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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 18th Oct 2014, 00:18
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Originally Posted by Dozy
Interestingly, the B777 bypass mode has never been used, even though there have been a couple of incidents where it could have come in handy (e.g. Malaysian 124 out of Perth [IIRC] springs to mind). The crews in the incidents didn't take advantage of it.
You still did not get what happened to that 777 ...
http://www.pprune.org/7022213-post1332.html

Airbus's system doesn't use force-feedback, so there's no need for that kind of failsafe requirement.
And you still did not get what would be the purpose of a DIRECT switch for the Airbus.
Some crews would have loved to have one :
http://www.pprune.org/tech-log/50207...oa-probes.html

More on the new Gulfstream :
GULFSTREAM INTRODUCES NEW AIRCRAFT FAMILY | Gulfstream Newsroom
The industry-first ACSs (active control sidesticks) offer enhanced safety and situational awareness over passive sticks through tactile feedback. With electronic linking of the ACSs, the pilot and co-pilot can see and feel each other’s control inputs, which helps improve pilot coordination in the cockpit.
The active control sidesticks enable both pilots to be consistently on the same page, enhancing safety
Common sense, but Airbus didn't think so ...
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Old 18th Oct 2014, 01:22
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Originally Posted by CONF iture
You still did not get what happened to that 777
http://www.pprune.org/7022213-post1332.html
Bad data got through to the EFCS and AP, causing an uncommanded pitch up and climb.

You say:
Originally Posted by CONF iture
For the 777 the AP then the pilot followed unrealistic FD commands.
The report :
http://www.atsb.gov.au/media/24550/a...503722_001.pdf

says different. More to the point, it doesn't alter the fact that the bypass mode was not used by the crew.

And you still did not get what would be the purpose of a DIRECT switch for the Airbus.
Some crews would have loved to have one :
I don't see anything in that thread from crews clamouring for such a switch - just the same old arguments we've always had.

More on the new Gulfstream :
...
Common sense, but Airbus didn't think so ...
"Common sense" is your opinion - I have yet to see any evidence that confirms or refutes that position. Furthermore this is just marketing bumph - they've decided to backdrive their sidesticks, therefore they're hardly going to say that doing so might be pointless. I'm not going to waste my time enumerating the accidents in which the linked yoke position was nevertheless ignored/disregarded, nor those in which the supposedly superior "tactile" stick-shaker was also ignored/disregarded - but the record speaks for itself.
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Old 18th Oct 2014, 06:09
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Originally Posted by Dozy
I have yet to see any evidence that confirms or refutes that position
This is your opinion. In some other peoples' opinion AF447 is one piece of evidence.


is just marketing bumph
I doubt that. I am sure there are some very smart pilots in Gulfstream that consider tactile feed back is superior


I'm not going to waste my time enumerating the accidents in which the linked yoke position was nevertheless ignored/disregarded, nor those in which the supposedly superior "tactile" stick-shaker was also ignored/disregarded - but the record speaks for itself.
What about enumerating the numerous instances where tactile feed back saved the day... oh, you cant, because by nature they were non events, so there is no record.

Last edited by Cool Guys; 18th Oct 2014 at 06:35. Reason: Grammar
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Old 18th Oct 2014, 09:03
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Embraer:
Embraer?s big bet on its largest airplane yet | Leeham News and Comment
Flight laws are similar to the Airbus FBW but with two distinctions: throttles are back-driven and the side-sticks are electrically inter-connected, meaning a instructor can see on his side-stick and feel what the trainee is doing with his side-stick. The FBW goes in and trims out the yaw imbalance after the loss of an engine after a slight delay. The trim delay is deliberate so that the pilot is fully aware that he has lost an engine and which side is affected. It was easy to fly the KC-390 with all engines operative or when one engine was inoperative.
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Old 18th Oct 2014, 16:32
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Originally Posted by Cool Guys
This is your opinion. In some other peoples' opinion AF447 is one piece of evidence.
Fair enough, but I'm not the only one of that particular opinion either.

