asynchronous sidestick

[zondaracer]

C17 is FBW but both sticks are mechanically linked.

[Clandestino]

Because Clandestino has decided the French BEA has to be the sole Reference ... ?

Sorry, lapsus; should have wrote AAIB. Care to provide reference?

[mm43]

Those sidesticks are not the best tool for CRM.

Wouldn't an "Iron Cross" flashing red on the largely blue FD have rung a bell or two?

[vinayak]

Clandestino,

I urge you to please not think that I think I'm smarter than any of the airbus certification test pilots

Infact, I know it's the other way around

I merely want to understand why chose one over the other! The "Dual input" and takeover button are IMHO very good design, but they probably wouldn't have to incorporte them if they weren't asynchronous, right?


Just trying to understand this from people such as yourselves

[CONF iture]

Originally Posted by clandestino

Care to provide reference?

AAIB Bulletin: 12/2008 G-DHJZ

Originally Posted by P10 - Simulator assessment

The AAIB investigator carried out an assessment exercise in a full flight A320 simulator taking the role of a ‘trainee’ pilot, together with an experienced A320 Type Rating Examiner (Aircraft) (TRE(A)). The TRE(A) was current in both line and base training of pilots of all levels of experience.
Having briefed the TRE(A) that he should act as he would during normal operations, the ‘trainee’ flew normal approaches and landings, interspersed with approaches and landings during which deliberate handling errors were made. No prior warning was given to the TRE (A) of these errors.
In the first of these ‘unusual’ approaches, a manual approach was flown with autothrust, but the ‘trainee’ ceased to make sidestick inputs at 50 ft RA. The TRE(A) was unable to intervene in time and the aircraft struck the runway without a flare. In other ‘unusual’ approaches, the TRE(A) was again unable to intervene, or intervened too late, to prevent a hard landing.

[DozyWannabe]

Originally Posted by vinayak

Having said that it is an engineers preference... They have not just left the side sticks control to being just asynchronous.

They have taken the pain of having the 'Dual Input' call outs and the take over push button as well, wonder what is the school of thought that has gone in.

Have a closer look at the relevant parts of the AF447 thread. The short version is that it was a "clean room" design. Believe it or not, airliner yokes weren't connected for the purpose of one pilot being able to follow through the other's inputs (strictly speaking that's only necessary on a trainer). They were connected in the days of direct cable control of flight surfaces, so that if something went awry, you'd have two sets of muscle force acting on the controls rather than just one. In today's airliners that are all-hydraulic, this feature is redundant. That's the main reason, but there are others.

Originally Posted by CONF iture

Because Clandestino has decided the French BEA has to be the sole Reference ... ?

What, you mean the French BEA who stated:

It is worth noting that the inputs applied to a sidestick by one
pilot cannot be observed easily by the other one

in the final report on AF447?

Originally Posted by CONF iture

AAIB Bulletin: 12/2008 G-DHJZ

You're playing fast-and-loose with that ol' devil called context again. The AAIB performed that test on the A320 in isolation, which is reflected in the later statement:

Therefore, the aircraft demands a relatively high level of ‘assured’ skill from the trainee; their ability to land the aircraft correctly, consistently, should not be in doubt before base training commences, and certainly not in doubt during line training where passengers are carried.

What they explicitly do not do is compare the A320 setup with conventional controls in a similar test - I'd be prepared to bet that more often that not, the same scenarios in a B737 sim would have the same outcome.

Difficulty in determining what the other pilot is doing with the stick is a factor of the design, sure - but that's a known thing, and given the safety stats, it has not proven detrimental to safe operation of the aircraft compared with a more conventional layout. It'll always split opinion, but you can't argue with the numbers.

[joema]

"Difficulty in determining what the other pilot is doing with the stick is a factor of the design, sure - but that's a known thing, and given the safety stats, it has not proven detrimental to safe operation of the aircraft "

This is correct and was discussed in detail in the book "Understanding Air France 447", by Bill Palmer, who was an A330 Check Airman for nine years.

