What to do in an
Emergency
Unfortunately, it is not always possible to avoid an
ash cloud and if a plane does enter one there are very specific steps
that the flight crew must take in order to increase the chance of
making it out of the dangerous area safely, according to Campbell
, 1994:
Immediately
reduce thrust to idle. This will lower EGT, which in turn
will reduce buildup on the turbine blades and hot-section
components. The volcanic dust can cause rapid erosion and damage to
the internal components of the engines.
Autothrottles
off (if engaged). The autothrottles should be turned off to
prevent the system from increasing thrust above idle. Due to the
reduced surge margins, limit changes with slow and smooth
thrust-lever movements.
Exit
volcanic cloud as quickly as possible. Volcanic ash may
extend for several hundred miles. The shortest distance/time out of
the dust may require an immediate, descending 180 degree turn.
Setting climb thrust and attempting to climb above the volcanic
cloud is not recommended due to acellerated engine damage/flameout
at high thrust settings.
Engine
and wing anti-ice on. All air conditioning packs on.
Start
the auxiliary power unit (APU), if available. The APU can be
used to power the electrical system in the event of a
multiple-engine power loss.
Oxygen
mask on and 100%, if required.
Ignition
on. For systems with autostart, switch to "on"
position.
Monitor
EGT. If necessary, shut down and then restart engines to keep
from exceeding EGT limits.
Close
the outflow valves.
Do
not pull the fire switch.
Leave
fuel boost pump switches "on" and open cross-feed valves.
Engine restart. If
an engine fails to start, try again immediately. Sucessful engine
restart may not be possible until airspeed and altitude are within
the airstart envelope. After the engine starts, land at the nearest
airport.