Easy Jet To Use Infra Red Cameras To Avoid Ash

[brooksjg]

Assuming the camera system gives an edge-on view of a VA cloud ahead of the aircraft, there's an immediate problem with ranging (ie. distance to the near and far edges of the cloud). Even if it's possible to determine these points and therefore the total depth of the field being observed, it still seems unlikely that an accurate ash-density number could be calculated per cubic metre. Once the near edge of the cloud is close to the aircraft (and therefore flying through it or not comes into question), it seems very unlikely that an InfraRed imaging system would give accurate (or indeed, any) data that could be used to calculate actual exposure.

This thought already led me to comment that a vertical shot through a cloud will be a much richer data-source. VA clouds tend to cover large areas in relatively thin layer(s), which will be much more easily measured and analysed from above or below (although such layers are much easier to see edge-on, as a dark line, using the Mk 1 Eyeball, this is not the same thing at all).

For these reasons, I cannot see how the proposed passive IR system could provide consistent or accurate data about VA actually flown through.

[Pace]

There's a bit of a difference between a request for a height / heading change (at least partly) for the comfort of pax and a 'must have' change because the current heading / height is not going to be 'safe' after another n minutes (where n is less than 5).

BrookSJG

Yes there is a hell of a difference between flying into a CB which does have a record of killing you and Ash which doesnt.

The must have are active CBs and I have never heard of ATC forcing a pilot into a CB against his wishes. Deviations are ALWAYS given even over busy London.

The London controllers really earn their Keep on such days a few ash deviations really wouldnt be a problem! Kids play in comparison

really where do some of you people get your assumptions because they dont match reality?

For these reasons, I cannot see how the proposed passive IR system could provide consistent or accurate data about VA actually flown through.

We have the same old problem from the Ash thread of differentiating between dense ash and light Ash. The dense ash will show up from satellite screening, on board sensing as well as the MK1 Eyeball. The light stuff wont show to anyone with accuracy and thats the problem! Thank God to date the light stuff doesnt appear to be a problem.


Pace

[brooksjg]

problem from the Ash thread of differentiating between dense ash and light Ash

Exactly. 'Light' in your categories means 'not visible' and unfortunately probably not visualised by the IR system discussed. But where do the current limits (2000 and 4000 microgrammes per cu metre) fit in? It's my understanding that even at the 4000 level, the cloud would still neither be easily visible nor detectable by IR. Presumably under optimum viewing conditions (eg. daylight, sun behind aircraft and shining towards VA cloud, good visibility, perhaps even contrasting cloud beyond the VA, plus a fairly thick layer of VA and/or viewing from slightly above / below) a cloud at 4000 microgrammes might be visible as a darker line or area. But once conditions become less optimal, a low-density cloud will not be visible by eye. Whether the Easyjet IR system can get useful data under poor viewing conditions is another matter. As far as has been publicly revealed so far, it's never been tested using a horizontal view of a VA cloud at low densities - only relatively close to erupting volcanoes where the ash density would be order(s) of magnitude greater.

[ozaub]

Ozzy Ash Detector

I posted about this back at beginning of the VA debacle. "Sadly nobody was interested when Australian scientists developed a volcanic ash detector ten years ago. See http://www.csiro.au/files/mediaRelease/mr2001/Prvolcanoash.htm "
The link is still worth a read.

[brooksjg]

I posted about this back at beginning of the VA debacle.

So you did! There it is on page 43!
What goes around comes around but don't sell yourself short: it'sentirely possible that someone at Easyjet picked up on your posting (when, it appears, no-one else did! ) and the rest may become history.

BUT CSIRO decided in 2004 (?) that VA was not going to be a viable investment (despite having had two goes at it with Dr Prata - satellite and aircraft based) and ditched it. Why? Who knows, unless they tell us. But my guess would be that someone concluded that VA problems were too infrequent, depite already having cost airlines $250m in 'damage due to undetected ash', and the deployment cost too high for a system that would hardly ever be needed. Given the 7 -9 year gap before airlines got badly hit again, CSIRO possibly made the right judgement. More so, if in practice the system cannot detect down to at least the 4000 microgramme level - no-one has yet said much yet about current and potential sensitivity of this system.

The Devil is in the Detail: seems to me that the current modelling system is probably accurate enough to predict where ash will get to for several days after it leaves the volcano, and at what average density over quite a large height range, given good data about how much was discharged in the eruption hour by hour. (Note the height ranges of the VAAC advisories) But the erupted volume is not accurately known and if the cloud height-range is too great, this is not so useful! The model might accurately predict an average of <4000 microgrammes over a layer 10000 feet deep when the VA has not spread that far vertically and is in fact still concentrated into a thinner layer only 2000 feet deep. Direct observation of the cloud appears to be the only practical answer but I have yet to see any real evidence whether the Prata system is capable of doing this and at what cost.