How safe is (airbus) fly by wire? Airbus A330/340 and A320 family emergency AD
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From http://www.atsb.gov.au/media/24550/a...503722_001.pdf
The article (which I found after Clandestino clued me in to the incident - don't hold him responsible for the content) appears substantially correct.
It seems that the crew were unaware that disconnecting autothrottle was insufficient, and even with AP disengaged, the protections would order a thrust increase if the autothrottle system was still set to "ARMED".
Note that I'm not disputing that the T7 system can be disengaged more thoroughly than the Airbus equivalent, but it can be seen - even with that ability - the T7's functions can and do catch crews unaware if there is a problem with the air data.
Lyman, we're talking about FBW here, not autoflight. Can we at least keep the discussion vaguely on track?
The pilot in command reported that he then disconnected the autopilot and lowered the nose of the aircraft. The aircraft autothrottle then commanded an increase in thrust, which the pilot in command countered by manually moving the thrust levers to the idle position. The aircraft nose pitched up again and the aircraft climbed 2,000 ft. The flight crew notified air traffic control (ATC) that they could not maintain altitude and requested a descent and radar assistance for a return to Perth.
The pilot in command reported that he attempted to disconnect the autothrottle by pressing the thrust lever autothrottle disconnect switches and pushing the autothrottle engage switch. The autothrottle arm switches had remained in the ‘ARMED’ position during the occurrence.
With the autothrottle armed it would automatically activate if the autopilot was not engaged and the airspeed was less than a flight management computer calculated value for 1 second, or the thrust was below that required for the mode of flight at the time.
It seems that the crew were unaware that disconnecting autothrottle was insufficient, and even with AP disengaged, the protections would order a thrust increase if the autothrottle system was still set to "ARMED".
Note that I'm not disputing that the T7 system can be disengaged more thoroughly than the Airbus equivalent, but it can be seen - even with that ability - the T7's functions can and do catch crews unaware if there is a problem with the air data.
Lyman, we're talking about FBW here, not autoflight. Can we at least keep the discussion vaguely on track?
Last edited by DozyWannabe; 4th Jan 2013 at 18:27.
Dozy
"... namely that you're not generally supposed to constantly monitor the PF through linked controls ... "
you are right, you said that badly. Monitoring is mostly an SA and mental function if you are not the pilot flying. Once again, I never implied that the monitoring was being done via linked controls.
The monitoring begins with performance: is it (he) doing what we expect it (him) to be doing, or are we in a
'what's he doing now?'
'what's it doing now?'
condition?
Enough. Been over this exact point time and again in the 447 thread. With you.
"... namely that you're not generally supposed to constantly monitor the PF through linked controls ... "
you are right, you said that badly. Monitoring is mostly an SA and mental function if you are not the pilot flying. Once again, I never implied that the monitoring was being done via linked controls.
The monitoring begins with performance: is it (he) doing what we expect it (him) to be doing, or are we in a
'what's he doing now?'
'what's it doing now?'
condition?
Enough. Been over this exact point time and again in the 447 thread. With you.
Last edited by Lonewolf_50; 4th Jan 2013 at 19:13.
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Lonewolf50
Have a nice rest. I will not let go of this purposeful obfuscation of the issues.
I am not the best one to persist, but if Dozy is the last one standing, the world will be a bit less safe.
No offense Doze, it is possible you do actually misunderstand the safety issues.
But to abandon the safety issues in favor of the status quo is ungentlemanly.
Have a nice rest. I will not let go of this purposeful obfuscation of the issues.
I am not the best one to persist, but if Dozy is the last one standing, the world will be a bit less safe.
No offense Doze, it is possible you do actually misunderstand the safety issues.
But to abandon the safety issues in favor of the status quo is ungentlemanly.
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I don't want to argue with you - it's just a basic misunderstanding that I could have avoided by being clearer. Hope we can leave it there.
Hello again, Clandestino, ˇFeliz ańo nuevo! *
After your 5 years or so on Airbus, you certainly cannot be accused of under-confidence... Anyway, glad you like the aircraft as much as I did.
Decisiveness and single-mindedness are laudable attributes in a pilot, but in a multi-crew environment they need to be tempered by a willingness to listen attentively, time permitting, before rubbishing the opinion or advice of other crew members. Dismissing reasoned arguments with sarcastic one-liners is not the way to win people round to your point of view.
