LH A320 Rough Landing @ Hamburg
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Yokes are old. They are on their way out. Yesterday's technology. Get used to it.
Boeing wont relinquish the moving yoke/ thrust levers for their air transports.No sir,not just yet.When the role of the pilot has been consigned to the rubbish-bin of history,then they might.
At the moment of touchdown at HAM,this air-transport was being flown single-crew with zero feedback for the hapless PNF.Give me an answer as to why this is good.
CONF iture, your personal view (#454) provides a succinct summary, but shouldn’t you have referenced the limiting crosswind, or at least the possibility that it was limiting, albeit unknown to the crew? Re earlier references to inaccuracies in wind measurement and reporting.
DozyWannabe, I don’t take CONF iture's comments on Airbus as harsh as you do. Although the aircraft in the incident was an Airbus and from the discussion above its systems (or the crew’s understanding of them) may have been a factor, these are all points which can apply to many aircraft types.
There has been a vast amount of debate on the knowledge (or lack of) of the control systems and ‘how to’, but very little on what I believe could be a major contributor, that of the crosswind limit, a crew’s knowledge (or lack of) of limit derivation, wind measurement and reporting, and thus the risks that crew’s are prepared to take.
Thus the debate should not be so much about knowing how to conduct a crosswind landing, but instead consider the assessment of whether it is safe to do so in the conditions, and thus if any safety margin is required when planning to operate within ‘a limit’.
- Was the steady value (30kts) within or at the demonstrated value / limit, or if greater was the attempted approach inadvisable?
- Alternatively do you or any other operator consider the gusts as the limiting value? I note Chris Scott’s positive response earlier.
- Is there a compromise for a limiting condition between the steady state and a gust, if so what would it be?
- How many operators make the demonstrated crosswind value a limit? Why?
DozyWannabe, I don’t take CONF iture's comments on Airbus as harsh as you do. Although the aircraft in the incident was an Airbus and from the discussion above its systems (or the crew’s understanding of them) may have been a factor, these are all points which can apply to many aircraft types.
There has been a vast amount of debate on the knowledge (or lack of) of the control systems and ‘how to’, but very little on what I believe could be a major contributor, that of the crosswind limit, a crew’s knowledge (or lack of) of limit derivation, wind measurement and reporting, and thus the risks that crew’s are prepared to take.
Thus the debate should not be so much about knowing how to conduct a crosswind landing, but instead consider the assessment of whether it is safe to do so in the conditions, and thus if any safety margin is required when planning to operate within ‘a limit’.
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During certification x-wind landing capability has to be demonstrated. The last aircraft I flew it was 29 knots because the day they certified it that was the actual wind. If the wind had been 30 knots that day, that would be the limit, that is why they call it demonstrated x-wind limit. It does not mean you can't land with a higher x-wind because the aircraft can't do it. Proper x-wind landing technique will always assure a safe approach and landing up to the limit every time. Improper technique as seems to be the case here will not. You never let the upwind wing come up in a x-wind landing. It doesn't matter if you do it with a yoke or side stick.
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Dual Input
Originally Posted by bubbers44
[...] does the computer average the two opposite inputs?
When he selects priority on his side does it disengage from the averaging of the two side sticks to full authority on the left side stick?
Bernd
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I assume the captain's button to take full control and disable the FO's side stick is almost never used so would not be instinctive like taking over with a yoke. If she was using left stick and he countered with right stick to prevent hitting the left wing but didn't press the disengage button how would you add his right input to her left? You said it is additive, not averaged up to full stick deflection. What you said seems to say he could not counter the left aileron without disengaging her side in the above example. Is that correct?
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"Priority Takeover Pushbutton"
bubbers44,
the resulting control input from both sticks is just the simple algebraic sum of both sticks' deflections. If the F/O makes a control input of, say, 7 degrees to the left (call it "-7"), and the Captain makes a 12 degree input to the right ("+12"), then the resulting control input is -7 + 12 = +5.
If the F/O had been using full left input, the best the Captain could achieve without using the takeover priority button would be neutral, by applying full right deflection.