The moment both pilots give sidestick commands, a synthetic voice loudly and repeatedly announces "Dual Input", and a light in front of each pilot flashes. There is both audible and visual indication of conflicting commands.

I worked at an airport where a student pilot stalled a light plane and refused to release full back pressure, no matter how loudly the the instructor shouted. This was similar to AF447. Finally the instructor struck the student with such force it broke several ribs and he finally released the controls. The instructor recovered the aircraft so low the landing gear was broken, but they both survived.

When total mental confusion and panic takes over, it can make little difference whether the indication of control conflict is audible, visual or tactile.

Bill Palmer analyzes several cases where similar situations happened in Boeing aircraft, and the conventional control system did not prevent an accident. It's not a pro-Airbus book, but analytically and impartially studies all data related to AF447.

[CONF iture]

Originally Posted by dozy

What they explicitly do not do is compare the A320 setup with conventional controls in a similar test - I'd be prepared to bet that more often that not, the same scenarios in a B737 sim would have the same outcome.

That's implicitly what they do by purposely setting the test on the A320 and not on an aircraft with linked flight control commands.
The Airbus sidestisk philosophy suppresses valuable information to a PNF.
That's explicitly what they mean by the following :

Originally Posted by P13 - Sidestick issues

During the landing phase of flight, an instructor pilot monitors the approach by assessing the aircraft's performance, ie, by visually scanning both the flight instruments and the ‘picture' through the flight deck windows. In addition, in a ‘traditional' aircraft, where the flight controls are fully interlinked, the instructor might also be able to monitor the direction and magnitude of any, albeit relatively small, control inputs made by the student by sensing their movements in a tactile manner. By doing so, they may be able to prime themselves for the flare motion on the control column and, if the motion is late or absent, make an appropriate input in sufficient time to attempt to avert a heavy landing.

In a fly-by-wire aircraft fitted with sidesticks, the instructor also monitors the approach by assessing the aircraft's performance, but does not have an option of sensing control inputs made by the trainee. By the time it is apparent that no flare, or an incorrect flare, has been made, it may be too late for the instructor to intervene and the aircraft to respond before a possible heavy touchdown occurs.

[DozyWannabe]

Again, context is key. I said they did not perform a similar *test* to the one they performed on the A320 sim with a conventional equivalent like a B737. The quotes are from completely different sections of the report.

Note the use of language - "might" and "may":

the instructor might also be able to monitor the direction and magnitude of any, albeit relatively small, control inputs made by the student by sensing their movements in a tactile manner. By doing so, they may be able to prime themselves for the flare motion on the control column...

But the kicker is that this section is speculative - it would seem that if it were a BEA report you'd be admonishing the above section for lack of clarity. In this section they are talking about conversion training - not line flying, as the gist of the report highlights the fact that the PF was not, in their opinion, sufficiently well-trained to be on the line yet.

If you pay attention to the wording of the AAIB report, you'd note that when they refer to the actual *test* they did in the A320 sim, the TRE was explicitly instructed *not* to act as an instructor, but to behave as if he was a senior line pilot in the PNF role. They did not then perform a test in a conventional-layout sim for comparison and thus are not trying to definitively compare the two. Some would argue that the Turkish B737 accident at Schipol illustrates that conventional controls didn't make any difference, because neither of the training pilots noted yoke or thrust lever position despite both being of the articulated kind beloved by the anti-Airbus brigade.

Oh, and I noticed this earlier:

Originally Posted by Capn Bloggs

I know you're on "our" side, Gums

CB - this makes me very despondent, because there shouldn't be any "sides". For what it's worth, gums and I have had some very civil and enlightening chats away from the public boards and while our backgrounds differ, meaning that we approach the subject from different angles, there's no animosity there.

As far as I'm concerned, we're all in this to try to make flying safer. While I won't hesitate to call out positions that I know to be misunderstood or misinformed, I don't do so to get into a slanging match - in fact it upsets me when things deteriorate to that level.

