSE WITH ATS 16

“Getting Close” with ATS

The Air Traffic Services Committee on

Separation Standards & Phraseology

This year’s Conference will see a Sunday afternoon Plenary place an unacceptable risk on separation minima. FANS 1/A
during which the Air Traffic Services (ATS) Committee will make equipped aircraft may be separated by as little as 30 nm laterally
a presentation highlighting some of their work. and 5 minutes longitudinally. When aircraft make a speed
The Air Traffic Services Committee covers subjects in 10 of the change and don’t advise ATC, longitudinal separation can erode
19 ICAO Annexes as well as PANS-ATM and PANS-OPS and quickly. Data shows that aircraft are frequently making Mach
provides representation on 10 of the ICAO Panels/Working speed changes of Mach .04 or greater and not advising ATC. A
Groups. The ATS Committee also works closely with the Mach speed change of M.04 equates to a change of around 26
International Federation of Air Traffic Controllers’ Associations knots. This means the ATC separation can erode by 6 nm before
(IFATCA). There is representation from IFATCA on the ATS the next ADS-C report can make ATC aware of the speed
Committee and ATS Committee representation on their Technical change. A 6 nautical mile erosion is 20 percent of the separation
Operations Committee. minima which creates a significant safety risk.
The subjects include Air Traffic Management, Communication, The issues with reducing the lateral separation can best be
Navigation, Surveillance and Supporting Logistics such as illustrated by what is happening in the North Atlantic.
Meteorology and Aeronautical Information Management. With the Reduced Lateral Separation Minima (RLatSM) in the North
development of new technology and procedures the ATS Atlantic (NAT) was introduced as a phased trial in December 2015
Committee reviews their interoperability and harmonisation using a single Oceanic Track FL350 -390. It involves half degree
(which sadly, is rarely achieved). spacing and reduces lateral separation from 60 nm to as low as 23
Separation standards are constantly being reduced, usually to nm. The operational requirements are ADS-C, CPDLC and RNP4.
facilitate efficiency in the system which relates to capacity. This, for Of the over 600,000 flights total in the NAT, only approximately
the most part, requires additional technology on board the aircraft 50,000 flights have participated in Phase 1.
and/or training for the crew to be able to utilise the technology. It There are several generic operational concerns affecting pilots:
is becoming evident however, that we may be reaching the limit for • Entry of the HALF degree waypoint requires typing all 13
reducing separation any further, be it vertically, longitudinally or characters of latitude/longitude
laterally. • High potential for data entry error
Just about everywhere employs Reduced Vertical Separation
Minima (RVSM) above FL 290 and in the majority of FIRs there are • Pilot display on FMC and ND of waypoint name for
few problems, except when there is a need to deviate from the route WHOLE and HALF degree waypoint identical (FMC/ND
or track due to weather and possible emergency. In addition, can only display 7 characters, must truncate and round data
turbulent weather conditions can affect the altitude control of the entry)
aircraft and it is important that these are always reported; in these • Use of NAV database naming convention (ARINC 424
cases it is possible that RVSM may need to be suspended. format) for WHOLE and HALF degree lat/long waypoints
Where RVSM relies upon the altitude control capability of the easily confused and it is difficult to identify errors with
aircraft, longitudinal separation relies upon its speed. Aircraft course/distance check
speed changes that are not requested or announced to ATC can
• Proper navigation relies on strict adherence to inflight pilot

InterPilot | The Safety and Technical Journal of IFALPA ISSUE 2 | 2017