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What Is It Like 'hand Flying' An Airbus?  
User currently offlineSmittyone From , joined Dec 1969, posts, RR:
Posted (2 years 4 months 3 weeks 5 days 8 hours ago) and read 10997 times:

Not trying to start a flame war or get into a gun battle over the different control philosophies here.

I'm just curious to hear from Airbus pilots - what is it like to fly with the side stick? Is it easier or harder than a conventional yoke? Does the computer system take up some of the workload of keeping the wings level or maintaining a desired pitch angle that you would have to do for yourself with a Boeing's yoke and trim controls?

Is there a mode where you are directly controlling the ailerons/elevators with no computer intervention? Seems like that would be much harder to do with a stick. Would you have to manually trim in that case?

I have about 40 hours in Cessna 172s so I have a rudimentary understanding of flight controls. But the Airbus system is a bit of a mystery still.

Thanks -

35 replies: All unread, showing first 25:
 
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17186 posts, RR: 66
Reply 1, posted (2 years 4 months 3 weeks 5 days 7 hours ago) and read 10970 times:

Quoting Smittyone (Thread starter):
Is there a mode where you are directly controlling the ailerons/elevators with no computer intervention? Seems like that would be much harder to do with a stick. Would you have to manually trim in that case?

Yes. This would be Direct Law. In Direct Law no pitch autotrim is available. However I don't know if any FBW Airbus has ever gone into Direct Law in line operation. There is also a "Mechanical Backup" law even "lower" than Direct Law, where all you have is stabilizer trim and rudder. I'm pretty sure that has never been degraded to.

See here for an excellent summary of control laws: http://www.airbusdriver.net/airbus_fltlaws.htm



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineairmagnac From Germany, joined Apr 2012, 321 posts, RR: 52
Reply 2, posted (2 years 4 months 3 weeks 5 days 6 hours ago) and read 10894 times:

Quoting Smittyone (Thread starter):
But the Airbus system is a bit of a mystery still.

Consider it as a translation device. It is translating pilot inputs (load factor/pitch rate, roll rate) into control surface deflection angles.
Here, translation means doing lots of relatively complicated calculations over and over again at a high frequency, with lots of variables. The human brain (=pilot's brain) is a wonderful computer, and does this work fairly well on traditional machines. But a dedicated computer does it a lot better, and can do a much more optimized job.
That's the whole point of flight control laws. And those are made much easier to implement with electronics and electric signaling, ie Fly By Wire.
These laws can be implemented on mechanical designs, but it is much more difficult. (after all, there is a simple law that transforms a single lateral demand into two surface deflection angles (ailerons) on your C172).

That's why we abusively talk about FBW or non-FBW, whereas the difference is more on the lines of "lots of sophisticated control laws" vs "a few relatively simple ones"


The idea is the same for any FBW aircraft, be it Airbus or Boeing or Embraer or Dassault or whatever. The main difference between A & B is that Boeing decided to use FBW and computers while keeping a traditional feel for the cockpit, whereas A decided to adapt their cockpit to the new control structure.

Quoting Smittyone (Thread starter):
Does the computer system take up some of the workload of keeping the wings level

If you leave the sidestick in neutral position, then you are asking for no roll rate. So the flight control computers will move the surfaces as required to maintain the current lateral attitude. So if you have wings level and stick neutral, the plane will work to maintain wings level without any pilot input.

Quoting Smittyone (Thread starter):
maintaining a desired pitch angle

Same as above : if you are in the stick's neutral position for pitch, you are telling the plane to hold its current attitude. (it's slightly more complicated because the input is actually a blend of pitch rate and load factor, but the general idea is the same)

Quoting Smittyone (Thread starter):
you would have to do for yourself with a Boeing's yoke and trim controls

Correction : you would have to do for yourself with a traditional mechanical linkage flight control design .
The critical difference is not in the cockpit design (yoke or stick), but in what is between it and the control surfaces.
A Boeing 777 or 787 or any other FBW aircraft will behave in approximately the same way, except that you have to trim for speed variations on the 7x7s.

