jayeshrulz
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Red Button In Airbus Sidesticks?

Tue Feb 16, 2010 4:40 pm

Hi guys


From a wrong time i have been wondering,what does the red button in the Airbus sidestick do?Its present in both the sidesticks.
Is it present in all next gen Airbus?

thanks!
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Airbus_A340
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RE: Red Button In Airbus Sidesticks?

Tue Feb 16, 2010 4:54 pm

There are mainly two functions for the red button.
If autopilot is engaged, it disengages it, secondly it also has a priority function.

The pilot can deactivate the other sidestick by continuously pressing the red (takeover) pushbutton, "Priority Left/Right" is announced by the computers. If the button is held down for 30 seconds or more, it deactivates the other sidestick completely. Control can be regained by pressing the takeover button on the deactivated sidestick to regain control.
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Mastropiero
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RE: Red Button In Airbus Sidesticks?

Tue Feb 16, 2010 5:45 pm

Quoting Airbus_A340 (Reply 1):
"Priority Left/Right" is announced by the computers. If the button is held down for 30 seconds or more, it deactivates the other sidestick completely.

For how long do you have to press the red button for a normal takeover, without deactivating the other sidestick?
 
JAGflyer
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RE: Red Button In Airbus Sidesticks?

Tue Feb 16, 2010 6:14 pm

Quoting Airbus_A340 (Reply 1):
Control can be regained by pressing the takeover button on the deactivated sidestick to regain control.

Would this not a bad thing in the event of a pilot attempting a suicide/kamakaze mission? I would think the other sidestick would be activated by the pilot who originally deactivated it.
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2H4
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RE: Red Button In Airbus Sidesticks?

Tue Feb 16, 2010 6:58 pm

Quoting JAGflyer (Reply 3):
Would this not a bad thing in the event of a pilot attempting a suicide/kamakaze mission?

I suspect if a pilot were faced with a suicidal captain/FO, he or she would ensure that the crazy person would not have an opportunity to reactivate the sidestick.

If it were me, I'd use the blunt end of the crash axe to properly 'deactivate' the offender for the remainder of the flight.
Intentionally Left Blank
 
jayeshrulz
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RE: Red Button In Airbus Sidesticks?

Tue Feb 16, 2010 7:02 pm

Quoting JAGflyer (Reply 3):
Would this not a bad thing in the event of a pilot attempting a suicide/kamakaze mission? I would think the other sidestick would be activated by the pilot who originally deactivated it.

Exactly, plus 30 secs is very long for activation.
If something happens to the co pilot and he falls down to the yoke, then it can be a risk.

Can the sidestick be pulled back?
Like if the co-pilot has lost his consciousness and leans on the stick, 30 secs can put the plane in dive.
SO how quick can the captain takeover?
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vandenheuvel
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RE: Red Button In Airbus Sidesticks?

Tue Feb 16, 2010 7:44 pm

Quoting jayeshrulz (Reply 5):
SO how quick can the captain takeover?

From what Airbus_A340 said I assume you already have control during this 'take-over' period.

I recall reading something about the FBW system using an average of both inputs. That is if non of the pilots is having priority. Is this correct?

[Edited 2010-02-16 11:46:57]
 
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Jetlagged
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RE: Red Button In Airbus Sidesticks?

Tue Feb 16, 2010 7:54 pm

Quoting vandenheuvel (Reply 6):
I recall reading something about the FBW system using an average from both inputs. That is if non of the pilots is having priority. Is this correct?

The sidestick inputs are summed algebraically and limited to the maximum value for full deflection of one sidestick.
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EMBQA
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RE: Red Button In Airbus Sidesticks?

Tue Feb 16, 2010 8:07 pm

Every aircraft with an autopilot has the same button... not just Airbus.
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vandenheuvel
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RE: Red Button In Airbus Sidesticks?

Tue Feb 16, 2010 8:19 pm

Quoting jetlagged (Reply 7):
The sidestick inputs are summed algebraically and limited to the maximum value for full deflection of one sidestick.

So this means that if the pilots are both pushing it in the exact opposite direction, there would be a neutral output?

