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-   -   Dual Input Airbus (https://www.pprune.org/tech-log/625705-dual-input-airbus.html)

Uplinker 24th Sep 2019 12:46

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.

Check Airman 24th Sep 2019 14:30

This represents the biggest design flaw of this airplane in my opinion. Not sure why the regulators allowed this to be certified, and (especially after AF447) continue to let it go unchecked.

dogsridewith 24th Sep 2019 14:36

Why is "I have control" not "Mine?"

Check Airman 24th Sep 2019 17:55


Originally Posted by dogsridewith (Post 10578369)
Why is "I have control" not "Mine?"

Depends on the airline. My previous company was much more aligned with Airbus SOP. We said “I have control”. Current company says “my aircraft”. They’re fairly strict on that in the training department. “My airplane” will get you slapped on the wrist.

sonicbum 24th Sep 2019 19:11


Originally Posted by Check Airman (Post 10578365)
This represents the biggest design flaw of this airplane in my opinion. Not sure why the regulators allowed this to be certified, and (especially after AF447) continue to let it go unchecked.

It works perfectly well if you know how to do it and set yourself some reasonable gates. Intervention training is generally part of upgrade courses and is a big part of TRI courses. When we do qualify TREs for base training we spend at least an hour each in the sim to practice all sort of mismanaged handling at low height, it just takes a bit of practice.

Uplinker 24th Sep 2019 19:21


Originally Posted by dogsridewith (Post 10578369)
Why is "I have control" not "Mine?"

Because in the heat of the moment, “mine” could be misheard, and misunderstood.

Many standard phrases might seem laborious, but they are designed to avoid any confusion, and be understood over background noises etc.

Check Airman 25th Sep 2019 00:04


Originally Posted by sonicbum (Post 10578557)
It works perfectly well if you know how to do it and set yourself some reasonable gates. Intervention training is generally part of upgrade courses and is a big part of TRI courses. When we do qualify TREs for base training we spend at least an hour each in the sim to practice all sort of mismanaged handling at low height, it just takes a bit of practice.

As Uplinker said bout the heat of the moment, sometimes there’s no time. An easy, intuitive solution to the problem they created is used by Boeing, Douglas (RIP) etc. Airbus put a lot of energy into human factors, but the uncoupled sidesticks (particularly in with the AP off) is a huge oversight, and fatal, as we’ve seen.

sonicbum 25th Sep 2019 08:17


Originally Posted by Check Airman (Post 10578721)
As Uplinker said bout the heat of the moment, sometimes there’s no time. An easy, intuitive solution to the problem they created is used by Boeing, Douglas (RIP) etc. Airbus put a lot of energy into human factors, but the uncoupled sidesticks (particularly in with the AP off) is a huge oversight, and fatal, as we’ve seen.

Sorry, but I disagree. You do have time to press the takeover pushbutton, it takes 1 millisecond regardless of the words You pronounce, if any. Being able to judge when it is appropriate to press this button is another question though and that comes also with experience, I believe we all acted with our thumb at least once either a bit too late or a bit too early (at least I did luckily without breaking anything). The basics is any time You are PM and need to act on the sidestick for whatever reason, You push the button.
Regarding the AF447 You are referring to, if You end up with 10 degrees ANU and TOGA at FL350 I believe (and much more important investigation bureaus believe) it is somewhere else we need to focus on rather than the mechanical connection between the sidesticks.

The Banjo 25th Sep 2019 09:09

Capt presses red button, aircraft announces, "priority left", capt lands aircraft and discusses flare technique with first officer at bay after shutdown.
No "tea n' bikkies" with management as heavy landing avoided, first officer's 21st century ego takes back seat and everyone goes home happy.
Not difficult.

vilas 25th Sep 2019 11:56


If a pilot does not flare at 10ft there isn’t really time to say I have control, you just need to take control.
if you are flying Airbus why do you have to say anything? The aircraft will say that for you. Priority left is same thing. Just press the take over button, flare and land. Tell the FO to do a better job next Landing.

ACMS 25th Sep 2019 12:28


Originally Posted by vilas (Post 10579109)
if you are flying Airbus why do you have to say anything? The aircraft will say that for you. Priority left is same thing. Just press the take over button, flare and land. Tell the FO to do a better job next Landing.