Quoting Smittyone (Thread starter):
Is there a mode where you are directly controlling the ailerons/elevators with no computer intervention? Seems like that would be much harder to do with a stick. Would you have to manually trim in that case?

Alternate control laws : pitch is still a load factor demand, so the computers still calculate the appropriate deflections of the elevators and pitch trim. Lateral is direct
Direct law : Aptly named as controls are direct. Including pitch trim (ie it has to be adjusted by hand)

If you go into more detail, in some specific modes of the normal law (like ground, or flare laws IIRC) the lateral control is direct. Also, if you revert to alternate law in flight, direct law will be engaged when the gear is down.



One "oh shit" can erase a thousand "attaboys".
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17186 posts, RR: 66
Reply 3, posted (2 years 4 months 3 weeks 5 days 5 hours ago) and read 10841 times:

Quoting airmagnac (Reply 2):
That's why we abusively talk about FBW or non-FBW, whereas the difference is more on the lines of "lots of sophisticated control laws" vs "a few relatively simple ones"

This is a big misunderstanding about FBW. FBW does not imply envelope protection or vice versa.

I like to define things roughly like this:


-Fly by wire. A means by which control surfaces are signaled with electrical impulses as opposed to wires and pulleys. Examples: F-16, 777, 330/340.

- Computer controlled flight. A means by which a computer controls the flight path. This is completely independent from fly by wire. Nothing stops a computer from controlling an aircraft with cables and pulley. In fact it happens every day in aircraft like the 747-400, where the autopilot controls the surfaces. Example: Any aircraft with an autopilot.

- "Computer interpreted flight" . A means by which computers not only control the surfaces during automated flight, but also interpret pilot commands. In this case, for example, a roll command is not sent directly to the surfaces, but stick side deflection is interpreted as a "desire" by the pilot to roll, and the surfaces are deflected in order to roll the plane in compliance with pilot desire. Surface deflection is not necessarily in proportion to stick deflection. Example: F-16, 330/340.

- Envelope protection. A further development on "computer interpreted flight" by which the computers not only interpret commands but protect the aircraft from commands that may damage it or create an unsafe condition like a stall. Example: 330/340.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineSmittyone From , joined Dec 1969, posts, RR:
Reply 4, posted (2 years 4 months 3 weeks 5 days 5 hours ago) and read 10799 times:

Quoting airmagnac (Reply 2):
Correction : you would have to do for yourself with a traditional mechanical linkage flight control design .
The critical difference is not in the cockpit design (yoke or stick), but in what is between it and the control surfaces.
A Boeing 777 or 787 or any other FBW aircraft will behave in approximately the same way, except that you have to trim for speed variations on the 7x7s.

I think I understand this, but help me out with a couple of examples here:

Say the pilot wants to keep the wings level (no roll rate). But wind or thermal effects raise one of the wings, rolling the aircraft slightly. As I understand the Airbus FBW, the computer would immediately roll the wings back to level without pilot input. On the other hand, the pilot of the Boeing FBW would have to physically move the yoke to roll the aircraft back to wings level (if he/she doesn't want to wait for the aircraft's designed-in stability to settle it out)...true?

I understand how conventional pitch trim works...in the sense that if you reduce power in a Cessna etc. the nose will drop to maintain the 'trimmed' speed and the aircraft will descend. Is this how it works on the Boeing FBW? In other words if I have a 777 trimmed to fly level at 200KTS and reduce thrust, will the nose drop and the aircraft descend in order to keep flying at 200KTS?

On the other hand, if I am flying level at 200KTS in an Airbus and then reduce power, will the nose drop and aircraft descend to maintain 200KTS or will it hold the commanded pitch angle while allowing speed to decay?

