Allegiant 227 A320, loses ~10k ft in ~3 min

[remi]

Wed July 12

https://flightaware.com/live/flight/AAY227/history/20230712/1820Z/KAVL/KPIE/tracklog

In the news this is characterized as "severe turbulence" so far, but it has to be an upset and/or flight control problem, right? It's an old(er) A320.

Any info from people who know more?

As an aside, what if anything have airlines and manufacturers done to try to reduce the likelihood and severity of injuries of cabin crew during CAT, upsets, and so on? They're almost always the worst injured and, although I'm guessing, must be a significant contributor to serious injuries in US aviation in-flight accidents.

[FUMR]

What do you propose? I can only think of providing no inflight service whatsoever and ensuring that passengers and cabin crew remain strapped in for the entire flight.

[meleagertoo]

Originally Posted by remi

Wed July 12
As an aside, what if anything have airlines and manufacturers done to try to reduce the likelihood and severity of injuries of cabin crew during CAT, upsets, and so on? .

"Cabin crew be seated immediately!"
That means in the nearest available seat, not returning to their stations. There's nothing more that can be done.

[Boeingdriver999]

What makes an Airbus lose 10,000ft in three minutes or… 4,4000ft in 30 seconds?

https://www.theregister.com/AMP/2017...issed_plummet/

[pattern_is_full]

https://ktvz.com/cnn-regional/2023/0...anding.”

[FUMR]

Originally Posted by meleagertoo

"Cabin crew be seated immediately!"
That means in the nearest available seat, not returning to their stations. There's nothing more that can be done.

Too late if you hit unexpected CAT !

[remi]

Originally Posted by Boeingdriver999

What makes an Airbus lose 10,000ft in three minutes or… 4,4000ft in 30 seconds?

https://www.theregister.com/AMP/2017...issed_plummet/

That's the point at hand, though. 10,000 feet in 2-3 minutes is not "turbulence." 200 feet in a few seconds is severe turbulence. It's an upset or flight control problem or a really strange piloting problem. So what exactly was going on there? In an AIRBUS? A random uncommanded "emergency descent" profile with no emergency, lasting two-three minutes? How can you even get the plane to do that?

Flight attendants pinned to the ceiling or crushed by carts is more often a product of upsets and control issues than turbulence. My point there was, given that there is a decades long history of cabin crew taking it on the chin, is there a plan to make it a safer job some day?

My offhand theory about this is that the aircraft was in a weird trim or control state due to something unrelated to turbulence, and the turbulence busted the limits and disconnected the AP, and from there someone piloted it down 10,000 feet including some negative gee before apparently somewhat smoothly pulling out.

It reminds me of Qantas 72 but I would imagine/hope that ADIRU failure mode has long been fixed.

[Boeingdriver999]

The CVR will be interesting listening unless it was “accidentally erased” after parking.

[remi]

Originally Posted by Boeingdriver999

The CVR will be interesting listening unless it was “accidentally erased” after parking.

One possible cause of the turbulence and upset could have been wake turbulence. I don't know if the pilots were completely surprised by the event, but on occasion aircraft fly in and out and back into wake turbulence where the second time causes an upset.

There have been occasional issues with A3xx responding confusingly to failed AoA sensors, despite redundancy. Incorrectly sensing an excessive AoA has caused inappropriate flight protection to be activated, resulting in uncommanded nose down until the AC is put into Alternate or Direct Law where the pilot can override the protection system.

Here's an incident in 2014 with a dual failure.

https://skybrary.aero/sites/default/...shelf/3229.pdf

The pilots regained control in this case. An acceptance fight with frozen AoA sensors didn't fare that well:

https://en.m.wikipedia.org/wiki/XL_A...ny_Flight_888T

Temporarily frozen pitot tubes caused inaccurate airspeed indications and led to the crash of Air France 447 when the pilot responded inappropriately to reversion to Alternate Law and flew the aircraft stalled into the ocean from cruising altitude.

https://en.m.wikipedia.org/wiki/Air_France_Flight_447

Airbus obviously builds very safe aircraft but there are occasional incidents and accidents caused by confusion regarding automation.

I don't know anything about this new incident, but it has the flavor of one of these incidents where the aircraft goes from behaving perfectly normally to suddenly behaving in a difficult to troubleshoot manner.

Boeing's MCAS automation led to similar difficult to understand aircraft behavior and two fatal accidents as well as numerous similar incidents from which pilots recovered.

Just observations. But I don't think 2+ minutes of 4000+ ft/min descent on approach is "turbulence."

[Boeingdriver999]

If it was an issue with flight control computers/normal law acting unusually then the pilots would have already said that and Airbus would be all over it like a rash.

And wake turbulence is transient, lasting a few seconds at most which can lead to an unusual attitude. The recovery from the upset should be performed within seconds also.

[remi]

It looks like the two preceding arrivals were also Allegiant A320s (AAY1024, AAY3225), spaced 5+ minutes, so severe wake vortex turbulence is an unlikely explanation. I can't find a (free) source for that day's METAR at KPIE, but the daily summary is normal temperature (80s), <10% cloud cover, "no significant weather." The incident is on the FAA blotter but there's no open NTSB investigation, yet, and no additional statement from Allegiant. I don't believe there's any open source ATC recording for PIE. :-/

Horrific dewpoints that day (78F!) but nothing else interesting. https://www.wunderground.com/history...date/2023-7-12

Idk, maybe the Allegiant QRH says the procedure for severe turbulence on approach is a sustained 4000 fpm descent starting at negative gee.

Originally Posted by Boeingdriver999

If it was an issue with flight control computers/normal law acting unusually then the pilots would have already said that and Airbus would be all over it like a rash.

And wake turbulence is transient, lasting a few seconds at most which can lead to an unusual attitude. The recovery from the upset should be performed within seconds also.

If you're saying obliquely that this is "Problem Exists between Seat and Joystick" scenario ... Bear in mind I don't think the numerous inadvertent MCAS activations prior to the two MAX accidents received any particular attention.

I don't have any idea whether Allegiant requires upset recovery training for its A320 pilots, but as far as I know, Airbus does not recommend upset training in simulators, as they believe it has the potential for negative training. I'm sure some carriers do it anyway.

https://safetyfirst.airbus.com/app/t...revision-2.pdf

[MarkerInbound]

The FAA requires Extended Envelope Training at all 121 airlines as part of initial training and at least every other year during recurrent. Quoting 121.423 -“Extended envelope training must include the following maneuvers and procedures:

(1) Manually controlled slow flight;

(2) Manually controlled loss of reliable airspeed;

(3) Manually controlled instrument departure and arrival;

(4) Upset recovery maneuvers; and

(5) Recovery from bounced landing.

(c) Extended envelope training must include instructor-guided hands on experience of recovery from full stall and stick pusher activation, if equipped.”