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A320 over controlling/PIO fix.

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A320 over controlling/PIO fix.

Old 20th Sep 2022, 19:01
  #21 (permalink)  

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Vessbot, you are scientifically correct on this one.

Mainitaining strict 1g would never achieve what Airbus FBW advertises to be doing and it actually does!

It is a short-hand written in the pilot's manual for 'flies itself steady where you point it to thanks to complex proprietary magic whose creators are sadly no longer with us'.

Have mercy not to hijack the thread. The FCOM/FCTM says 1g and has a little picture of transition and a steady climb (not a 1g segment opposing the explanation itself) thus sometimes when not relevant we just say 1g. It does not hurt that much because nobody knows how large 1 g is or needs to be for level flight anyways.



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Old 20th Sep 2022, 21:08
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Hi Vessbot

FCOM explains it better. “With the sidestick at neutral, wings level, the system maintains 1 g in pitch (corrected for pitch attitude), and there is no need for the pilot to trim by changing speed or configuration. Therefore pilots only need to perform minor corrections on the sidestick, if the aircraft deviates from its intended flight path. [bold]If the pilot senses an overcontrol, the sidestick should be released.[/bold]

Pitch trim is automatic both in manual mode and when the autopilot is engaged. In normal turns (up to 33 ° of bank) the pilot does not have to make any pitch corrections once the turn is established.”


So stick free and with wings level the system maintains 1g.
With up to 33° of bank, the system will maintain 1g in the vertical direction but the wings will be pulling >1g due to the centripetal acceleration in the horizontal plane.

Last edited by Goldenrivett; 22nd Sep 2022 at 09:28. Reason: Typo + my bold for avoidance of PIO
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Old 22nd Sep 2022, 17:51
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Originally Posted by Dan Winterland View Post
I was told to treat the sidestick like it's your mates dick. Touch it as little as possible! Good advice at it worked for the ten thousand hours I flew on the Airbus FBW types.
Several people told me similar things, but it was very unhelpful to me because it did not explain what I was doing wrong, (which was not centring the stick after every input: I was holding each input too long, and the attitude went beyond what I wanted so I had to correct in the other direction, hence a PIO). Vilas's reply in #12 explains the system and use of the arm rest very well and would have helped a lot.

After teaching myself how to correctly use the side-stick and FBW combination, I became quite proficient in handling the aircraft, (he says modestly ).
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Old 23rd Sep 2022, 14:29
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Originally Posted by Uplinker View Post
Several people told me similar things, but it was very unhelpful to me because it did not explain what I was doing wrong, (which was not centring the stick after every input: I was holding each input too long, and the attitude went beyond what I wanted so I had to correct in the other direction, hence a PIO). Vilas's reply in #12 explains the system and use of the arm rest very well and would have helped a lot.

After teaching myself how to correctly use the side-stick and FBW combination, I became quite proficient in handling the aircraft, (he says modestly ).
A very early Airbus publication A320 Flight Deck and Systems Briefing for Pilots had this to say:
"control inputs are made to alter the flight path, not to hold it."
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Old 23rd Sep 2022, 16:40
  #25 (permalink)  
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Thankyou everyone for your replies and insights. Genuinely very helpful.

Uplinker did try and find that video on YouTube o the Tornado sidestick but sadly couldn’t find it.

With pedal positioning I was reminded recently to set your shoe size (UK).

Remembering my airbus type I remember lots of colourful ways to describe what to think the sidestick is in order not to touch it much but I think it’s the point that Vilas just made on the previous post which maybe should have the more emphasis.

With spring rates in the sidestick does anyone know if it’s different for the NEO. I find it definitely feels different.
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Old 24th Sep 2022, 02:49
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Hi Mooneyboy,

I’m assuming that you are new to Airbus and are asking for yourself, not to help others with this problem.
There has been some great information here but talking from personal experience, the big issue that you’re struggling with is trying to convert all that technical stuff into something practical that you can use.

Knowing the technical is required. Knowing how to convert that into “the performance” is also required.
Seating position, as discussed, is very important. Keep in mind that you need to start with the correct eye height. Some aircraft have systems for getting this step correct. Some Airbus types have balls set on small posts set to align when eye-height is correct. Then set armrest and then set rudder pedals so you can achieve full travel AND brake input. Please don’t set shoe size.
Also keep in mind that you need to check that this position still is correct when you are hands on side stick and thrust levers. Seat back position needs to be the same, as this will change your armrest and position. You will also potentially be a little shorter by the end of a long day, changing eye height. Think how you get into your car to drive home and need to adjust your rear view mirror.

