Airbus prepares safety warnings following A321 incident

[hetfield]

They were lucky, don't do it! The EMER ELEC genie may drop out.

[Mad (Flt) Scientist]

Originally Posted by Safety Concerns

I don't think so. The NTSB statement is quite specific and has no place in the accident report unless it was related to the accident. It doesn't mention handling it mentions STALL

Reading the report, it actually seems a bit ambivalent on the operation of the flight envelope protection. Section 2.7.2 states:

The airplane’s airspeed in the last 150 feet of the descent was low enough to activate the alpha-protection mode of the airplane’s fly-by-wire envelope protection features. The captain progressively pulled aft on the sidestick as the airplane descended below 100 feet, and he pulled the sidestick to its aft stop in the last 50 feet, indicating that he was attempting to raise the airplane nose to flare and soften the touchdown on the water. The A320 alpha-protection mode incorporates features that can attenuate pilot sidestick pitch inputs. Because of these features, the airplane could not reach the maximum AOA attainable in pitch normal law for the airplane weight and configuration; however, the airplane did provide maximum performance for the weight and configuration at that time.

The Airbus simulation indicated that the captain’s aft sidestick inputs in the last 50 feet of the flight were attenuated, limiting the ANU response of the airplane even though about 3.5° of margin existed between the airplane’s AOA at touchdown (between 13° and 14°) and the maximum AOA for this airplane weight and configuration (17.5°). Airbus’ training curricula does not contain information on the effects of alpha-protection mode features that might affect the airplane’s response to pilot sidestick pitch inputs. The flight envelope protections allowed the captain to pull full aft on the sidestick without the risk of stalling the airplane.

The NTSB concludes that training pilots that sidestick inputs may be attenuated when the airplane is in the alpha-protection mode would provide them with a better understanding of how entering the alpha-protection mode may affect the pitch response of the airplane. The NTSB recommends that the FAA require Airbus operators to expand the AOA-protection envelope limitations ground-school training to inform pilots about alpha-protection mode features while in normal law that can affect the pitch response of the airplane.

So while the alpha protection did prevent a stall, it also reduced the ability to flare. Overall it turned out ok, but there's a suggestion that might not always be the case.

[Safety Concerns]

its hard to see how stalling could have helped here. The system helped sully by keeping the aircraft at max performance for the configuration.

[goldfish85]

Safetyconcerns wrote

It is shocking how many posters claiming to be pilots do not understand FE protections.

I think that's true for pilots who have not been trained on envelope protection. I know I was until my training. I also think Airbus did not go a very good job of training in the first few years of A-320 (Habsheim, Bangalore). I had a one-hour sim exposure to the A-320 in the mid '90s. The sim instructor over-emphasized using the protections. At one point he had me select landing configuration at about 300 knots, pointing out that I no longer had to worry about limit airspeeds -- the airplane would lower the gear and flaps when the speed was right.

In the mid 2000's, I went through Airbus training at MIA. The first sim session was flown in Direct Law -- See it's an airplane. I think they realized they had made the wrong impression in the early 90's.

Envelope protection had saved many airplanes. An FAA review of upsets shows this clearly. (Lambregts, AIAA Paper 2008-6897)

Goldfish

[ECAM_Actions]

'ECAM_actions' and all others who are in denial about the merits of the protections afforded by Normal Law....Read Fly By Wire by William Langewiesche. You will find that during the flare over the water at max Alpha, the Stall / High Alpha protection did indeed play a small but significant part in saving the day.

bubbers44 said it nicely.

I think you also failed to understand my point that so long as you don't get close the edges of the "envelope" defined by Normal Law, whether Normal or Direct Law is active is moot.

Alpha prot only helps if you're near the stall, bank angle prot only works when you're trying to roll more than 67 degrees, and g load demand only prevents a pull-up exceeding 2.5 g.

I doubt very much that Sully attempted any of those things, so it rendered the protections utterly useless.

I'm more interested in why the tests in the sim failed to have a good outcome. Hasn't this been found to be the case before, that what happened in reality couldn't be replicated in the sim?

ECAM Actions.

[Safety Concerns]

Alpha prot only helps if you're near the stall,

got it in one.

[Locked door]

Exactly the point of protections, they are there in the background but should never, ever activate.

To ditch an a/c you want to be as slow as possible with the minimum v/s possible. The advantage of FBW is that if you misjudge it or there's a wind shift, you won't drop a wing and cartwheel, all that will happen is your v/s will increase to the new minimum possible.

I don't know the ins and outs of the Hudson incident, but the best possible outcome was achieved regardless.

LD

[CONF iture]

Goldfish
AIAA-2008-6867
Airplane Upsets: Old Problem, New Issues
Is it the document you refer to ?
Would you have a link to the full paper ?

