Volcanic ash: who says flying’s not safe?

The problems with decisionmaking about whether to fly – or not – in the volcanic-ash-affected skies over Europe is that so little is known about these circumstances. The situation is unique in that this ash cloud is affecting a large area of intense aviation activity.


Dornier wing.jpg

The Met Office weather research Dornier 228 at work

Vocanoes somewhere on the planet erupt frequently, but normally the ash they produce affects areas in which aviation activity is far less intense. The tactic for dealing with ash clouds, until now, has been to fly around them. We never needed to understand them, just avoid them.

Engine manufacturer Rolls-Royce has, today, absolutely refused to comment or to answer questions about anything to do with the current volcanic ash threat.

UK air navigation service provider NATS, in contrast, has been immensely helpful, but honestly admits that the biggest problem it has in making decisions about opening or closing airspace is lack of data about the risk associated with these precise circumstances, and the lack of precision reporting about the position of the ash cloud.

NATS quotes its remit – one which all ANSPs are supposed to follow: they are “not to direct flights into a known flight hazard”. If they were to do so, their position would be morally and legally parlous. The question is, is this a “known” flight hazard, or just a suspected one?

Unfortunately in this case European airlines, and airlines bound for European destinations from outside, cannot fly around the ash cloud because it fills the sky above almost the entire continent. Unless it moves, they cannot arrive or depart without flying through it.

One of the consequences of applying the traditional technique of ash avoidance until now is that the aviation industry has never had to research the risk of damage, particularly to aero engines, of flight through areas of widely dispersed upper airspace volcanic ash, rather than the volcanic plume itself. 

The industry fully understands the effects of flying through volcano ash plumes downwind of the eruptions. This concentrated ash clogs the hot section and abrades the cold section of turbine engines, stopping them or dramatically reducing available engine power. Engine core repair following this damage is usually unfeasible, making replacement the only option.

But volcanic plumes themselves are easy to avoid. They don’t cover a wide area and Satellites can track them accurately. Unfortunately satellites cannot detect the type of widely dispersed very fine ash particles over Europe at present. Their progress is estimated by computer modelling and atmospheric sampling. But the particles remain abrasive to moving parts in engines. 

There are greater and lesser concentrations of particles at different vertical levels, their distribution determined by a combination between the strength of the individual eruption that projected the ash skyward, then by the weather system. Meanwhile below these layers, the dust is constantly drifting down from the upper air to the ground, so no-where is absolutely ash-free. My car, parked outside in SW London, is covered by a thin layer of ash.

It looks as if today’s videoconference of European ANSPs, aviation authorities and transport department officials has produced a decision to try to re-start operations in some of Europe tomorrow. The main reason appears to be a weakening of the volcanic activity – but that weaker level of activity is not guaranteed to be sustained.

Weather patterns, unfortunately, look as if they will sustain a drift of ash from Iceland toward Europe for the next five days at least.

In addition, consideration must have been taken of the results of test flights by aircraft of KLM, Lufthansa, Air France, British Airways and others. Their experience was universally benign. But did they get lucky? We don’t know. What’s more we don’t yet know whether low level abrasion has affected the efficiency of the engines. An increase in fuel consumption for the life of an engine would be a high price to pay for an early return to the skies.

A fully-instrumented Met Office Dornier 228 returned from its flight yesterday saying it had found levels of ash that would probably represent a risk to flight safety.


Met Office Dornier.jpg

The Met Office Dornier 228

And on 15 April a pair of Finnish Air Force Boeing F-18 Hornet fighters took off and had serious problems with their engines. When they returned, the inspected engines showed classic internal volcanic ash damage and they may never power an aeroplane again.


Finally, it is not just the Icelandic volcano that has provided Europe with this problem, it is the combination of the volcano and an untypical weather system for the time of year over the British Isles and northern Europe. High pressure and northerly winds have dominated for more than two weeks now, and look as if they will continue to do so.

If only typical April weather for the region were to return, the normal south-westerlies would bring frontal activity and rain showers, and they would drive the ash cloud north east toward northern Siberia, leaving Europe in the clear. 