To someone who forty years ago was flying big jets at present-day speeds and cruise altitudes with no FMS or A/THR; with AP/FD systems that needed to be told what (changing) pitch attitude to fly in the climb and descent, and could barely lock on to an ILS - let alone perform an autoland; it’s faintly amusing to have one’s careful explanation of the mis-selection of an FMGS mode dismissed with:
“know where you are, know where you need to go and don't trust the autopilot blindly or basically: Flight order says you are a pilot, so act like one for ******’s sake!”
* (Carefuly preserved the ~ for you...)
After your 5 years or so on Airbus, you certainly cannot be accused of under-confidence... Anyway, glad you like the aircraft as much as I did.
Decisiveness and single-mindedness are laudable attributes in a pilot, but in a multi-crew environment they need to be tempered by a willingness to listen attentively, time permitting, before rubbishing the opinion or advice of other crew members. Dismissing reasoned arguments with sarcastic one-liners is not the way to win people round to your point of view.
To someone who forty years ago was flying big jets at present-day speeds and cruise altitudes with no FMS or A/THR; with AP/FD systems that needed to be told what (changing) pitch attitude to fly in the climb and descent, and could barely lock on to an ILS - let alone perform an autoland; it’s faintly amusing to have one’s careful explanation of the mis-selection of an FMGS mode dismissed with:
“know where you are, know where you need to go and don't trust the autopilot blindly or basically: Flight order says you are a pilot, so act like one for ******’s sake!”
* (Carefuly preserved the ~ for you...)
Awwwww, folks, don't take it personally. Despite increasing numbers of participants in our chat getting (auto)biographical, this thread is still about technical (and somewhat HF) subject and what we are discussing is a part of objective reality that doesn't care much (if at all) about someone's opinions.
If one is not seriously involved in the business of confirmation bias then one is obliged to recognize that not only such a system can counter unreasonable command but that it was a main reason why it was developed in the first place.
Yup. Couple of seconds or couple of degrees difference might mean we'd still operate old, flawed FCUs nowadays. Makes me wonder whether we'd have EGPWS today if B757 had speedbrake autostow like 320. Effing blood priority.
Now watch usual suspect rise to the bait.
Originally Posted by CONF iture
I know about my airplane which is able to give full priority to a wild protection and blind fully ignoring my more reasonable command.
Originally Posted by Dozy Wannabe
Or the ATCO - he gave an incorrect radar vector that put them significantly left of centreline.
Now watch usual suspect rise to the bait.
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Originally Posted by Clandestino
If one is not seriously involved in the business of confirmation bias then one is obliged to recognize that not only such a system can counter unreasonable command but that it was a main reason why it was developed in the first place.
If one + the Manufacturer are not seriously involved in the business of confirmation bias then one + the same Manufacturer are obliged to recognize that such a system can produce nonsense that reasonable command could not counter ... but such eventuality was simply not foreseen in the first place.
If the aroplane's attitude doesn't follow your sustained input, you are in much, much bigger trouble than simple FC mode change.
Last edited by CONF iture; 5th Jan 2013 at 22:44.
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Found following article in my archive folder, I don know the source nor date published.
5. ENHANCED DUAL INPUT AWARENESS
All Airbus FBW aircraft are fitted with uncoupled sidesticks. This choice of the sidestick was taken prior to the launch of the A320 due to the obvious benefits it provided for the operation of a Fly-by-Wire aircraft. The choice of non-coupled sticks, also taken at that time, was dictated by the available technology. With the technology of the eighties the only real choice was to couple both sidesticks mechanically; this would have unduly increased the complexity of the system and would have left the aircraft prone to failure cases (stick jamming) and common point typical of (and unavoidable) "mechanical" aircraft. With over 10 million FH of the AI FBW aircraft and over 15000 pilots qualified the initial debate on the merits and drawbacks of non-coupled sidesticks has ceased because flight crews have learnt to appreciate the advantages brought by the current system.
The feed-back received at Airbus from operators and pilot unions and the routinely analysis of in-service events indicate that there are still two areas where some pilots would appreciate some enhanced feed-back of "what the other pilot is doing".
