Storm ice suspected in Etihad A340 cruise incident

[airman1900]

From Flightglobal, 10:47 2 Apr 2013:

Storm ice suspected in Etihad A340 cruise incident

Pilots of an Etihad Airways Airbus A340-600 diverted to Singapore after a sudden encounter with turbulent weather during cruise generated unreliable airspeed data and left the jet unable to maintain altitude separation requirements.
While en route to Melbourne at 35,000ft, and approaching the PIPOV waypoint over the Indian Ocean, the returns from the aircraft's weather radar - which had no auto-tilt function - suddenly intensified to indicate surrounding convective weather.
Airspeed on the captain's primary flight display rapidly dropped from 283kt to 77kt before fluctuating, and the standby instrument recorded a fall from 280kt to 142kt. The first officer's reading stayed stable.

[despegue]

This is a SAFETY post, important for ALL Professional Flightcrews.
Deleting this thread would against all what we stand for as crewmembers.

[PPRuNe Towers]

Huh? That would be, like, so uncool Bro

Rob

[BOAC]

Short memories?

Back to topic - a most definite echo of AF447, this time with what is described as an 'inadvertant climb'. What mix of pitot probes - do we know?

Flight Global implies that Etihad crews need a bit more training on radar usage. As despegue says, an important safety message for all.

[SMOC]

Yes I got that impression that the tilt was possibly still pointing up?

[BOAC]

I think it safe to assume it wasn't where it should have been

[Taildragger67]

Any relation / similarities to the QF72 (A333) incident?

[BOAC]

I don't think there was any suspicion of pitot icing in QF72?

[4Greens]

They didn't have an engine spew bits out.

[BOAC]

While we are here, is 'Storm Ice' defined anywhere? Is it different to ice in and around CBs etc? Google only finds it via Flight Global, so have they 'invented' it?

[Mr Good Cat]

Yes I got that impression that the tilt was possibly still pointing up?

Gain on auto, tilt -0.8 manual.

While we are here, is 'Storm Ice' defined anywhere? Is it different to ice in and around CBs etc? Google only finds it via Flight Global, so have they 'invented' it?

No, it's absolutely real.

It's not simply a case of leaving your tilt below the horizon... If you don't have the latest 'virtual' scanning radars then you need to be aware that undetectable ice crystals can build up thousands of feet above the tops of CBs in IMC conditions, especially in tropical areas such as the Indian Ocean.

They cant be detected by radar hence why you need to scan well below your altitude and avoid any IMC in the levels ABOVE the tops of the CB.

Plenty of bulletins and info available from the last couple of years... will try to find some links...

[Centaurus]

I haven't operated modern radar but certainly we used maximum manual gain at high altitude cruise in the 737 with Collins WXR-700 radar over the Pacific and that would pick up CB tops which had little moisture. It would show as a tiny echo at 40 miles or thereabouts but enough to alert an alert pilot of something big ahead. All you did then was use the tilt control to scan below and pick up the body of the CB and take it from there - ie divert around it. The auto gain control was useless at high altitude which is why MAX gain was used to scout for CB tops.

[BOAC]

Good Cat - aware of that, and above lenticular clouds too, but never heard it called that. (Nor has Google)

[Nemrytter]

I've most frequently heard it called either 'High Ice Water Content' (HIWC) or 'High Altitude Ice Crystals' (HAIC). The former seems favoured by Boeing whilst the latter I've seen mainly used within Airbus.
Never heard it called storm ice though.

[RAT 5]

This very informative about the use of Wx radar gain. I've not heard it explained so, and not read it either, even in user's guides. Asked around in our training dept. EU based; puzzled looks. CB's can go high in Europe as well. Seems there's a lack of guidance out there.

Considering the unreliable/disagree airspeed; that's a gotcha as we usualy use the 2 out of 3 is correct rule. ln this case they were all different. Bring Gnd Spd into your scan; essential, and perhaps AF447 would have survived. Deciding that F/O's was correct, but I suspect there were some furrowed brows over that. Did the Capt's side give stick shaker?

[BOAC]

Originally Posted by Rat

This very informative about the use of Wx radar gain. I've not heard it explained so, and not read it either, even in user's guides. Asked around in our training dept. EU based; puzzled looks. CB's can go high in Europe as well. Seems there's a lack of guidance out there.