, ,

14 Responses to Volcanic ash: who says flying’s not safe?

  1. diana 19 April, 2010 at 4:28 pm #

    the most informed article I’ve read about the situation by far, brilliant analysis

  2. Dean K 19 April, 2010 at 4:44 pm #

    Mr. Learmount -

    Do you know whether turboprop aircraft would have any advantage in ash cloud conditions?


  3. David Learmount 19 April, 2010 at 5:32 pm #

    They process less air internally than turbofans, and the hot section operates at slightly lower temperatures, but they could sustain the same type of internal damage.

  4. Lucasmaximus 20 April, 2010 at 11:25 am #

    Thanks for this informed and well balanced aritcle. Although this no-fly zone is an extreme incovience its great to see that an international body is taking passenger safety before profit margins.

    Mr Learmount, do you think this would have been the case during previous generations especially the 70′s and 80′s or is this a mark of how far avaition safety has come or is it just as the sceptics would say a knee jerk reaction to the general fear of lawsuits?

  5. Christopher Orlebar 20 April, 2010 at 5:13 pm #

    Frequently Saharan sand can be seen deposited on cars in the UK. Has this ‘cloud’ of sand ever damgaged a jet engine? How much damage do military gas turbines sustain when they are operated from a base in the desert? How does desert sand compare to the ash from the Icelandic volcano? Finally: how difficult is it to develop an ash detector?

  6. Caio Nery 20 April, 2010 at 5:31 pm #

    Great article!

  7. Daniel Voss 20 April, 2010 at 6:55 pm #

    The Danish CAA decided also to ground gliders!

  8. Terry 22 April, 2010 at 1:31 pm #

    I am also curious about the effects of sand… I’ve spent many years working in African countries which are annually subjected to a weather phenomena called Harmattan. Essentially huge areas sometimes entire countries would be engulfed in a haze of Saharan dust and sand for weeks on end. The sky would remain white rather than blue, visibility would be greatly impaired and the sand just got everywhere. Yet hardly ever did I hear of flights (international long haul included) cancelled as a result

  9. David Connolly 24 April, 2010 at 1:03 pm #

    Ashes to ashes, dust to dust, we are all humbled before Vulcan’s tectonic Icelandic throne. On April 13th I landed in Dublin, as I always try to do since 2005, for the annual “al-fresco” commemoration performance of Handel’s oratorio, “Messiah”, echoing in Fishamble Street-Handel on Fishamble, finishing with a rousing Hallelujah chorus. It’s world premiere was there in the Musick Hall @12:00 on April 13 1742 with Herr Handel on hand, so to speak. That day in 2010 was an acoustic and meteorological joy in unison with a street audience of 1000 with gin-like severe clear Wx. CAVOK clearly, Hector O’ Pascall was sitting High and Handel was smiling-it felt- from history, I filmed it and it is on Youtube, “Messiah on the street” among many others. This was it’s 18th consecutive year of commemoration. Tradition is not always the spoiled child of bad habit.
    Unfortunately Iceland’s Eyjafjallajokull was projectile vomiting lava and belching ash and all of northern Europe was to be humbled with the unusual and perfect geo-met collusion of Hector O’ Pascall. Europe wanted Iceland’s cash back, but received ash in exchange, fiction is made redundant again. I was stranded from Ash Thursday April 15 ,until April 22. I fared lightly in this high pressure situation, with a diversion after a salute to Arthur Guinness’s Liffey water to Cork’s superior Lee water, Beamish and Murphys imbibing. I kept the CG in optimal MAC % equilibrium range daily swim and gym. It was liberating to be back in a pre-aviation non-contrail age of no choice, with a new focus on the joy of the journey by sea. Now that the dust has settled the recriminations are flying thick and fast in general and from IATA in particular, with some justification.
    Regarding operational non-operational particulars, I take particular note of KLM’s CEO Peter Hartman on Ash Saturday and BA’s CEO Willie Walsh on Ash Sunday of leading from the front in partaking of their respective test flights to mitigate the effect of regulatory prohibition of allowing flight in “known or suspected hazards” . This was part PR, normally the inverse square root of BS, and a lot more part frustration of regulatory blanketing of a single European sky in an ash of ignorance. These were the exceptions that made this rule. Regulation of course has always been and shall be forever in perpetuity, political vindication allied with public comfort, ask any investment bankster. Zero tolerance regulation is blind to common sense of subjective proportionality.
    Hopefully actual science, will inform the next regulatory de-facto prohibition on N1 dust abrasion limits, when Hector O’ Pascall allies with Ejafjallajokull or one of it’s tectonic neighbors creating another perfect geo-met anticyclonic storm. Needless to say the Climate Research Unit of the University of East Anglia should have no input whatsoever. If those environmentalist or just plain mental muppets have any input, then we shall all be reciting a requiem of “ashes to ashes and dust to dust” for all aviation at it’s graveside. Like psychiatry, they make organized religion look scientific. GDP in Modern Greek accounting mythology is today translating as Greek Decimal Point and IMF as It’s Mostly Fiscal. In the same spirit of revisionism, lets translate and update RIP as Research In Perpetuity. University of East Anglia’s CRU ?…No thank U !