It is shocking how many posters claiming to be pilots do not understand FE protections.

Safety Concerns
I do not know if you claim to be pilot, but reading your discourse I can tell you do not understand FE protection ...
Just curious here : Have you ever flared an aircraft ?

This seems to have been confirmed in NTSB tests carried out after the accident in the simulator where all 4 pilots crashed under similar circumstances.

Totally erroneous, please start reading the full NTSB report first and especially page 49-50 for the simulations ...

[Clandestino]

Originally Posted by CONFiture

Which limitation did they try to bend on QF72, please remind me Clandestino.

So what happened there? There they were, cruising serenely at FL370, when all at sudden, malfunctioning protection activated and sent them to their whopping 680ft plunge, following by another enormous 400 ft dive. "Yes they were lucky this time, what would have happened if they were on short final", I can hear you scream. Well, they were unlucky to have it happened at the first place. There are no records of it happening before or after, anywhere in the world, on any FBW Airbus AFAIK. We stil don't know what triggered the alpha prot, one of contributing factor to our continuing ignorance certainly being extreme rarity of such an events. DP Davies has treated the subject of statistically acceptable risk of protections activating when not required in chapter discussing the stickpushers. If you have third edition, it's page 131. Nothing new under the sun.

Originally Posted by CONFiture

Why don't you question SC ... He wrote that 'the protections are there in the first place because you lot kept crashing'
Can you produce figures that would support such statement ?

My apologies, I got the wrong impression you were talking about FBW Airbi hull losses, while you were referring to the loss of control accidents of non-protected aeroplanes. Aviation safety network is good starting point for research, yet again as accidents are very rare compared to number of operations, it's better to concentrate on case studies instead of statistics. Functioning protections prevent from spiral dive, stall, overspeed and overstress. It is empirically proven that one can remain within protection boundaries and turn FBW Airbus into scrap metal.

Originally Posted by CONFiture

If the XL Airbus in Perpignan don't follow the pilot request in the final dive, that's because of the G load protection to make sure that the aircraft is intact up to the crash site.

Nope. It didn't follow it because THS remained at full nose-up position throughout the event. Elevator would be unable to overpower it even if the puzzled computers had operated it in demanded sense. Again, it has everything to do with DP Davies and nothing with Ziegler's concierge.

Originally Posted by nilcostoptionmyass

If i'm on my 'dinosaur' aircraft flying at 330kts and want to pull up to 60 deg up and wash the speed off, i can, because i.m in control.

All well if your dinosaur is F-4. In the enlightened age of FDM, this would be career ending event if performed while flying transport category aircraft.

Originally Posted by jcjeant

Rocking chair in front of breakfast TV.

Anyways pilot or not we will all obtain this rating

That's an extremely optimistic view. I used to know a decent bunch of pilots who were never able to put it on their licences despite their best efforts.

Originally Posted by PBL

Originally Posted by DozyWannabe

I don't think there's a single incident where the protections have caused a hull loss - at least not when there hasn't been a major malfunction.

Yes, but please don't forget that Hamburg came very close!

I disagree. Hamburg was not protection issue, one of the contributing factors was halving the control travel while transitioning from normal to ground law. However, wrong stick input was used during decrab in winds that exceeded demonstrated crosswind component by the test pilots, aeroplane was landed on the downwind wheel and they got away with scraped wingtip fence. That's good enough control authority in my book.

There were two accidents that involved SA Airbi making heavy landings during turbulence that triggered alpha prot - St. Johns in 1999 and Bilbao in 2001. After Bilbao, alpha prot got relaxed by desensitizing it to high AoA rate of change. Of course, we don't really know whether the outcome would be better or worse in either of the cases if the protections didn't intervene.

Originally Posted by Locked Doors

To ditch an a/c you want to be as slow as possible with the minimum v/s possible.

Perhaps on some aircraft, not on A320. Desirable method is going for 11° pitch with RoD as little as possible. If you can't make the RoD, you don't sacrifice the pitch to get it. Capt Sullenberger did hell of a job out there, there's no point in second guessing what he actually ment to do or how could he done it better. I can only hope that I'll be as good as him if my time comes.

[bubbers44]

I think Sully knew airspeed and attitude was the only thing that was going to matter in his splashdown. He was too good a pilot to depend on automation to help him so he obviously used his flying skills to make sure he had the right speed to flare and zero out his sink rate before ditching. People who love Airbus and think that saved the day are totally wrong. Sully saved the day by being a good pilot. He saved the day, it didn't matter what he was flying.

[DozyWannabe]

Originally Posted by bubbers44

People who love Airbus and think that saved the day are totally wrong.

I'm pretty sure no-one on this thread has suggested that. The most that has been said is that the protections may have provided a valuable backstop if things became more difficult prior to touchdown, which they didn't.

