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very finite battery power and with
the pressurisation system failing,
among many other complications. The
abrasive nature of the ash can erode
the entire airframe, but the immediate
threat is posed by the damage to
the windscreen, limiting the pilots’
forward visibility on the approach and
landing.
As the volcanic ash absorbs water,
it has the potential to create short
circuits across the electrical system
and avionics, while the cabin air
may become heavily contaminated,
requiring flightcrew to don their
oxygen masks.
For an aircraft inadvertently
entering the ash cloud, a number
of accompanying symptoms can
occur. The smell of sulphur, or an
electrical burning smell can pervade
the aircraft and a haze can fill the
cabin and flightdeck with dust settling
on all surfaces. The fluctuating
pressurisation system can be felt in
the passengers’ ears if subtle, or worse
if the system fails altogether. From
their windows they may see torching,
flashing from the rear of the engines,
or the electrical tentacles of St Elmo’s
Fire creating an eerie glow on the
airframe and the engine inlets.
On the flightdeck the same light
show can be seen, while the static
discharges interfere with the radios
and communications. The airspeed
can begin to fluctuate rapidly and
erroneously, triggering spurious
warnings, as the outside sensors begin
to clog with ash. The engines begin to
surge and protest, choked of airflow
until the point of strangulation before
flaming out into silence. With the
engines failed, the electrical generators
are also compromised and on board
the cabin lights go dim as the airliner
is forced into a descent by a lack of
thrust and the forces of gravity.
This is the situation Speedbird 9
found itself in that night to the
south-east of Jakarta, when all four
engines failed. Thirty-five years ago,
the crew did not have the benefit of
the awareness or education in the
ways of volcanic ash that we have
today. Furthermore, the encounter
occurred at night when there was not
the ability to see the ash cloud loomingahead while the weather radar is
only suitable to detect exactly that- weather. Airborne radar systems
can detect moisture, but not the
components of volcanic ash.
The fact that the crew were able to
restart their engines and safely land at
Halim Airport is a testament to their
ability in a dire situation. Fortunately,
much has changed in the intervening
years and airlines and pilots alike
are far more educated in the ways of
volcanic ash.
A global awareness
According to the United States
Geological Survey, there are about
1,500 potentially active volcanoes
worldwide, of which about 500 have
recorded eruptions. Some volcanoes
are tracked by Volcanic Observatories
which take seismic readings, measure
deformations, and monitor gases
among other warning signs. However,
around the world more than half of
the volcanoes are not monitored.
The International Civil Aviation
Organization (ICAO) has established
International Airways Volcano WatchEyjafjallajokull volcano eruption
in 2010 caused chaos for the
world’s airlines.