There is a known incident in which the Takeover button was used successfully in an emergency situation. The Captain's sidestick was connected in such a way that the roll input was reversed. The F/O noticed the problem just in time, pressed the takeover button, and landed the aircraft safely. See also the entry Lufthansa A320, incorrectly-wired sidestick, Frankfurt am Main, March 2001 in our Compendium CRICA.
There are also cases where cross-controlling without using the takeover button occurred. I assume it's a matter of training, and the fact that this happens is the strongest argument against the non-backfed, uncoupled sidesticks. For this to develop into a real problem usually also involves a serious breakdown of CRM.
The takeover button also serves to disconnect the autopilot, e. g. when taking over for the manual landing after an autopilot approach, so it may be a well-trained thing to do when starting to move the stick. (One can also disconnect the A/P by overcoming a restraining force that is keeping the sidestick "lcoked" with A/P active.)
Bernd
the resulting control input from both sticks is just the simple algebraic sum of both sticks' deflections. If the F/O makes a control input of, say, 7 degrees to the left (call it "-7"), and the Captain makes a 12 degree input to the right ("+12"), then the resulting control input is -7 + 12 = +5.
If the F/O had been using full left input, the best the Captain could achieve without using the takeover priority button would be neutral, by applying full right deflection.
There is a known incident in which the Takeover button was used successfully in an emergency situation. The Captain's sidestick was connected in such a way that the roll input was reversed. The F/O noticed the problem just in time, pressed the takeover button, and landed the aircraft safely. See also the entry Lufthansa A320, incorrectly-wired sidestick, Frankfurt am Main, March 2001 in our Compendium CRICA.
There are also cases where cross-controlling without using the takeover button occurred. I assume it's a matter of training, and the fact that this happens is the strongest argument against the non-backfed, uncoupled sidesticks. For this to develop into a real problem usually also involves a serious breakdown of CRM.
The takeover button also serves to disconnect the autopilot, e. g. when taking over for the manual landing after an autopilot approach, so it may be a well-trained thing to do when starting to move the stick. (One can also disconnect the A/P by overcoming a restraining force that is keeping the sidestick "lcoked" with A/P active.)
Bernd
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The training *makes* it instinctive - it's the whole point of training.
Rananim - I know how you feel about cockpit automation because we've butted heads over the subject before. I'm more than happy to agree that the AI FBW does have some drawbacks as well as numrous advantages, but a lot of the perceived disadvantages that you bring up are more to do with your distaste for what you see as marginalisation of the pilot than actual, known problems with the design.
Boeing didn't consider changing their flight control input method for financial, not technical reasons - they already had 5 or 6 jetliner types in the sky to maintain as much commonality between as possible, whereas Airbus, who had 2 (effectively one, A300/310) did not have the asme baggage. Of course, the press-induced backlash in the wake of Habsheim and Strasbourg as well as a distaste for FBW by some in the pilot community probably strengthened the case for them. But still, their latest offering is full digital FBW with a computerised backdriven force-feedback system - just as prone to problems as the A320 digital FBW setup.
Rananim - I know how you feel about cockpit automation because we've butted heads over the subject before. I'm more than happy to agree that the AI FBW does have some drawbacks as well as numrous advantages, but a lot of the perceived disadvantages that you bring up are more to do with your distaste for what you see as marginalisation of the pilot than actual, known problems with the design.
Boeing didn't consider changing their flight control input method for financial, not technical reasons - they already had 5 or 6 jetliner types in the sky to maintain as much commonality between as possible, whereas Airbus, who had 2 (effectively one, A300/310) did not have the asme baggage. Of course, the press-induced backlash in the wake of Habsheim and Strasbourg as well as a distaste for FBW by some in the pilot community probably strengthened the case for them. But still, their latest offering is full digital FBW with a computerised backdriven force-feedback system - just as prone to problems as the A320 digital FBW setup.
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A320 xwind limits
bubbers44,
why app autopilot (autoland) is limited to just 20 kts xwind component
while manual operation limits are much higher however typical
(33G38 kts) ?
why app autopilot (autoland) is limited to just 20 kts xwind component
while manual operation limits are much higher however typical
(33G38 kts) ?
bernd;
"Dual input" on sidesticks was considered so serious an operational issue that when we created our FDM 320 event set we designed and included an event to monitor such dual input. We do see the event trigger from time to time, sometimes in training circumstances, sometimes not.
