nick14

Hello all,

The air France accident has sparked some investigation into high altitude ice crystals. I'm in the process of finding out as much as I can around this subject, in particular their effect on the pitot static system.

Does anyone know of any good resources I could get my hands in relation to this?

safetypee

http://icingalliance.org/meetings/RI...ersion_nss.pdf

http://www.boeing.com/commercial/aer..._article05.pdf

http://www.ukfsc.co.uk/files/Safety%...Oct%202009.pdf

http://www.specinc.com/publications/...craft_1998.pdf

http://www.sae.org/events/icing/pres...sopenmason.pdf

http://icingalliance.org/collaborati...oject_2007.pdf

IASCC - International Air Safety & Climate Change conference
Workshop 1. day 2. Eric Duvivier, EASA - "High Altitude Icing Environment"

nick14

Super thanks!

IGh

Question, request of the 23rd:
"... investigation into high altitude ice crystals.... in particular their effect on the pitot static system.[?]"

During the past decade, the interactions of ICE CRYSTALS was not only with Pitot-Static "system". This sole case in the NTSB dB is also similar to several others not recorded by NTSB:

Spirit / 4Jun02 MD82 N823NK:
http://www.ntsb.gov/aviationquery/br...12X00866&key=1

Prior discussions:
ICE crystals
http://www.pprune.org/tech-log/41797...titudes-2.html

FlareArmed

A Bombardier Global Express had a temporary double-engine wind-back at high altitude because of ice crystal contamination in some engine probes. That is an incident worth chasing up for your research.

Lyman

Do not ignore the discussion of Water Ice in fuel. See BA038.

Microcrystalline water ice was held to blame, as the theory had to do with "hitherto unknown characteristics of water ice..."

No new research to see, meanwhile Rolls Royce fit new Heat exchangers to its
Trent 700.

Ice has been a punching bag of late..... Welcome to the devil you don't know, ignore the devil you do...

Jet aircraft have been flying up to 60,000 feet everywhere on the globe for sixty years....funny how we need to know more about water ice at 35,000. Are pitot tubes on ETOPS a/c especially susceptible to ice? So one would think...

gas path

Not only pitot probes. The GE90 is very susceptible to ice damage to the HP compressor stage 1 blades. Flight through high level 'ice clouds' builds up a deposit on the p25 probe this then breaks free and bends a blade. They are big blades as well approx 9ins x 5ins. At best its a borescope inspection for area 'blockage' that has to be calculated and at worst it's an engine change.

Lyman

The knock on the pitot tube Thales that AF 447 was sporting was that the drains were susceptible to corrosion. Whether or not this came up for the AD I cannot find...

Not only does crystalline ice need to melt to drain, any corrosion on the drain would nucleate new formation of ice crystals...

So gas path, what is the nature of this deposit, 'blockage'?

gas path

The ice forms on the P25 probe and eventually breaks free clouting one of the blades putting a bend/curl on the tip of the blade this reduces the area between the blades (blockage) therefore upsetting the airflow. Usually picked up by a decrease in compressor efficiency..read higher N2. Another sign is the engine makes a hell of a 'howl' during crz upsetting the pax sitting near the front end.

FullWings

I had one of those "howling" engines the other day and was glad the tech. log entry said it might be noisier than usual. I think one of the HPC blades had been damaged, like you say.

It WAS noisy! We looked at each other across the cockpit just after setting power and if I hadn't been pre-warned I might have been tempted into a low-speed RTO...