Truth be told, if it were up to me I'd be all in favour of having you guys handfly as much as you want as long as it is safe to do so, and I'm all in favour of the industry compelling more sim training in the nuances of handflying - especially for those who have had less opportunity to do so on the line. More to the point, I have always held this position - take a random dip into my post history if you don't believe me!

Where my position differs from some is that I think it is counter-productive to get into the blame game, especially as far as automation is concerned. What I find especially saddening is the adoption of an "us and them" siege mentality, usually defined as a nefarious collusion of airline management, engineers and the dreaded "beancounters" versus pilots. At the very least it's not that cut-and-dried, and I for one don't think it's even true. As a techie and reasonably frequent SLF, I have no problem with the use of technology in terms of making your lives easier and civil aviation safer and more efficient. But I'm just as opposed as you are to misuse of that technology to drive down costs and deprive you of the ability to keep your basic piloting and airmanship skills well-honed.

Surely, by any reasonable measure that puts me on your "side", if it must be put that way.

[jcjeant]

In addition, in a ‘traditional' aircraft, where the flight controls are fully interlinked, the instructor might also be able to monitor the direction and magnitude of any, albeit relatively small, control inputs made by the student by sensing their movements in a tactile manner

The facts are:
In a "traditional" aircraft the relatively small control inputs will be sensed by the other pilot and he will react if necessary or will not react even if it's necessary and we will call this a human error
In the "non traditional" aircraft small control inputs will never be sensed by the other pilot and so he will not react even if it's necessary and we can not call this a human error

[DozyWannabe]

Originally Posted by jcjeant

In the "non traditional" aircraft small control inputs will never be sensed by the other pilot and so he will not react even if it's necessary and we can not call this a human error

They will if the other pilot is doing his or her job - I've seen TREs do it in the sim with a combination of instrument scan and experience.

[FullWings]

I'm a believer in force-feedback, coupled controls and so on but it does seem to be secondary to crew training/currency/experience. In the recent B777 Asiana crash at SFO, the PF must have had the control column well aft, against some fairly high trim forces for quite a while but no-one noticed.

That said, it appears you do have to be on your "A" game near the ground as a line trainer on the Airbus (going off others' anecdotes rather than personal experience...)

[Capn Bloggs]

They will if the other pilot is doing his or her job

You're defending the indefensible.

As I was bumping down the (hand flown, "through" the FD) ILS last night I also thought of the incapacitation situation. If I was to become subtly incapacitated, it would become immediately obvious to my FO because the control column would stop moving or be not moving in accord with what was required, and well before any callable deviation occurred. On a "normal" approach, the control column is alway moving and is plainly visible to the other pilot. Not so a sidestick.

[RunSick]

Dozy, I do respect you post a lot, mostly because they are well fundamented and I personally consider them a good source of info about the aircraft I fly, the Airbus. But please, stop thinking that because you read something it is like that.

When somebody that ACTUALLY FLIES THE PLANE says something like "it is hard to see what the PF is doing on an Airbus" pause for a second and before coming back with what the Manual/Test/Simulator/Report says, consider that this person has been there for real and is telling you his real life experience.

You have already said that you are not a pilot, just an aficionado (and I must admit one of the better informed I have ever seen) and that´s OK but consider also that your situation has it´s limitations. You just don´t know what is REALLY happening up there. Real life is not the Simulator checkride, nor the manuals certification process, nor the nuances of a report wording...

I love the Airbus but I (as I´m sure many other pilots) can also vouch for the fact that it is EXTREMELY hard to know what the PF is doing on his sidestick, evenmore if we´re talking about small inputs. I´m not going to debate wheter it is right or wrong but I can tell you it IS so.

And please don´t reply with "I have seen an experienced instructor with excellent monitoring skills do so.." Just think about it for a while and maybe include it in your ideas about how Airbus and aviation could be safer in the future.

Cheers

[DozyWannabe]

Originally Posted by RunSick

When somebody that ACTUALLY FLIES THE PLANE says something like "it is hard to see what the PF is doing on an Airbus" ... consider that this person has been there for real and is telling you his real life experience.