We are also working on in-depth TCAS events but that is another thread.
PJ2
"Dual input" on sidesticks was considered so serious an operational issue that when we created our FDM 320 event set we designed and included an event to monitor such dual input. We do see the event trigger from time to time, sometimes in training circumstances, sometimes not.
We are also working on in-depth TCAS events but that is another thread.
PJ2
bubbers44 Re:
You assume too much. It is not necessarily true that 30kts would be the limit; the test team on another day might find that 30kts could not be demonstrated. In that case, the demonstrated value (29kt) would be moved to the limitations section of the AFM as a 'limit' (CS 25 AMC 25.158). The terms used are ‘demonstrated’ or ‘limit’, not both together.
Answers to the questions in #458 might conclude that a crew should not consider landing above any demonstrated value.
Even landings within the limit cannot be assured to be safe; consider the occurrence of a gust which might mean ‘at that critical time’ the wind is well above the demonstrated value.
The industry applies a safety margin to most parameters which if encountered in normal operation could be hazardous, e.g. approach speed / stall speed 30%, or landing distance 60%+. Then why not consider a safety margin for crosswind, which is a parameter that can result in loss of control?
cjt, crosswind values for manual landings are determined from a qualitative assessment by a test team. Normally they are judged not to be limiting nor require exceptional skill or knowledge (certification requirements).
For autoland certification, the manufacturer has to show statistically and in part by demonstration, that the landing will be safe (a high level of probability); this normally results in a lower crosswind value, which is published as a limit
… The last aircraft I flew it was 29 knots because the day they certified it that was the actual wind. If the wind had been 30 knots that day, that would be the limit, that is why they call it demonstrated x-wind limit.
It does not mean you can't land with a higher x-wind because the aircraft can't do it. Proper x-wind landing technique will always assure a safe approach and landing up to the limit every time.
Even landings within the limit cannot be assured to be safe; consider the occurrence of a gust which might mean ‘at that critical time’ the wind is well above the demonstrated value.
The industry applies a safety margin to most parameters which if encountered in normal operation could be hazardous, e.g. approach speed / stall speed 30%, or landing distance 60%+. Then why not consider a safety margin for crosswind, which is a parameter that can result in loss of control?
cjt, crosswind values for manual landings are determined from a qualitative assessment by a test team. Normally they are judged not to be limiting nor require exceptional skill or knowledge (certification requirements).
For autoland certification, the manufacturer has to show statistically and in part by demonstration, that the landing will be safe (a high level of probability); this normally results in a lower crosswind value, which is published as a limit
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gonebutnot forgotten
Quote : My only quibble with the chap who originally wrote it was his introduction that said :
"Despite rumors, the Airbus uses conventional crosswind landing technique'"
It may be an unfortunate choice of words but he meant that , contrarily to existing wisdom - one could side-slip an Airbus.
After all, as pilots we just make do with the tools we are given ; for example, in order to maintain a steady turn on a big aircraft , we usually need to apply reverse aileron and to my knowlwdge, that has bothered nobody. Same technique -the sideslip -, different ways of achieving it.
Quote : "there is a substantial body of A320 pilots (including the fellow whose hand appears in the video some way back - I have sat jump seat behind other coffee stirrers like him - and all those who regularly hit the roll stops) who really don't know what their flight controls are doing, haven't thoroughly thought through how the machine works, and haven't been taught to do so. I find that rather worrying. "
I can undestand your feeling, and to a point -though it pains me - I could agree with you. Perhaps have we gone too far in trying to insist on how NOT different the 320 is ? It is also a matter of demography :The populations who got the gospel from Airbus are fewer and fewer, the generation of the airmanship-holding baby boomers is no longer and they are being replaced by younger generations with less and less time (constraints of growth, mainly) to pass on the good practices.
But that problem is not only an Airbus one but general.
