Navigating through the ash

Dr Fred Prata is one of the boffins working with EasyJet and Airbus to test the feasibility of deploying passive infra-red sensor systems on aircraft to enable pilots to navigate safely through airspace contaminated with volcanic ash.

In fact this passive IR ash detector system, called AVOID, was developed some years ago by the Climate and Atmosphere Department of the Norwegian Institute for Air Research, where Dr Fred works, but no-one took up the idea until now.

I challenged him to convince me that AVOID could really deliver benefits. He did.

Basically, I asked him whether we really know sufficient about the way in which ash distributes itself in the atmosphere following a volcanic eruption to be pretty sure that giving pilots the ability to “see” the stuff would enable them to thread their way through it with safety. Surely, I suggested, the ash is more or less homogenously distributed through large areas of the sky, so it’s either thin enough to fly through, or if it’s thick you have to navigate around the contaminated block of airspace?

Actually, he explained, we do know a lot about three-dimensional ash distribution in the atmosphere, but tracking its position and density precisely is difficult. So being able to see it is the key, he says.

I’ll let Dr Fred explain:  

“We know quite well how ash distributes itself in the atmosphere.  We know about layering (typically 500-2000 m thick) and we know that it tends to occur in “channels” like plumes. 

“This knowledge has come from extensive satellite (infrared measurements, lidar and UV/VIS data) and from ground-based lidar and some airborne research measurements.

“Armed with this knowledge we believe that the system can be used in a tactical manner to observe ash clouds in the distance (up to 100 km seems very feasible).  At this distance a pilot would be able to make slight adjustments to the aircraft’s course and avoid the ash. 

“This does not mean that there would be aircraft making diversions all over the airspace because the plan is to transmit the data back to the ground to be used by air traffic controllers, airlines and the UK Met Office to produce more accurate [real-time] dispersion model and forecasts.

“EasyJet are thinking of fitting a dozen or so “pathfinder” aircraft and the [UK Civil Aviation Authority] seem to be supporting this idea, but of course endorse nothing.  AVOID must first be tested and validated against independent data – this will happen in the next 2-3 months – volcano permitting.

“I think it needs to be stressed that volcanic ash never fills the skies and there are always routes around the hazard – after all this is what happens in most parts of the world now, especially, Alaska, Japan and Indonesia where airlines make quite large costly diversions to avoid ash clouds forecast by models and observed from satellites.  With AVOID fitted these diversions would be much shorter, and more direct routes could be found.”

One Response to Navigating through the ash

  1. Mervin Coghlan 10 June, 2010 at 10:59 pm #

    The scientists at Airborne Research Consultants consultants have been studying volcanic emissions for over 40 years and in that time have found the “infra-red” technology to be unreliable to say the least!
    They use direct particulant measurement and developed a system for the very use we are discussing a considerable time ago, yet as per this infra-red system no one wanted to take them on board…..
    So go on all you airlines and manufacturers get in contact!!!!