[Edited 2012-08-02 09:54:53]

User currently offlineairmagnac From Germany, joined Apr 2012, 321 posts, RR: 52
Reply 5, posted (2 years 4 months 3 weeks 5 days 4 hours ago) and read 10757 times:

Quoting Smittyone (Reply 4):
But wind or thermal effects raise one of the wings, rolling the aircraft slightly. With the Airbus FBW, the computer would immediately roll the wings back to level without pilot input - true?

Yes, but I wouldn't say "immediately" in general. The dynamics will depend on the situation.

Quoting Smittyone (Reply 4):
the pilot of the Boeing FBW would have to physically move the yoke to roll the aircraft back to wings level

No
In lateral, Boeing FBW is just like any other FBW. It will cancel out undesired movements on its own.

The difference is in longitudinal control. To keep the "usual airplane feeling", Boeing introduced a special control law to mimic the usual speed stability that you describe. Or as you say :

Quoting Smittyone (Reply 4):
if I have a 777 trimmed to fly level at 200KTS and reduce thrust, will the nose drop and the aircraft descend in order to keep flying at 200KTS?

=> Yes

However

Quoting Smittyone (Reply 4):
if I am flying level at 200KTS in an Airbus and then reduce power, will the nose drop and aircraft descend to maintain 200KTS or will it hold the commanded pitch angle while allowing speed to decay?

It will hold the load factor, and allow speed to vary freely. In the case it decays, then AOA will be increased to hold the load factor, but eventually it will reach the stalling point. That is a reason why an Airbus needs hard limits.


Speaking of which :

Quoting Starlionblue (Reply 3):
This is a big misunderstanding about FBW. FBW does not imply envelope protection or vice versa.

I did not have envelope protections in mind there, even though I agree with you. My point was that "FBW" in a litteral sense relates to the physical way to transmit information to the control surfaces. But when talking about FBW we are often actually bundling several separate, abstract functions together :
- the control laws, which convert (translate) pilot inputs into surface deflection angles.
- envelope protections
The reason why we mix the terms is that both these functions are so much easier to implement when information is moving around electrically (and even more so if the electrical info is digitally coded as 0s and 1s)



One "oh shit" can erase a thousand "attaboys".
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 6, posted (2 years 4 months 3 weeks 5 days 4 hours ago) and read 10749 times:

Quoting Smittyone (Reply 4):
Say the pilot wants to keep the wings level (no roll rate). But wind or thermal effects raise one of the wings, rolling the aircraft slightly. As I understand the Airbus FBW, the computer would immediately roll the wings back to level without pilot input. On the other hand, the pilot of the Boeing FBW would have to physically move the yoke to roll the aircraft back to wings level (if he/she doesn't want to wait for the aircraft's designed-in stability to settle it out)...true?

No. Airbus and Boeing (now) both control roll rate. If you get an upset in roll the computer will stop the upset (get zero roll rate) but won't go back to level unless the pilot tells it to.

A 777 would need a yoke input to even stop the upset; it has a different lateral/directional control law than a 787. The 777 in roll is a good example of FBW without a (relatively) complex control law.

A 787 controls roll rate (like an Airbus) so it will always try to stop any uncommanded roll.

Quoting Smittyone (Reply 4):
I understand how conventional pitch trim works...in the sense that if you reduce power in a Cessna etc. the nose will drop to maintain the 'trimmed' speed and the aircraft will descend. Is this how it works on the Boeing FBW?

Yes. The 777 and 787 use very similar pitch laws.

Quoting Smittyone (Reply 4):
In other words if I have a 777 trimmed to fly level at 200KTS and reduce thrust, will the nose drop and the aircraft descend in order to keep flying at 200KTS?

Yes.

Quoting airmagnac (Reply 5):
In lateral, Boeing FBW is just like any other FBW.

No. Although they fly similarly, the 777 and 787 use very different lateral control laws.

Tom.