Regards
Quote : My only quibble with the chap who originally wrote it was his introduction that said :
"Despite rumors, the Airbus uses conventional crosswind landing technique'"
It may be an unfortunate choice of words but he meant that , contrarily to existing wisdom - one could side-slip an Airbus.
After all, as pilots we just make do with the tools we are given ; for example, in order to maintain a steady turn on a big aircraft , we usually need to apply reverse aileron and to my knowlwdge, that has bothered nobody. Same technique -the sideslip -, different ways of achieving it.
Quote : "there is a substantial body of A320 pilots (including the fellow whose hand appears in the video some way back - I have sat jump seat behind other coffee stirrers like him - and all those who regularly hit the roll stops) who really don't know what their flight controls are doing, haven't thoroughly thought through how the machine works, and haven't been taught to do so. I find that rather worrying. "
I can undestand your feeling, and to a point -though it pains me - I could agree with you. Perhaps have we gone too far in trying to insist on how NOT different the 320 is ? It is also a matter of demography :The populations who got the gospel from Airbus are fewer and fewer, the generation of the airmanship-holding baby boomers is no longer and they are being replaced by younger generations with less and less time (constraints of growth, mainly) to pass on the good practices.
But that problem is not only an Airbus one but general.
Regards
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A 320 Cross wind technique
Lemurian, you are probably right, maybe the chap was talking about sideslip, and not how to achieve it, but there are many contributors to this thread who really do appear to think conventional control inputs work for an A 320, including all those who talked about into wind aileron.
I remember many years ago a thread running on the BA/BALPA compuserve forum which started with some A 320 chap complaining about the lack of roll authority and how this was the first aircraft he had flown that required full aileron in gusts and how that often wasn't enough. Many others joined in to agree (some to their credit didn't) and the discussion droned on until it was abruptly shot down by the intervention of none other than Bill Wainwright, then Airbus CTP (how did he get into the private forum?). He patiently explained as was done earlier in this thread, that full stick gave 10 deg/sec roll rate, but that the controls were capable of much more (did I see 25 deg/sec?), and that a roll rate control just wasn't the same as aileron after the intial application. That shut everyone up. But the real issue is how on earth did such erroneous ideas take hold in the first place. What were the guys being taught? I think someone in Toulouse should be thinking very carefully about the standard of understanding being shown here, and what to do about it. There is a lot to learn when one changes the fundamentals of flying (and a lot to unlearn when one converts back to a conventional machine). With any luck , there are many A 320 crew who have read this thread and are thinking about what they do, but what about the rest out there?
Note for potential flamers out there, I am not saying there is anything wrong with the machine or the way it works, just that it needs to be taught properly and respected. I fully agree with Lemurian:
I remember many years ago a thread running on the BA/BALPA compuserve forum which started with some A 320 chap complaining about the lack of roll authority and how this was the first aircraft he had flown that required full aileron in gusts and how that often wasn't enough. Many others joined in to agree (some to their credit didn't) and the discussion droned on until it was abruptly shot down by the intervention of none other than Bill Wainwright, then Airbus CTP (how did he get into the private forum?). He patiently explained as was done earlier in this thread, that full stick gave 10 deg/sec roll rate, but that the controls were capable of much more (did I see 25 deg/sec?), and that a roll rate control just wasn't the same as aileron after the intial application. That shut everyone up. But the real issue is how on earth did such erroneous ideas take hold in the first place. What were the guys being taught? I think someone in Toulouse should be thinking very carefully about the standard of understanding being shown here, and what to do about it. There is a lot to learn when one changes the fundamentals of flying (and a lot to unlearn when one converts back to a conventional machine). With any luck , there are many A 320 crew who have read this thread and are thinking about what they do, but what about the rest out there?
Note for potential flamers out there, I am not saying there is anything wrong with the machine or the way it works, just that it needs to be taught properly and respected. I fully agree with Lemurian:
Perhaps have we gone too far in trying to insist on how NOT different the 320 is ?
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With any luck , there are many A 320 crew who have read this thread and are thinking about what they do, but what about the rest out there?
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Originally Posted by Lemurian
I can undestand your feeling, and to a point -though it pains me - I could agree with you. Perhaps have we gone too far in trying to insist on how NOT different the 320 is ?
