There is nothing wrong with Airbus or FBW technology, it does seem to me the interface between this technology is easier to understand and work with on a Boeing than an Airbus. How can anybody forget the early accidents on the A320, the Bangalore one, for example, where the crew were in 'open descent' with 'zero altitude' selected in the window. With an Airport elevation of 1800' they flew a perfectly serviceable aircraft into the ground, simply because they did not understand the mode they were in. I don't hate Airbuses I prefer Boeings.

Enderby-Browne
 

I think it's you who is being a little naïve.

What is the difference between "for Airbus'/Boeing's sake" and for safety's sake?

How long do you think a company in this business would last if it got a reputation for doing less than maximum to ensure the safety of its planes? Product liability lawyers would descend on them like locusts and devour everything.

The company could spend 30 years building a business and reputation only to lose it, with all the customers, overnight. Bankrupt. No chief executive could risk it.

freightmaster
 

You should get more information before you write something that's so patently wrong : The roll rate of a 737 is nowhere near what can be achieved with an A320.
As for avoidance, have a look into the BEA reports on a collision that was avoided near Montpellier between an A320 and a glider. The conditions were : The 320 under autopilot, descending toward the MPL pattern and suddenly a glider fills the windscreen ; the captain just punched the side-stick to the right to full deflection...roll rate achieved over 60°/s...the tip of the glider's fin nicked the outer underside of the A320 left wing and the glider pilot didn't even realise that he was millimeters from certain death.
Now put another type of airliner in the same situation, think of the effort needed to get out of A/P and the inertia of control cables, rods (you name it)...That exercise has been simulated and the result is exactly the opposite of your assertion.
The beauty of that set-up on the 'Bus is that the pilot can have a totally care-free handling of his aircraft within the limits of maximum performance, in the case above 67° of bank, without the hindrance of "increased yoke effort" some advocate as being the best solution.
Having flown both types, I certainly know where my preference is.

B737 roll rates?
 

Hmmmm.... er,... a roll rate in excess of 180 degrees a second probably would beat the A320, and we have recorded that off a B737 before today. Now, the aircraft was aerodynamically stalled and with a substantial yaw rate, but... there you go. :}

Then again, the A320 has achieved some wild roll rates when the flight control laws got messed up a bit too, with the gain of the spoilers being incorrect for the TE flap configuration, the dreaded OEB 117 badness. Now it only got about 100 deg/sec on that, but still quite surprising.:)

:Ejust to put oil on the fire, the A320/330 have pretty nice controls, compared to the B737, most planes do. Heck even the B777 while possibly BAC's nicest equipment to date is not as nice on the control laws (in normal law) as the A330. System logic/crew interface is something altogether different.... ;). whatever floats your boat.

Are you flying a Mirage ... Lemurian ?

That being said, it does not mean I share the view expressed by fr8tmastr in his last comment.

Since geese fly in formation at same exact altitude, to slipstream the one ahead, a sharp bank upon seeing a gaggle ahead would double the chance of one engine eating some, while reducing the chance of a multiple engine strike to near zero. Seems like a good gamble, if the FAs don't get upset.

GB

Hello,

Dunno wich Mirage fly Lemurian .. but for the Mirage 2000 .. 60°/S roll rate is peanuts :)

Regards. http://smilies.sofrayt.com/%5E/a/bye.gif

No doubt ... but in our airliner's world 270 is not that common and 60 must be 4 times what Lemurian's plane would deliver ...
It does not really help a demonstration when numbers are over exaggerated.
I have not much respect left for the BEA but not sure they would write such thing ...

Please note that the value of 60°/s is achievable on direct law. On the incident I referred to,the rate was around 20 to 25°/S instantaneous. On a normal flight, the average is 15°/s.
Please don't tell me it was normal OPS :)

Since certain recent Airbus FBW 'events' appear to have been caused by shoddy maintenance organisations not following correct LRU installation requirements, would the ability to provide 'Direct Law on Demand' actually work under such circumstances?

