Sahara Sands v Volcanic Ash

[ChippyChop]

So my car is now covered in far more Sahara Sand than it was ever covered in volcanic ash when we were all banned from flying by the boffins. So why can it be safe to fly in this stuff but not the ash?

Cheers
Chippy

[ShyTorque]

The sand is more politically acceptable?

[JimL]

Simplistically; sand/dust results in abrasion (to the rotor blades as well as the compressor blades) but volcanic ash, with its much lower melting point, can result in glassification of the turbine blades as well. It is not the abrasion that results in engine failures (although it will affect their efficiency), it is melting ash in the hot end. That is how it can kill all engines within a short period of time.

Jim

[nigelh]

I am sure all the people who carried on flying during the last ash scare have all had engine problems ......NOT !!! Obviously you would not fly through a visible cloud of ash or sand .

[John R81]

Or an invisible ash cloud, for that matter.

I kept on flying through the last 'crisis' because I (correctly, as it turned out) believed that on the evidence available there was no ash cloud along our planned route. Otherwise my machine would have remained in the hangar with the doors firmly shut.

Plenty of pictures available on the internet to show what ash does to a jet engine. Volcanic Ash Gives Jet Engine a Turbocharge : Discovery News (http://news.discovery.com/earth/jet-engine-guts-volcanic-ash-holy-crap-swiss-cheese.htm)

[Swinging Spanner]

Hi all

I think its a combination of many things when it comes to the sand/dust in the ME. The sand part of the sand/dust does have abrasion qualities mentioned, but the dust has similar qualities to ash with regards to effects on aviation turbine engines-in particular the blocking of pneumatic system filters, blocking of cooling holes or cavities in turbine sections and silica deposits on turbine blades.
But because there is sand and dust, the sand part abrades what is slowly deposited onto turbine blades....that and the fact that if it were measured in parts per million (ppm) the sand/dust compared with flying through an ash cloud you would find to be very different.

Just my 2 cents worth ;)

[nigelh]

Just making the point that i know of many operators who worked ( cleaned up financially ) during the ash cloud fiasco , both jets , prop planes and helicopters and i dont know of one engine problem . Maybe there are ...if so let us know . Even some of the big passenger planes specifically flew through the clouds to get more info ....did they all replace engines ??

[John R81]

Nigel

My machines did continue to work and no, there were no engine problems.

The point was that Class A air space closed on the basis of a mathematical model of location / density of ash. The actual location / density of ash did not match the model and hence no problems for those that did fly in the S. of England outside of actual ash contamination.

I have no idea whether anyone did fly a turbine helicopter through ash, but I don't fancy that one myself. abrasion of rotors would be significant, windscreen abrasion and all of the engine problems / risks (in a single)?

[nigelh]

John , My point really was that we ( Helicopter boys ) didnt need telling not to fly , especially VFR , as we could see if there was significant ash and keep away from it . In the countries with active volcanoes , they fly around them all the time and just use common sense !!!
Also if it is sand then flying through some for a short while shouldnt be a problem with a particle seperator ....

[Clever Richard]

Went to the Big Island, Hawaii, a few years ago and took a sight-seeing flight around the active volcano to the south. There were many aircraft, fixed wing and rotary, buzzing around the caldera.

They didn't seem too bothered!:confused: