A320 over controlling/PIO fix.

[Mooneyboy]

I’m looking at trying to find reasons reasons for A320 pilots over controlling resulting in PIO.

There’s the obvious factor of not fully understanding the airbus FBW concept but I’m more looking at effects of seat and armrest positions causing over controlling the sidestick.

I think there’s an airbus article saying armrest position can negatively effect physical control of the sidestick but I’m wondering what the extremes could mean? For example would too high armrest position does this result in not enough control? Too low an armrest position too much?

Likewise with pedal positions. I’ve seen 6ft tall pilots have pedal positions at 2 or 3. Surely this could result in strange arm settings and thus increase chance of over controlling?

I’m interested in finding a correlation between over controlling and physical seat/armrest position so hopefully can help with over controlling in not just inexperienced but also experienced crew.

Would be interested to hear other viewpoints or advice on fixing this. Thanks

[FlightDetent]

Don't know why but this resurfaced back to consciousness...

[Goldenrivett]

I’m looking at trying to find reasons reasons for A320 pilots over controlling resulting in PIO

If this is happening in the simulator, then turn the motion off for a while. Sometimes the lag between input and expected motion clue can affect some pilots more than others.

If this is happening in real life - then let go of the stick between each “nudge of attitude change”.

[Mooneyboy]

Originally Posted by Goldenrivett

If this is happening in the simulator, then turn the motion off for a while. Sometimes the lag between input and expected motion clue can affect some pilots more than others.

If this is happening in real life - then let go of the stick between each “nudge of attitude change”.

Thanks for the reply. Very much looking on the line not the sim. Yes I think this method certainly helps let’s say down to a 100ft but below that and into the flare I’m not so sure ( just trying to think what I do).

What sometimes surprises me is on turnarounds is the vastly different pedal and arm rest positions for pilots of roughly the same proportions. I also see different ways pilots handle the aircraft and wondered wether there’s a link as the airbus magazine suggested.

Getting back to basics if you have a brand new pilot to the A320 how are they taught to find the right pedal and armrest positions?

[Goldenrivett]

Yes I think this method certainly helps let’s say down to a 100ft but below that and into the flare I’m not so sure.

This picture from DSC-27-20-10 Normal Law shows that Lateral Control control is still in Normal Law until touchdown (then blends into Ground Mode over 0.5 sec). Most PIO I've witnessed below 100 feet was in Roll because of continued roll input whilst applying back pressure during the flare. Roll control must still be "nudged" rather than held.

Whilst on the ground, I suggest you ask your student to show that that they can hold a bit of constant back pressure whilst they "nudge" a roll input left then right. If they can't - then get them to change their arm rest position until they can.

[nickler]

Originally Posted by Mooneyboy

I’m looking at trying to find reasons reasons for A320 pilots over controlling resulting in PIO.

There’s the obvious factor of not fully understanding the airbus FBW concept but I’m more looking at effects of seat and armrest positions causing over controlling the sidestick.

I think there’s an airbus article saying armrest position can negatively effect physical control of the sidestick but I’m wondering what the extremes could mean? For example would too high armrest position does this result in not enough control? Too low an armrest position too much?

Likewise with pedal positions. I’ve seen 6ft tall pilots have pedal positions at 2 or 3. Surely this could result in strange arm settings and thus increase chance of over controlling?

I’m interested in finding a correlation between over controlling and physical seat/armrest position so hopefully can help with over controlling in not just inexperienced but also experienced crew.

Would be interested to hear other viewpoints or advice on fixing this. Thanks

On SIM day 1 of any airbus fbw type rating in the history trainees are told how to “consider” the side stick to avoid PIO. The abundance nowadays of politically correct makes it difficult to use the same comparison though.

[iggy]

Originally Posted by Goldenrivett

This picture from DSC-27-20-10 Normal Law shows that Lateral Control control is still in Normal Law until touchdown (then blends into Ground Mode over 0.5 sec). Most PIO I've witnessed below 100 feet was in Roll because of continued roll input whilst applying back pressure during the flare. Roll control must still be "nudged" rather than held.