What if both pilots give the same input? Will the FBW system take the average or the accumulation?

I know this sounds strange. But I can't find another reason why the total output should be limited to the maximum value for one sidestick.

[Edited 2010-02-16 12:25:33]
 
mandala499
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RE: Red Button In Airbus Sidesticks?

Tue Feb 16, 2010 10:41 pm

Quoting Airbus_A340 (Reply 1):
If the button is held down for 30 seconds or more, it deactivates the other sidestick completely.

Recommended 40 secs though...

Quoting Mastropiero (Reply 2):
For how long do you have to press the red button for a normal takeover, without deactivating the other sidestick?

Press it less than 30 secs and the other guy doesn't press it during that time takes control on your stick during that the time you press it. Once you release that, both sticks are working.
Press it more than 30 secs (recommended 40secs) if you want to deactivate the other stick for longer periods... saves you from pressing it all the time.

Quoting JAGflyer (Reply 3):
Would this not a bad thing in the event of a pilot attempting a suicide/kamakaze mission? I would think the other sidestick would be activated by the pilot who originally deactivated it.

When LATCHED, anyone can retake priority by pressing the button... and anyone can release priority by pressing the button. You don't like the other guy taking priority? Well press the button... "the last person pressing the priority button has priority", so the other guy latching it can have it unlatched by you pressing yours. If both try to latch it, the last person pressing wins. So, the other guy tries to kill you by pressing the priority button? you press yours... he releases and presses? You do the same... now, if both rapidly presses and releases, the stick commands just switches from one to the other and back again and again... so any full deflection moves will effectively be reduced/muted or even eliminated (given repeat pressing and directly opposite stick commands).

Plus, what kind of suicide/kamikaze are you talking about? A spiral dive out of control? The flight envelope protection prevents that (although it doesn't prevent you from smashing into something)...
Want to break the plane in flight by pulling some Gs, it won't let you...
Want to break the plane by doing a loop, it won't let you...
Want to break the plane by rolling over, it won't let you...
Want to make it fall out of the sky by stalling it, it won't let you...
Want to dive into vertical... it won't let you...
Want to break the plane by overspeeding it, it won't let you...

So, that makes suicide less simple... However, press the right buttons on the overheads, the protection can reduce or be eliminated... but it won't be quick and stealthy suicide move I tell you... But, one could do perfectly coordinated barrel rolls if one wants to... but WHY???

Quoting 2H4 (Reply 4):
If it were me, I'd use the blunt end of the crash axe to properly 'deactivate' the offender for the remainder of the flight.

That is a universal procedure... be it on an Airbus, Boeing, Bombardier, Embraer, Antonovs, Ilyushins, Tupolevs, Sukhois, Yakolevs or whatever else...   

Quoting jayeshrulz (Reply 5):
Exactly, plus 30 secs is very long for activation.
If something happens to the co pilot and he falls down to the yoke, then it can be a risk.

Can the sidestick be pulled back?
Like if the co-pilot has lost his consciousness and leans on the stick, 30 secs can put the plane in dive.
SO how quick can the captain takeover?

That's why you need to latch the priority... on a latched priority situation, the other stick can do whatever it wants without interfering with the aircraft, except, if the red button is (accidentally pressed) on the deactivated stick.
See the less than and more than 30 secs effect above.

Quoting EMBQA (Reply 8):
Every aircraft with an autopilot has the same button... not just Airbus.

For the autopilot disconnect function, yes.

Quoting vandenheuvel (Reply 9):
So this means that if the pilots are both pushing it in the exact opposite direction, there would be a neutral output?

Correct.

Quoting vandenheuvel (Reply 9):
What if both pilots give the same input? Will the FBW system take the average or the accumulation?

Under a no priority situation, it will accumulate the commands, with a limit on equivalent of full deflection on a single stick... as Jetlagged said... Plus, aural warning "Dual Input" will sound whenever both sticks are positioned more than 2 degs off center.

Quoting vandenheuvel (Reply 9):
But I can't find another reason why the total output should be limited to the maximum value for one sidestick.

