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10. Flight Operations in Volcanic Ash
10.1 Severe volcanic eruptions which send ash into
the upper atmosphere occur somewhere around the
world several times each year. Flying into a volcanic
ash cloud can be exceedingly dangerous. A
B747−200 lost all four engines after such an
encounter, and a B747−400 had the same nearly
catastrophic experience. Piston−powered aircraft are
less likely to lose power but severe damage is almost
certain to ensue after an encounter with a volcanic ash
cloud which is only a few hours old.
31 JULY 08
ENR 5.7−8 AIP
15 MAR 07 United States of America
Nineteenth Edition Federal Aviation Administration
10.2 Most important is to avoid any encounter with
volcanic ash. The ash plume may not be visible,
especially in instrument conditions or at night; and
even if visible, it is difficult to distinguish visually
between an ash cloud and an ordinary weather cloud.
Volcanic ash clouds are not displayed on airborne or
ATC radar. The pilot must rely on reports from air
traffic controllers and other pilots to determine the
location of the ash cloud and use that information to
remain well clear of the area. Every attempt should be
made to remain on the upwind side of the volcano.
10.3 It is recommended that pilots encountering an
ash cloud should immediately reduce thrust to idle
(altitude permitting), and reverse course in order to
escape from the cloud. Ash clouds may extend for
hundreds of miles, and pilots should not attempt to fly
through or climb out of the cloud. In addition, the
following procedures are recommended:
10.3.1 Disengage the autothrottle if engaged. This
will prevent the autothrottle from increasing engine
thrust.
10.3.2 Turn on continuous ignition.
10.3.3 Turn on all accessory airbleeds including all
air conditioning packs, nacelles, and wing anti−ice.
This will provide an additional engine stall margin by
reducing engine pressure.
10.4 The following has been reported by flight crews
who have experienced encounters with volcanic dust
clouds.
10.4.1 Smoke or dust appearing in the cockpit.
10.4.2 An acrid odor similar to electrical smoke.
10.4.3 Multiple engine malfunctions, such as
compressor stalls, increasing EGT, torching from
tailpipe, and flameouts.
10.4.4 At night, St. Elmo’s fire or other static
discharges accompanied by a bright orange glow in
the engine inlets.
10.4.5 A fire warning in the forward cargo area.
10.5 It may become necessary to shut down and then
restart engines to prevent exceeding EGT limits.
Volcanic ash may block the pitot system and result in
unreliable airspeed indications.
10.6 If you see a volcanic eruption and have not been
previously notified of it, you may have been the first
person to observe it. In this case, immediately contact
ATC and alert them to the existence of the eruption.
If possible, use the Volcanic Activity Reporting Form
(VAR) depicted at the end of GEN 3.5. Items 1
through 8 of the VAR should be transmitted
immediately. The information requested in items 9
through 16 should be passed after landing. If a VAR
form is not immediately available, relay enough
information to identify the position and nature of the
volcanic activity. Do not become unnecessarily
alarmed if there is merely steam or very low−level
eruptions of ash.
10.7 When landing at airports where volcanic ash
has been deposited on the runway, be aware that even
a thin layer of dry ash can be detrimental to braking
action. Wet ash on the runway may also reduce
effectiveness of braking. It is recommended that
reverse thrust be limited to a minimum practical to
reduce the possibility of reduced visibility and engine
ingestion of airborne ash.
10.8 When departing from airports where volcanic
ash has been deposited it is recommended that pilots
avoid operating in visible airborne ash. Allow ash to
settle before initiating takeoff roll. It is also
recommended that flap extension be delayed until
initiating the takeoff checklist and that a rolling
takeoff be executed to avoid blowing ash back into
the air.
11. Emergency Airborne Inspection of
Other Aircraft
11.1 Providing airborne assistance to another
aircraft may involve flying in very close proximity to
that aircraft. Most pilots receive little, if any, formal
training or instruction in this type of flying activity.
Close proximity flying without sufficient time to plan
(i.e., in an emergency situation), coupled with the
stress involved in a perceived emergency can be
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