Sorry if the question appears unduly elementary, but how does this sidestick control actually work? From what I gather, to bank say right, you move the sidestick say two inches to the right, and then let go (and, being spring-loaded, the sidestick centres itself). The aeroplane then banks right.
As I understand it, to cancel the command and level out, you have to move the sidestick the same distance in the opposite direction - precisely two inches to the left - and then release it again; and the aeroplane will then level out.
My question is, lacking the 'feedback' and self-centring that aeroplanes with normal controls provide, how do you know that you have exactly cancelled the previous bank command; and not either left some bank on, or corrected too far the other way?
Seems to me that there are only two ways that you could be certain. Either by observation (if the aeroplane doesn't level out, you've either overdone or underdone the correction) or by looking at some sort of instrument on the panel that shows the 'aileron command' situation?
Maybe I'm over-simplifying - I've certainly never tried to land a 60-ton airliner in any conditions. But I HAVE done plenty of crosswind landings - and I can't readily imagine a situation where I had to wait to see what the aeroplane did, or look at anything other than the yoke, to find out whether I had actually given the aeroplane the 'command' I intended or not?
Hope someone can enlighten me - and preferably tell me that Airbus controls don't actually work like that?
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left or right sidestick commands rollrate.
This means that upon releasing the stick to neutral, zero rollrate is commanded and roll stops.
You do not need to stop the roll by using opposite stick. in fact if you do that the roll will be reversed.
This means that upon releasing the stick to neutral, zero rollrate is commanded and roll stops.
You do not need to stop the roll by using opposite stick. in fact if you do that the roll will be reversed.
Last edited by sleeper; 14th Mar 2008 at 15:25. Reason: -
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RWA :
"...when coordinating ailerons, rudder, and elevators became automatic..."
The 320 does that *automatic* bit for you. Through the FCS.
..."From what I gather, to bank say right, you move the sidestick say two inches to the right, and then let go (and, being spring-loaded, the sidestick centres itself). The aeroplane then banks right..."
No ! Once again, the side-stick displacement commands a roll rate, or in other terms how fast you're gonna bank that airplane. leaving it in that position, the bank angle will keep on increasing at the same rate.When you move it then toward the centre, you'll slow the rate and annull it when the side-stick is centered : you have just asked the FCS to fly a new flight path with a G-demand, and it'll stay there until you cancel it. To that effect, move the stick in the opposite side and the stick will demand how fast you'll be having a bank command to that side, whether in order to reduce the rate of turn, to achieve a wings-level flight or to do a spiral in the opposite direction...within 5 degrees of wings level, it will center by itself.
There is no perceivable lag between command and aircraft response.
..."My question is, lacking the 'feedback' and self-centring that aeroplanes with normal controls provide, how do you know that you have exactly cancelled the previous bank command; and not either left some bank on, or corrected too far the other way? ..."
The true red herring...As far as I know, there is no *self centering* in any airplane I know except Airbus products : the pilot constantly moves the flight controls in any given circumstances...if not, he has achieved a damn good trim and his "stability augmenting system" is outstanding...until the next disturbance...
As for feed-back, I probably do not understand the term as it is meant by others. I will do what is necessary to get the response/state I require from the aircraft, on some, I may need some reverse aileron to maitain a given turn...on the Airbus, I get exactly what I want in the simplest way possible.
..." I HAVE done plenty of crosswind landings - and I can't readily imagine a situation where I had to wait to see what the aeroplane did, or look at anything other than the yoke, to find out whether I had actually given the aeroplane the 'command' I intended or not?..."
As I said, one moves the flight controls in order to achieve a given manoeuvre, regardless of the kind of airplane one is flying, regardless of the system one's airplane is operating on, be it even a side-slip. Piloting is about making sure that the airplane is EXACTLY placed, in the right configuration where it should be, as the pilot has decided.
In that respect, the precision of the Airbus system is peer-less, and a lot more intuitive than non-Airbus pilots would ever imagine.
Big problem is they don't imagine. Easier to criticise out of spite, prejudice, ignorance...
Their loss.