Why not? Does 2 persons rolling a yoke on a Boeing full left make the plane roll to the left faster than if 1 puts it on full left? Nope. 1 Yoke can take full control of the aircraft, and so does 1 sidestick... why should it be different? (unless you want to reinvent the wheel).

The sidestick fully deflected on the roll axis gives 15degs a second roll rate already. If you want more, consider flying fighters and aerobatic aircraft instead. Besides, U're limited to 66deg bank angle on full deflection held.

Fully push one stick or both sticks, will limit you one stick's limit of -1G trajectory. Pull it fully on one or both, it'll be 2.5G trajectory... and U're limited to -15deg nose down to 33deg nose up anyways as well as the G-trajectory command limits on the stick. If you want more, and gets more, you'd get pax screaming (if not already), puking (if not already) and/or the plane may have started falling apart (>2.5G).

Mandala499
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tdscanuck
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RE: Red Button In Airbus Sidesticks?

Wed Feb 17, 2010 1:15 am

Quoting vandenheuvel (Reply 9):
I know this sounds strange. But I can't find another reason why the total output should be limited to the maximum value for one sidestick.

Adding one thing to Mandala499's excellent explanation above...even though there are two sidesticks, there's only one flight control system and, at the end of the day, only one set of commands can go to the control surfaces. If you could handle two full deflections then, when you're in the normal situation of one pilot, you'd only ever be using half the control authority, wasting a bunch of weight and control power.

Tom.
 
tb727
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RE: Red Button In Airbus Sidesticks?

Wed Feb 17, 2010 3:36 am

I thought that was the "Easy" button. Just push it, sit back, enjoy the flight!
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mandala499
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RE: Red Button In Airbus Sidesticks?

Wed Feb 17, 2010 3:45 am

Quoting tb727 (Reply 12):
I thought that was the "Easy" button. Just push it, sit back, enjoy the flight!

The easy buttons exist in both Airbus and Boeing... They're called the "Autopilot" and "A/T" buttons...   
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
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EGTESkyGod
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RE: Red Button In Airbus Sidesticks?

Wed Feb 17, 2010 4:02 am

Quoting jayeshrulz (Thread starter):
what does the red button in the Airbus sidestick do?

Release the missiles...  
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vandenheuvel
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RE: Red Button In Airbus Sidesticks?

Wed Feb 17, 2010 8:32 am

Quoting mandala499 (Reply 10):
Why not?

Mandala499, thanks for your great explanation.

I fully understand why this limit is applied. The only thing I was wonderring is why this would be done when the average is taken. As the average can never be more than the maximum input of one single side-stick. Since this is not the case, it makes a lot of sense.
 
jayeshrulz
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RE: Red Button In Airbus Sidesticks?

Wed Feb 17, 2010 9:49 am

Does Boeing have this fantastic technology?

Quoting mandala499 (Reply 10):
Want to break the plane in flight by pulling some Gs, it won't let you...
Want to break the plane by doing a loop, it won't let you...
Want to break the plane by rolling over, it won't let you...
Want to make it fall out of the sky by stalling it, it won't let you...
Want to dive into vertical... it won't let you...
Want to break the plane by overspeeding it, it won't let you...
Keep flying, because the sky is no limit!
 
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Starlionblue
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RE: Red Button In Airbus Sidesticks?

Wed Feb 17, 2010 11:22 am

Quoting jayeshrulz (Reply 16):
Does Boeing have this fantastic technology?

If you're referring to envelope protection, yes and no. A 777 (and 787) will let you exceed the limits, but it will make the required control forces very high.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
jayeshrulz
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RE: Red Button In Airbus Sidesticks?

Wed Feb 17, 2010 11:43 am

Quoting Starlionblue (Reply 17):
If you're referring to envelope protection, yes and no. A 777 (and 787) will let you exceed the limits, but it will make the required control forces very high.

Explain in a simpler way please?
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Starlionblue
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RE: Red Button In Airbus Sidesticks?

Wed Feb 17, 2010 2:14 pm

I'll try. However I caution you that I am just an interested amateur.