  10. Don Turner 27 April, 2010 at 7:41 pm #

    Desert sand can reduce the overhaul life of an engine by 50% mainly because of erosion.

  11. Orlando Giacich 15 May, 2010 at 11:14 am #

    I cam across these comments today and the Desert Sand phenomenon is one of the first things that hit my mind during this confusing sequentce of islandic volcanic event.
    To my knowledge only two events highlighted the problem when flying into volcanoic ash: The BA747 (famous for its all engines out scare) and the DC8 43 (NASA’s?) flying into finite volcanic ash, while circumnavigating the plume, which deposited volcanic dust in the turbines. I believe the ash was detected quite some time later and led to the complete overhaul of the engines.
    In Italy we have Mount Etna that often erupts copiously and never caused the complete closure of any part of the Italian airspace. Only the closure of the Catania airport. FYI Palermo, Trapani, Reggio Calabria airports, all quite close to Catania, have always been unaffected. I can’t tell for sure but something is not right with the NATS reaction

  12. Brian Millo 16 May, 2010 at 10:49 pm #

    I agree that your analysis is helpful, David, but:
    1. couldn’t commercial aircraft fly below the “cloud”? Higher fuel consumption, I guess, but at least they’d be flying.
    2. what’s the difference between these Icelandic ash-clouds and the Mt St Helens ash-clouds of … was it really 25 or so years ago?
    And we all wonder about how the southern Italians get away with Etna eruptions (as indicated by correspondent Orlando Giacich on May 15).
    (If my name’s familiar, find me on Facebook. We’re still at No.5!!!)

  13. David Learmount 17 May, 2010 at 9:53 am #

    The anwers to your questions are embedded in what I already wrote, but specifically: for Etna and Mt St Helens, the volcanoes are not in areas with lots of airports and masses of aviation activity, like the British Isles and northern Europe. Where there is much less traffic to disrupt, much less traffic gets disrupted.

    For related reasons, in the case of both these volcanoes it was/is almost always possible to avoid the denser parts of the cloud by flying around them. You can do that when the cloud is not parked over the top of you. Etna is in the middle of the Med, and Mt St Helens is in the middle of the Rockies. But flying DOES get affected locally when either erupts. It’s less likely to be stopped by it, but extensive re-routeing takes place.

    Finally, can you fly below it? Yes, sometimes, but ash drifts down gradually and settles on the ground, on your car (and on the glass-topped table in my garden near Heathrow, as an example), so that is one of the risks the aviation authority has to calculate before it clears a given airspace sector.

  14. Mike Hindson-Evans 17 May, 2010 at 11:00 pm #

    Interestingly, I’ve received a mailshot tonight from Flybe, infoeming me that (quote) “FLYBE welcomes new CAA fules for Q400 flying” (unquote).

    Forgive me, but what’s a fule??

    Mike Hindson-Evans