Volcanic Ash Aviation Hazard
• from 1935 to 2003 102 aircraft
concentrations of volcanic ash
• ash is not detectable by
weather radar as it is dry
• ash can reach cruise
altitudes in five minutes
• stratospheric ash concentrations
may remain at circa 20,000 metres.
SEVERITY OF ENCOUNTER
0: acrid odour, electrostatic discharge
1: light cabin dust, EGT fluctuations
2: heavy cabin dust, external and internal
abrasion damage, window frosting,
3: engine vibration, erroneous instrument
readings, hydraulic-fluid contamination,
damage to engine and electrical system
4: engine failure requiring in-flight restart
5: engine failure or other
damage leading to crash
No class 5 encounters have occurred so far.
Level 4 incidents
KLM Asia Boeing 747
BA Boeing 747 G-BDXH
BA Flight 9 London to Auckland: 24-6-1982
• Mount Galunggung, Indonesia
• four engines surged and flamed out
• 12-minute gliding time, 7000 m descent
• no. 2 engine failed again at 4000 m
• landing made
KLM Flight 867, Amsterdam-Tokyo
15 December 1989
• eruption of Redoubt
Volcano, Anchorage, Alaska
• all four engines failed leaving only critical
systems on backup electrical power
• battery loading caused temporary
blanking of flight instruments as
attempts made to restart engines
• $80 million damage,
all four engines written off.
What is the safe level of volcanic
ash concentration in the stratosphere
for commercial aviation flights?
Eyjafjallajökull eruption of 1821-3:
• started 19-12-1821, ended 1-1-1823
• central vent, subglacial explosive eruption
• volcanic explosivity index VEI=2
• 4 million m3 of tephra emitted
Eyjafjallajökull eruption of Apr-May 2010:
• started 20-3-2010, ended(?) 21-5-2010
• VEI 2-3
• vulcanian eruption style
• maximum plume height 13 km
• ash had 58% silica concentration.
• the safe level had never been established
• the general circulation is dynamic
• many forms of remote sensing do not
give accurate readings of ash conc.
• main risks ascending and descending
through ash strata in upper
troposphere and lower stratosphere
• 'safe corridors' could close before
flights along them can be completed.
Surveillance and warning
International Civil Aviation Organisation
Internat'l Airways Volcano Watch (IAVW)
London IAVW: for UK, Iceland
and N.E. N Atlantic Ocean
Meteorological Watch Offices (MWOs)
issue significant met. information
National Air Traffic Control Services
On 20 April 2010:-
• No Risk: below 200 μgm-3
• Enhanced Procedures Zone (EPZ)
(Red Zone): 200 μgm-3 to 2000 μgm-3
• No Fly Zone (NFZ) (Black Zone):
above 2000 μgm-3
On 11 May: removal of 60 nautical mile
buffer area around black zone.
On 17 May: creation
of 'flyable' grey zone
"The ALARP* level is only reached when the
time, effort and cost of further reduction
measures become disproportionate to the
additional risk reduction obtained. The
original values that defined the ALARP
upper and lower limits in this case, viz.
2000 μgm-3 and 200 μgm-3 are ad hoc and
without scientific basis and were generated
by a Met Office program that was designed
designed for entirely different purposes.
*ALARP: As Low As Reasonably Possible
The ALARP concept Unacceptable risk
ALARP or tolerability
region: risk assumed
only if benefit warrants it
region (no need for
detailed work to
demonstrate ALARP) Negligible risk
• was it right to ban all flights?
• slow response with four-day delay
• response was country level
more than Europe-wide.
UK Cabined Office
Monday 19 April:
began at 12:00
Thursday 15 April
Volcanic ash was
not in the UK
Hard times for the travelling public
• 6.8 million travellers stranded
• max stranding about 3 weeks
(in Asia and Latin America)
• bone marrow for transplants delayed
• lack of interconnectedness of
different transportation modes
• UNNECESSARY RISK AVERSION?
"The havoc arising from the eruption
of Eyjafjallajökull has been presented
in many circles as being a consequence
of the event being both unprecedented
and unexpected – neither is the case."
Possible future scenario
• much larger, longer eruption
(Katla? - last erupted 1918)
• civil aviation shut down for months
... or years ...?
• need to integrate alternative
transport modes for mass transit
• need to integrate European
Volcanic emergencies are not totally
predictable, can last a very long time,
may be very expensive and can cause
enormous disrpution (as well as major
effects on weather and climate).
Did planes or the volcano emit the most CO2?
European aviation Eyjafjallajökull
344,109 150,000 tonnes
206,465 tonnes CO2 saved by
cancelling flights across Europe