User currently offlineSmittyone From , joined Dec 1969, posts, RR:
Reply 7, posted (2 years 4 months 3 weeks 5 days 4 hours ago) and read 10742 times:

Quoting airmagnac (Reply 5):
It will hold the load factor, and allow speed to vary freely. In the case it decays, then AOA will be increased to hold the load factor, but eventually it will reach the stalling point. That is a reason why an Airbus needs hard limits.

Interesting...so when controlling an Airbus in the pitch dimension, it is quite a bit different from the less complex, non-FBW aircraft that pilots "grow up" with. It's like they've decoupled speed from pitch. I guess I can see why Boeing intentionally programmed their FBW to mimic what pilots are accustomed to. Is the Airbus system difficult to get used to?

Quoting tdscanuck (Reply 6):
No. Airbus and Boeing (now) both control roll rate. If you get an upset in roll the computer will stop the upset (get zero roll rate) but won't go back to level unless the pilot tells it to.

So even with roll controls in place there's still work for the pilot to do!


User currently offlineDocLightning From United States of America, joined Nov 2005, 20363 posts, RR: 59
Reply 8, posted (2 years 4 months 3 weeks 5 days 3 hours ago) and read 10686 times:

I have a question that is tangential to this topic:

There are a lot of Boeing fanboys who claim that Airbus's envelope protection overrides the pilot's final authority and could be dangerous.

Has there ever been an accident or serious incident in which envelope protection was implicated as a primary or secondary cause or a contributing factor?

*disclaimer: I am a reformed Boeing fanboy, now having a healthy respect and disrespect for both A and B.


User currently offlinetom355uk From United Kingdom, joined Nov 2007, 336 posts, RR: 3
Reply 9, posted (2 years 4 months 3 weeks 5 days 2 hours ago) and read 10654 times:

Quoting DocLightning (Reply 8):

Not as far as I am aware. I'd be willing to bet my house (if I owned one, crummy global recession) that envelope protections have saved far more lives than they have cost.



on Twitter @tombeckett2285
User currently offlineDavid L From United Kingdom, joined May 1999, 9546 posts, RR: 42
Reply 10, posted (2 years 4 months 3 weeks 5 days 1 hour ago) and read 10591 times:

Quoting DocLightning (Reply 8):
Has there ever been an accident or serious incident in which envelope protection was implicated as a primary or secondary cause or a contributing factor?

On a related note, I've asked several times over several years here if an accident involving a Boeing, MD or other type of airliner was ever avoided by banking more than 67o, stalling or in any way busting the limits that the Airbus protections would have prevented. All I've seen so far are suggestions that it might happen one day.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 11, posted (2 years 4 months 3 weeks 5 days ago) and read 10537 times:

Quoting DocLightning (Reply 8):
Has there ever been an accident or serious incident in which envelope protection was implicated as a primary or secondary cause or a contributing factor?

Not that I'm aware of. The only thing I can think of are some near-misses that, (very) arguably, might have not been "near" if envelope protection had been involved. As far as I know, this line of reasoning has only ever been invoked for mid-air collisions.

Tom.


User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 32
Reply 12, posted (2 years 4 months 3 weeks 5 days ago) and read 10509 times:

Quoting DocLightning (Reply 8):
Has there ever been an accident or serious incident in which envelope protection was implicated as a primary or secondary cause or a contributing factor?

The incident always cited by FBW critics is the A320 on June 28, 1988 at Mulhouse-Habsheim, LFGB, where the A320 flew spectacularly into the trees after a low pass over the runway.

When folks cite that crash as an example - they ignore the facts and the physics.

1) After the plane got so low and slow - it was going to crash. Period. It did not have enough speed, energy, thrust to climb out of the situation the pilot put the plane into.

2) The Envelope Protection did keep the pilot from standing the plane on its tail and causing it to stall and roll and pitch over to hit the ground inverted or at a sharp angle. Rather than losing a few people in the level descent into terrain, without EP it is likely most of the people on the plane would have perished and the survivors horribly burned.


