Volcanic Ash Clouds And Aviation

Question 1

What are the two key general references for this topic?

Answer 1

Davison and Rutke, 2014

Witham et al., 2011

Question 2

How many above water eruptions are there per year?

Answer 2

50-60, with 10-15 occurring at the same time

Wunderman et al., 2004

Question 3

What is happening in Hawaii?

Answer 3

Kilauea, 2018 eruption currently occurring on Hawaii’s Big Island
13th May - aviation red alert - no fly zone around the volcano (New York Post)
Important as Hawaii relies on a significant proportion of money through tourism

Question 4

What types of eruption don’t pose a threat to aviation?

Answer 4

Vulcanian and surtseyan eruptions could disrupt aircraft operations locally
With Strombolian and Hawaiian eruption posing no threat
It is plume generating (e.g. Plinian) eruptions that are worrying

Question 5

Outline aircraft encounters since 1953:

Answer 5

Guffanti et al., 2010

94 confirmed, with around 25% resulting in engine damage or failure
9 of these had temporary engine shutdown during flight

These demonstrate the danger of volcanic ash to aviation and the necessity of being able to predict the location of ash plumes - although there has been no loss of life!

Question 6

What happened at Mt Redoubt?

Answer 6

Casadevall, 1994

14-15 December, 1989
Alaska
KLM 867 en route to Anchorage
All 4 engines stalled, and the aircraft lost 10,000 feet before a successful restart
Losses to company were >$150mn

Question 7

Which countries have volcanoes within the proximity to major air corridors?

Answer 7

Japan and Indonesia
Alaska
Italy and Iceland

Question 8

Which volcanogenic products are most damaging to aviation?

Answer 8

Ash and dusts - however sulphur can increase engine corrosion if high enough

Question 9

What is the best way to monitor ash cloud dispersal for the purpose of aviation?

Answer 9

Satellite observations - these can provide real-time data

Although these are limited by temporal resolution, and constraints of modelling

Question 10

Outline how ash can affect airplanes (4)

Answer 10

1) Engine damage
2) Interference with radios
3) Interference with navigation equipment
4) Window damage (reducing visibility)

Question 11

Outline how ash can damage engines:

Answer 11

Ash has a melting point that is much lower than the working temperature of an engine, so upon entry it melts
However as soon as it reaches cooler parts of the engine it freezes to form a solid
The particles will melt if the turbine inlet temperature exceeds the melting point of the ash - and the melt temp. Of the ash varies depending on composition - thus it is critical to know plume composition to determine the threat of an ash cloud

Question 12

What are the three major forms of engine damage caused by volcanic ash?

Answer 12

1) deposition of ash on turbine nozzles and blades
2) the erosion of compressor and turbine blades
3) carbon deposits on fuel nozzles

Question 14

Who are the ICAO?

Answer 14

International Civil Aviation Organisation

Regulate international air aviation

Question 15

What are VAACs and what do they do?

Answer 15

Dacre and Harvey, 2018

Volcanic Ash Advisory Centres
There are 9 VAACs around the world - they detect, monitor, and forecast the dispersion of ash clouds
Use satellite, on the ground and aircraft measurements to model volcanic ash transport and desperation (VATD)
Each VAAC styles their products slightly differently, but they all simulate an eruption every other week or so to check preparedness

Question 16

What is the ICAO three step plan?

Answer 16

1) Report eruptions
2) Detect ash clouds, and forecast their expected dispersion
3) Issue special warning messages

Question 17

What makes the VATD models complex?

Answer 17

Servanckx and Chen (2004)

The processes governing the dispersal of tephra is itself complex
Must understand both emission source and meteorological setting
On top of this processes such as the chemical and physical removal of ash (so depositional processes e.g. aggregation) are key

Question 18

Outline the impacts of the Eyjafjalljokull eruption

Answer 18

2010 eruption
Caused US$1.7bn loss from airline industry
10 milllion passengers had their flights cancelled, on 107,000 airplanes

Question 19

What was the aviation guidance before and after Eyjafjallajokull?