"...when coordinating ailerons, rudder, and elevators became automatic..."
The 320 does that *automatic* bit for you. Through the FCS.
..."From what I gather, to bank say right, you move the sidestick say two inches to the right, and then let go (and, being spring-loaded, the sidestick centres itself). The aeroplane then banks right..."
No ! Once again, the side-stick displacement commands a roll rate, or in other terms how fast you're gonna bank that airplane. leaving it in that position, the bank angle will keep on increasing at the same rate.When you move it then toward the centre, you'll slow the rate and annull it when the side-stick is centered : you have just asked the FCS to fly a new flight path with a G-demand, and it'll stay there until you cancel it. To that effect, move the stick in the opposite side and the stick will demand how fast you'll be having a bank command to that side, whether in order to reduce the rate of turn, to achieve a wings-level flight or to do a spiral in the opposite direction...within 5 degrees of wings level, it will center by itself.
There is no perceivable lag between command and aircraft response.
..."My question is, lacking the 'feedback' and self-centring that aeroplanes with normal controls provide, how do you know that you have exactly cancelled the previous bank command; and not either left some bank on, or corrected too far the other way? ..."
The true red herring...As far as I know, there is no *self centering* in any airplane I know except Airbus products : the pilot constantly moves the flight controls in any given circumstances...if not, he has achieved a damn good trim and his "stability augmenting system" is outstanding...until the next disturbance...
As for feed-back, I probably do not understand the term as it is meant by others. I will do what is necessary to get the response/state I require from the aircraft, on some, I may need some reverse aileron to maitain a given turn...on the Airbus, I get exactly what I want in the simplest way possible.
..." I HAVE done plenty of crosswind landings - and I can't readily imagine a situation where I had to wait to see what the aeroplane did, or look at anything other than the yoke, to find out whether I had actually given the aeroplane the 'command' I intended or not?..."
As I said, one moves the flight controls in order to achieve a given manoeuvre, regardless of the kind of airplane one is flying, regardless of the system one's airplane is operating on, be it even a side-slip. Piloting is about making sure that the airplane is EXACTLY placed, in the right configuration where it should be, as the pilot has decided.
In that respect, the precision of the Airbus system is peer-less, and a lot more intuitive than non-Airbus pilots would ever imagine.
Big problem is they don't imagine. Easier to criticise out of spite, prejudice, ignorance...
Their loss.
Sidestick abuse... and how to avoid it.
In the light of all these illuminating exchanges more recently, I have EDITED my post on A320 side-stick [Mar04/18:07, currently Page12, #229]. These amendments have now also been added below during EDITing.***
Quote from gonebutnotforgotten [Mar12/20:46, currently #452]:
I have sat jump seat behind other coffee stirrers like him - and all those who regularly hit the roll stops) who really don't know what their flight controls are doing, haven't thoroughly thought through how the machine works, and haven't been taught to do so. I find that rather worrying.
[Unquote]
Having arguably over-contributed to this Thread (20 posts at the last count...), I see that the sidestick-abuse
issue is still worthy of further comment. I made little attempt to describe how to handle the stick in my previous post, except to express the opinion that, with notable exceptions, inputs should be "short and often". The alarming over-control exhibited in the "instructional" (ouch!) video [see link in lamer's post of Mar06/11:49, currently Page 18 #345], is even worse than what I often observed from the detached point of view of the jump seat in about 12 years as a specialist line-checker on the A320 family.
Full stick one way followed by the exact opposite a split-second later, such as in the video, could be most kindly described as nervous "occupational therapy", in my opinion, whether the air is rough or smooth.
LET THE DUTY ELAC/SEC DO THE WORK...
Last month, there was a good discussion on this Forum; "Fly by Wire questio0n" (sic):
http://www.pprune.org/forums/showthread.php?t=313926
This was my two-pence-worth on how to use the sidestick, for the uninitiated (and the habitual "stirrers")
, slightly clarified:
Re the sidestick, it's worth mentioning that there is a special armrest, adjustable in height and rake, for each pilot. The idea is to rest the flat of your forearm on it, wrist slightly raised. You do not actually touch the stick until you need to make an input.