The argument is that some believe a pilot could manually fly the aircraft closer to the edge of a stall than a computer. I'm in the group which believes the computer can do a better job. A pilot might be able to get closer to the edge, but a pilot is also more likely to cross the boundary.


User currently offlineairmagnac From Germany, joined Apr 2012, 321 posts, RR: 52
Reply 13, posted (2 years 4 months 3 weeks 5 days ago) and read 10508 times:

Quoting tdscanuck (Reply 6):
Quoting airmagnac (Reply 5):
In lateral, Boeing FBW is just like any other FBW.

No. Although they fly similarly, the 777 and 787 use very different lateral control laws.

Tom.

Ouch, mixed up several architectures there, thanks for correcting me Tom, I feel like an i****t. Sorry everyone.
Note to self : avoid posting in a hurry before leaving to the cinema with girlfriend  
Hoping to get it right this time : the 777 lateral law is rather "conventional" (apart from the integration into a single set of computers of associated functions such as gust alleviation, yaw dampening, and protections) whereas the 787 introduces the roll rate/sideslip-angle commands ?



BTW on the subject of lateral laws, here is a nice illustration that I wanted to post earlier :
http://www.youtube.com/watch?v=VdhEc07mB9Q

Watch the ailerons move all over the place, it's quite fascinating. The A380 has 2x three ailerons ; when calculating the deflection angle for each one, the flight control computers add a scheduling to dampen some wing structural modes



One "oh shit" can erase a thousand "attaboys".
User currently offlineimiakhtar From , joined Dec 1969, posts, RR:
Reply 14, posted (2 years 4 months 3 weeks 4 days 23 hours ago) and read 10505 times:

Quoting tom355uk (Reply 9):
Not as far as I am aware.
Quoting tdscanuck (Reply 11):
Not that I'm aware of.

Incorrect. There was an incident involving an IB A320 whereby the protections activated and prevented the aircraft from raising the nose during a go-around attempt in gusty conditions. Aircraft suffered a nose gear collapse and was written off (5G landing). I can't find the report online but I do have it on my hard drive. PM me for a copy.


User currently offlineViscount724 From Switzerland, joined Oct 2006, 26021 posts, RR: 22
Reply 15, posted (2 years 4 months 3 weeks 4 days 23 hours ago) and read 10488 times:

Quoting imiakhtar (Reply 14):
Quoting tom355uk (Reply 9):
Not as far as I am aware.
Quoting tdscanuck (Reply 11):
Not that I'm aware of.

Incorrect. There was an incident involving an IB A320 whereby the protections activated and prevented the aircraft from raising the nose during a go-around attempt in gusty conditions. Aircraft suffered a nose gear collapse and was written off (5G landing). I can't find the report online

Summary here:
http://aviation-safety.net/database/record.php?id=20010207-0


User currently offlinetom355uk From United Kingdom, joined Nov 2007, 336 posts, RR: 3
Reply 16, posted (2 years 4 months 3 weeks 4 days 23 hours ago) and read 10474 times:

I'll be honest, I hadn't heard of that incident until now, so thanks for that.

However, the key question is this:

"Would the incident have had a less desirable outcome had the envelope protections not been available?"

For example, an aggressive full elevator up deflection in such a low energy state may have actually resulted in a full stall and ended up as a broken wreck on the runway?



on Twitter @tombeckett2285
User currently offlinezeke From Hong Kong, joined Dec 2006, 9240 posts, RR: 76
Reply 17, posted (2 years 4 months 3 weeks 4 days 22 hours ago) and read 10437 times:

Quoting Starlionblue (Reply 1):
However I don't know if any FBW Airbus has ever gone into Direct Law in line operation.

I have, lots have. A number of failures where you are in alternate law will give you direct law on gear extension.

Quoting Starlionblue (Reply 1):
There is also a "Mechanical Backup" law even "lower" than Direct Law, where all you have is stabilizer trim and rudder.