These areas are:
Electronically coupled sidesticks (so called active sidesticks) offered by various aerospace equipment manufacturers have been evaluated and analyzed by Airbus Industrie. Despite the diversity of the proposed solutions, all the systems rely on high speed torque motors to move one sidestick to the same position of the other sidestick. All suppliers provide adjustment capabilities (forces, thresholds, displacements...) to match the sidestick characteristics and feel to the current Airbus sidesticks.
The evaluations of electronically-coupled sidesticks covered the following issues: System safety analysis, integration to the AI FBW/AUTOPILOT architecture, pilot interface and simulator tests in normal/abnormal/emergency scenarios.
Our underlying premise during this evaluation was that the coupled sidesticks should not degrade the reliability, the feel, the consequences of failure cases and the pilot interface of the current non-coupled sidesticks.
The main items identified during this activity were:
a) The increased complexity of the coupled sidestick makes it very difficult to closely match the current feel of the Airbus sidestick which is appreciated by flight crews.
The "copy" function of the active sidestick is accurate.
The implementation of coupled sidestick would require a modification of the current simple principle of "algebraical addition of both sidesticks orders".
c) The current capability for the PNF to instinctively take control of the a/c, with or without the use of the priority pushbutton, must be kept.
The identification of the sidestick movements of a trainee under normal circumstances is improved. There is a clear benefit for the training scenario.
e) Due to the small deflections of the Airbus sidestick in high stress situations it is difficult to clearly identify what the PF is doing with the sidestick, namely if the motions are small and rapid.
f) When the PNF makes a small correction to the PF, here again in abnormal or emergency situations, the input from the PNF will, in most of these cases, go undetected.
g) Motion of the PNF sidestick can be distractive and in most circumstances can drive the attention away from the most important parameters or cues to be monitored.
h) There is a clear risk for injury if the sidestick hits the hand of either pilot following any runaway of the control system.
i) The active sidesticks introduce a number of new failure situations (runaway, jam...) and a common point which are significantly more severe than with the current AI system. To minimize the impact of these failure cases major modifications to the current flight control system architecture would be required.
Based on the analysis of these results it was concluded that:
a) The current technology for active sidesticks provides a marked improvement relative to that available at the time of launch of the A320: it improves the PNF awareness of the PF actions during training flights.
b) With characteristics of the AI sidestick, dual input situations can remain undetected with coupled sidesticks specially under stress situations (which is where the dual inputs tend to occur).
c) The increased complexity of the sidestick assembly and of the integration to the AI FBW architecture will unavoidably reduce the overall reliability of the system.
d) Work should be launched to develop alternative means to improve the detection of dual inputs situations since it was demonstrated that the coupled sidestick cannot provide a 100% detection rate.
5.2. Dual input detection enhancements
5.2.1. Description
As a complement to the active sidestick evaluations, various new features have been developed to improve the crew awareness of dual input situations on the FBW aircraft. The main objective of these features is to provide warnings which will prevent long duration dual input situations.
The following visual, aural and tactile cues have been tested with the active participation of pilots from Airbus, airlines (Cathay, DLH, Sabena), unions (ALPA, SNPL, German Cockpit) and Airworthiness Authorities (CEV, CAA, FAA, Transport Canada).
VISUAL CUE
When both sidesticks are deflected simultaneously (for more than 0.5 sec), the CAPT and F/O captions of the Sidestick Priority Light on both glareshields are illuminated flashing in green. As soon as the priority p/b is pressed on either sidestick, the glareshield lights revert to the classical priority configuration (CAPT and arrow or F/O and arrow). The principles of this visual indicator are identical for all FBW aircraft.
AURAL CUE
A "DUAL INPUT" audio message is triggered when both sidesticks have been simultaneously deflected for a certain time. The timing of the audio message has been adapted on the A320/A321/A31 and A330/A340 families due to the different systems architecture such that, on all cases, the message is triggered after the illumination of the glareshield lights. In this way, there is a degree of sequencing such that the aural warning will only be triggered if the dual input situation is prolonged.
The "DUAL INPUT" audio is repeated every 5 sec. It has the lowest priority of all the audio (voice) messages but can be generated simultaneously with any other non-voice audio warnings.
When the priority p/b is pressed on either sidestick the warning is canceled except if it has already started (i.e. it cannot be interrupted).