At 10’.........too late, all over red rover by then......

vilas 25th Sep 2019 16:30


Originally Posted by ACMS (Post 10579127)
At 10’.........too late, all over red rover by then......

Not necessarily. All you need is to break the descent. It can be done at 10ft. But if you feel it's too late then you should do it while crossing 20ft. In the aircraft some one needs to do what is required to be done. If AP doesn't then pilot, if PF doesn't then PM has to. And the last barrier needs to be defined according to individual judgment. Cannot continue accepting hard Landings till the FO develops the judgment.

Check Airman 25th Sep 2019 19:42


Originally Posted by vilas (Post 10579342)
Cannot continue accepting hard Landings till the FO develops the judgment.

Who said anything about FO’s doing hard landings?

:}


On a more serious note, it is concerning when airlines never allow FO’s to fly in challenging conditions, then hand the keys to the jet to those same FO’s after upgrade.

iceman50 26th Sep 2019 02:16

You are all obviously talking about the A320 variants as flaring at 10' on A330/A340/A350 will only drive the mainwheels into the ground harder! Intervention should have happened well before then.

vilas 26th Sep 2019 03:14

Iceman, no! I didn't suggest flaring at 10ft. but ten ft as salvaging point in A320.

PGA 26th Sep 2019 03:30

Also an important thing to note:

dual input as opposed to pressing the takeover button can save the day sometimes. If your colleague doesn’t flare enough, the moment you press the button the flight control does what.......? Back to neutral until, your input is established, which could make matters worse temporarily.

hikoushi 26th Sep 2019 05:20

Sometimes a combination of instinct and procedure is the right technique. The time that most of us will instinctively move the stick (“DUAL INPUT!!!”) before pressing the takeover PB is either a quick pull when the guy forgets to flare, or a quick lateral move when the guy over-banks suddenly. The “OH S#!T” pull will always happen before the button gets pressed! Adrenaline will ensure this!

In the opposite situation with someone over-flaring, we will naturally tend to press the button first. This will in actuality return the controls to neutral since we likely will not have actually moved the stick yet... which is exactly what we need to do.

Simply following instinct will always work, as long as we remember to press the takeover button at some point in the proceedings. To prevent a hard landing or a wing/pod strike, make the instinctive move first and then press the takeover button while applying the stick pressure. For a high/ over-flare, press the button first and then fly the airplane where you want it to be. Either way is natural and is what most of us will do without thinking about it.


vilas 26th Sep 2019 05:27

There's a difference between not flaring and not enough flaring. In not flaring at all the PF stick is in neutral so if the other pilot flares then it's single input and the aircraft response is normal. Not flaring enough the PF stick is out of neutral, here any input from the other side will be additive to it. Since flare and Landing is a visual manoeuvre if one is able to differentiate the change in flight path and adds his input accordingly then it will still produce the desired result even with dual input warning. The problem is if the PF for some reason pushes the side stick forward then the PM input will be cancelled and aircraft will continue it's Flight path. So the gist is if is you want to salvage the Landing you will have to do something in an approved or not approved manner. If the result is not satisfactory execute a GA. This the Achilles heal of Airbus FBW so perhaps the discomfort makes each one find his own solution.

tcasblue 2nd Apr 2020 04:17

I found this statement from another forum to be interesting. Perhaps not in the original design......

"There is a "dual input" audio callout. It was a early A320 mod, but I think it was standard before the A319 came out."

Loose rivets 3rd Apr 2020 01:04

I suppose flying allows one to get good at expecting the unexpected, but having got old, and sitting in an ATR watching a very able young man fly the sector, I was reasonably relaxed as we passed 200'. At some point, I'm not sure when, the concrete suddenly looked like it was coming through the windshields.

I'm not sure why it happened, or even how he managed it, other than it was flown, not mushing. What I do know is that with any delay, the aircraft would not have survived the impact. My frantic tug allowed one of those 3-point landings that don't allow the wheels to skid before spinning up. Despite my best efforts, exchanges in English were somewhat limited and I'll never understand, but it seems to me that a large aircraft, stacked with computing power, should be capable of protecting itself from pilot input that makes no sense.

As an example, was the 447 computer so deprived of sensory inputs that it couldn't protect the aircraft from nonsensical control inputs - or is there no such software? It seems incredible that systems wouldn't know inputs were illogical. I'm attempting to make a clear distinction between inputs and net flightpath.




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