On an Airbus with FBW (318-380), the flight control system WILL NOT allow the pilots to exceed envelope protection limits. On a Boeing with FBW (777-787) the flight control system WILL allow the pilots to exceed envelope protection limits. However the forces required (how much the pilots need to pull at the controls) become very high as the limits are reached and exceeded.

In other words, Airbus will prohibit while Boeing will "strongly hint". Airbus thinks the pilots should never have a reason to exceed limits. Boeing thinks the pilots may have a reason.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
mandala499
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RE: Red Button In Airbus Sidesticks?

Wed Feb 17, 2010 5:24 pm

Quoting Starlionblue (Reply 19):
'll try. However I caution you that I am just an interested amateur.

As long as it's correct in terms of understanding, who cares if you're an amateur, professional, or was actually clueless? Correct is correct, wrong is wrong... but wrong has many shades of grey as to why it is wrong... whilst correct has less shades...    (and U're correct! Amateur? U need to convince me more that U're "just an amateur"!  &nbsp 

Anyways, let me elaborate...

Quoting jayeshrulz (Reply 16):
Does Boeing have this fantastic technology?

Yes, it does. There is a difference in how Boeing and Airbus writes their manuals, on Boeing FBW, it does not specify what the envelope protection limits are, because you can always use brute force to override it... On the Airbus, because you cannot override the protection (unless you press several switches, ie: less straight forward), it does specify what the protections are and where it kicks in.

On the Boeing...
Flight Envelope Protection
The flight envelope protection system reduces the possibility of inadvertently exceeding the airplane's flight envelope. The flight envelope protection system provides crew awareness of envelope margins through tactile, aural, and visual cues. The protection functions do not reduce pilot control authority. The protection functions are described later in this section and include:
• stall protection
• overspeed protection
• roll envelope bank angle protection.


So, it gives protection but "does not reduce pilot authority"... how does it work?
Let's have a look at Stall Protection.
When approaching a stall, a few things happen, the trim goes to where it thinks it is needed but not beyond the point where it would cause the stall... When you near the stall, the feedback mechanism makes it harder and harder for you to maintain pull up on the yoke... (Autothrottles would kick in regardless if engaged, not engaged, or not even armed), to maintain anything from idle to the max available (given the environmental limits) to keep you away from the stall... Whether maintaining nose up command on the yoke results in you entering the stall or staying just outside it, is not specified.

What it does specify is only that you must maintain full nose up on the yoke to go below the minimum manouvering speed (which is just before the stall conditions). I assume on the Airbus equivalent is that in maintains you on A-max, and not A-CLMAX (1g stall). My understanding of this is therefore, NO, IT WON'T LET YOU STALL.

Let's look at high speed protection...
The 777, like the 320, trim is frozen. On the 777 it specifies that you must maintain nosedown on the yoke to maintain airspeed above the maximum operating speed. This logic also applies to the Airbus, which speficies nose down stick authority is reduced once you go above the max operating speed, and FBW will progressively introduce a nose up command to aid recovery... so when you go a certain speed above the maximum operating speed, your stick nosedown command will be ignored. I understand this as identical in understanding, but the Airbus specify 2 green bars on the speed tape at 6 knots above max operating speed as a sign the overspeed protection is active. Both aircraft will allow you to go above the maximum operating speed and will fight you to go below it, but I do not think any of the two will allow you to go beyond the "never exceed speed", which is where fluttering can start and you start having structural failures.

Let's move to the Roll Protection... which is where the 2 differ!
On the 777, if you roll the aircraft beyond 35deg bank, the FBW will command a roll back to below 30deg if you leave the yoke alone (and the yoke will show a command to move back to 30deg), and maintains 30deg afterwards if it's untouched. You can however, continue to apply force to the yoke to go beyond 35degs, but you have to overcome the force applied by the FBW on the yoke to return to 30deg... max yoke roll input = max control surface deflection. Which means, beyond 35degs, your input to the yoke will be a direct law input (and you fight the force put by the FBW).

The Airbus is the same in this aspect of returning to a 33deg bank angle (not 30 though) if you leave the stick alone from a steeper bank. BUT, you can maintain full roll deflection on the stick, and the airplane will roll to 67degs... and no more.