TACTILE CUE (BUZZER)
The sidestick is fitted with a small electrical motor which rotates an unbalanced weight and thus generates a vibration of the sidestick. The level of vibration depends on the rotation speed and on the weight of the rotating mass.
When both sidesticks are deflected for a certain time, the buzzer on both sidesticks are activated to produce a series of intermittent vibrations. Since the level of buzzer vibration could not be increased at will due to various reasons (e.g. rattling noise on the lateral console) the principle of intermittent "shots" was selected to improve the detection of the buzzer activation.
The timing of the buzzer activation has been adapted on all the FBW aircraft such that the buzzer is activated simultaneously or slightly after the illumination of the glareshield lights.
When the priority p/b is pressed on either sidestick the buzzer is stopped immediately.
5.2.2. In-flight evaluation campaign
The in-flight evaluation process was split into two phases: An initial period devoted to the definition of the various features and a demonstration phase where the visual, aural and tactile cues were presented to non-AI pilots in various scenarios. The tests were conducted on the in-house test A340 and A330-200 aircraft.
The initial development and definition phase concentrated on:
a) Adjustment of the activation thresholds
b) Relative timing of the three features
c) Adjustment of the buzzer vibration levels and frequencies
d) Adjustment of the quality and level of the audio message
c) Simulator and in-flight evaluation in various normal, abnormal and emergency scenarios
d) Definition of an evaluation program for non-AI pilots (airlines, unions, Authorities)
During the demonstration phase the modifications were presented to pilots from airlines, Airworthiness Authorities and Unions. In each flight the guest pilot flew the aircraft and the AI pilot made unannounced dual inputs. The dual inputs were performed in the following scenarios:
5.2.3. Results of the in-flight evaluation campaign
There was a clear consensus of the evaluating pilots on the following issues:
5.2.4. Conclusion
a) The definition and inflight evaluation of the aural and tactile warnings is completed.
b) These features will be presented for Certification.
c) The visual, aural and tactile cues will enhance the detection of dual input situations. These features will not prevent dual inputs, but the likelihood of having prolonged dual input situations will be greatly reduced.
d) These features may be proposed as Standard Options grouped as follows:
All Airbus FBW aircraft are fitted with uncoupled sidesticks. This choice of the sidestick was taken prior to the launch of the A320 due to the obvious benefits it provided for the operation of a Fly-by-Wire aircraft. The choice of non-coupled sticks, also taken at that time, was dictated by the available technology. With the technology of the eighties the only real choice was to couple both sidesticks mechanically; this would have unduly increased the complexity of the system and would have left the aircraft prone to failure cases (stick jamming) and common point typical of (and unavoidable) "mechanical" aircraft. With over 10 million FH of the AI FBW aircraft and over 15000 pilots qualified the initial debate on the merits and drawbacks of non-coupled sidesticks has ceased because flight crews have learnt to appreciate the advantages brought by the current system.
The feed-back received at Airbus from operators and pilot unions and the routinely analysis of in-service events indicate that there are still two areas where some pilots would appreciate some enhanced feed-back of "what the other pilot is doing".
These areas are:
- Training flights.
- In a high stress environment there have been prolonged and undetected dual input situations.
- Evaluation of electronically coupled sidesticks
- Evaluation of features which may prevent prolonged dual input situations
Electronically coupled sidesticks (so called active sidesticks) offered by various aerospace equipment manufacturers have been evaluated and analyzed by Airbus Industrie. Despite the diversity of the proposed solutions, all the systems rely on high speed torque motors to move one sidestick to the same position of the other sidestick. All suppliers provide adjustment capabilities (forces, thresholds, displacements...) to match the sidestick characteristics and feel to the current Airbus sidesticks.
The evaluations of electronically-coupled sidesticks covered the following issues: System safety analysis, integration to the AI FBW/AUTOPILOT architecture, pilot interface and simulator tests in normal/abnormal/emergency scenarios.
Our underlying premise during this evaluation was that the coupled sidesticks should not degrade the reliability, the feel, the consequences of failure cases and the pilot interface of the current non-coupled sidesticks.
The main items identified during this activity were:
a) The increased complexity of the coupled sidestick makes it very difficult to closely match the current feel of the Airbus sidestick which is appreciated by flight crews.
The "copy" function of the active sidestick is accurate.
