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S7 A321 Unreliable airspeed event, Magadan, 02 Dec 2021

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S7 A321 Unreliable airspeed event, Magadan, 02 Dec 2021

Old 4th Dec 2021, 06:32
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S7 A321 Unreliable airspeed event, Magadan, 02 Dec 2021

Not seen this one announced here but the plane, an S7 A321, took off from Magadan and got into issues.... apparently the autopilot system disconnected, there was an onboard electronics failure and the fuselage was covered in ice - five minutes after taking off from Magdan airport in eastern Russia.

The captain declared a Mayday but pilots were unable to dump fuel and land in the departure airport, despite circling overhead several times. Instead, they were forced to fly on over mountain ranges, towards the next nearest airport Yakutsk before finally landing in Irkutsk five and half hours later as the temperatures in Yakutsk were -30, but only -1 at Irkutsk

Anyone got any more info?
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Old 4th Dec 2021, 06:46
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The pilots' reported inability to dump fuel might have something to do with the fact that they were flying an A321.
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Old 4th Dec 2021, 06:59
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You learn each day. But coming back to the incident, they first circled over the airport a number of times, then elected to go to another nearby airport where they saw it was even colder and risk of ice was more severe so they flew further where It took them - apparently - 3 hours to reach their cruising altitude at which time they'd burnt off so much fuel that they couldn't reach their destination of Novosibirsk.
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Old 4th Dec 2021, 08:12
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Ice builds from liquid water. If your choice is only sub-zero temperatures, broadly speaking , colder is better.
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Old 4th Dec 2021, 09:36
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Could you change the topic name? It's misleading. If you don't have any information apart from what you've posted, how can you say "incorrect / counterfeit de-icing fluid"?
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Old 4th Dec 2021, 12:31
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Incident on AvHerald

Guessing the deicing fluid used doesn't has much to do with this... It will never protect the aircraft after the takeoff roll is started.

Last edited by Cough; 4th Dec 2021 at 12:43.
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Old 4th Dec 2021, 14:18
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This sounds like deicing fluid may have been applied around pitot and static ports.
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Old 4th Dec 2021, 15:44
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The idea that ground de-/anti-icing had something to do with the incident can be safely disregarded. If one has really bad case of iced wing one either: 1) fails to get airborne 2) gets airborne but then mush in ground effect until hitting the obstacle 3) stalls after leaving ground effect 4) gets wing ice ingested by tail mounted engines with consequential trust loss. Since this birdie has flown for hours, obviously it left ground effect at the good side of the trust curve. Even if the aeroplane was not de-iced properly, the aerodynamic effect of contamination was not enough to induce the upset.

Now, there is a picture making circles and it's been claimed it represents the QAR readout of the incident flight. Provided it's real, the triggering event was control law degradation to ALT1. I cannot figure out what caused it; G trace doesn't show any significant turbulence while left and right IAS and baro alt are consistent all throughout the upset. There are intermittent faults of both yaw dampers, but they got recorded later, before and after the wildest of gyrations. It looks like F/O was PF but the captain took over the controls and pushed the nose down, reaching minimum of -8.2, before pulling up to about 30. Some interesting pitch, roll and speed excursion followed, probably helped by large and alternating stick displacement. Picture resolution is too low to figure out whether occasional dual input exacerbated or damped the ride. Control law degraded to direct but restored to ALT1 after about five minutes. There were some stall, some overspeed and some unspecified red warnings. Eventually everything settled down.
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Old 4th Dec 2021, 18:51
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Bandures

Because the report I read said the authorities were investigating the fact that it was something to do with the deicing fluid used.....
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Old 5th Dec 2021, 08:10
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How long did they fly in direct law?
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Old 5th Dec 2021, 16:29
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About five and half minutes.
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Old 5th Dec 2021, 23:38
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Direct Law....so what?

I've landed a 321 in Direct Law, after a longish straight-in approach. No biggie. (Caused by port icing initially, hours before)
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Old 10th Dec 2021, 04:04
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Rosaviatsia updates Dec. 9 -

- aircraft suffered ADR #1, #2, #3 faults after takeoff, resulting in large excursions in roll and pitch
- aircraft was deiced in two stages. Type I fluid, then type IV. Fuselage was NOT deiced, only airfoils.
- Suggestion that snow on fuselage, in particular cockpit windows, melted once window heat was turned on. This continued during taxiing.
The runoff then froze again lower on the nose, disrupting airflow to the pitot tubes.

Incident: S7 A21N at Magadan on Dec 2nd 2021, unreliable airspeed
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Old 10th Dec 2021, 14:04
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I have personally experienced airspeed fluctuations due to heavy icing whilst going round in the hold in UK at around FL100. The aircraft was in a steady state with a known power set. My (LHS) airspeed fluctuated 50kts or more over a period of 30 seconds whilst IAS 2+3 remained reading the same steady state. I considered executing the UAS abnormal procedure but with traffic in the hold both above & below us I considered doing nothing was the safest option. My only action was to retard the thrust levers to current power & disengage the ATHR to make sure there was no ATHR misbehaviour. After 60-90 seconds we made VMC and all indications went back to normal. The aircraft remained in normal law throughout. During the encounter we picked up serious amounts of icing around the windscreen.
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Old 10th Dec 2021, 14:07
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Imagine this with a single pilot cockpit or even unmanned aircraft.
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Old 11th Dec 2021, 02:23
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Originally Posted by Less Hair View Post
Imagine this with a single pilot cockpit or even unmanned aircraft.
The initial actions are not exactly Mars orbiter logic. Without coherent speed data:
= wings level + N1 60% + N.U. 6

Whereas the report will have 4 pages on why the crew couldn't do exactly that.

​​​​​​​

Last edited by FlightDetent; 11th Dec 2021 at 07:23.
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Old 11th Dec 2021, 05:45
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Imagine this with a single pilot cockpit or even unmanned aircraft.
The single pilot in cockpit, let's say in A350 will just watch the aircraft inform him that it has automatically changed to backup speed which is mathematically derived synthetic speed not requiring any pitot static data. So what's the problem? Also even with triple ADR problem control laws stay in alternate law but without any protection. Only with gear down will go to direct law.
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Old 11th Dec 2021, 08:41
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90 degrees of bank are the problem. No reliable data to feed the systems or displays and an airframe moving to raw physical flight with maybe one stalled wing or similar.
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Old 11th Dec 2021, 09:44
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Given all the problems caused by pitot tubes over the years (AF447,2xMAX) and more, surely there must be better technology that perhaps an air-computer could compare pitot readings to, see if it's likely the aircraft is in icing conditions or the pitots are just plain likely to be giving duff info, then suggest to the pilots to switch to an alternate system until the disagree is resolved?
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Old 11th Dec 2021, 16:58
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Brilliant suggestion arf23, I wonder why Airbus never thought of that..
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