757 pilot had history of hairy landings
- The faster you go, the more the sidecar drags you towards the near side of the road.
- Under acceleration the sidecar tries to make you spear off the road.
- Under brakes the sidecar tries to steer you into oncoming traffic.
And now your comments have me wondering whether it would be possible to dynamically adjust these "trim" conditions at least for different speeds.
Or I could just keep a safe distance from my friend's sidecar. My inner engineer is finding it difficult to resist getting involved, even as the bit of my brain that tried to ride one 39 years ago is howling in protest.
Last edited by nonsense; 30th Aug 2020 at 16:14.
Brilliant ! 
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Can you explain how does it compensate for thrust changes.
* Pitch/power couple is almost entirely removed through software on a fly-by-wire aircraft.
* The 777/787 will pitch to maintain airspeed with a power change - add power, pitch will gradually increase to maintain the trimmed speed and vice-versa. An Airbus (with plain old C* law) will maintain flight path at the expense of speed until another limit in the flight path envelope is reached.
Personally I prefer the stability of the Airbus - on a gusty day with significant speed changes the flight path on approach tends to be nailed. Speed changes on a Boeing result in flight path changes.
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Personally I prefer the stability of the Airbus - on a gusty day with significant speed changes the flight path on approach tends to be nailed. Speed changes on a Boeing result in flight path changes.
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Can you explain how does it compensate for thrust changes. In speed stable system if thrust is increased and if the flight path is maintained i.e. if the nose doesn't come up speed will increase. Similarly if the thrust is decreased if the nose doesn't drop speed will decrease. That's what happens in Airbus. What happens in 777?
It does not "compensate" as in, prevent the attitude from changing; this would, of course, vary the speed and go against the fundamental point of the control law (and would essentially turn it into the Airbus control law, as you note)
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Can you explain how does it compensate for thrust changes. In speed stable system if thrust is increased and if the flight path is maintained i.e. if the nose doesn't come up speed will increase. Similarly if the thrust is decreased if the nose doesn't drop speed will decrease. That's what happens in Airbus. What happens in 777?
Last edited by spanner the cat; 31st Aug 2020 at 06:53.
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When training a new Line Check Airman I have a :45 minute brief I give called, “Verbally Managing the Landing.” (A319/320 - when training new Bus pilots I give a trainee version of this brief to them. This will familiarize them with the commands I will state in the landing phase and their expected appropriate response)
50’ AGL is where the start point of the brief and the selection of reverse is the end point. I identify gates, trainee action or inaction, verbal check airman commands (One - two words, easily said, easily understood), trainee response correct or incorrect and then further check airman verbal commands or, most likely, take over. Anticipation underpins all. (Obviously with no yoke, there’s no tactile nor visual feedback, that’s tough for a new check airman, one has to think about the landing phase differently when teaching IMHO)
You are correct you don’t have to intervene “at the first sign of trouble.” (Unless late in the landing phase) But I have found in almost all cases you should intervene at the second sign of trouble.
my 2˘.
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There's actually a silver lining to the lack of connection between the controls on both sides of an Airbus. It is that, unless they hear "DUAL INPUT" (or "I have control" if things go south far enough), the trainees can be totally certain that it was them and only them at the controls all the way through. In this way, it's a bit more clear-cut what works and what doesn't. In an aircraft with proper dual controls, some instructors may do subtle interventions on their side without later explaining that to the trainee - and, hence, the trainee can be left with a somewhat flawed impression of what needs to be done because he doesn't factor in that subtle, unmentioned input from the instructor.
That's the glass-half-full viewpoint though. The glass-half-empty one is that teaching and intervention indeed become more difficult and are well worth some dedicated discussion during LTC/TRI training (and, if you ask me, during every Airbus pilot training as part of the pilot incapacitation topic). The standard rules for taking over in the event of suspected incapacitation are not always safe enough close to the ground as you might not have the time to wait for a response to two consecutive deviation callouts. Conversely, if you always take control as soon as anything deviates from normal, that may be detrimental to the trainee's learning. It can be a tough call - and one that only comes with experience.