I am sure there are some very smart pilots in Gulfstream that consider tactile feed back is superior
Just as there were very smart pilots at Airbus who felt differently.

What about enumerating the numerous instances where tactile feed back saved the day... oh, you cant, because by nature they were non events, so there is no record.
I think you're missing the cut of my jib. I'm not saying tactile feedback is never beneficial, I'm just illustrating the point that it doesn't always make a difference (and furthermore that there have been cases where connected controls have hindered things).

You pays your money and takes your choice, but it's foolish to state that one method is definitively better than the other.
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Old 18th Oct 2014, 18:51
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Hi DozyWannabe,
More to the point, it doesn't alter the fact that the bypass mode was not used by the crew.
It was a good job that this alert crew invented their own "bypass mode switch".
Link
see slide 7

"With pitch attitude continuously decreasing, PF reacted by applying permanent (for about 20s) sidestick order in the full backward position.
• Pitch angle continued to decrease and AC to descend"

Last edited by rudderrudderrat; 18th Oct 2014 at 19:17.
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Old 18th Oct 2014, 22:32
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Originally Posted by CONF iture
And you still did not get what would be the purpose of a DIRECT switch for the Airbus.
Some crews would have loved to have one :
I have always wondered why there wasn't one - there is no engineering difficulty as it is there on test flights (they always start test flight program in direct and then add FCS laws in).

I wonder if it has to do with certification, in response to one of my previous posts some have suggested that the reversion laws are not tested in compliance with the regs (and special conditions) but only as failure conditions. If so, maybe putting it there as a pilot option makes the certification more complicated. Note: that would all be stupid IMHO, but then I thought that each reversion law would have meet certification standards in itself.

If it was there, I am not sure it would help much though - the Boeing one is apparently little used if ever - and it might just become another way to put blame back onto the pilot. After all (thinking about LOC with a flyable aircraft), if the crew punches out to direct law and still crashes it will be their fault, while if they could have done but didn't, and it might have helped, then same again.

More on the new Gulfstream :
GULFSTREAM INTRODUCES NEW AIRCRAFT FAMILY | Gulfstream Newsroom

Common sense, but Airbus didn't think so ...
I think you are being unfair on them there. I am pretty sure that Airbus at the time thought that contemporary engineering technology wasn't up to it. I have seen other research that concludes that that was still the the case some years later. I am pretty sure that what Airbus thought was that the benefits of sidestick and C* fbw would outweigh that disadvantage. In terms of accident rates, I would suggest that time has proved them correct in that (or at least that there was no significant overall safety disadvantage).

The developer of the new sidestick is BAE Systems, by the way, and if you go back 30 years, guess which commercial aircraft consortium they were part of ? What is happening with sidesticks now is exactly what Airbus did then - contemporary military tech is being migrated to civil, but when Airbus did it, contemporary was passive.

At some point Airbus will need to weigh catching up with the rest of the world against maintaining interface compatibility across its model range (which it has made a big selling point) - perils of being a first-mover. Boeing will need to too, because if I had to bet I'd say the future pilot interface looks like (better) sidesticks, fbw, and moving thrust levers - and neither A or B called it totally right.

Most interesting thing (and it is difficult to judge for a few pictures) for me is that the active sidestick units look to be physically smaller than the Airbus passive spring units - probably due to major advances in actuator tech. If so, given that the rest of the puzzle is software, a retrofit might even be possible - from an engineering POV, I doubt it ever will be from commercial.
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Old 19th Oct 2014, 01:37
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the Boeing one(DIRECT Switch) is apparently little used if ever - and it might just become another way to put blame back onto the pilot
Would be something new to hear about Airbus accused of an accident or incident. Isn't it?
Apparently nobody can touch the arrogant nose that keeps pitching up


Last edited by _Phoenix_; 20th Oct 2014 at 04:37. Reason: Spelling
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Old 19th Oct 2014, 02:04
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Engineers are engineers...