[CONF iture]

Originally Posted by Safety Concerns

The NTSB statement was completely unnecessary if the aircraft manual control inputs had remained within safe limits throughout the ditching. The reality is the system intervened to aid a perfect landing. In fact some have suggested that the FE protections allowed the crew to trade every available knot for a reduction in vertical speed.

And who are those "some" that don't understand either what a flare is all about ?
Direct me to the data in the report that support such statement ...

Originally Posted by bubbers44

... and zero out his sink rate before ditching.

That's right, Sully tried its best in that perspective, but the flight control computers as they are programmed decided they knew better and didn't have to follow the pilot's request ...

What amazes me is that among all the simulations that have been performed afterward in Toulouse, no one thought to put the aircraft in beautiful DIRECT LAW to get rid of all those supposedly marvelous and magical features and/or protections, and see how a guy with some experience can actually nicely flare that aircraft ... !?

Is it that no one thought about it ... or is it that no one did really want to embarrass Airbus ... ?

[Safety Concerns]

A few salient points

The NTSB concludes that the captain’s difficulty maintaining his intended airspeed during the final approach resulted in high AOAs, which contributed to the difficulties in flaring the airplane,

When the airspeed is high enough, such as the airspeed recommended in the QRH, the AOA never reaches the flight envelope protection activation threshold.

The flight envelope protections allowed the captain to pull full aft on the sidestick without the risk of stalling the airplane.

The captain’s difficulty maintaining his intended airspeed during the final approach resulted in high angles-of-attack, which contributed to the difficulties in flaring the airplane, the high descent rate at touchdown, and the fuselage damage.

The professionalism of the flight crewmembers and their excellent crew resource management during the accident sequence contributed to their ability to maintain control of the airplane, configure it to the extent possible under the circumstances, and fly an approach that increased the survivability of the impact.

the NTSB concludes that the captain started the APU, which improved the outcome of the ditching by ensuring the airplane remained in normal law and maintained the flight envelope protections, one of which protects against a stall.

[bubbers44]

Capt. Sully - Why Ditched the Flight 1549 in the Hudson River?

An interview with Sully.

[lotusexige]

In the P-47 Thunderbolt Flight Manual is a chapter on Ditching. It is three sentences long.

Don't Stall.
Don't Ever Stall.
Don't Ever Ever Stall.

The nose will Pitch Pole, and disintegrate. No more Sully, no More Skiles, and probably most the rest. FBW not an issue, whatever. IMO.

In his book 'Make Better Landings' Alan Bramson refers to the myth of the full stall landing. He said 'What happens when a well behaved aircraft stalls? The nose drops. What happens when a not so well behaved aircraft stalls? The nose and a wing drop.'
I might not be quoting exactly as its aboy 25 years since I read it but you get the drift.

[bubbers44]

P47 Don't ever ever stall. That works equally well in any airliner including an A320. Sully knew that so wouldn't have stalled prior to splashdown. If the Airbus computer didn't give him the last 3 degrees of AOA in the flare before stall it still worked so everybody got out alive. The next A320 crew might add 20 knots to the approach speed to counteract the computer to get a zero descent touchdown. You still touch down at the minimum speed since you have a long river and can flare as long as you want. I loved his video. He was totally in control. He knew he had to have the wings perfectly level on touchdown. I loved his book.

[PBL]

How has a thread on safety warnings following an A321 incident morphed into yet another interminable discussion on the Hudson River landing?

PBL

[jcjeant]

Hi,

Some update from Airbus .... interesting
Google Vertaling

Original link:
Airbus*: bulletin d'alerte sur les sondes Pitot de l'A330 - CONSTRUCTION AERONAUTIQUE AIRBUS
But what this will change ?
What will be the result ?

[bubbers44]

In the B727 days everything was simple. You looked at your FE panel and cockpit display and things were crystal clear what had to be done. Now with the automated everything it is much more difficult to resolve failures vs the 1980's. Is this progress? Too much information when you only want to deal with the main problem can be a hinderance to a safe solution. KISS comes to mind. Keeping things simple always seems to work best. Always worked for me. Does it work for anybody else? Remember, I don't have a college degree.

[DC-ATE]

bubbers44 -
In the B727 days everything was simple. You looked at your FE panel and cockpit display and things were crystal clear what had to be done. Now with the automated everything it is much more difficult to resolve failures vs the 1980's. Is this progress? Too much information when you only want to deal with the main problem can be a hinderance to a safe solution. KISS comes to mind. Keeping things simple always seems to work best. Always worked for me. Does it work for anybody else? Remember, I don't have a college degree.

Hey.....I got someone who agrees with me !! I'm with you there, bubbers44 !! Only replace that B-727 with a DC-8 !!