Now write the software loop to handle possible erroneous vertical speed signals and/or attitudes? It does not get easier with 'automatics'. You may well find you will create another 'trap'.

@jcjeant:
 

They...Airbus... offered the BUSS option even before AF447.
But it will never be a standard for the A330 if not mandated so by the autorities.
AFAK it is standard on A380 and will be on A350.

Recently I heard about upcoming 'firmware' updates (Don't have it on paper yet):

The ECAM announcement of transition to another law will be accompanied with a brief statement for the reason why the transition took place.

The PDF message "USE MAN PITCH TRIM" will show up always when automatic trim is not available.
(e.g. Abnormal Attitude ?)

@ BOAC
 

.......which is why I said "There has to be a tade off between safety features and system complexity" and why designers are paid to analyse these trade offs and make a judgement.

There are potential traps with many safety features which is why they all have pre set limits and automatic self checking and should generate fault messages when they are no longer working, and switch themselves off.

The decision to inhibit stall warning was most likely based on a balance between nuisance / erroneous warnings causing a hazardous situation in a circtical phase of flight and the likelihood of a plane still being airborne at less than 60kts.

For some safety features, the extra complexity is justified especially if the probability of failure of the safety feature is sufficiently remote and consequences fully understood and protected against, and also if it lets you know when it has thrown in the towel.

As I suggested in my post, deep stalls are probably not common enough to merit the added complexity of warning that an aircraft is in one, so our views may be overlapping a little here. I was just suggesting that a deep stall may possibly be detected without pitot pressure or normal stall protection.

I understood your suggestion, but the SIMPLE way to handle deep stalls is not through software but by LESS reliance on automatics/cradle-grave protections and the like and just encouraging basic flying skills - which appear to have been absent in this 'first level' airline. The more the psychology encourages 'reliance' on something telling you you have screwed up, the more likely it is you will, as opposed to making sure you don't, and that is ignoring all the pitfalls of a software based system reliant on voting on multiple sensors.

A much simpler and reliable solution is to latch the stall warning once a (fully developed?) stall is detected then do not clear the condition until sensors show the aircraft to be flying (unstalled) again.

While clearly not the "cause" of this accident the stall warning re-appearing when the correct (ND) input was applied could not have helped.

Maybe if stall warning is understood and respected for what it is, the airplane will not "deep" stall?

Precisely, HN39

Define "sensors show the aircraft to be flying (unstalled) again" in the case where those sensor values are out of valid range. That is where the complex software comes back in with all the associated problems / risks.

Then consider dealing with a latched warning which is spurious (for reasons of sensor failure or whatever) and is going to block out other lower-level warnings you may actually need to deal with the real problem.

Think maybe the latched warning is going to need a cb / off switch ?
This crew ignored stall warning for some time. Thinking it was spurious ?
Think the 447 crew would have pulled that cb / switch ?

Post 1087 ....very very relevant. I would read and re-read it and then only come to making even the glimmer of a statment!
Read it. It has huge undertones and even bigger hidden statments.
I know the fella who wrote it ..
Read and then re-read!
;)

If the sensors are out of valid range, for example airspeed <60kts, then the aircraft is not in a normal flying range and since it was last known to be stalled it most likely still is.

No need for fancy checks. the currently inhibited (likely to reduce spurious alarms on landing etc) "stall states" such as air speed <60kts would not be able clear the warning.

Importantly they would continue to inhibit -entering- the stall warning state.

As to spurious warnings due to (undetected) sensor failure the current logic would likely continue the stall warning if the sensor failed in a way to inidicate a stall so things would be no worse than they are now.

Mainly just pointing out that considering a bit of recent state history can allow for a more robust desging compared to trying to determine current state from a single snapshot of data.

Far too complex and fraught with bear pits, boys and girls.

Far simpler/cheaper to put pilots in the cockpit who know that flying with 12 degrees nose up or so at FL380 is not a good idea, and you never know, they might be able to sort out some other problems too.:ugh:

@ A380 Jockey
 

My post is even better if you click on the link! :}

Much of the article expresses ideas that have been posted in these threads (and argued about endlessly). But it was refreshing to see these opinions confirmed by a very experienced type-rated pilot, who also went out of his way to praise aspects of the airplane; clearly not a Boeing axe-grinder. These forums are so anonymous that it's hard to really know the AB experience of those expressing opinions on these problems.