Let's face it, Doze is a die hard engineer that designs and implements systems that may or may not have been tested or designed by the end user - the pilots. "Works according to the spec". So I throw the B.S. flag.

Many features of the 'bus system seem very logical and could/should reduce workload ( whatever that is for pilots). However, there comes a time or situation that the basic flight controls and aerodynamic response to control inputs and such must revert to basics that we saw a hundred years ago.

I do not feel we should go to a "direct" law post haste, as even that requires electrons from the flight controls to the control surface actuators. But the plethora of modes and sub-modes on the 'bus puzzle me. I can understand the argument that the system would degrade gracefully. But the reality is some things work, some don't and some can't. Sheesh. Give me a back up mode I can trust and not go thru ten pages of manuals, footnotes and .....!!

Tust me, I am not a dinosaur. I flew the first FBW jet produced in significant numbers ( no offence to Concorde folks). We learned a lot about the failures of the "engineers" that could not fathom the unplanned tests we normal pilots would expose to the jet to, heh heh.

I enjoyed the opportunity to fly the neat little jet, and I knew deep down that we would find some things that the engineers never thought of. And we did.
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Old 19th Oct 2014, 06:14
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Originally Posted by rudderrudderrat
It was a good job that this alert crew invented their own "bypass mode switch".
Right - though technically that was a drop to Alternate Law, not Direct. The crew observed Rule No. 1 - "know your aircraft".

Originally Posted by infrequentflyer789
I have always wondered why there wasn't one
Because as originally designed and certified, it's not necessary. See my previous post re: B777 force feedback.

I am pretty sure that Airbus at the time thought that contemporary engineering technology wasn't up to it.
I don't think it was a case of the tech not being up to it, so much as it would effectively double the complexity of the required software systems and add complexity elsewhere to little real benefit - again see previous posts re: fully hydraulic controls - two pairs of hands on the controls wouldn't make any difference in the way it used to.

@_Phoenix_ : The A310 has a completely different flight control system, and furthermore the pilot in the Orly incident pulled up in response to the SW. The XL888 accident grew from improper cleaning/maintenance procedures causing failure of the AoA vanes.

Originally Posted by gums
Let's face it, Doze is a die hard engineer that designs and implements systems that may or may not have been tested or designed by the end user - the pilots.
You misjudge me - and furthermore ignore the fact that the Airbus FBW control system was designed by pilots.

...must revert to basics that we saw a hundred years ago.
Why? I don't understand this need to hold aviation development hostage to a de facto standard that dates back to (and is derived from the limitations of) pre-WWII technology. Among other things, we've been to the moon and back eight times since then (in a lander that used passive sticks, no less).

We learned a lot about the failures of the "engineers" that could not fathom the unplanned tests we normal pilots would expose to the jet to, heh heh.
Fair enough, but remember that the lead pilot engineer on the A320 project was the test pilot who succeeded D.P. Davies (of "Handling The Big Jets" fame) at the ARB.
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Old 19th Oct 2014, 09:45
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Thank you gums!

Dear gums, your post is the first specification for every aeroplane. Pilots to survive need to live. Your important message facing a large business is a life's philosophy, and the message of your Country choices, success, before, during and after WWII and how Freedom may change the World. Not only the "free" (? I doubt) decision of a little team, or one pilot put alone, but the freedom degrees let to every pilot in emergency in the sense of mechanic laws, and freedom in the human natural sense, and confidence in well selected, taught, trained pilots who are considered as Men, not throwable things designed by stats and without ejection seat!
Thank you so much, gums.
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Old 19th Oct 2014, 14:51
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Hi Gums,
While I feel quite humble comparing my experience to your time developing the F16 FBW, I have to agree with your sentiment regarding the complexity of the FBW law degradation. With one of my first projects as a young engineer I happened to be working with an old guy (who would be deemed a dinosaur in PRRUNE) who said to me “Whatever you do keep it simple” as he proceeded to literally throw in the bin an extraneous controller (PLC) that had been causing us no end of trouble. I have applied this for the last 30 years and it has never let me down. This does not mean “don’t use automation” but it means “do not over use automation.”
While I haven’t flown a modern jetliner from what I have read the automation seems excessively complex, and I’m not referring to just AB products. Complex things confuse people and confused pilots don’t fly planes very well. Yes, I know pilots should be trained adequately but training can fail just like a pitot tube.
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Old 19th Oct 2014, 14:59
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No flame wars, just honest inputs