Mechanics back is just replacing the electrical lines between the cockpit and the hydraulics, it is not moving the the actual flight controls.

Quoting airmagnac (Reply 5):
It will hold the load factor, and allow speed to vary freely. In the case it decays, then AOA will be increased to hold the load factor, but eventually it will reach the stalling point. That is a reason why an Airbus needs hard limits.

That is not correct, one would never be able to do an emergency descent. If you have a selected speed, and auto thrust off, reduce the thrust back to idle, the elevator will maintain whatever speed in selected.

Quoting DocLightning (Reply 8):

Has there ever been an accident or serious incident in which envelope protection was implicated as a primary or secondary cause or a contributing factor?

I do not think so.

Quoting rfields5421 (Reply 12):

The argument is that some believe a pilot could manually fly the aircraft closer to the edge of a stall than a computer. I'm in the group which believes the computer can do a better job. A pilot might be able to get closer to the edge, but a pilot is also more likely to cross the boundary.

It is the environmental factors which are unknown, computers are quicker at picking up those trends.

Quoting imiakhtar (Reply 14):
There was an incident involving an IB A320 whereby the protections activated and prevented the aircraft from raising the nose during a go-around attempt in gusty conditions. Aircraft suffered a nose gear collapse and was written off (5G landing).

I would have thought the primary cause there was not flying a go-around with the correct technique, the protections prevented the aircraft from stalling. Lowering the nose probably reduced the rate of descent protecting the crew and passengers.

AoA sensors are not immune from environmental turbulence, regardless of what they feed into. On a Boeing, exceeding the sensed AoA would result in stick shaker, and nose down bias, in both cases the sensor is telling the aircraft is it about to stall. The aircraft flight control system does not know it is just about a runway, it is behaving like it is at 1000 ft.

if you try hard enough, you can bend anything




We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineredflyer From United States of America, joined Feb 2005, 4376 posts, RR: 28
Reply 18, posted (2 years 4 months 3 weeks 4 days 22 hours ago) and read 10426 times:

Quoting David L (Reply 10):
On a related note, I've asked several times over several years here if an accident involving a Boeing, MD or other type of airliner was ever avoided by banking more than 67o, stalling or in any way busting the limits that the Airbus protections would have prevented. All I've seen so far are suggestions that it might happen one day.

Haven't there been some incidences where the plane ended up in an upset and the pilots recovered it with some actions that might not have been possible in an EP system, with damage occurring to the airframe? The infamous TWA 727 comes to mind, whereby the pilots decided to finger-f**k the flap system in cruise flight, resulting in a departure from controlled flight. They were able to recover the aircraft before kissing the ground, but not before they had pulled some wild recovery maneuvers, including deploying the landing gear at near Mach 1 speeds. I don't think an EP system would have allowed that. On the other hand - and before anyone mugs me for this example - an EP equipped aircraft would never have allowed the pilots to engage the flaps at cruise to begin with.  
Quoting airmagnac (Reply 13):
BTW on the subject of lateral laws, here is a nice illustration that I wanted to post earlier :
http://www.youtube.com/watch?v=VdhEc...7mB9Q

Great video and pretty amazing how those ailerons work.

Now, if only people would let the rest of us airplane fans just listen to the sound of the engines instead of forcing us to listen to their favorite songs during these aerial demonstration videos then we would all get along.

[Edited 2012-08-02 16:04:51]


My other home is a Piper Cherokee 180C
User currently offlinezeke From Hong Kong, joined Dec 2006, 9240 posts, RR: 76
Reply 19, posted (2 years 4 months 3 weeks 4 days 21 hours ago) and read 10374 times:

Quoting redflyer (Reply 18):
They were able to recover the aircraft before kissing the ground, but not before they had pulled some wild recovery maneuvers, including deploying the landing gear at near Mach 1 speeds. I don't think an EP system would have allowed that.