The implementation of coupled sidestick would require a modification of the current simple principle of "algebraical addition of both sidesticks orders".
c) The current capability for the PNF to instinctively take control of the a/c, with or without the use of the priority pushbutton, must be kept.
The identification of the sidestick movements of a trainee under normal circumstances is improved. There is a clear benefit for the training scenario.
e) Due to the small deflections of the Airbus sidestick in high stress situations it is difficult to clearly identify what the PF is doing with the sidestick, namely if the motions are small and rapid.
f) When the PNF makes a small correction to the PF, here again in abnormal or emergency situations, the input from the PNF will, in most of these cases, go undetected.
g) Motion of the PNF sidestick can be distractive and in most circumstances can drive the attention away from the most important parameters or cues to be monitored.
h) There is a clear risk for injury if the sidestick hits the hand of either pilot following any runaway of the control system.
i) The active sidesticks introduce a number of new failure situations (runaway, jam...) and a common point which are significantly more severe than with the current AI system. To minimize the impact of these failure cases major modifications to the current flight control system architecture would be required.
Based on the analysis of these results it was concluded that:
a) The current technology for active sidesticks provides a marked improvement relative to that available at the time of launch of the A320: it improves the PNF awareness of the PF actions during training flights.
b) With characteristics of the AI sidestick, dual input situations can remain undetected with coupled sidesticks specially under stress situations (which is where the dual inputs tend to occur).
c) The increased complexity of the sidestick assembly and of the integration to the AI FBW architecture will unavoidably reduce the overall reliability of the system.
d) Work should be launched to develop alternative means to improve the detection of dual inputs situations since it was demonstrated that the coupled sidestick cannot provide a 100% detection rate.
5.2. Dual input detection enhancements
5.2.1. Description
As a complement to the active sidestick evaluations, various new features have been developed to improve the crew awareness of dual input situations on the FBW aircraft. The main objective of these features is to provide warnings which will prevent long duration dual input situations.
The following visual, aural and tactile cues have been tested with the active participation of pilots from Airbus, airlines (Cathay, DLH, Sabena), unions (ALPA, SNPL, German Cockpit) and Airworthiness Authorities (CEV, CAA, FAA, Transport Canada).
VISUAL CUE
When both sidesticks are deflected simultaneously (for more than 0.5 sec), the CAPT and F/O captions of the Sidestick Priority Light on both glareshields are illuminated flashing in green. As soon as the priority p/b is pressed on either sidestick, the glareshield lights revert to the classical priority configuration (CAPT and arrow or F/O and arrow). The principles of this visual indicator are identical for all FBW aircraft.
AURAL CUE
A "DUAL INPUT" audio message is triggered when both sidesticks have been simultaneously deflected for a certain time. The timing of the audio message has been adapted on the A320/A321/A31 and A330/A340 families due to the different systems architecture such that, on all cases, the message is triggered after the illumination of the glareshield lights. In this way, there is a degree of sequencing such that the aural warning will only be triggered if the dual input situation is prolonged.
The "DUAL INPUT" audio is repeated every 5 sec. It has the lowest priority of all the audio (voice) messages but can be generated simultaneously with any other non-voice audio warnings.
When the priority p/b is pressed on either sidestick the warning is canceled except if it has already started (i.e. it cannot be interrupted).
TACTILE CUE (BUZZER)
The sidestick is fitted with a small electrical motor which rotates an unbalanced weight and thus generates a vibration of the sidestick. The level of vibration depends on the rotation speed and on the weight of the rotating mass.
When both sidesticks are deflected for a certain time, the buzzer on both sidesticks are activated to produce a series of intermittent vibrations. Since the level of buzzer vibration could not be increased at will due to various reasons (e.g. rattling noise on the lateral console) the principle of intermittent "shots" was selected to improve the detection of the buzzer activation.
The timing of the buzzer activation has been adapted on all the FBW aircraft such that the buzzer is activated simultaneously or slightly after the illumination of the glareshield lights.
When the priority p/b is pressed on either sidestick the buzzer is stopped immediately.
5.2.2. In-flight evaluation campaign
The in-flight evaluation process was split into two phases: An initial period devoted to the definition of the various features and a demonstration phase where the visual, aural and tactile cues were presented to non-AI pilots in various scenarios. The tests were conducted on the in-house test A340 and A330-200 aircraft.