No problem, Doze. I feel we both appreciate the opportunity to exchange opinions and lifetime experiences regarding engineering. I was fortunate to be on both ends of the process as an end user and a designer/tester on the other end.

My main concern is we seem to be assigning more and more "operation" to the machines at the expense of human judgement and decision-making and experience. How do we "train" a machine to handle an event that has not been anticipated by the design engineer? And worse, how do we design a machine to anticipate unusual human actions and "protect" them ( God, how I hate that term, and prefer "limit")

Gotta think about this more, so gone for now......
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Old 19th Oct 2014, 15:30
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I don't understand this need to hold aviation development hostage to a de facto standard that dates back to (and is derived from the limitations of) pre-WWII technology.
This is a very good question. Perhaps because the “de facto standard” is based on the laws of physics which are constants, people can learn them starting from primary school, become familiar with them in many areas of life, discuss them freely, they are the same for newbies and dinosaurs, they remain the same from one century to the next, they are natural. The more software you get between the pilots physical senses and the control surfaces the more it flies based on how some one believes it should fly. This is very fluid, the persons inventing it may not document it adequately, other inventers may disagree with it and design theirs differently, it can change between America and Europe and from year to year, as technology changes people may discover it actually is not the best way and a change is necessitated. It may actually not be the best way of controlling the plane.
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Old 19th Oct 2014, 18:11
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Hi DozyWannabe,
Among other things, we've been to the moon and back eight times since then (in a lander that used passive sticks, no less).
I think you'll find there was only one control stick - hence active feed back not necessary. Also the Lunar module is unstable in flight and must be computer controlled - hence no "Direct Law" so side stick control is a perfect solution.

the moon - Why did Armstrong pilot the LM, when Aldrin was tasked as Lunar Module Pilot? - Space Exploration Stack Exchange
"According to Tales From The Lunar Module Guidance Computer by Don Eyles, Armstrong and Aldrin never switched places during the LM powered descent and landing phase. Armstrong was on the left side of the LM cockpit where the manual controls were, and Aldrin on the right and responsible for working the DSKY (Lunar Module Display and Keyboard Unit), essentially instructing the flight computer."

More fascinating info on the software programming here:
Apollo 11 and Other Screw-Ups
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Old 19th Oct 2014, 22:47
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@DozyWannabe,
and furthermore the pilot in the Orly incident pulled up in response to the SW. The XL888 accident grew from improper cleaning/maintenance procedures causing failure of the AoA vanes.
Are you kidding me? Watch again the video. It includes the actual CVR. The Stall Warning came on at 1:06, during recovery phase!!! No stall warning during vertical climb or at peak point.
Funny thing, the aerobatic maneuver starts at 0:10 with captain's question :
Hé ! qu'est-ce qu'il fait !?
see CVR transcript, page 53 of report below, the stall warning at 10h:44m:44s
http://www.bea-fr.org/docspa/1994/yr...yr-a940924.pdf

https://www.faa.gov/other_visit/avia...8/FSAT9513.pdf

About XL888, of course, if isn't the pilot then must be the mechanic...