The FBW + protections would have stopped the upset to start with, one of the advantages of FBW+protections is the ability for the aircraft to use any combination of flight controls to get the desired flight path. Prevention is better than the cure. One is not restricted to aileron in roll for example. Similar with China Airlines 006, that would not have happened in a FBW aircraft with protections.

If an Airbus does get in an extreme upset, the protections are basically removed, the aircraft is back in direct law. It will remain in normal law if it can, it will provide the best recovery load protection for the airframe.

Quoting redflyer (Reply 18):
On the other hand - and before anyone mugs me for this example - an EP equipped aircraft would never have allowed the pilots to engage the flaps at cruise to begin with.

Nothing stopping you putting flaps out above 20,000 ft.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17186 posts, RR: 66
Reply 20, posted (2 years 4 months 3 weeks 4 days 20 hours ago) and read 10354 times:

Quoting airmagnac (Reply 5):
Quoting Starlionblue (Reply 3):
This is a big misunderstanding about FBW. FBW does not imply envelope protection or vice versa.

I did not have envelope protections in mind there, even though I agree with you. My point was that "FBW" in a litteral sense relates to the physical way to transmit information to the control surfaces. But when talking about FBW we are often actually bundling several separate, abstract functions together :
- the control laws, which convert (translate) pilot inputs into surface deflection angles.
- envelope protections

Sorry airmagnac. On re-reading I realize my answer sounds like I might disagree with you. But I do agree with you!

Quoting imiakhtar (Reply 14):
here was an incident involving an IB A320 whereby the protections activated and prevented the aircraft from raising the nose during a go-around attempt in gusty conditions. Aircraft suffered a nose gear collapse and was written off (5G landing)
Quoting Viscount724 (Reply 15):
Summary here:
http://aviation-safety.net/database/...207-0

Interesting. There's a note at the end of that page about a change to the software following the incident.

Quoting redflyer (Reply 18):
Now, if only people would let the rest of us airplane fans just listen to the sound of the engines instead of forcing us to listen to their favorite songs during these aerial demonstration videos then we would all get along.

  



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 21, posted (2 years 4 months 3 weeks 4 days 20 hours ago) and read 10324 times:

Quoting airmagnac (Reply 13):
Hoping to get it right this time : the 777 lateral law is rather "conventional" (apart from the integration into a single set of computers of associated functions such as gust alleviation, yaw dampening, and protections) whereas the 787 introduces the roll rate/sideslip-angle commands ?

Dead on. The 777 lateral control, although FBW (with a pair of cable-controlled spoilers as final backup), is very conventional in that yoke deflection = aileron deflection (with some speed scheduling like any other Boeing). The 787 lateral control law is a combined roll rate/sideslip angle law (called p-Beta...p is roll rate, Beta is sideslip angle).

Quoting imiakhtar (Reply 14):

Quoting tdscanuck (Reply 11):
Not that I'm aware of.

Incorrect. There was an incident involving an IB A320 whereby the protections activated and prevented the aircraft from raising the nose during a go-around attempt in gusty conditions.

I wasn't aware of that event. So, technically, correct! But for the wrong reasons. Interesting case though, I'm curious what would have happened without the protection.

Quoting zeke (Reply 19):
Quoting redflyer (Reply 18):
On the other hand - and before anyone mugs me for this example - an EP equipped aircraft would never have allowed the pilots to engage the flaps at cruise to begin with.

Nothing stopping you putting flaps out above 20,000 ft.

Not sure about Airbus, but Boeing locks out the flaps above FL200.

Tom.


User currently offlinezeke From Hong Kong, joined Dec 2006, 9240 posts, RR: 76
Reply 22, posted (2 years 4 months 3 weeks 4 days 20 hours ago) and read 10316 times:

Quoting tdscanuck (Reply 21):
Not sure about Airbus, but Boeing locks out the flaps above FL200.