Whilst on the ground, I suggest you ask your student to show that that they can hold a bit of constant back pressure whilst they "nudge" a roll input left then right. If they can't - then get them to change their arm rest position until they can.

Another thing to teach the trainees that will help them is that, to make a pitch input, the sidestick has to be handled slightly to left hand side (for an FO sitting on the RHS). The ergonomy of the side stick dictates it to be slightly tilted to the left hand side to accomodate to the natural position of the right hand when it is resting. On ground, and with the engines running, ask them to make a pitch-only input on the side stick, and observe the cross on the PFD, Vast majority of them will pull or push the side stick following a perfect vertical motion, making the cross go up (or down), while turning slightly to the right. Let them find their own way with the side stick until they are able to make a pure pitch input, so when they flare they don't inadvertently command a roll as well.

Sounds complicated (even more so when English is not my mother tongue), but once they see it they understand what it is all about.

And, about arm rest position, they should be able to make a round circle on the side stick without having to move or elevate the wrist, to avoid having some positions of the side stick in which they'll be using the full weight of their arm, which may cause them to overcontrol. As for the legs, same old thing: full pressure on either pedal should be achieved with the leg slightly bent, not perfectly straight, to make sure they can hold the pressure without shaking during an engine failure.

About the height, I teach them to find the height where the top frame of the PFD touches the bottom side of the FCU panel, and do to it with the seat in an upright position. Much easier for them to get their visual references right for landing.

No trainee of mine has crashed so far during landing, so I guess these tips helped them...

[iggy]

Originally Posted by nickler

On SIM day 1 of any airbus fbw type rating in the history trainees are told how to “consider” the side stick to avoid PIO. The abundance nowadays of politically correct makes it difficult to use the same comparison though.

During the first sessions I ask the trainees to open the hand if they are not making any input. As soon as they get adapted to normal law they forget about it and leave the hand on the side stick, where it should be.

I started telling them this when I realized that many times they were making random inputs on the side stick without being aware of it, most probably out of pure stress.

In the airplane this also helps them, when I see that they don't stop "stirring the coffee" I tell them to open the hand for one second or so, let the airplane stabilize, and then correct the trajectory, if needed.

[70 Mustang]

Often happens in Cessnas, Pipers and B737s

I had the “mistake” yelled out of me by my first, and best Flight Instructor. He flew Hueys in Vietnam and demanded a soft touch and would not tolerate any over controlling.

[Uplinker]

The SIM phase of my Airbus FBW type rating was badly taught.

The instructor told us nothing about how to set the seat or the rudder pedals or how to control the aircraft, despite my saying more than once that I had never used a side-stick so would need some instruction.

It was day 2 or 3 when I was struggling and making PM and TRE feel sick when he leaned over and said "no wonder you are having difficulty, you're not using the arm rest" I said "what arm rest?". Every day when we got in it had been left vertical, and in the dark cockpit I had never noticed it, and the TRE never said anything about it or how to use it

Also nobody ever gave me any sensible advice about how to use the side-stick and FBW combination, so I was over-controlling and getting into PIOs.

I eventually taught myself how to use it after happening to see a film of a Tornado bomber, which I believe has a similar joystick and FBW system. The Tornado pilot was making inputs to adjust the attitude and returning the 'stick to neutral after every input. And each input was a nudge. So nudge, neutral. nudge neutral etc. Works like a dream. You can hold the 'stick properly in a full pistol grip, as long as you nudge and return to neutral. As soon as the aircraft starts responding to your input; return to neutral. On very turbulent approaches you might need to hold full travel until the aircraft responds - to pick up a wing for example - but as soon as it does, release to neutral.

And of course, if you realise that the FBW will help you by holding the attitude you set, (within reason), your controlling will become an order of magnitude better

[Max Angle]

Interesting to note that the force required to move the stick in roll is different for the outboard and inboard movement, your arm has more strength moving in the inboard direction than the other so to make the stick feel consistent in both directions they used different spring rates.

