Dual Input Airbus

[Lord Bracken]

Aren't the fact the sidesticks are not linked a matter of principle, not complexity/weight?

[vilas]

In post #38 I have termed the dual input or noncoupled side sticks as the Achilles heel of Airbus. So I haven't denied that. I had commented on 447 thread that even if it was empathized in classroom that in alternate law you should not pull full back stick even with GPWS could have saved both the aircraft. Airbus by it's philosophy is automation. Now it has come out with alternate speed where with unreliable speed situation aircraft tells pilot it has switched to alternate speed and he doesn't do a thing. Accidents happen even with everything in place as it should be. My point was 447 has been discussed threadbare and we should not be trading the worn out path.

[FlightDetent]

Aren't the fact the sidesticks are not linked a matter of principle, not complexity/weight?

My understanding is negative on this one. To have them the way they are is not a result of applying any specific operational philosophy. I.e. it was not a design objective to create a solution with separate sticks.

Building them connected and movable, with sufficient reliability while observing fail-safe/operational criteria, was such an engineering and economical puzzle that decision was to go independent-redundant. So I was told. The present configuration has a number of its own unique benefits as well.

Good skills of a proficient operator are built around the fact they are not interconnected. Tools to mitigate the undesirable consequences are provided in hardware, software and liveware. Using those instinctively, as a reflex action, that is where the chosen solution cannot compare to connected yokes. https://www.alamy.com/stock-photo-co...-73187853.html

[Uplinker]

Originally Posted by Check Airman

It’s my opinion that the PM would’ve been able to rectify the situation, had he realised the PF was pulling back the whole time.

I agree with you on that, (but no pilot should ever think it acceptable or correct to apply full pitch up at 36,000 in the first place, no disrespect intended to the AF447 crew).

In theory, the side-sticks could be linked mechanically with a series of 90° cranks and two control rods crossing from one stick to the other just behind the lower part of the instrument display panel, and a release pin in each rod could be pulled in an emergency to separate the sticks.

Knowing what the other side-stick is doing need not require mechanically linked sticks: The Maltese cross and four corner display used for control ground checks could be brought onto both PFDs in flight under certain circumstances, so the other pilot would see what control inputs were being applied, and thus be aware of the need to apply their take-over button if required.

[tcasblue]

Still haven’t had any confirmation that the original A320 did not even have the Dual Input warning and that it was a modification. Can anybody confirm this.

[Goldenrivett]

Originally Posted by Uplinker

In theory, the side-sticks could be linked mechanically with a series of 90° cranks and two control rods crossing from one stick to the other just behind the lower part of the instrument display panel, and a release pin in each rod could be pulled in an emergency to separate the sticks.

I think these active side sticks will be the final solution

Active Side Sticks

[vilas]

The Connected SS can be helpful but I think the tactile feed back and soft stop is not in synch with Airbus FBW i.e. flight path stable. It will be too much contradiction. The other thing I want to know is in any aircraft in instrument conditions when a pilot wants to make a pitch change isn't he supposed to look at the PFD to know it's happening? Maybe if instinctively an input is given without reference to PFD but at least afterwards is he not supposed to check that the correct amount of change has happened? In 447 case a very high input was given and was never checked by any of them. OK the side sticks are not connected but in clouds with AP disconnected the PM never looks at PFD then what was he monitoring?

[FlightDetent]

vilas Agreed 100%.

Uplinker The risk of overloading pilots with clutter on the PFD is real. Hence the removal of non-essential indications during abnormal attitudes, on various installations. Having said and personally being happy with that, I cannot stop thinking every now and then if the maltese cross could be helpful. OTOH, being devils advocate against myself:
- The improper use of maltese cross has caused trouble before and due to P.C. / L.o.F issues, the indication is somewhat exiled.
- There would be a need for training and assuring proficiency. An argument is raised such training effort and resources are better utilized to help pilots excel in using the present configuration.

tcasblue Posted in #66 https://safetyfirst.airbus.com/app/t...ick-inputs.pdf, the end of the article has an inset.

HOW TO UPGRADE YOUR SA AND LR AIRCRAFT ? The light and aural indicators are basic and free of charge on retrofit, on the A320 family and A330/A340. It requires FCDC and FWC to be at a given standard already available on production line: • A320: FWC E2 Standard - FCDC 53 Standard • A330/A340: FWC K3/L7 Standard - FCDC M11/L14 Standard Pin progra

. Not a direct proof though.

Chris Scott Hope all is well, good sir. Any war stories to share?

[Vessbot]

Originally Posted by vilas

The Connected SS can be helpful but I think the tactile feed back and soft stop is not in synch with Airbus FBW i.e. flight path stable. It will be too much contradiction. The other thing I want to know is in any aircraft in instrument conditions when a pilot wants to make a pitch change isn't he supposed to look at the PFD to know it's happening? Maybe if instinctively an input is given without reference to PFD but at least afterwards is he not supposed to check that the correct amount of change has happened? In 447 case a very high input was given and was never checked by any of them. OK the side sticks are not connected but in clouds with AP disconnected the PM never looks at PFD then what was he monitoring?

I don't see a contradiction between linking the sticks and the Airbus control law. That just means the other pilot's hand force is fed into your stick, and doesn't necessitate anything more.

If, additionally, a force proportional to speed deviation is fed back, that would make it speed stable and incompatible with what Airbus does. But nothing means that has to happen. The only other force could be a spring force from center, as is the case now.

[Denti]

Originally Posted by Goldenrivett

I think these active side sticks will be the final solution Active Side Sticks

Airbus considered active side sticks during development, the DLR (back then DFVLR) had test items, including interconnect, developed for a test rig, but it never went very far as other decisions had been taken quite early, vilas explained it quite nicely why it doesn't work well with the current FBW philosophy of airbus.