Last edited by _Phoenix_; 21st Oct 2014 at 01:04. Reason: added ref
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Old 20th Oct 2014, 03:26
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Originally Posted by IF789
I have always wondered why there wasn't one
We have to remember what is the Airbus leading concept :
Our technology is here to save the pilot from his own mistakes, not the opposite ...

I think you are being unfair on them there. I am pretty sure that Airbus at the time thought that contemporary engineering technology wasn't up to it.
I don't think to be unfair, had it been really important for them, they still would have had the possibility to adopt the coupled control columns we saw a few years later on the 777.
Now, it will be interesting to follow up on the Airbus position after the Gulfstream and Embraer announcements ...

Originally Posted by Dozy
Right - though technically that was a drop to Alternate Law, not Direct. The crew observed Rule No. 1 - "know your aircraft".
You are totally beside the point - the crew applied an unpublished procedure to take back control over a mad system that was supposed to protect them.
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Old 23rd Oct 2014, 00:35
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What moved THS?

Winnerhofer,

In alternate law automatic pitch trim is available.
The THS was moved at constant rate of 1deg/6 seconds, SW online
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Old 25th Oct 2014, 09:07
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Hi CONF iture,
Now, it will be interesting to follow up on the Airbus position after the Gulfstream and Embraer announcements ...
NBAA: Safran reveals active sidestick development project - 10/22/2014 - Flight Global
http://www.safran-na.com/spip.php?article3249&lang=en

"The dual sidesticks are also electronically linked, so the co-pilot’s stick imitates the movements of the pilot’s control inputs. In a sense, it reintroduces the aircraft feedback loop normally associated with mechanically-linked control systems into a new generation of fly-by-wire aircraft.

At the moment, Sagem has not signed up any customers, although it has briefed Dassault, Airbus, Boeing and the French air force, says Phillippe Arnaud, senior vice-president of sales and marketing for Sagem."

"Incorporating a number of proprietary Sagem innovations, this side stick controller features very high dispatch reliability, a robust design that stands up to all types of contingencies and an optimized architecture supporting the real-time adjustment of force feel laws. Thanks to its stick shaker / Stick pusher function and the fine synchronization between all side stick units, this system greatly facilitates pilot/co-pilot coordination and the management of stressful situations."

Last edited by rudderrudderrat; 25th Oct 2014 at 13:17.
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Old 25th Oct 2014, 21:34
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Originally Posted by John Tulamarine
Done .. JT
Thanks!

Originally Posted by OK465
IIRC OG suggested that the system will then 'see' the g is not as commanded and then continue to increase elevator deflection to eventually match the commanded or available g for a much lower speed than 330 KIAS. (My observations showed some number of seconds involved)
While precise and correct answer could be provided only by Airbus FBW experts - and I strongly suspect any of them reading AF447 threads must be howling with laughter - I find such interpretation quite implausible because:

1. certifying the FCS that significantly increases your pitch rate over couple of seconds while holding the constant stick deflection would be waaay too much even for the most corruptostupid aerogovernmental people inhabiting the imagination of PPRuNe's resident Airbus bashers.

2. From my 320 initial training I remember that FBW was trying to mask the fact it was losing control authority as much as it was practicable. Stabilizer lost or one elevator on vacation with other limited to 50% throw not to overtorque the empennage? No problem or perceptible difference as long as the speed was up. Maneuvering for approach with two hyds shot up felt normal enough but when abrupt maneuver at low Q needed to be performed, i.e. last moment go-around, it tended to turn quickly into wrestling match with the aeroplane.

3. Final report says:

Originally Posted by Page 186
In alternate 2 law, the longitudinal control law remains a load factor law and the
lateral control law is a direct law. In the specific case of alternate 2B law, some
coefficients used in the longitudinal flight control law become speed-independent
and are set for the maximum speed for the aeroplane configuration (330 kt in clean
configuration). This hardly modifies the behaviour of the aeroplane in comparison
to normal law, but can nevertheless induce an unusual response dynamic when the
aeroplane has an abnormally low speed for the configuration.
Originally Posted by Waldo Cerdan
Was the risk adequately appreciated?
Yes. Thirty cases with not as much as scratch to anyone or anything were appreciated enough... till the 20-20 hindsighters took over.

