Tuesday, June 21, 2011

Are Aircraft Cancellations Really Necessary for Ash Clouds from Volcanoes Thousands of Miles Away?

There are four well described cases of flameouts caused by volcanic ash clouds which have been extensively studied and recorded. The article linked here by Marianne Guffanti discusses all these episodes and reviews the issue of volcanic ash in detail. One concludes from the article that there is actually very little data available on the subject.
The most famous near-crashes are:
1982, BA 9, Boeing 747, London to KUALA-LUMPUR to PERTH, Mount Galunggung volcano, Indonesia. Distance from Volcano = 100-200 km.
1982, SQ, Boeing 747, probable international flight, Mount Galunggung volcano, Indonesia. Distance from Volcano = Uncertain - but nearby.
1989, KLM, Boeing 747, Near Redoubt volcano Alaska, about 135 km from Anchorage.
2000, Unknown airline, Boeing 737-800, Mijake-jima volcano, Distance from Volcano = about 130 km (near Narita airport).
In all cases the plane was practically in sight of the volcano and flew into a dense cloud.
Mt Redoubt is 135 km from Anchorage so that ash cloud was very fresh. Actually, the KLM pilot described it as a "black" cloud.
The British Airways flight 9 to Perth was 100 km from the active volcano Mt Galunggung volcano and experienced a total flameout. The other episode occurred a few weeks later in the same area and that plane landed on two remaining engines somewhere in Indonesia.
There is only one likely report of engine damage after a faint ash cloud was penetrated by a jet. In the detailed report linked here, Thomas J. Grindle describes the case of a research DC-8 NASA jetplane which flew into a cloud of ash coming from Mt Hecla in Iceland. The cloud was not noticed by the crew but instruments recorded the event and they did not the absence of stars for 7 minutes. Aerosol of 20,000 particles per cm^3 were detected for seven minutes, as well as sulphur. The flight path was 800 miles north of the volcano and supposedly 200 km away from the cloud. The plane flew normally for another 47 hours then was inspected. There was internal abrasive engine damage probably caused by the ash cloud, although it is admitted that it had flown through a sandstorm a few days earlier after which no damage was discovered on internal inspection. This event is taken as evidence that even an invisible ash cloud can damage a plane. However, it is possible that the cloud was much denser than they thought since it was nighttime. Also, it was surprising that the windshield was not abraded, just the engine, which would support the sandstorm hypothesis since "sand blasting" was only seen in the engines. If the inspection after the sandstorm was deficient, would they have questioned it in the official report when at the time, it had little relevance?
Based on these data, should Australian travellers be grounded? The idea that an ash cloud could circumnavigate the globe and then, even though it appears to be a transparent brown stain on a satellite image, could noticeably affect a plane, has been accepted without question by Australian airlines. This is clearly a situation far beyond the actual recorded cases.
Presently, ash from Chilean volcano Puyehue must cross the Atlantic and Southern Oceans, a shortest distance of about 11,000 km and a "cloud path" distance of 19,000 km. The "ash cloud" is visible in thin streaks of light brown transparent air by satellite images. There is no apparent data as to how much ash is actually present. However, it logically would be extremely diluted. Its transparency must indicate a very small amount indeed.
An animated image of the ash cloud is shown below.

Like many things airlines do, cancelling Australian flights because of a Chilean volcanic eruption, has very little basis in fact. It might have about the same safety benefit as preventing people reading their Kindle during landing. The current cancellations of flights in Australia have affected more than 100,000 travellers but no-one has looked again at the evidence base for cancelling flights. Meantime it costs aviation, and the public, tens of millions of dollars (in Australia) and probably hundreds of millions in Europe and the USA (but there they are at least much closer to the volcano - typically planes are flying close to iceland and parallel to the ash cloud).
It would make sense to have research planes fly through the transparent ash cloud and take measurements so that we know how much ash is actually present when a cloud is visible. After that, the engine effects could be correlated with the air sample measurements. These could be posted on the web as ash concentration charts. Then we would know. There are other dissenting voices on the web, read the pilots forums.

June 21st 2011

Wednesday, January 12, 2011

My Latest Genome SNP report from DeCodeMe

This post is an update on my SNP genome scan report in which there has been a few developments. It came about because my dad (Bob Marshall) had his 80th birthday last week and we made a detailed report on his ancestry based on DeCodeMe. By the Y-chromosome he was related to Somerled the Viking-Scottish 12th century king (as are millions of other caucasians). However, I noted the high risk he has for macular degeneration (5x, 46%). This rang a bell because his grandmother (Jessie Boneham) went blind after "she had her cataracts removed but the operation didn't work" suggesting retinal disease after age 85 years. Anyway I looked again at my age related macular degeneration risk and see a lesser but elevated risk (2.88x, 23%). Last month my eye exam was normal except for early arcus senilis and slight refraction problems. I'll continue with a two yearly check. This year I decided to seriously attend to my blood pressure (erratic and about 20mm above ideal levels if not treated) and also my cholesterol. My SNP risks reflect a 50% risk of hypertension, as well as diabetes, obesity and heart attack (although modestly elevated). Good news is that my risk of muscle damage from my statin is low so I can take these with impunity. My recent blood pressure readings are graphed in one of the documents on the web site. An episode of angioedema caused me to change my ACE inhibitor to an ACE receptor blocker and so far I have not had any more side effects.

You can read my full SNP report plus other health reports here: http://www.bajama.mine.nu/~barry/decodeme/ . I also include an AVI file showing a movie of my coronary calcium CT scan and you can go into the directory below to see my actual raw SNP data in case you want to research it. I don't know what use this information is but I do want to hold true to my idea of a public health record. More and more people care less and less about this type of data - its becoming so common.

What else is new? Well, I am saving up to have my total genome done. I would also like to do my whole family, but the Western Australian DNA bank refuses to store the DNA at present. They are so precious that they only do storage for bona-fide research projects, not for people like me who are just exploring their own family. So I may just keep it frozen in the back of my -80C refrigerator at the H.pylori Research Lab.