Thanks for the heads-up. However, I have to take some pains to point out that what I'm saying isn't just coming from theoretical book learning, but also from long conversations I've had with pilots who fly the FBW Airbii. Many of them started out worrying about that aspect of the design, but quickly grew to realise it wasn't as much of an issue as they'd feared. Some never had an issue with it. Some still don't entirely feel at home in that flight deck - but acknowledge that it may be down to their own perceptions rather than the flight deck layout itself.

@CB - there's a flipside to the incapacitation scenario - namely that if your opposite number slumps over (or otherwise fouls movement of) the control column, then you have to shift their weight from it. In an upset scenario, that's going to be extra difficult, but in the FBW Airbus, you just push a button and it is no longer an issue.

[joema]

"When somebody that ACTUALLY FLIES THE PLANE says..."it is hard to see what the PF is doing on an Airbus"...consider that this person has been there for real and is telling you his real life experience."

As I mentioned above, Bill Palmer who has nine years experience as an A330 Check Airman discussed this in his recent book. He also flew the AF447 scenario in multiple commercial simulators, although dual control conflict was only one factor in that case.

He explained the issue isn't simply whether the async sidestick design makes it difficult to see what the other pilot is doing. Rather it's what material difference does that make, and in what situation. He said: "While it is difficult to see the other pilot's sidestick position, there is rarely a reason to."

Also, dual control input is enunciated by a voice warning, plus a warning light on the glare shield. In the AF447 case, both pilots were also pressing their "takeover priority" button trying to lock each other out. Each time they did this an additional red warning light notified the locked out pilot his stick was taken over, plus an additional "priority left/right" voice warning. They obviously knew the other pilot was interfering, else they wouldn't be fighting over the controls -- repetitively. In a mechanically linked system it would be a "force fight", or maybe it would degenerate to a fist fight. That would be better in some cases but how representative is that?

On the opposing viewpoint, see this critical history of the AirBus async control design and various steps taken to improve it: Pilots in the Loop? Airbus and the FBW Side Stick « Critical Uncertainties

[CONF iture]

Yes dozy, "might" and "may" are of circumstance to signify that the possibility does exit compare to to the unlinked sidesticks where such possibility simply does not.

[CONF iture]

Originally Posted by joema

In the AF447 case, both pilots were also pressing their "takeover priority" button trying to lock each other out. Each time they did this an additional red warning light notified the locked out pilot his stick was taken over, plus an additional "priority left/right" voice warning. They obviously knew the other pilot was interfering, else they wouldn't be fighting over the controls -- repetitively.

... far from it according to the published data ... What are your sources ?

[gums]

sides

Sides

I gotta tellya. Only "side" I am on is the one that emphasizes safety via airmanship. Of most incidents I have reviewed, most had more airmanship factors than design factors.

Except for my war experience, most fatalities I was close to were due to poor airmanship and not aircraft design.

Only "crew" jet I flew had a radar guy in the back seat and no dual controls. Only "override" he had was the ejection seat. And he didn't know what I was doing with the controls, only what the jet was doing.

I fully appreciate the inputs here from the "engineers" that have credibility from close contact with the pilots and also actual flying experience of their own. Nevertheless, I shall still maintain a position, or "side", that favors the pilot inputs to design of a jet.

I must admit that the roles and missions I flew necessarily flavor my bias, as my experience in the high performance jets is not akin to the commercial jets with a crew of two or more that are jointly responsible for the safe conduct of the mission assigned. Only exception was when I was the pilot-in-command in a family model.

My first 1,000 hours in a family model resembled the 1950's designs, about the time the jet was designed. Pure mechanical controls to the control surfaces and mechanically-connected sticks. The brakes were not "summed" and I had a tire blowout one day when the nugget in the other seat wasn't braking hard enough and my "extra" pressure locked up a tire and it blew! Caught a lotta flak for that one, heh heh.

My second 1,000 hours as an IP was in a single seater. I flew close chase ( figure 30 - 40 feet) and tried to figure what the nugget was doing with the controls. It was easy to see what his jet was doing with zero feel for his inputs. And I would make "suggestions". So my conversion to the Viper was no big deal.