Originally Posted by Lonewolf50
Based on the limited evidence available to us, which is some of the CVR transcript, I'll suggest that neither Bonin nor Robert ever got to the "frightened" stage. They remained in the "what is going on?" stage, though Robert seems to have been more aware of the aircraft's flight condition than Bonin, coupled with frustration and confusion.
Oh, they quickly went from frightened to completely shocked. They were climbing with 7000 fpm, above their performance ceiling and could not connect the fact with blaring stall warning. It's textbook panic - very unlike the Hollywood one.

Originally Posted by PJ2
"...over the ocean" makes no difference, neither should night-time if one is an instrument pilot
WoCL is a four lettered word.

Originally Posted by Owain Glyndwir
The question is WTH was this not carried over to Alternate laws???
Because ALTN laws are made (inter alia) for cases of air data getting screwed up! It would be no good if false data unnecessarily rob the pilot of control authority. No matter what John Cashman, Bernard Ziegler or CONF iture might say, in FBW Airbi pilot still has the ultimate responsibility to recognize the problem and more than enough control to solve it properly.

Originally Posted by RetiredF4
The manuals are comparable to instruction manuals without comunicating the basic knowledge layer behind those instructions.
How many times have I posted the disclaimer from the very beginning of Airbus manual in previous AF447 threads? IIRC at least three.

Originally Posted by gums
The insidious effect of the implementation and the lack of speed/AoA stability until in direct law was a very big player.
Not in AF447 case as it didn't pitch up with neutral stick.

Originally Posted by BOAC
So, we are back to having something saying "That's enough mose-up THS, boys and girls - if you really want more push this over-ride button" - what is wrong with the concept?
Maybe not completely wrong but surely it's spectacularly incongruent to bash Airbus FBW for taking away the full control authority from pilot and then cry: "Help automatic trim cut-out, save us from ourselves!"

Originally Posted by roulishollandais
Boeing's Synthetic airspeed, Airbus BUSS, safe USN's AoA, or Klopfstein's old inertial HUD.
...can not alter the fact the unreliable airspeed procedures work when applied even with no alpha gauge, HUD, BUSS or whatever.

Originally Posted by RetiredF4
Correct would be the airplane will maintain a loadfactor of 1g.
It would be correct except for the fact it isn't.

Originally Posted by RetiredF4
That mindset "set the pitch and it will stay there (and go there) might have influenced Bonins actions with the SS.
So, he was desperately trying to achieve 20 degrees pitch on cruise level?

Originally Posted by tartare
Big, vulnerable ocean liners of the sky that are pretty much optimised to point directly into a high mach airflow, and stay there.
'Tis a miracle thousands of them keep themselves pointed into high mach airflow day after day, year after year and survive despite their vulnerability.

Originally Posted by gums
I do not feel we should go to a "direct" law post haste, as even that requires electrons from the flight controls to the control surface actuators. But the plethora of modes and sub-modes on the 'bus puzzle me.
You are puzzled because you have never tried them, in the sim at least, but rather built up your misunderstanding of Airbus FBW on usual PPRuNe mix of prejudice, ignorance and outright libel.

Originally Posted by Flightglobal
Safran’s exhibit featured a two-seat cockpit simulator with sidesticks on either side. Unlike passive sidesticks found commonly on Airbus commercial airliners, the active system integrates a digital feedback loop. It allows pilots to feel how the aircraft responds to control inputs. As control forces climb higher, for example, the stick feels heavier. Over-speeding the aircraft triggers a vibration in the control stick to warn the pilot.
Stickshaker as overspeed warning.... now that makes almost as much sense as 12 threads on AF447 here.

Now back to our usual reaction eliciters.
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