FL200 is the limit, but nothing to stop you from deploying them. Just excess speed will stop gear or flap deployment.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineprebennorholm From Denmark, joined Mar 2000, 6544 posts, RR: 54
Reply 23, posted (2 years 4 months 3 weeks 4 days 18 hours ago) and read 10276 times:

Quoting DocLightning (Reply 8):
There are a lot of Boeing fanboys who claim that Airbus's envelope protection overrides the pilot's final authority and could be dangerous.

Actually A and B envelope protections are so similar that it is trivial.

B planes say: I protest because if you pull any harder you break off the wings. A planes say: You are about to break off the wings, I'm not going to do that.

B says: I protest because if you roll any harder you are asking me for a spiral dive which eventually will break off the wings. (If, however, you are at an air show and want to demonstrate a barrel roll, please go ahead). A says: You tell me to enter a spiral dive, which eventually will break off the wings. I will give you the maximum roll rate which will prevent a spiral dive at maximum wing load, and therefore prevent breaking off the wings.

B says: I protest because if you pull any harder, we will stall, and you will be in one hell of a mess. A says: You ask me for a stall. You must be crazy, I'm going to the limit for helping you, but you are already in a mess and I refuse to make it even worse for you.

Etc...

Could the envelope protections be more similar without being totally identical?

There are significant differences in the ordinary control philosophies between A and B, but exactly envelope protection differences are trivial. And BTW, 99+% of all A and B drivers should hopefully reach retirement age without ever getting close to the envelope limits. Except in the sims, of course.



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlinespink From United States of America, joined Aug 2005, 319 posts, RR: 1
Reply 24, posted (2 years 4 months 3 weeks 4 days 14 hours ago) and read 10165 times:

Quoting DocLightning (Reply 8):
Has there ever been an accident or serious incident in which envelope protection was implicated as a primary or secondary cause or a contributing factor?

I'm sure that has been at least one, though in theory it would be because of incorrect software/bug. The other side of the situation that a pilot has to be aware of is to not be too dependent on the EP that in case of failure, etc, where the EP isn't available that you mistakenly rely on it. This is something that can only really be handled through repeated continuous training and is something that you have to be aware of with any system that normally tries to prevent you from doing bad things.


25 Post contains images airmagnac : No problem, if we both agree ! I've been burned once already with that post, and you have much more expertise than I do, so please don't hesitate to
26 Post contains links David L : There's a bit more perspective here: http://www.iasa.com.au/folders/Safety_Issues/others/Bilbao.html It seems to me that there was more involved than
27 tdscanuck : Ah, ok. Same limitation, different implementation. On a modern Boeing, if you move the flap handle above FL200 nothing will happen. I believe they we
28 Post contains images David L : D'oh. Of course... flaps without slats. That's why the CB had to be pulled.
29 ricknroll : Much like the A320 crash, no point letting a pilot attempting to pull up if the computer has worked out that all you will do is stall if it lets you.
30 Pihero : That's quite incorrect. If you handfly level and pull the T/L to idle two thinghs will happenn in succession : 1/- The "Pitch Normal Law " will keep
31 Jetlagged : I'm not an Airbus pilot, but I have flown A320 full flight simulators on many occasions, as well as conventional and FBW Boeings. The Airbus sidestic
32 Post contains images Pihero : Now to answere nthyen OP. An incredible precision of piloting. It's surprisingly easy tto adapt to the sidestick... It feels natural after five minute
33 Smittyone : Thanks for all the thoughtful replies, very interesting stuff. Pihero, do you think it would be hard for you to go back to the old school column/trim
34 Pihero : First of all, I wouldn't want to - I've been assimilated by the 'Bus Borgs ! Two remarks, though : 1/- Quite a lot of my colleagues flew the 320, the
35 Post contains images mandala499 : It will hold load factor, and speed AND pitch will vary to maintain that load factor. Use a Boeing CWS... it'll hold pitch and roll if you leave the
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