Knowns and unknowns Crystal icing

[Thruster87]

Knowns and unknowns

 

Crystal icing is deadly because unlike normal

 

icing, it is hard to detect or predict, and we

 

have no defences against it

 

Crystal icing is implicated in a growing number

 

of insufficiently explained crashes

 

below freezing up to zero – a sign that ice was

 

building up on it.

 

Crucially, Ratvasky was able to confirm the

 

association between HWIC and convective

 

storm systems, and identify the mechanism:

 

the strong updraught from the storm sweeps

 

water vapour to much higher altitudes than

 

normal. The effect does not seem to appear

 

when the convection is strongest, but when

 

the storm is dying down, for reasons we don’t

 

yet fully understand.

 

The hope is that all the data gathered will

 

yield a distinct signature that corresponds to

 

HWIC. This will enable “now casting” – using

 

satellite data to predict where aircraft are

 

likely to encounter dangerous conditions.

 

Researchers are also working on modifications

 

to existing radar that allow them to detect

 

crystal-icing conditions.

 

That’s a few years away, but at least it’s closer

 

than a full engine redesign. What’s more, the

 

team managed to establish a makeshift HWIC

 

detection method: by pointing the aircraft’s

 

weather radar downwards, you can see if you

 

are flying over patches of heavy rainfall and

 

should consider changing course.

 

Even better, Fuleki and his team have

 

cleverly hacked existing instruments to create

 

two sensors. The first, a beer-can-sized device

 

called the particle ice probe, is mounted

 

outside the aircraft and detects the presence

 

of small particles by the way they change the

 

air’s electrical characteristics. It was originally

 

designed to detect debris from the engine,

 

but the team modified it to distinguish the

 

particular signal of ice crystals.

 

The other device – an ultrasound ice accretion

 

sensor – directly measures ice

 

inside an engine. A series of dime-sized

 

sensors sends ultrasonic pulses whose

 

reflection changes as ice builds up. Both

 

devices are advanced enough that Fuleki

 

is now in talks about turning them into

 

commercial products.

 

Even when planes get the new sensors and

 

radar, however, we’re not out of the woods.

 

For one thing, we are still not done tallying

 

up the true toll of crystal icing. Speculation is

 

building on its role in yet more unexplained

 

crashes, such as that of Air Algérie flight 5017

 

in 2014, which killed 116 people.

 

We know about flight 447’s blocked pitot

 

tube because of the flight recorder, but with

 

some other incidents we may never know

 

for sure. Sometimes there is characteristic

 

physical damage, but aside from that, all

 

traces of crystal icing tend to vanish below

 

10,000 feet, whether the plane survives or not.

 

There’s even a chance the problem could get worse. The warmer, moister world

 

predicted by climate change will have more

 

convective instability, “ says Sue Gray, a

 

meteorologist at the University of Reading,

 

UK. “These systems will be more vigorous

 

and more frequent.”

 

And according to a recent analysis by

 

Rolls Royce engine labs, these increases in

 

extreme weather could make the conditions

 

in which crystal icing flourishes more

 

frequent. In a presentation, Rory Clarkson,

 

an engine specialist with the company, offered

 

an inconvenient but undeniably safe answer:

 

“Restrict operation during severe weather.” ■

 

 

[facthunter]

Smart pilots avoid the big storms. This can use more fuel. Airline managements don't want you to use more fuel. You might not be carrying it either. In some airlines the pilot (although he/she has the responsibility by law) get the fuel load from the company. If you want to carry more you can be under a lot of pressure and even get the sack. That makes others think twice before being brave. Nev

 

 

[Old Koreelah]

As in many things, the bean counters measure short-term impacts of decisions. Does the airline's balance sheet put a price on safety? Some operators are more profitable and have more demure cabin staff, but I'm happy to pay a little more to fly with the world's safest airline; where it matters, Qantas people get it right.

 

 

[Yenn]

After reading all that first post I am left wondering. What is crystal icing and HWIC?

 

 

[Subsonic]

High Ice Water Content?

 

https://www.ral.ucar.edu/sites/default/files/public/events/2015/friends-and-partners-in-aviation-weather/docs/culver-and-fahey.pdf