So, the 777 will allow you to roll over if you insist, the 320 doesn't. So, in this is where it's different... other differences is that the 777 does not specify any G-load protection (apart from "beyond normal envelope", which MIGHT include G-load protection) or any pitch limits...

So for the 777, my understanding is as follows (some/many might disagree):
Want to break the plane in flight by pulling some Gs, it might not let you...
Want to break the plane by doing a loop, it might not let you...
Want to break the plane by rolling over, you gotta work hard for it!!!
Want to make it fall out of the sky by stalling it, it won't let you...
Want to dive into vertical... you gotta work hard for it!!!
Want to break the plane by overspeeding it, you gotta work hard for it!!!

Quoting Starlionblue (Reply 19):
the flight control system WILL NOT allow the pilots to exceed envelope protection limits.

After disecting the sentences above, on the overspeed function, it will allow you to exceed, but only temporarily... but it will not allow you to exceed the aircraft's capability. The reason I've worded it like that is that it does allow you to momentarily exceed the Maximum Operating Speed (Vmo/Mmo) during the recovery to go back below it... but this is only for the pedantic to dwell on!

Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
jayeshrulz
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RE: Red Button In Airbus Sidesticks?

Thu Feb 18, 2010 9:20 am

thanks mandala, you are awesome.

Are you a real life pilot?
Keep flying, because the sky is no limit!
 
mandala499
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RE: Red Button In Airbus Sidesticks?

Thu Feb 18, 2010 2:26 pm

Quoting mandala499 (Reply 20):
(Autothrottles would kick in regardless if engaged, not engaged, or not even armed)

I must correct myself on the above quoted. On the 777 (and 787 aswell), the A/T will not kick in to assist in the stall protection if it is not armed.

Quoting jayeshrulz (Reply 21):
Are you a real life pilot?

Would one need to be to answer the above?   
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
bri2k1
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RE: Red Button In Airbus Sidesticks?

Thu Feb 18, 2010 3:34 pm

Quoting mandala499 (Reply 22):
Would one need to be to answer the above?

It couldn't hurt. Your profile says "Deskpilot," which could be interpreted in American English in a number of ways. In the US Air Force, to say that one "flies a desk" means he is not qualified to hold a flying position and so works a desk job instead. Based on your many thoughtful, insightful, and factually correct responses, I seriously doubt this is your personal situation. Perhaps you have been a for-hire pilot for many years and now work in administration for an airline or air force? Of course, it could also mean that you are an avid flight simulator pilot, but perhaps you write manuals or specifications for an airline. I would be interested to know how you became so knowledgeable about so many different aircraft and their systems.
Position and hold
 
mandala499
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RE: Red Button In Airbus Sidesticks?

Thu Feb 18, 2010 6:42 pm

Quoting bri2k1 (Reply 23):
It couldn't hurt.

Of course it wouldn't...   
Deskpilot is a term we use in Indonesia for someone who flies on MS FlightSim   But obviously, that's not the only thing I do. There are also people in the airlines who are not pilots but need to fully understand how the plane works, like the Operations Control/Monitor guys. There can also be non-pilots in a flight safety team (but not lead it). There are also performance engineers who need to understand the systems and its effects on the airports, and come up with tweaked performance numbers of the aircraft.
Then there are people outside the airlines who "assist" on a professional basis on various matters (ranging from toilet cleaning to do multidisciplinary reviews of fleet procurement/type choice).
There are also people who collect FCOMs and study them for a hobby...  

To be honest, in real life and in the virtual world, I'm getting tired of being asked if I'm a pilot or not... Unless discussing about me sitting on the front seat in flight, my standard answer has always been, "does it matter?"

All I can say publicly is that I am one (or more) of the above.    And depending on the level and extent of one's interest in aviation... you might have actually seen my face somewhere.

But, one thing is for sure, I love aviation and the knowledge sharing/interchange that goes on... that's why I hang around here in the virtual world. Whilst at times I may get fed up with the industry, it never ceases to interest me... Check your PM...

Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !

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