For simple roll-rate demands, you can use your thumb for one way, and 1 - 3 fingers for the other way. For up demands, use your fingers; for down demands, your thumb. To do these different tasks, your wrist will twist to the necessary angle, but will not move up or down, or significantly sideways. Inputs are normally the most successful when small, short-duration, and frequent. The obvious exceptions are rotation on take-off, and a simple roll from one side to the other. ***
The stick can be moved in any direction, of course. ...the stick does take account of your hand's hook-action being stronger than its "slice". Although the pitch and roll-rate resistances are well harmonised, combinations of the two are the easiest to get wrong. The sticks do not move to reflect autopilot inputs. Normally the signal to the EFCS is the algebraic sum of the 2 sticks. But if one pilot wants to take control, he/she can press a red button on the stick (eliciting a 'gringo' announcement and warning lights). The red button is also used for AP disconnect.
*** [EDITING CLARIFICATION]
Pitch inputs are also best small, short-term, and often; except (1) rotation; (2) the flare, when countering the progressive forward trimming in land-mode; and (3) in recovery from a dive or steep climb.
CROSSWIND LANDING
In airborne sideslip, (usually delayed until decrab) the sidestick roll-input must be released as soon as the desired bank is achieved. However, the opposite rudder will have the effect of lifting the lowered wing again, so you may need to reapply the roll command intermittently, elsewhere referred to as "bumping". [See Post #449, et al.] Once both main L/Gs have touched down firmly, the stick can be kept slightly displaced in the direction of the sideslip. 5 seconds later, the FBW will revert to roll-direct mode (stick-to-aileron), and continuous into-wind aileron can (and should) be applied - in the conventional manner - until the wing ceases to be vulnerable to side-gust.
CROSSWIND TAKE-OFF
A small amount of into-wind aileron can be selected before starting the T/O run, avoiding "cracking" the spoilers.* During rotation, the upwind wing tends to rise in the conventional manner, and can be countered by retaining into-wind aileron. As the main L/G lifts off, any downwind rudder will be eased off, yawing the aeroplane into wind. This will temporarily assist the aileron. Half a second after lift-off, however, Normal Law in roll is introduced (AND the white cross on the PFDs has disappeared). At that point, any remaining roll input needs to be released.
5 seconds after main L/G lift-off, Normal Law also becomes fully effective in pitch. Stick-to-elevator control is now removed, and pitch-attitude can be refined by small nudges of sidestick.
* Roll-spoiler deployment can be avoided by placing the PFD white-cross so that its inner edge is not noticeably to the side of the centre spot.
Quote from gonebutnotforgotten [Mar12/20:46, currently #452]:
I have sat jump seat behind other coffee stirrers like him - and all those who regularly hit the roll stops) who really don't know what their flight controls are doing, haven't thoroughly thought through how the machine works, and haven't been taught to do so. I find that rather worrying.
[Unquote]
Having arguably over-contributed to this Thread (20 posts at the last count...), I see that the sidestick-abuse
issue is still worthy of further comment. I made little attempt to describe how to handle the stick in my previous post, except to express the opinion that, with notable exceptions, inputs should be "short and often". The alarming over-control exhibited in the "instructional" (ouch!) video [see link in lamer's post of Mar06/11:49, currently Page 18 #345], is even worse than what I often observed from the detached point of view of the jump seat in about 12 years as a specialist line-checker on the A320 family. Full stick one way followed by the exact opposite a split-second later, such as in the video, could be most kindly described as nervous "occupational therapy", in my opinion, whether the air is rough or smooth.
LET THE DUTY ELAC/SEC DO THE WORK...
Last month, there was a good discussion on this Forum; "Fly by Wire questio0n" (sic):
http://www.pprune.org/forums/showthread.php?t=313926
This was my two-pence-worth on how to use the sidestick, for the uninitiated (and the habitual "stirrers")
, slightly clarified:Re the sidestick, it's worth mentioning that there is a special armrest, adjustable in height and rake, for each pilot. The idea is to rest the flat of your forearm on it, wrist slightly raised. You do not actually touch the stick until you need to make an input.