Perhaps there needs to be some form of 'idiot proofing' to make it physically impossible for maintenance people to replace FBW LRUs incorrectly?

Easy to figure out in a few words : keep it simple !

Not looking for an equipment which does miracles but just something that behaves with consistency, something easy to read, nothing more.

Said many times before : Put on the market a more humble version of the 320 and you’ll have a fantastic equipment.

And if FBW Airbus was that ultimate tool that Bernard Ziegler always claimed it was, it would show immensely in the accident / incident database …

What are you referring too?

about Are you flying a Mirage ... Lemurian ?
The roll rate of the A320 in normal law is 15 degrees per second
That is with sidestick fully to the side. And only below 250 knots because as speed builds up above Va the full authority is progressively reduced. Luckily the A320 which met a glider was at 250 knots and flight level 80 or thereabout.
The captain used full rudder to increase roll rate and that probably helped a lot, but the plane never could exceed 15 degrees of bank per second. Which is quite fair for an airliner.
The problem which could happen (and did not in that case) would be the pilot flying deciding to bank left while the Captain taking over in a reflex action banks right…not much time for a briefing in those circumstances…maybe it is easier when you see those big hairy paws jumping on the yoke, instead of those unseen subtle movements behind the scenes…

".....the pilot flying deciding to bank left while the Captain taking over in a reflex action banks right....."

Interesting question. Who wins in a conflict like that? The strongest, or does the Captain's sidestick have priority?

Narval stated:

"The problem which could happen (and did not in that case) would be the pilot flying deciding to bank left while the Captain taking over in a reflex action banks right…not much time for a briefing in those circumstances…maybe it is easier when you see those big hairy paws jumping on the yoke, instead of those unseen subtle movements behind the scenes…"

I think your logic is self defeating. In an airbus the standard procedure for taking control, and ensuring that you have control, is to press the red button and keep it pressed (whilst stating "I have control"). You then have absolute control and you decide which way you are going to turn. In a Boeing I would suggest that control would be dictated by whoever had the biggest biceps attached to those hairy paws! Could be a costly battle if they didn't agree which direction they were going don't you think?!

It is dis-appointing that threads such as this one have become another forum for the constant airbus v boeing slagging matches. This thread is about a serious accident where people have died. Instead of debating this in a factual way it becomes a forum for anonymous posters to display their prejudice. Could we not acknowledge that both Boeing and Airbus build generally excellent aircraft. Whilst they may have a different design philosophy they each have lots of strengths and fortunately very few weaknesses.

Some of the level of debate on this thread further erodes the credibility of Pprune as a forum for professional pilots. In order that each posting gains the appropriate credibility perhaps each poster could add their experience on type(s) before commenting. It might help separate the wheat from the chaff.

night_flight99

10,000 hours
(Current on 757 with 7,500 hours on 320 series).

DC-ATE
 

When someone posts "does the Captain's sidestick have priority?", I wonder where they have been these past 30 years.

You now have the answer.

The Airbus FBW family has sold 5 times as many as the your darling "fly-by-cable" DC-8, and it's now the industry standard, along with the latest Boeings. All those 777 (soon to be 787) pilots will agree. Wake up.
.

Dysag -
"When someone posts "does the Captain's sidestick have priority?", I wonder where they have been these past 30 years.
You now have the answer.
The Airbus FBW family has sold 5 times as many as the your darling "fly-by-cable" DC-8, and it's now the industry standard, along with the latest Boeings. All those 777 (soon to be 787) pilots will agree. Wake up."


It just so happens I've been retired for nearly twenty years, and know absolutely nothing about the Airbus fleet. So, please don't tell me to "wake up". I thought my question had some merrit for someone who does not know.

Sorry if I offended you.

Very sorry DC-ATE, I just hope I make it to 20 years in retirement. We need the experience of guys like you.

My beef is more with youngsters who think the 737 is modern. When we were young we reached for the stars, even if we fell short. Now the kids are very happy with the old junk.