I was shocked that the first post to respond to it said it had appeared here many times (?) and that it was nonsense. Then we had a feller who disagreed with that, and that was the end of that discussion.

Well heck, since you drive the Big Boy, go ahead and try to make a glimmer of a statement!

Then perhaps you should ask him to have a look in his manuals a bit more often and also have a look at the interim reports. There seems to be some things he has forgotten or don't know.

I do feel certain that were you to spring this scenario on pilots in a simulator without warning,less than half of them would have a successful outcome.

Safely flying Airbus requires something of a non-pilot mindset.




I guess this is why I never chose to fly the AB.

Since you've never flown it, I'd like to know how you came up with that conclusion? :confused: The majority of pilots whom I've flown the A330 with would have handled it just fine, because they knew how to handle UAS events at altitude.

I quoted the sim part at the top but chose to stay away after my friend told me his story landing at MIA when they couldn't control the aircraft so went around knowing they were going to crash, just didn't know where. Eventually they regained control and landed.

Something about a side stick control doesn't give me the confidence, especially if the FO is flying, of what is going to happen next. Mix that with a guy with low experience and another with not much more experience than the guy flying. Two pilots in a full stall and neither one could figure out why they were falling out of the sky? At least a yoke in both belly's would give them a clue. Maybe not in this case.

Why the question mark? It -has- appeared here many times. Read the thread.

With regard to post 1087's link. Not rubbish at all.
For example this quote from the original article:
About a month and a half ago I concluded over on the tech thread that this was initially a roll PIO event as best I could figure from the data. It really stands out as unusual in the period leading up to the stall (well, that and the high nose attitude.)
Call in overcontrol if you wish, but if it was really PIO, it was worse than that as far as demanding a response from the pilot.

The guys with the minimalist approach to aircraft control will probably never see PIO. If you are not that type of pilot though, you could have an unpleasant encounter.

PIO is funny, in that it is hard to stop once started.:eek:, and it requires a change in piloting strategy to stop it.

That's why the O stands for oscillation.

...but the more important letters are the P & I...

Actually not. Agreed that if you are flying, it is your problem to solve right now. Later, if you are still among the living, it becomes someone else's problem.

But the causative factor is really a problem in control design that can be overcome by the control design engineers.

If you blame yourself for the problem (when you find it) and don't write it up, it won't get fixed. As long as the maintenance folks have not changed the way the aircraft flies by ill-advised maintenance, the problem belongs with the certifying authority and the guys and girls with slide rules.

Actually a 'PIO' has little to do with the aircraft and a lot more to do with the 'P', and hence its name. I don't think 'writing it up' will work!

"I induced a PIO - aircraft u/s":)

But the BUSS has not been designed to exit a fully developed stall. BUSS is not the solution either to unreliable speed indication above 25000 feet. Would the AF447 crew have attempted to select all ADRs OFF passing FL250 in order to activate the BUSS ... ? What would have been the BUSS indication ? Is it designed for 45 deg of AoA ?
I have some doubt about the BUSS ... but I have never experienced it in the simulator.
A more simple AoA indicator could be a better option maybe ...

Glider PIO's can be due to CG out of range, eg someone accidentally leaving a ballast weight in or in my case on one flight, a loose trim tab that moved every time I moved the elevator. Too fwd a CG can lead to you running out of elevator authority and too rear can lead to too twitchy elevator!

A simple AoA indicator already is an option, I believe. Just not one that many airlines seem to specify.

And if the final report recommends AoA inidcator be mandatory, it won't be the first to do so. Maybe one day the regulators will act on it.

@stepwilk
I have, I did. All of them. Thoroughly.

BUSS - BackUp Speed Scale
 

As you said the BUSS is activated by switching off all 3 AirData sources, this action will also force the flight control Alternate Law.
Its advised to not use it above FL250 because theres the assumption there is sufficient altitude to recover an UAS.

From the FCTM:
‐ At high altitude, typically above FL 250, the cases of unreliable speed situation are mostly a
temporary phenomenon: They are usually due to contamination of the pitots, by water or ice,
in particular meteorological conditions. In-service experience shows that such a contamination

typically disappears after few minutes, allowing to recover normal speed indications.

It comes with an ECAM drill...then the question is:
Would the AF447 crew had followed the drill passing FL250?

