EUROCONTROL has received reports where flight safety was compromised because 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 cleared route.
Doc 4444 PANS-ATM - 8.6.9 Information Regarding Adverse Weather:
188.8.131.52 “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.”
184.108.40.206 “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.
Avoiding adverse weather conditions places increasing demands/workload on pilots and controllers, in particular in congested airspaces. Consequently, they should work together utilising the best information available to ensure the safe passage of aircraft around areas of adverse weather.
In Oceanic airspace, depending on the circumstances, it may be permissible for pilots to return to the previously assigned route without prior notification to ATC.
In non-Oceanic airspaces, whilst pilots are usually very diligent in informing ATC/obtaining ATC clearance to avoid adverse weather, uncoordinated turns by them to return to their assigned route once clear of the adverse weather may affect the controller’s planning, further disrupt the flow of air traffic and induce conflicts with other aircraft.
Pilot and Controller Considerations
In case of adverse weather avoidance, controllers should, whenever appropriate, and as part of the clearance limit, include a request to the pilots to report when clear of weather and able to resume the flight plan route.
Pilots should, in situations in accord to the above, once manoeuvred around the area of adverse weather, request ATC clearance/confirm with the controller before turning back to their previously assigned route.
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.