[vilas]

The purpose of setting arm rest is to remove the forearm involvement in moving the stick. With the forearm involved it is difficult to make precise inputs to side stick. With forearm resting it is easier to make the small inputs that are needed for flight path change with only the wrist. Second, any time the stick is out of neutral it's ordering the computers to change something. So after achieving the intended change to the flight path the stick must neutralized. stick free the Airbus maintains 1g path with whatever bank or wings level. It's intermittent contact handling. Pilot handles controls(side stick) only to change the flight path but not to maintain it. That's done by the aircraft automatically. That's the way it is designed. This needs to be emphasized often initially because it differs from non FBW aircraft. Any undesired aircraft movement is pilot induced and answer to that is to leave the stick alone and start again.

[Vessbot]

Originally Posted by vilas

stick free the Airbus maintains 1g path with whatever bank or wings level

I've never flown an Airbus, but from reading stuff over the years I thought it maintained level flights with no pitch input in turns?

[vilas]

Originally Posted by Vessbot

I've never flown an Airbus, but from reading stuff over the years I thought it maintained level flights with no pitch input in turns?

In a turn it maintains the AoA and bank if within 33°. If in a level, climb or descent stick free it maintains 1g. To elucidate, in a stick free level flight if thrust levers are brought to idle the nose doesn't drop but keeps pitching up trying to maintain 1g path and speed drops.

[vilas]

Originally Posted by Max Angle

Interesting to note that the force required to move the stick in roll is different for the outboard and inboard movement, your arm has more strength moving in the inboard direction than the other so to make the stick feel consistent in both directions they used different spring rates.

Is there any document which says so? Because it only the spring which brings back the stick to neutral and when moved out the rate of roll or g demanded is linear. How a spring could have differential force inboard and outboard is not understood. May be you feel so.

[fab777]

FWIW, I have seen PIO routinely, in any heavy aircraft I have flown: A320/330/350, but also B737/777. The problem lies not so much in the flight control laws, but rather in the fact that some pilots will give an order, and then the opposite order without waiting for the aircraft to complete the first order. Any heavy aircraft has inertia and will take some time before executing what you request from it. Be patient…

[Max Angle]

How a spring could have differential force inboard and outboard is not understood. May be you feel so.

I guess it is probably hydraulic valving rather than springs that creates the different stick force but either way its quite obvious if you hold the stick from above with your other arm and move it side to side, you can clearly feel the different resistance. The fact that nobody notices (as intended) in normal operation shows how well judged the mechanism is.

Here is a scan from "The Airbus Fly-by-wire".

[Dan Winterland]

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.

[FullWings]

Originally Posted by fab777

FWIW, I have seen PIO routinely, in any heavy aircraft I have flown: A320/330/350, but also B737/777. The problem lies not so much in the flight control laws, but rather in the fact that some pilots will give an order, and then the opposite order without waiting for the aircraft to complete the first order. Any heavy aircraft has inertia and will take some time before executing what you request from it. Be patient…

And we have a winner!

It’s a feedback loop and the general answer is to reduce the gain and increase the time constant if you find yourself in the PIO zone. Some pilots make measured, controlled inputs between periods of inactivity and some seem to flail away with the stick/yoke constantly. It’s like the two different kinds of drivers: one saws at the wheel all the time and the other just makes corrections when needed using a relatively soft grip. There must be some kind of primacy here, so it’s really down to their first flight instructor for not teaching them properly and/or sorting it out before it becomes habitual...

[Vessbot]

Originally Posted by vilas

In a turn it maintains the AoA and bank if within 33°. If in a level, climb or descent stick free it maintains 1g. To elucidate, in a stick free level flight if thrust levers are brought to idle the nose doesn't drop but keeps pitching up trying to maintain 1g path and speed drops.

The manual says "In normal turns (up to 33° of bank), the pilot does not have to make any pitch corrections once the turn is established."

Assuming that they mean maintaining altitude through the turn is the task that the pitch corrections (don't) have to be made for, then... it will maintain altitude. Does it actually do that? If so, then then it's increasing AOA and G, and not maintaining them.