That's the glass-half-full viewpoint though. The glass-half-empty one is that teaching and intervention indeed become more difficult and are well worth some dedicated discussion during LTC/TRI training (and, if you ask me, during every Airbus pilot training as part of the pilot incapacitation topic). The standard rules for taking over in the event of suspected incapacitation are not always safe enough close to the ground as you might not have the time to wait for a response to two consecutive deviation callouts. Conversely, if you always take control as soon as anything deviates from normal, that may be detrimental to the trainee's learning. It can be a tough call - and one that only comes with experience.
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Only half a speed-brake
But then, after all, it will fool a human exactly the same as the 757 discussed above: https://assets.publishing.service.go...DHJZ_12-08.pdf
“THE FLARE WAS RATHER LATE THERE……..BUT THEN I SHOULD HAVE TAKEN OVER”.
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Auto thrust off? In Gusty winds? That's not what airbus wants.
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But then, after all, it will fool a human exactly the same as the 757 discussed above:
Not sure what you mean here. With auto-thrust off you still follow the magenta speed bug right?.......which on approach is indicating ground speed mini.......which reacts to wind gusts.
So if the auto-thrust is going up and down 'ad nauseam' to follow the bug speed, then so should you be if you use manual thrust.
Boeing has a different way of calculating the approach speed, and you shouldn't substitute the Boeing method in the Airbus.
If you ignore Airbus ground speed mini you could end up in a very sticky situation.
Not what Airbus wants but much smoother controls and manual thrust does a much nicer job in gusty conditions than the A/THR does. A/T works well in certain situations, but find it really can't compete with manual control on gusty, sheery days. It can get out of sync with the gusts and start an almost PIO type inputs. Much simpler to just fly it manually.
And also fully in compliance with Airbus' golden rules and principals of "If it's not doing what you want take control", and "use the appropriate level of automation for the task at hand".
And also fully in compliance with Airbus' golden rules and principals of "If it's not doing what you want take control", and "use the appropriate level of automation for the task at hand".
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And also fully in compliance with Airbus' golden rules and principals of "If it's not doing what you want take control", and "use the appropriate level of automation for the task at hand"
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A positive gust increases your IAS, but the Vapp target increases as well. Only a small thrust increase should be required to compensate for the extra headwind.
A negative gust decreases your IAS, but the Vapp target decreases as well.
I think that misd-agin is referring to the A/THR overcorrecting in gusty conditions. Which it does. With the risk of reducing or adding too much power just before or during the flare.
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Airbus states that A/THR should be used, not shall.
They also state that the A/THR should be disconnected in case of unsatisfactory performance. Chasing the speed or overcorrecting can be seen as unsatisfactory performance. It would be the case for a trainee or a pilot being checked, so why wouldn’t it apply to the automation?
Everyone has their preference, and I agree that it’s easier to land without the A/THR making excessive thrust changes.
They also state that the A/THR should be disconnected in case of unsatisfactory performance. Chasing the speed or overcorrecting can be seen as unsatisfactory performance. It would be the case for a trainee or a pilot being checked, so why wouldn’t it apply to the automation?
Everyone has their preference, and I agree that it’s easier to land without the A/THR making excessive thrust changes.
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My experience is that GS-mini more or less eliminates “hunting” by the auto thrust in gusty conditions. I used to fly regularly without auto thrust at my previous operator and I’m embarrassed to say that it usually did a better job than me. I think I’ve flown one approach without auto thrust in the last eight years, and that was only because it was decided that VLS-5 was its new favourite speed, in an A321 at max landing weight and conf 3.
The 787 auto thrust, on approach, is excellent in my opinion. It obviously biases speeds above vref, but in general is completely reliable and unobtrusive. The exception is on intermediate approach when it frequently seems to forget that it’s responsible for the speed control during level-off, even with the speed trend arrow going well south of the bugged speed.
The 787 auto thrust, on approach, is excellent in my opinion. It obviously biases speeds above vref, but in general is completely reliable and unobtrusive. The exception is on intermediate approach when it frequently seems to forget that it’s responsible for the speed control during level-off, even with the speed trend arrow going well south of the bugged speed.