Seems I owe you a beer, or three. By the way, I loved the DC-8, second only to the Convair 880/990.

But, seriously, FBW is now the standard, love it or hate it. It's the old fly-by-cable which is exotic.
.

Dysag -
"Very sorry DC-ATE, I just hope I make it to 20 years in retirement. We need the experience of guys like you.
Seems I owe you a beer, or three. By the way, I loved the DC-8, second only to the Convair 880/990.
But, seriously, FBW is now the standard, love it or hate it. It's the old fly-by-cable which is exotic."

Thanks for the offer. Wish I drank beer...I'd collect!
Don't know 'bout that..."...loved the DC-8, second only to the Convair 880/990." The 990 was certainly the fastest over the fence! But, to each his own. I got my foot stuck between the armrest and the wall on an 880 on the way down as it depressurized. Fuselage, was kinda skinny!

I'd still like to know, being as how the side sticks are not 'connected', what happens when one pushes one way and the other guy pushes the other.

Thanks.

DC ATE

If one pushes left and the other pushes right the result is zero.

I also believe that if they both push half left the result is the equivalent of one pilot pushing full left. The system sums the input of both controllers.

There is a sidestick priority button where by one pilot can override the other. It works on the basis that the last person to press the button gets priority.

SW

DC-ATE
 

The two sidestick inputs are normally summed by the computer, unless one side takes control by pressing the red button.

I just have a problem with youngsters who do think their old junk is great because they don't know any better.

Anyway, all modern planes are FBW, and there's no going back.

Agreed.

Before you know it they will all be FWP as well. That's "Flight without Pilot" for those who are wondering. FBW is just another step towards this, and yes there is no going back.

That's the procedure as it is written in the manuals and it looks good on paper, that’s also how it is teach in the simulator and that works just fine, but in real life, when the unexpected comes around, incident reports show that more often that we may think, the instinctive reflex is to simply grab the stick and move it resulting in a dual input … Only after a few seconds the red button is usually pressed.

Regarding the seriousness of the thread, it would be easier if guys pretending demonstrating something based on a specific report could restrain from publishing numbers nowhere to be seen in that very report …
Thanks for your attention Lemurian.

Back on thread?
 

Okay I haven't seen anything new coming out of official sources recently. Has anybody else seen anything new?

The debate on ABS performance, ABS design theorum, ABS ops, ABS software heirarchy, ABS v BOE, etc., is great but what's going on with the accident investigation?

DC-ATE;

This is likely in the thread earlier on but I'm just lighting up the computer after a few days away.

As Dysag says, the 320 sidestick inputs are summed but the important point is, they are summed algebraically.

Double sidestick input is a serious no-no in 320-type aircraft. It continues to occur however, at least as shown in flight data analysis. Usually it's a training-line indoc situation. That said, CONF iture, you are absolutely right in what really happens.

What some transitioning to fbw (Airbus style) initially may not appreciate because it may not be emphasizd in training is, the stick does not control ailerons/elevators; - it "requests" a roll-rate or a g-force. You may still recall a CWS mode - Control Wheel Steering - where, when engaged the airplane "stayed" in the last attitude set by the controls before engaging. That is essentially what fbw/sidestick control is. "No input, no change".

The autoflight-autothrust-flight director-flight management guidance computer systems are deeply intertwined with one another, all talking to each other. The non-moving thrust levers is a non-issue in such a system as the various flight modes look after thrust when the levers are set in their normal flying position, called the "CLB" or climb position. In this mode depending upon climb, cruise or descent, the engines will respond to airspeed, rate of climb or cruise speed commands from the FMGC, (Flight Management Guidance Computer).