Answer 19

Before - there was a zero-ash tolerance, which meant models simply had to predict the presence of ash and no flying would occur
Now models must predict both the concentration of ash, and where it is located
“Limits” now exist - >4mg/m3 equates to a no-fly zone
This occurred due to pressure from the industry, allowing airlines to make their own decisions about safety

Question 20

What are the challenges to having a quantitative system rather than a simply no-fly zone?

Answer 20

1) there must be very accurate mass eruption rates

2) uncertainties are very large

Question 21

Why can’t aircrafts detect ash themselves?

Answer 21

Current aircraft weather radars are designed to detect moisture in clouds, so therefore cannot detect dry ash
However there is talk of new technology termed the Airborne Volcanic Objective Imaging Detector (AVOID) that can be installed on the wings of the plane, with a horizontal detection range of 100km and a vertical range from 5000 to 50,000 ft (EasyJet, 2013)

Question 22

Outline Mt St Helens case study:

Answer 22

Gabbard et al., 1982

C-130 (military transport) aircraft encountered the ash cloud 12 minutes after take-off, having departed 50 minutes after the eruption began - these planes cost a minimum of US$10mn
This occurred at an altitude of 12,000-13,000ft
After 2 to 3 minutes of exposure, one of the engines began to stall and surge, becoming uncontrollable and requiring shut down - another engine surged and was shut down 2 minutes after

Question 23

Outline the case study of the Galunggung eruption

Answer 23

1982
Witham et al., 2011

Best-known example - a major milestone in the recognition of the threat of volcanic ash to aviation
British Airways 747 aircraft over Indonesia, during a flight from Kuala Lumpur to Perth
In-flight failure of all four engines, and the abrasion of windshield and wing surface
All four engines did restart as the aircraft descended below the plume to Jakarta
Abrasion to the cockpit windsheilds meant that it was practically impossible to see out of the cockpit on the final approach

Question 24

Outline the case study of the Redoubt Eruption

Answer 24

Casadevall, 1994

1989
There was very good information available on the aircraft location and flight path, which is important in determining how much ash the aircraft encountered and therefore modelling how much aircrafts can withstand
Model simulated that the flight encounter a maximum of 70 mg/m3 when the engines stalled

Question 24

Outline the case study of Pinatubo

Answer 24

1991
Between the 12th and 18th of June, 16 damaging in-flight encounters were recorded between jet aircraft and ash cloud, MANY UP TO 2000KM FROM THE VOLCANO
17th of June 747 lost two engines
In total 10(!!!) engines needed to be replaced - one jet engine can cost anything from US$10-40mn
This example shows why understanding plume dynamics and dispersal is so important

Question 26

Outline the case study of Grimsvotn

Answer 26

2011
Eliasson et al., 2011
Cooke et al., 2014

Highlighted the importance of understanding ash impacts separately from SO2
SO2 is easier to track, so it was often taken as a proxy for ash dispersal
However, it can actually travel in very different directions, and model did not used to constrain this well
The models from this study highlighted that models were significantly improved when ash and sulphur were modelled separately

Question 27

Outline the case study of Mount Kelut

Answer 27

2014
Kristiansen et al., 2015

Indonesia
Ash-rich eruption that led to the cancellation of 40 different flights
Commercial jet flying from Perth to Jakarta accidentally encountered the ash cloud, observing St Elmo’s Fire in the cockpit and fumes in the cabin - despite having executed avoidance actions (different route and lower altitudes)
This case highlights the importance of modelling processes such as ASH FALL from umbrella clouds which can mean that ash particles descend to lower altitudes, leading to aircraft encounters
The amount of ash the aircraft encountered is thought to be 2x the limit set by the European Commission during the Eyjafjallajokull eruption