- that worries me greatly - there is so much information and knowledge about radar handling that your folk (and you) must have had their fingers in their ears! The use of gain and tilt has been much covered both here and in books and training courses. Where were you?

Gobona - you are right - I thought we had discovered something new rather than something that has been known for decades. Good old Journos

[Clandestino]

Great, another aeronautical moral panic, started by not completely up-to-date journo. This time topic is : "pilot's today don't know how to operate wx radar".

Folks, have a go at AF447 report; that nasty ice that tries to clog your pitots lurks around storm cells. Somewhere around them, not necessary above them. It is so elusive a beast that we so far know it is associated with deep depressions and that's about it. You can avoid echoes religiously and still hit it. Most of the time, you even won't know you did.

Originally Posted by David Kaminski-Morrow

the returns from the aircraft's weather radar - which had no auto-tilt function - suddenly intensified to indicate surrounding convective weather.

As they usually do when penetrating area of high moisture content (Boeing's acronym does make sense) or when radome gets iced over. It's not a bad thing. Gives clueless folks additional avoidance margin.

Originally Posted by David Kaminski-Morrow

But the circumstances bear a similarity to those preceding the Air France flight AF447 accident in June 2009, when an A330 cruising at 35,000ft flew into a storm cell, suffering icing of its pitot system.

It never flew into a storm cell but don't let the facts ruin a good story.

Originally Posted by RAT 5

we usualy use the 2 out of 3 is correct rule.

If 2 of 3 show 80 while they were showing 280 a couple of seconds before, no significant deceleration was felt and aeroplane still maintains altitude with 2° pitch, well so much for the rule-based knowledge.

Originally Posted by RAT 5

This very informative about the use of Wx radar gain. I've not heard it explained so, and not read it either, even in user's guides. Asked around in our training dept. EU based; puzzled looks. CB's can go high in Europe as well. Seems there's a lack of guidance out there.

Sad but true. A certain company back in 90-ies produced book called "Flight Crew Manual", for internal use strictly, with all the arcane stuff from manufacturer's manuals presented in non-politically-correct way, including practical tips&tricks on Wx radar use. Wonder if it is still in print.

Originally Posted by RAT 5

Did the Capt's side give stick shaker?

No stick shakers on the bus.

[BOAC]

Sad but true. A certain company back in 90-ies produced book called "Flight Crew Manual", for internal use strictly, with all the arcane stuff from manufacturer's manuals presented in non-politically-correct way, including practical tips&tricks on Wx radar use. Wonder if it is still in print.

- not really needed - there is enough information out there and, believe it or not, there are some pilots who actually know what to do - one could try asking them. I am getting the impression that aviation is indeed stuffed with automaton pilots, who switch on the radar, set 'Auto' gain, 5 degrees up and never touch it again until shutdown - including some pretty experienced ones. "Well, they never trained me or gave me a manual". You would think curiosity might encourage them to at least move the odd knob or two and see what happens to that picture of the CB on the nose. Then, of course, you could search for Archie T's excellent work.

Rather like the BA co-pilot I had once who flew back ATH-LGW, daytime, CAVOK all the way with the radar on at 5 up - and the moon didn't paint once. He's probably a Captain now - hope he has learned a thing or two.

[PJ2]

A couple of use-of-radar references:

Archie Trammell's radar4pilots site

Dave Gwinn

Weather Radar Operating Principles & Interpretation - Ian Gilbert

PJ2

[safetypee]

Assuming that the incident involved ice crystal particles in the vicinity of Cbs, then a lesson to be learnt is that these conditions are difficult to detect, and particularly that the ‘ice’ may not be detected by WXR.
With good WXR management the storm centre can be detected; however the ice threat conditions can exist some distance from the Cb core, particularly downwind of the storm and in/under the anvil, and thus a large deviation may be required.
Crews need knowledge of the threat, and appropriate judgement in avoiding these situations.
Also, assuming that at least one pitot probe was to the latest standard, then another lesson is that faults due to ice blockage can still occur, and possibly with modified probes if the conditions are severe enough. The alleviations are avoidance, less chance of simultaneous failure, and shorter duration if the storm is given a wide margin – Airbus 20nm upwind .
Also see
http://www.boeing.com/commercial/aer..._article05.pdf