ICE CRYSTAL ENCOUNTER

[flyby797]

Hello everyone,
I'm looking for informations regarding ice crystal ENCOUNTER. Let me explain the issue: Boeing is addressing the Ice Crystal Icing through FCTM, FCOM (adverse weather) and QRH (NNC). For the NNCs, the whole fleet is concerned EXCEPT the B737 (although you find a note on the last FCTM 737 rev 11:737-300 - 737-500 Note: An Ice Crystal Icing NNC is available in the QRH which is obviously an error).
In my Company, we had several ice crystal ENCOUNTER which were apparent to the crews as a TAT anomaly.
Do you have any idea WHY the B737NG has NO NNC ICE CRYSTAL ICING?
Furthermore, how does AIRBUS deals with this issue?
Thanks

[PantLoad]

Airbus

15th Performance and Operations Conference
Puerta Vallarta 23-27 APR 2007
Operation in Icing Conditions in Flight
Ice Crystals: An Environmental Threat
by Helene Rebel
Head of A330/340 Operation Standard

[flyby797]

Thanks Pantload

[BARKINGMAD]

I believe I may have had 2 such encounters in 73NGs whilst transitting through what we as a crew believed were innocuous remains of old cunimbs with little or no radar echoes at our level.

Symptoms: Light chop, reduced vis, SAT-55c but didn't note the TAT beyond not needing engine anti-ice, speed began to reduce, aft-facing side of winscreen wiper assembly, normally matt black, turned white indicating some form of accretion NOT airflow impacted.

Quiet panic set in, don't recall anything like that in the Met theory, engines to MCT, switch on engine anti-ice for fear of what may happen to them if not protected. Avoided wing de-icing due double bleed-trip caution in NNC above FL350, speed got to touch amber bar, but luckily fell out the far side of the line of diffuse tops without stalling practice and further abnormalities.

My theory about the "lee side" ice accretion is that our airframe is probably charged up with static electricity by air friction and we've provided an attractive parasitic host to several billions of ice crystals oppositely charged after being spat out by a previously active, now decayed cumulo-nimbus.

Following the 2nd episode I submitted ASR and asked for the FDR to be pulled for investigation but never got any feedback and the company folded not long after. (Not my fault gov!)

Hope this helps a little?

[flyby797]

Thanks Barkingmad for sharing your experience. Makes sense that it might have been ice crytals encounter/icing? Encounters that we had here were located in SubSaharian Africa with TAT anomaly (confirmed by FDR) and all other ice crystal indications: light to moderate chops, in the vicinity of CB, NO weather radar return, "rain" sound...
Why Boeing doesn't address it with a NNC on B737NG is a mystery...
On the Airbus side, thanks to the document PantLoad provided, it seems like there has been some engine modification.

[Avenger]

Boeing perhaps thinks that the " Flight with unreliable Airspeed" section of the NNC would cover this..the other airmanship items are self explanatory and are also covered in Adverse Weather Operations.. I guess there is a limit to how much advice the manufacturer can offer..the Boeing presentation on this matter is very good general advice.

[flyby797]

Ok but in that case Avenger why is there a NNC "Ice Crystal Icing" for the B...787? Besides the conditions associated with Unreliable Airspeed NNC are:"The pitch attitude is not consistent with the phase of flight, altitude, thrust and weight, or noise or low frequency buffeting is experienced". Do they address the conditions experienced with an Ice Crystal encounter/icing or a TAT anomaly? I'm not sure but i stand to be corrected.