For example, in a climb, with autothrust engaged but the a/c being manually flown, power is "on the elevator". That means power is adjusted by FADEC to match the thrust required to maintain an airspeed which is set by the cost index. Usually that's the old max continuous, about 92% N1. If one pulls back, the airspeed will bleed off only because 92% isn't sufficient thrust to keep both the climb and the speed, but power is still governed "by the elevator" in manual flight. To understand this better, take the opposite case where the rate of climb is reduced by gently pushing forward on the stick - the rate of climb will decrease, but without touching the thrust levers, the power will come back to match the speed being commanded by the FMGC.

In descent, the usual auto-flight modes are either "IDLE, OPEN DESCENT" or VNAV. VNAV is a calculated path that is managed by both the autothrust and autopilot - the speed is permitted to vary to take advantage of energy before bringing up the power from Idle.

"OPEN DESCENT" means the engine thrust is commanded to idle, (about 35% N1). The autothrust will not bring the power up until the selected altitude is captured. In this case, it is airspeed, not power, that is "on the elevators". To better understand this, if the sidestick is pulled back slightly, the airspeed will reduce and continue to do so until a minimum speed calculated by the flight augmentation computers using weight, angle-of-attack and CAS is reached, at which point the autothrust will revert from "IDLE" to "SPEED" and the "OPEN DESCENT" mode to "V/S", (to prevent a huge power increase to "chase" the originally targeted speed).

For this reason, in manual flight the flight directors must either be followed or turned off as they are indicating the "thinking" behind the autothrust system. If turned off, the autothrust reverts to the "SPEED" mode to again protect the airplane.

The other vertical modes are either variations on this theme or protections which guard against speed gain/loss or v/s excursions higher than certain values.

The sidestick is a very powerful little handle and is best flown gently, usually with the hand near the base to avoid large inputs.

As an aside, while the US Airways flight will have had "Alpha-prot", (stall protection), the fbw system would not have protected this airplane from stalling in this case because the engines were incapable of delivering TOGA (Takeoff/Go Around) power. In "Alpha-prot", the airplane is not pitched down to reduce the AoA - the only airplane response is to increase power, so Captain Sullenberger had to fly the speed indicated on the PFD, (Primary Flight Display) just above the alpha-max stall speed and by the initial indications, this is just what he did. See the graphic below - likely he would have flown between Vls and Alpha Prot but we'll know more after the reports.

http://img131.imageshack.us/img131/3...normlawig3.png

Thank you Sky Wave, Dysag and PJ2 for the info on the side sticks. It still scares me!

Dysag - "I just have a problem with youngsters who do think their old junk is great because they don't know any better."

Well, I'm working on becoming an octogenarian. Not sure that qualifies me as a "youngster" or not. I feel like one anyway! Probably act like one at times as well. I just have a problem with some of this newer equipment that is slowly taking the pilot out of the loop. But, PLEASE don't call "my" DC-8 "old junk". Not while I'm still around anyway. Those and the Connies (along with a couple of others) took good care of me for thirty years.

Understand! But it works beautifully, even elegantly.

The '8 was my "first love" in the late 50's/early 60's and I had the good fortune and pleasure of a few thousand hours in it before transitioning to the 727, then the 1011, then the 76'.

Congratulations on the octagenarian goal - I would not have guessed that from your writing - like Dysag, I hope to make it as well.

Cheers, sir.

PJ2 -
"Congratulations on the octagenarian goal - I would not have guessed that from your writing..."

Well, thank you. I'm not there yet; got a few to go, but hopefully, I'll make it. Even though airplanes might've given me the grey hairs I still have, it might have also given me some extra time.

Hope you all enjoy the "new age" of aviation. Good luck!

