Eurocontrol - Adverse Weather

Adverse weather deviations - ATC clearance and pilot and controller actions


Synopsis

In July 2011, a EUROCONTROL Safety Reminder Message (SRM), Pilot actions on completion of an adverse weather deviation - ATC clearance, was released following concerns raised by ANSPs that some pilots in adverse weather avoidance scenarios do not ask for prior ATC clearance/inform ATC when they are clear of the weather and are returning to their previously assigned route.

This updated version of the SRM retains this theme and stresses that it is also normal procedure before commencing an initial weather avoidance manoeuvre to request permission to deviate from the current ATC clearance.
ICAO Provisions

• Doc 4444 PANS-ATM - 8.6.9 Information Regarding Adverse Weather:
  • 8.6.9.1 “Information that an aircraft appears likely to penetrate an area of adverse weather should be issued in sufficient time to permit the pilot to decide on an appropriate course of action, including that of requesting advice on how best to circumnavigate the adverse weather area, if so desired.

  Note - Depending on the capabilities of the ATS surveillance system, areas of adverse weather may not be presented on the situation display. An aircraft’s weather radar will normally provide better detection and definition of adverse weather than radar sensors in use by ATS.”

  • 8.6.9.2 “In vectoring an aircraft for circumnavigating any area of adverse weather, the controller should ascertain that the aircraft can be returned to its intended or assigned flight path within the coverage of the ATS surveillance system and, if this does not appear possible, inform the pilot of the circumstances.

  Note - Attention must be given to the fact that under certain circumstances the most active area of adverse weather may not be displayed.”

• Special procedures apply to weather deviations in Oceanic airspace and these are contained in PANS-ATM, 15.2, § 15.2.3.

Analysis

• Avoiding adverse weather is necessary to maintain flight safety. The PIC has the ultimate responsibility for the safety of the aircraft, crew and passengers and, whilst pilots are usually very diligent in obtaining prior ATC clearance to deviate from their clearance in order to avoid adverse weather, it is recognised that sometimes it may not be possible to do so.
• Avoiding adverse weather conditions can increase pilot and controller workload in congested and/or complex airspace. Consequently, it is important that they share the best available information in a timely fashion and use it to ensure the continued safe passage of aircraft which are in the vicinity of adverse weather.
• In Oceanic airspace only, depending on the circumstances, it may be permissible for pilots to return to the previously assigned route without prior notification to ATC.
• However, in non-Oceanic airspaces, returning to a previously assigned route without obtaining re-clearance once clear of the adverse weather may prejudice controller planning, further disrupt the flow of air traffic and lead to conflict with other aircraft.

Pilot and Controller Considerations

• It should be possible in most cases for pilots to advise ATC in sufficient time of their need to deviate from their clearance to avoid areas of adverse weather before manoeuvring the aircraft. Similarly, once pilots have flown around the area of adverse weather, they should request ATC clearance/confirm with the controller prior to turning back to their previously assigned route.
• In case of adverse weather avoidance, whenever appropriate, controllers should include a request to the pilots to report when clear of weather and able to resume the flight plan route as part of any clearance limit.

Your Attention is Required
Aircraft Operators and Air Navigation Services Providers are invited to note the subject, follow the guidance as appropriate and share any relevant operational experiences concerning the issue.
Further Reading
SKYbrary

• ATC Operations in Weather Avoidance Scenarios
• EUROCONTROL Safety Reminder Message (SRM)

ICAO

• ICAO Doc 4444, PANS-ATM: § 8.6.5.1.d Vectoring and § 8.6.5 Navigation Assistance.

For more information contact, EUROCONTROL Safety Alerts Coordinator, Richard Lawrence