For simple roll-rate demands, you can use your thumb for one way, and 1 - 3 fingers for the other way. For up demands, use your fingers; for down demands, your thumb. To do these different tasks, your wrist will twist to the necessary angle, but will not move up or down, or significantly sideways. Inputs are normally the most successful when small, short-duration, and frequent. The obvious exceptions are rotation on take-off, and a simple roll from one side to the other. ***
The stick can be moved in any direction, of course. ...the stick does take account of your hand's hook-action being stronger than its "slice". Although the pitch and roll-rate resistances are well harmonised, combinations of the two are the easiest to get wrong. The sticks do not move to reflect autopilot inputs. Normally the signal to the EFCS is the algebraic sum of the 2 sticks. But if one pilot wants to take control, he/she can press a red button on the stick (eliciting a 'gringo' announcement and warning lights). The red button is also used for AP disconnect.
*** [EDITING CLARIFICATION]
Pitch inputs are also best small, short-term, and often; except (1) rotation; (2) the flare, when countering the progressive forward trimming in land-mode; and (3) in recovery from a dive or steep climb.
CROSSWIND LANDING
In airborne sideslip, (usually delayed until decrab) the sidestick roll-input must be released as soon as the desired bank is achieved. However, the opposite rudder will have the effect of lifting the lowered wing again, so you may need to reapply the roll command intermittently, elsewhere referred to as "bumping". [See Post #449, et al.] Once both main L/Gs have touched down firmly, the stick can be kept slightly displaced in the direction of the sideslip. 5 seconds later, the FBW will revert to roll-direct mode (stick-to-aileron), and continuous into-wind aileron can (and should) be applied - in the conventional manner - until the wing ceases to be vulnerable to side-gust.
CROSSWIND TAKE-OFF
A small amount of into-wind aileron can be selected before starting the T/O run, avoiding "cracking" the spoilers.* During rotation, the upwind wing tends to rise in the conventional manner, and can be countered by retaining into-wind aileron. As the main L/G lifts off, any downwind rudder will be eased off, yawing the aeroplane into wind. This will temporarily assist the aileron. Half a second after lift-off, however, Normal Law in roll is introduced (AND the white cross on the PFDs has disappeared). At that point, any remaining roll input needs to be released.
5 seconds after main L/G lift-off, Normal Law also becomes fully effective in pitch. Stick-to-elevator control is now removed, and pitch-attitude can be refined by small nudges of sidestick.
* Roll-spoiler deployment can be avoided by placing the PFD white-cross so that its inner edge is not noticeably to the side of the centre spot.
Last edited by Chris Scott; 15th Mar 2008 at 15:30. Reason: By request, improvements to #229 incorporated here, with minor corrections; including one for CONFiture
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Lemurian:
Easier to criticise out of spite, prejudice, ignorance...
Easier to criticise out of spite, prejudice, ignorance...
It's a shame that it was so advanced that they didn't have the now ubiquitous car technologies of traction control and the like to compare it to at the time, because while not 100% accurate it is the best analogy I can think of.
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Chris,
Read your updated post.
I disagree with your editing. It needs to be here.People generally don't bother to go back that far .
As for the video I haven't seen ( I'm only on pge 12) before, I AM APALLED !
That idiot went into the stops, and more than once ! to achieve what ?
Definitely an example of *what certainly not to do*. In fact, I am quite sure that in calm conditions, the airplane would be jerking a bit with no visible results in terms of achieved flight path. Talking about PIO would be charitable.
As for the flying technique, I've striven to reach that level of de-contraction for years. I do most of the time...most of the time...
Cheers
Read your updated post.
I disagree with your editing. It needs to be here.People generally don't bother to go back that far .
As for the video I haven't seen ( I'm only on pge 12) before, I AM APALLED !
That idiot went into the stops, and more than once ! to achieve what ?
Definitely an example of *what certainly not to do*. In fact, I am quite sure that in calm conditions, the airplane would be jerking a bit with no visible results in terms of achieved flight path. Talking about PIO would be charitable.
As for the flying technique, I've striven to reach that level of de-contraction for years. I do most of the time...most of the time...
Cheers