The initial development and definition phase concentrated on:
a) Adjustment of the activation thresholds
b) Relative timing of the three features
c) Adjustment of the buzzer vibration levels and frequencies
d) Adjustment of the quality and level of the audio message
c) Simulator and in-flight evaluation in various normal, abnormal and emergency scenarios
d) Definition of an evaluation program for non-AI pilots (airlines, unions, Authorities)
During the demonstration phase the modifications were presented to pilots from airlines, Airworthiness Authorities and Unions. In each flight the guest pilot flew the aircraft and the AI pilot made unannounced dual inputs. The dual inputs were performed in the following scenarios:
- Precise tracking tasks in the normal flight envelope (tight turns, manual ILS approach)
- Take-off rotation
- Flare for landing and GA
- High speed dives entering the HSP and triggering the Overspeed Warning
- Stall Warning in Alternate law
- Low speed maneuvering during approach
- Maneuvering in the AOA-prot range (Avoidance maneuvers and GPWS pull-ups).
5.2.3. Results of the in-flight evaluation campaign
There was a clear consensus of the evaluating pilots on the following issues:
- The sidestick buzzer does not interfere in the normal piloting tasks
- The illumination of the glareshield lights may go unnoticed specially in daylight conditions
- The sidestick buzzer is probably the only useful cue in high stress situations
- All of the features improve the dual input detection capability
5.2.4. Conclusion
a) The definition and inflight evaluation of the aural and tactile warnings is completed.
b) These features will be presented for Certification.
c) The visual, aural and tactile cues will enhance the detection of dual input situations. These features will not prevent dual inputs, but the likelihood of having prolonged dual input situations will be greatly reduced.
d) These features may be proposed as Standard Options grouped as follows:
- Light only (option already available)
- Light + Audio
- Light + Buzzer
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Thanks A33Zab.
The above is part of a larger article found at www.oavia.com, and appears to have been published circa 2000.
The above is part of a larger article found at www.oavia.com, and appears to have been published circa 2000.
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A33Zab:
I remember this pamphlet. It had been dicussed ad nauseam.
Basically it turned out to be biased and sometimes outright silly.
1. The statement that flight crews learnt to appreciate the advantages of the system shows the bias. There is no proven advantage to take away tactile feedback. The crews simply got used to its absence and some even liked it (mostly the lesser gifted pilots ….) To claim that pilots appreciated non existing advantages mainly serves to cover up the fact that many disapproved of its apparent and admitted disadvantages. It’s like eternally reiterating that pilots were involved in the design, as to enhance its credibility. Most linepilots do not really think big of management- or factory-pilots, because they wear one hat too many.
2. Stating that control interconnection would increase chances of injury is silly. The conventional layout is still predominant in modern aviation and that would mean all other aircraft than Airbus would be exposed to such danger. As I said: Silly.
3. The most silly statement however is the following:
“Motion of the PNF sidestick can be distractive and in most circumstances can drive the attention away from the most important parameters or cues to be monitored”.
How about the movement of the conventional dual commands? What about the capability of humans to process visual and tactile inputs in parallel (as opposed to two visual inputs)?
Really no comment needed.
4. The argument that incorporating electronic interconnection would increase the chances of malfunction, due to increased complexity, is equally flawed. Why would we allow all the new gimmicks into our cockpits then? TCAS, EGPWS, Smart Landing System with all their interconnections, warnings and protections surely increase complexity. Just because every now and then one of these systems goes hayward was never cited or accepted as a reason not to implement them. Why should that now suddenly apply for a safety enhancement in flight controls?? That's a double standard.
PS @ Dozy: If you write your unavoidable spin to this, draft it to the community, no answer to me, I can no longer read your contributions.
I remember this pamphlet. It had been dicussed ad nauseam.
Basically it turned out to be biased and sometimes outright silly.
1. The statement that flight crews learnt to appreciate the advantages of the system shows the bias. There is no proven advantage to take away tactile feedback. The crews simply got used to its absence and some even liked it (mostly the lesser gifted pilots ….) To claim that pilots appreciated non existing advantages mainly serves to cover up the fact that many disapproved of its apparent and admitted disadvantages. It’s like eternally reiterating that pilots were involved in the design, as to enhance its credibility. Most linepilots do not really think big of management- or factory-pilots, because they wear one hat too many.