The Viper was designed as a single seater, so not much thought as to connected sticks. When we got the family model, the engineers and pilots decided that we did not need to mechanically connect the sticks.. Further, that design would have been awkward, as the origianl design did not involve a stick that physically moved!!! Those things, and the first 40 or so models, had zero stick movement, including the family models.

I can fully appreciate the value of physical feedback as to what the other "crewmember" is trying to do. But I also question some of the actions of the "other" crewmember in accidents such as AF447 and the recent Asiana one. In both cases, I believe that just seeing what the jet was doing should have been enough to forcefully talk about or even take control. I can get a "feel" for the problems with crew coordination when things go to hell. But I cannot fully appreciate all the problems due to my background.

So my "side" is for super airmanship and to hell with the specific design of the jet, O.K.?

[DozyWannabe]

Originally Posted by CONF iture

Yes dozy, "might" and "may" are of circumstance to signify that the possibility does exit compare to to the unlinked sidesticks where such possibility simply does not.

Through control feedback no, but the instruments and the view out of the window should work just as well. The use of "might" and "may" is also important in another sense, namely that they were unable to prove it one way or another - and based on the historical record it has made far less of a difference than some like to claim. The point the report was making is that taken in isolation, it is unwise to train a pilot on the line in an A320 if that pilot is not yet confident when it comes to approach and landing, and they should have that mastered in the simulator first. The report touches on the possibility of following through with conventional controls, but it does not directly compare the two - probably because even in a conventionally laid out flight deck, there should be no "follow through" necessary when training on the line. In normal operations, only one pilot should have their hands on the PFC in a control sense if going by the book.

As a general aside, I've just had a very entertaining read of Captain Richard de Crespigny's book on QF32. I won't link to it lest I incur the wrath of the moderators, but one of the aspects I found most interesting was this. Capt. de Crespigny is an ex-RAAF pilot who trained in Macchi fast jets, was posted to fly STOL Caribous, thence to Iroquois helicopters and back to Macchis as a training pilot, only missing out on F111s due to his age on transfer. He started his civil career flying 747 Classics, then the 747-400, got his command on the A330 and finally the A380.

Now with a CV like that I don't think it's possible to say anything other than he's a very experienced "pilot's pilot", and if such pilots are usually averse to the sidestick concept, he'd be at or near the head of the queue - especially given what happened over Singapore.

But he isn't. He admits to being a technophile (in fact he ran a software company with his wife in the late '80s and early '90s), but what he seems to be more than anything is a born nuts-and-bolts engineer (from his youth, putting old motorcycle engines back together). Rather than seeing the concept as antagonistic, he seems to have gone above and beyond in trying to understand the reasons behind it from the beginning - not just *how* it works, but *why*. He makes a point of stating that based on his own research the Airbus FBW concept was designed to *help* pilots, not hinder them, and he has nothing but positive things to say about his time on the A330 and A380.

The reason I'm summarising what I've just read is that it just goes to illustrate the dangers of generalisation. Ultimately your aircraft is a tool, and no matter what control setup it has, you'll get the best out of it by taking the time to understand it - and in doing so start (as best you can) with no preconceptions. By which I mean if you go into training or conversion to an Airbus FBW type with the belief that the FBW systems are there to hold you back, ignoring the fact that they're also there to assist you - then you're not going to get the best out of the aircraft you're flying.

EDIT:

Going back to the OP-

Originally Posted by vinayak

I understand that airbus is the only successful commercial jetplane maker to use side sticks.

True enough, but as alluded to earlier they account for around 50% of the market at this point, because there are only two major civil airliner manufacturers in the West.

What needs to be understood is that even if you restrict your field of comparison to the US from the '60s to the early '80s, you used to have three airliner manufacturers (Boeing, McDonnell-Douglas and Lockheed), and even with all their products of the time having "conventional" control layouts, they all worked slightly differently, and a technique that worked in one type might have disastrous consequences in another.