Some have mentioned to watch your PFD during the control check. I like to also check the Flight Control SD page. You’ll see exactly the moment that any pitch input invokes lateral output and vice versa. Practice this so that you can “disconnect” the two axis.
Our job is all about “output” when it comes to hand flying. Telling you what inputs to make is pointless but understanding that the Flight Control Computers are flying the aircraft in parallel with you is important to always remember. It’s a bit like having another pilot maintaining the attitude that you demand through stick position and that pilot is still under training! As Vilas said, the aircraft maintains flight path but only in a “book” sense. For example, a disturbance on short final such as a wing drop will have you now aiming at a new aim point after the “aircraft” makes inputs to return to the demanded attitude. YOU now have to make an input to reacquire the aim point. If you react to the turbulence by flying via the “seat of your pants”, you will be effectively making a “dual input” and will have demanded a roll that now makes you opposite wing down. PIO, here we come! Factor in that, as you progress down the funnel of your approach path, you can’t really sit back and wait for the aircraft to make it’s input, so you’ll have to anticipate both your inputs and what the aircraft inputs will be.
The unfortunate gulf between how the simulator presents it’s reality and how the real world is, doesn’t always set you up to succeed. In the sim, you can fly a very good approach off an IP almost without making any inputs until the flare. Try this on the line and you will most likely have the PM take over as you lose the aim point. If the sim was set up to have varying layers of W/V as one descended to the runway, the vagaries of the wind on a real life approach would be more realistically represented.
Approaching the flare, having made sure that you held the aim point, now consider how flare law changes pitch and therefore trim and how lateral is the same, ie lateral disturbance will induce an input from the aircraft. You’ll probably have to make one too but DON’T do the dual input thing, anticipate your input. In crosswind, if you “rush” the rudder input, the aircraft will roll and your input to counteract this will be demanding an opposite roll. Once you touchdown and Ground Law takes over, understand these changes too.
If you are making corrections to aim point or the Autothrust is reacting to speed changes as you pass through 100’, you may now have an out of trim aircraft, so flare as required not from memory.
Finally, treat this aircraft like a conventional aircraft whilst considering the above and don’t forget to keep your sky pointer in your scan and you’ll get your head around her.

Sorry for the lengthy post and good luck.
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Old 24th Sep 2022, 07:38
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The environment keeps displacing any aircraft from it's present State. The question is how to restore the status quo in Airbus. Correct that's not in order like any other aircraft but after that leave it alone. As posted previously input to change but not to maintain flight path. It's definitely different but easier not difficult.
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Old 24th Sep 2022, 10:42
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Originally Posted by Mooneyboy View Post
Thankyou everyone for your replies and insights. Genuinely very helpful.

Uplinker did try and find that video on YouTube o the Tornado sidestick but sadly couldn’t find it.
Sorry, I cannot offer an address for it - I just happened to see it somewhere down a youtube rabbit hole one day.

The Tornado was flying up a valley in Wales or Scotland I think, and you saw a view over the pilot's shoulder of his cockpit. You heard him say to his navigator through his oxygen mask, "I am coming left 10°". You could see his hand on the joystick, and he just went: nudge nudge, In other words; nudge - centre - nudge - centre, in very quick succession of less than a second - more of a digital input than an analogue one, almost like clicking a switch. You could see the aircraft bank and then stay in the new attitude he had put it in, without any further inputs from him.

Suddenly, everything about the Airbus Side-stick and FBW made sense for me, and the next time I flew the A320, I operated it in a similar way and it was a revelation to me.
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Old 24th Sep 2022, 11:04
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As well as centring the side-stick between inputs, the thing to realise is how the FBW will assist you; (it never "fights" you, despite what some might say).

In a turbulent approach with say a wing drop, you will sometimes need to hold full opposite side-stick for a couple of moments to pick it up. Meanwhile the FBW will be doing the same. You have 25°, the FBW has 15°, so between you and the FBW, you have the 40° roll demand*.

The crucial thing to do is: As soon as the wing starts picking up, bring the side-stick back to neutral - to reach side-stick centre neutral at the same moment the aircraft reaches zero bank. If you hold the side-stick over until you have zero bank, you will bank too far the opposite way and get into a PIO.

*Please note the figures I give here are from memory - no time to check, but it is the principle that is important.
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Old 24th Sep 2022, 14:33
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Originally Posted by Uplinker View Post
....In a turbulent approach with say a wing drop, you will sometimes need to hold full opposite side-stick for a couple of moments to pick it up. Meanwhile the FBW will be doing the same. You have 25°, the FBW has 15°, so between you and the FBW, you have the 40° roll demand*.
Hi Uplinker, This is where we differ in our understanding of the system.
From FCOM Normal Law Roll Control:
"When the aircraft is in the “in flight” mode, normal law combines control of the ailerons, spoilers (except N° 1 spoilers), and rudder (for turn coordination). ….. it also limits the roll rate and bank angle, coordinates the turns, and damps the dutch roll.
The roll rate requested by the flight crew during flight is proportional to the sidestick deflection, with a maximum rate of 15 °/s when the sidestick is at the stop."

The instinctive reaction to a wing drop is to do as you say and use full side stick - but it is only necessary to hold a small side stick deflection to request say 5 °/s roll rate. The FBW system will now command up to full aileron / spoiler deflection to achieve that requested roll rate.

I have found myself reverting to previous Boeing type handling in roll during turbulence and had to remind myself to only give small roll requests on the side stick in order to avoid PIO.
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Old 24th Sep 2022, 15:13
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OK maybe it is the other way round: 15° and 25° instead of what my dodgy memory tells me.

I am not sure which of us is correct about the FBW - I just know that I have had times on turbulent approach while holding full side-stick deflection to pick up a wing when I have thought: if this doesn't respond in the next 2 seconds; I am going around.

.

Last edited by Uplinker; 29th Sep 2022 at 09:52. Reason: clarification
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