This article provides guidance for controllers on what to expect of an aircraft experiencing problems associated with volcanic ash and some of the considerations which will enable the controller to provide as much support as possible to the aircraft concerned.
An aircraft encountering volcanic ash may experience engine problems; in some cases, aircraft have lost all engines as a result of ash ingestion and the subsequent formation of deposits on critical engine surfaces from the burning, melting and re-solidification of particles from the ash cloud.
Care should be taken not to route aircraft through clouds of volcanic ash where forecast on SIGMET charts. Where possible route aircraft upwind of the ash cloud.
Relay available ASHTAM information by reporting volcanic ash hazards to all aircraft concerned.
Note that weather radar will not detect the small particles in the ash clouds and crews may not get any advance warning of entering the ash cloud. ATC radars will not detect the presence of volcanic ash for the same reasons.
Communications with aircraft may suffer interference because of the electrical charges within the ash cloud.
What to Expect
Aircraft are expected to take the shortest way out of the cloud, usually by descent and possibly by making a descending 180 degree turn.
Aircraft affected by engine malfunction may not be able to maintain height.
The flight crew will likely reduce thrust in order to prevent engine damage thus limiting the aircraft ability to climb.
Communication difficulties in case of oxygen mask use.