2. Stating that control interconnection would increase chances of injury is silly. The conventional layout is still predominant in modern aviation and that would mean all other aircraft than Airbus would be exposed to such danger. As I said: Silly.
3. The most silly statement however is the following:
“Motion of the PNF sidestick can be distractive and in most circumstances can drive the attention away from the most important parameters or cues to be monitored”.
How about the movement of the conventional dual commands? What about the capability of humans to process visual and tactile inputs in parallel (as opposed to two visual inputs)?
Really no comment needed.
4. The argument that incorporating electronic interconnection would increase the chances of malfunction, due to increased complexity, is equally flawed. Why would we allow all the new gimmicks into our cockpits then? TCAS, EGPWS, Smart Landing System with all their interconnections, warnings and protections surely increase complexity. Just because every now and then one of these systems goes hayward was never cited or accepted as a reason not to implement them. Why should that now suddenly apply for a safety enhancement in flight controls?? That's a double standard.
PS @ Dozy: If you write your unavoidable spin to this, draft it to the community, no answer to me, I can no longer read your contributions.
Last edited by Gretchenfrage; 6th Jan 2013 at 05:40.
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Hi,
Gretchenfrage
Beautiful argumentation
This is what I call "turning a pancake without dropping from the pan"
Gretchenfrage
Basically it turned out to be biased and sometimes outright silly.
This is what I call "turning a pancake without dropping from the pan"
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For those who think that the protections are gentle or gradual and that time is available... Thats especially for you dozywannabe. I just received some more info regarding the incident from my company:
And had that A330 been fitted with BUSS:
Switching off those 3 ADR's could have been a major problem, making things worse. So there goes the theory that they followed an established procedure.
These guys were badly caught out by the FBW protection in a rapidly developing situation.
Luckily they managed to get everything under control. But if there was ever an argument for a button to deactivate normal law, this is it.
In the recent event, all three probes became frozen and the aircraft erroneously detected an ‘incorrect angle of attack’ scenario which triggers Alpha Prot. As the AOA probes are frozen Alpha Floor will not be activated as the triggering AOA limit is not reached . As designed, the aircraft protection activated and a nose down input was introduced.
Unfortunately, as the probes were frozen (and continually sensing the incorrect alpha), the AOA did not reduce and the flight controls continued to demand a pitch nose down. Within 10 seconds, the aircraft had achieved 12 degrees nose down pitch and a rate of descent of 9400 fpm.
Aft sidestick input had no effect and the aircraft continued to pitch nose down.
Unfortunately, as the probes were frozen (and continually sensing the incorrect alpha), the AOA did not reduce and the flight controls continued to demand a pitch nose down. Within 10 seconds, the aircraft had achieved 12 degrees nose down pitch and a rate of descent of 9400 fpm.
Aft sidestick input had no effect and the aircraft continued to pitch nose down.
• Back Up Speed Scale (BUSS), which is fitted onto newer aircraft relies upon AoA inputs. It must not be used, so DO NOT switch off more than 2 ADR’s.
These guys were badly caught out by the FBW protection in a rapidly developing situation.
Luckily they managed to get everything under control. But if there was ever an argument for a button to deactivate normal law, this is it.
Last edited by flash2002; 6th Jan 2013 at 12:12.
Hi A33Zab,
Thanks for all that. Don’t know how you reproduced it here, but can you confirm that the actual text of Para 5.1.(b) has not been omitted?
It looks familiar to me, which is not surprising if it’s from the 20th century. Even wrinklies like me are now using domestic electronic devices far more complex and reliable than we were in the year 2000, so perhaps AI is revisiting this design area. If they are, they wouldn’t be shouting about it from the rooftops, for obvious reasons.
Thanks for all that. Don’t know how you reproduced it here, but can you confirm that the actual text of Para 5.1.(b) has not been omitted?
It looks familiar to me, which is not surprising if it’s from the 20th century. Even wrinklies like me are now using domestic electronic devices far more complex and reliable than we were in the year 2000, so perhaps AI is revisiting this design area. If they are, they wouldn’t be shouting about it from the rooftops, for obvious reasons.
