Another 747-8 Ice Crystal Icing Incident?
 

Quote from Aviation Herald.



Incident: Airbridge Cargo B748 near Hong Kong on Jul 31st 2013, both left hand engines surged at same time, one right hand engine damaged too

By Simon Hradecky, created Tuesday, Aug 6th 2013 17:24Z, last updated Wednesday, Aug 21st 2013 16:54Z

An Airbridge Cargo Boeing 747-800, registration VQ-BGZ performing freight flight RU-349 from Moscow Sheremetyevo (Russia) to Hong Kong (China), was enroute at FL410 about 80 minutes prior to estimated landing when both left hand engines (GEnx) surged simultaneously, engine #2 (inboard) temporarily shut down and auto-started again. The aircraft continued to Hong Kong for a safe landing on all 4 engines about 80 minutes later.

Rosaviatsia reported on Aug 6th 2013 that the aircraft entered a zone of dramatic temperature fluctuations, the temperature changing between -53 and -33 degrees C, when the engines surged, #2 spontaneously shut down and auto-started again without crew intervention. Both engines received damage to high pressure compressor blades.

In a safety message to operators released on Aug 20th 2013 Rosaviatsia rated the occurrence a "very serious incident" reporting that engines 1,2 and 4 were affected. Ice accumulated on unheated parts of the high pressure compressor in unpredictable and poorly understood meteorological conditions leading to the disruption of air flow inside the engine causing surges of the left hand engines. The flight was continued to destination, a post flight examination showed "unacceptable damage" to the high pressure compressor blades of engines 1,2 and 4 (both left and outboard right hand engine). Rosaviatsia is investigating the occurrence together with Boeing and General Electric, the FAA and EASA have been notified about this very serious incident.

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Incident seems very interesting: the described jump in (apparent) temperature could well point to ICE CRYSTAL ICING.
The remark of "ice on unheated engine parts" and "unpredictable and poorly understood meteorological situations"also seem to point in this direction.
Would be a first case of BIG engines being so influenced, so far smaller (business jet types) have been influenced.
It does seem to indicate GE's are indeed a bit touchier than P&W with regards to icing matters.

The first sentence is not true. There has been ice crystal icing events across the Boeing and Airbus range over the last decades. Comparatively few bizjets were affected (if the Boeing bulletin is any indication).

The second part is definitely true. The 748 (GenX) has already been involved in a few such incidents during its short career. Those modern engines seem a lot more prone to it than before. Effect of the larger bypass maybe?

But it's okay, there's an NTC out telling us to avoid ice crystal icing. So next time it happens, it's going to be our fault.

Of course none of these phenomena are yet fully understood, but that's not the point...:hmm:

Would be interseted to know if the crew switched on the TAI or disregarded it due to temp being below -40c.
90 perc of local crew dont select tai during descent against boeing fcom.
Not being familiar with the 747 if it has auto TAI like the 787 for example,it would be interesting to know if TAI was on/operative or not.

748 and some variants of 744 ( ERF) for example, have auto NAI and WAI. Very rare indeed to see the auto icing come on for any form of ice encounter. In fact we belt and brace it by selecting it manually on if we require ground de-icing; for a while on a/c entry to service we were manually selecting it anyway in the dash 8. The auto WAI comes on quite frequently on the dash 8 , in situations quite devoid of apparent icing; the mid span section is lift critical hence this fix
I seem to recall the V2500 engines ( or possibly CFM56 ) had similar issues ??
Your right ; the NTC helps tremendously !!

Not only is the auto Nacelle/Engine Anti Ice not very reliable at preventing icing (dependent on the sensitivity of the ice detection probe, which does not detect all kinds of icing), but, in the case of ice crystal icing, it is also completely useless, even when selected on.

It heats the nacelle intake leading edge, while ice crystal icing happens at the compressor inlet, around the first stages of compressor disks and vanes. In these huge bypass engines, those are miles away from each other...

And yes, the ABC crew did select the EAI ON before the event.