The yellow AOA indicator line [Current AOA] would have been at the bottom of the SLOW side of the scale.

http://i474.photobucket.com/albums/r.../BUSSScale.jpg

It is based on Inertial data instead of AirData and always available as long IRs not failed, since the AOA is now also available when AirData is not (e.g. CAS <60Kts) the stall warning would not have silenced.

Maybe, but the AOA limit (in Alternate and Direct Law) is a function of MACH, Speedbrake and Flap/Slat settings.
Then a crew needs to know its limits for MACH/CONFIG or the bug needs to be automated and that will make it more than just a simple indicator.

BTW The BUSS is not adopted for use of Speedbrake

Far simpler is a table in the QRH to cross refer to and select AOA in the AIDS ALPHA parameter call up menu.

RE:

a. the stall warning trigger threshold "cooks off" at a LOWER AoA and remains silent at deep-stall AoA's (i.e. any attempt to stick fwd [and thus lower the nose] triggers a quite deterrent aural stall warning – so any prudent pilot unstalling actions are thwarted).

>>Bonin: 'But I have been pulling back on the stick all the way for a while.'
>>Dubois: 'No, no, no, don't climb.'
>>Robert: 'Ok give me control, give me control.'
>>Dubois: 'Watch out you are pulling up.'
>>Robert: 'Am I?'

Perhaps "prudent pilot unstalling actions" are thwarted by the automation, but I don't see any prudent pilot unstalling actions here TO THWART!

Also, although I fly Boeing and am thus not familiar with the Windows Vista flight control system of more "advanced" aircraft, I wonder: did the pilot have authority over pitch trim, or was that removed from his crib like a dangerous toy also?

The usual cause of PIO landing a glider is insufficient airbrake.

Is that inertial data + raw AoA, or does the BUSS not use AoA vane angle at all?

A33Zab,

First, thanks for the documentation as the information on the BUSS is IMO seriously insufficient. A video animation for anyone who operates such equipment should be readily available ...

If I get you right, the green - red scale is fixed on the PFD, green always in the middle. Only the Current AoA line is moving.
Now, is it possible for the AF447 scenario, that the Current AoA line would not have been visible at the bottom of the SLOW side of the scale as the CAS was already well below VLS, and the red lower area is for a CAS above VLS ?

The QRH leaves no latitude at all - It is a 2 cases scenario - Either you're above FL250, either you're below.
If above, you're good for a 4 pages QRH procedure ...

@HN39:
 

For the BUSS it is Inertial Data + the AOAi (Indicated AOA) which IMO is identical as what you call the 'Raw AOA'.

All three were clueless. Bonin flew that plane into a stall condition, not on purpose but it doesn't matter really except that he did. Robert became more preoccupied/obsessed on giving the controls back to the captain instead of taking charge of the airplane and the situation. The captain arrived too late and the plane had already stalled and time-left was fast becoming shorter.

I can accept that only the captain had received the training to escape stall conditions but that doesn't mean the other two didn't know/hear/read/test about them. How can you get an air pilot license without completely know about airplane stalls? How could they possibly ignore the First time "Stall + Calvary" warning? Not the second or third one or even less the 70+ time. How one pilot, after hearing the warning for the first time asked: What is that? and the other one didn't reply?

How do three professional pilot lose sight of altitude until 28,000ft were gone-by? Then another 6,000ft? Then, at less than 4000ft, one of them realized the possibility of death.

:confused:

- I sincerely hope you are wrong!

Every airline I flew with all pilots knew how to fly as well as the captain. I know things have gone downhill but hope not too far..

Not being able to tell your crew to push the SS down because you are stalled is an obvious fix but they probably wouldn't have known how to do it. They seemed to not understand the fundamentals of stall recovery. Push down. Works every time. At least for me.

I was looking at the FCOM and things are described a bit differently :

So that yellow line stays in the middle and probably and hopefully the GREEN area with the target speed (GREEN triangle) remains visible at the top of the scale whatever the current stall speed/AoA is.

For the Red SLOW area :
Those checked on the 380 probably know more as the BUSS seems to be standard equipment.

Hey, bubbers44.....maybe they were from the "school" where they were taught that if you pull back, you go up, and if you pull further back, you go down !!!:O

No, obviously they were NOT from that school. But they should have been.