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I have mentioned the dichotomy in the discussion prior. A very few adherents have interpreted the topic masthead as "how safe is Airbus"?
The opinion displayed becomes: "Quite safe". But that is not the question.
As I read it, it is: "How safe is AB flight control system when compromised?"
How is it doing in failure?
Gretchenfrage's analysis of the shiny pamphlet is instructive. He describes how prose can dazzle, and convince, to accomplish subtle goals.
One can only guess how the incident turns out if Roll Direct had challenged the crew.
Twelve degrees ND, and 9400 fpm descent. Without (commanded) elevator effect.
Charming.
The opinion displayed becomes: "Quite safe". But that is not the question.
As I read it, it is: "How safe is AB flight control system when compromised?"
How is it doing in failure?
Gretchenfrage's analysis of the shiny pamphlet is instructive. He describes how prose can dazzle, and convince, to accomplish subtle goals.
One can only guess how the incident turns out if Roll Direct had challenged the crew.
Twelve degrees ND, and 9400 fpm descent. Without (commanded) elevator effect.
Charming.
Last edited by Lyman; 6th Jan 2013 at 13:21.
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@Chris
so perhaps AI is revisiting this design area.
Checked it with the link provided by mm43, it is also missing on the site.
IMO the ref b) starts with "The implementation of coupled sidestick..."
and the ref d) with "The identification......."
SYMMETRY of PROBES
A33Zab,
What next...? Thanks.
Just wondering if flash2002's post should be duplicated on the A330/A340 EAD (AoA PROBES) thread, which is currently moribund.
And I remain curious as to if and how the respective probes seem to pack up (due icing) more-or-less simultaneously. Unless it’s something to do with this:
“...I sometimes used to ponder, during my walkrounds, on the pros and cons of locating Pitots 1 & 2 at precisely symmetrically-opposite positions on the fuselage (Pitot 3 being the odd one out). Then I would remind myself that the same applied to the AoA probes. It seemed to me that this might be a recipe for (roughly) simultaneous ice accretion of numbers 1 & 2.”
What next...? Thanks.
Just wondering if flash2002's post should be duplicated on the A330/A340 EAD (AoA PROBES) thread, which is currently moribund.
And I remain curious as to if and how the respective probes seem to pack up (due icing) more-or-less simultaneously. Unless it’s something to do with this:
“...I sometimes used to ponder, during my walkrounds, on the pros and cons of locating Pitots 1 & 2 at precisely symmetrically-opposite positions on the fuselage (Pitot 3 being the odd one out). Then I would remind myself that the same applied to the AoA probes. It seemed to me that this might be a recipe for (roughly) simultaneous ice accretion of numbers 1 & 2.”
Last edited by Chris Scott; 6th Jan 2013 at 14:41. Reason: Link added.
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Would it not have more to do with simultaneous ice pack of 1 and 3?
One and three have more in common in asymmetric airflow. No?
From a statistical point of view, cruise flight would generally represent most of the aircraft's exposure to symmetric airflow. In areas where particulate water Ice is present, a very small portion of total time in cruise, Ice is associated with turbulence, hence a higher chance that Ice would hobble vanes and pitots when unstable air is encountered. This suggests a higher probability that pitots located in close proximity would fail simultaneously.
Chris Scott:
"Can anyone cite an accident prior to AF447 that was related to the icing of a properly-heated pitot probe or AoA probe? Right now, I can't think of one, nor of a type that regularly experienced UAS problems in any flight-phase."
Not an accident, no. Incidents? Of course.... The AD is a place to start, re Thales.
One and three have more in common in asymmetric airflow. No?
From a statistical point of view, cruise flight would generally represent most of the aircraft's exposure to symmetric airflow. In areas where particulate water Ice is present, a very small portion of total time in cruise, Ice is associated with turbulence, hence a higher chance that Ice would hobble vanes and pitots when unstable air is encountered. This suggests a higher probability that pitots located in close proximity would fail simultaneously.
Chris Scott:
"Can anyone cite an accident prior to AF447 that was related to the icing of a properly-heated pitot probe or AoA probe? Right now, I can't think of one, nor of a type that regularly experienced UAS problems in any flight-phase."
Not an accident, no. Incidents? Of course.... The AD is a place to start, re Thales.
Last edited by Lyman; 6th Jan 2013 at 16:22.