Clandestino
 

I'm very sorry to disagree with you Clandestino, but:
I was "proposing" a "solution" that would put the pilot always in control. On the T7, pilots are always in control of the aircraft, because the system allows them to override protections...
One has to choose: either one has "your" type of protections and face the risk of being a "hostage" of an aircraft that flies the way it was designed/programmed to fly or, one has the chance to really have control of it flying a bird that allows those protections to be overridden.
I know what I would choose, if I had the chance to...:sad:

PJ2Sorry, but there is a rat here :
On the 320, "Alpha prot" is just an AoA protection : between "prot" and "max", the side stick commands alpha directly. However, the angle of attack will not exceed alpha max even if the pilot pulls the stick all the way back. If the pilot releases the stick, the airplane will return to alpha prot and stay there. That,regardless of the thrust you have available.
On the other hand, Alpha floor is the protection which is triggered with a high AoA and the airplane would go into a TOGA mode.
With the obvious lack of thrust, the system stays in AoA protection mode.
That's in all probability what happened to US 1549 as one of the NTSB press conferences mentioned that at their point of ditching, they were two knots below "prot" speed and just five knots above "alpha max" speed for their configuration.

Lemurian;

Thank you - I should have remembered that and you are absolutely correct.

Cheers.

PJ2 - sorry, but I do not recognise some of the A320 I fly from your post :ugh:

:ooh: In V/S maybe, but normal (OP) CLB modes it is juts like a Boeing or C152 - Climb Power and Pitch controls IAS...

Ditto - V/S only (and just as a Boeing).

Again, and as corrected above by Lemurian, not correct... IMHO ;)

Alpha Max / Alpha Prot are not speeds - they are Alpha values. VLS is a "speed"... and hence why in a turn or level off, the 2 Alpha values will increase, and potentially mask VLS.

I flew B757/767 prior A320 (and after A340)... The AP modes, once you "translate them" are fairly similar... the FBW protections only come into play when you exceed what you would fly in normal flight. Alpha Floor / Max only come into play with serious abuse, and after a Stick Shaker would have gone off on a Boeing. And in the 1549 case, I doubt any FBW "protections" were invoked, though as above, the Alpha Prot area seems to have been entered... if it was entered gently, Alpha Floor (TOGA) is only asked for "somewhere" in the Alhpa Prot area, and there are a couple of other reasons why it might not have been triggered here (<100R / Engine Out + Slats/Flaps). And even if it was triggered, seems it was not going to get anything :{

NoD

It appears to me that you A-320 drivers can't agree on just what goes on with your FBW systems during various phases of flight.:bored:

Quote Night Flight99: I think your logic is self defeating. In an airbus the standard procedure for taking control, and ensuring that you have control, is to press the red button and keep it pressed (whilst stating "I have control").
Thank you for your answer. I did not go to the end of my reasoning (such as it is) wishing to be short…my mistake. I did not criticize the A320 which I have flown a few years, nor the FBW system, but the side stick in that case…as opposed to a yoke as in the 777 for example. You are right in your description of the priority system but I hope you do not imagine that with a glider filling the windscreen, somebody will say I have control (the captain did not) and push the priority button etc…it is all reflex action. In that case the captain acted on the sidestick laterally and the pilot in the pitch axis (down). I just tried to say that the copilot seing the hands of the captain jumping on the controls will stop doing anything (that’s the best decision in such cases).
As for the original subject of the thread, I shall wait with you for more information, feeling very sad for the crew, and having a thought too for the mechanics who work very well in Perpignan, as elsewhere. I flew many test flights there after heavy overhauls, plus painting jobs, and I can tell you that static ports, pitot tubes, angle of attack vanes were checked on the ground by the mechanics then by the crew before the flight.

"I can tell you that static ports, pitot tubes, angle of attack vanes were checked on the ground by the mechanics then by the crew before the flight."

Makes one wonder, then, if the letter from Airbus isn't a diversion..

GB

Keyword being "appears".

Not everyone discussing here is an Airbus driver, nor is discussion limited to bus drivers only.

Not everyone claiming to be Airbus driver actually is one.

Rules of the game are quite simple: anyone can have his say but the FCOM trumps all.

Is "FCOM" your acronym for Flight Computer?

Are you an Airbus driver?

FCOM = Flight Crew Operating Manual.

Flight Crew Operating Manual

But there again Beagle you never flew the Airbus, did you?