[vilas]

I am basically reluctant to reopen AF447 because it's waste of time. There were 22000 posts before it closed and I don't think anything new can be added. Also Airbus gave a thought about linking SS but didn't. If it didn't happen then it's not going to happen now.

[tcasblue]

Originally Posted by FlightDetent

tcasblue Posted in #66 https://safetyfirst.airbus.com/app/t...ick-inputs.pdf, the end of the article has an inset.
. Not a direct proof though.

Thanks,

If true, there could be some aircraft out there without the Dual Input upgrade. Anybody have that situation at their airline?

[Uplinker]

Agree with the last few posts.

I personally think the Airbus FBW is a fantastic piece of design, and is well developed and thought out; credit to the design team. I find it a delight to fly and, coming from an old style basic jet, (the BAe 146), I found Airbus FBW easy and completely intuitive, (I do have an electronics background, and can appreciate why the system works the way it does - perhaps that helps).

I was type rated onto a B737-300/400 for a season two years ago and that was like something from the stone-age, by comparison. (Now happily back on A330 again, Covid 19 allowing).

As far as Dual Input goes and without contradicting myself, I would be curious to know the Airbus design team's reasoning on the cadet 'no flare' scenario and the other situation of not always being able to see the other side stick, particularly on a dark flight deck with the opposite tray table out.

[vk757320]

Originally Posted by Uplinker

If a pilot does not flare at 10’ there isn’t really time to say I have control, you just need to take control. With a conventional yoke system, a Trainer or Captain could apply back pressure on their yoke which would save the landing and give feedback to the trainee, (followed by a debrief).

The Airbus FBW side-sticks do not move to mirror each other’s inputs - (I think they should) - so instead there is an algebraic addition of deflections. This means that in a no flare situation, the Trainer/Captain could quickly pull back and save the aircraft, but it is not correct for both pilots to be operating the controls, hence the “dual input” warning if the take-over button is not also pressed.

Airbus FBW nosewheel steering is also additive, and I once saved a Captain who suddenly veered over (for some reason) while taxying, and I grabbed my tiller and saved any embarrassment. There wasn’t time to alert him or say I have control.

Is dual input required at such late stages? If the Capt moves his stick below 50ft then it should automatically inhibit FOs sidestick with no disturbing aural alert. Just a visual green blinker.

[CayleysCoachman]

If some of you are actually airline pilots, this is a profoundly disturbing thread. The AAIB report referenced above laid bare the appalling weaknesses in airbus philosophy. I’m sympathetic to how they got there, but not their absolute refusal even to discuss that they might be wrong. Declining professional standards plus this kind of nutty design add up to foreseeable problems that may kill.

To answer Uplinker , I asked them, from a professional position of authority, and they didn't have an answer. Being ‘able’, in terms of flight deck layout and illumination, to see the opposite sidestick, and being able to monitor it continuously and effectively and in a sufficiently granular way without detriment to more general situational awareness, are hugely different things. Interconnected controls, and the fabulous nature of the human haptic system, are the answer, unless you live in Toulouse.

[Cak]

Originally Posted by CayleysCoachman

If some of you are actually airline pilots, this is a profoundly disturbing thread. The AAIB report referenced above laid bare the appalling weaknesses in airbus philosophy. I’m sympathetic to how they got there, but not their absolute refusal even to discuss that they might be wrong. Declining professional standards plus this kind of nutty design add up to foreseeable problems that may kill.

To answer Uplinker , I asked them, from a professional position of authority, and they didn't have an answer. Being ‘able’, in terms of flight deck layout and illumination, to see the opposite sidestick, and being able to monitor it continuously and effectively and in a sufficiently granular way without detriment to more general situational awareness, are hugely different things. Interconnected controls, and the fabulous nature of the human haptic system, are the answer, unless you live in Toulouse.

It might not be the best solution, but it works quite effective. There are procedures to follow and "override" function. Illumination is just the indication. If you need to take-over, illumination will not happen.

After operating Toulouse engineered aircraft for almost 20 years and instructing almost half of that time, I never had a single issue with that design. And I trained quite significant number of cadets, including base training.

Comparing a Toulouse designed aircraft with a Seattle ones, there is quite obvious difference in the number of incidents recorded by NTSB

[Vessbot]

Originally Posted by Cak

Comparing a Toulouse designed aircraft with a Seattle ones, there is quite obvious difference in the number of incidents recorded by NTSB

Not so. I started a new thread to address that: Boeing vs Airbus accident rates

[CayleysCoachman]

Wow, Cak that graph is an appalling abuse of data, as Vessbot explains on his thread. The central point is that the use of FBW should, if correctly executed, have had a positive impact on risk. It hasn’t, and while we will never know which deaths were prevented by it, we know that deaths have been caused by it, IN THE WAY THAT AIRBUS INSISTED UPON ENGINEERING IT (sorry for shouting but the point needs to be made forcefully).

Their corporate mental model that it was a cure-all was equally damaging - I still have a copy, somewhere, of their letter to operators which stated that UA recovery was not a necessary syllabus item on their products.

[pineteam]

« It’s not the plane. It’s the pilot ». Not taking any sides. Let’s be real: Any competent pilots should be able to fly safely an Airbus or a Boeing. But the outcome might have been very different in the Hudson river case if it was a conventional aircraft; Not taking any credits from Cpt Sully, he did an amazing job. Just stating facts: Side stick was held fully back but thanks to the protection they did not stall. Also Alpha floor had saved many aircraft from stalling in some cases like interception from above going seriously wrong like in the case of Air France 7512.

https://bea.aero/fileadmin/user_uplo...19-0731.en.pdf

[sonicbum]

Ah, the good old Airbus vs Boeing threads! We were missing it!

Come on, “can we get serious now?”