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#3520096 - 02/16/12 03:27 PM Q for Pilots on 'Sticks and Gimbals
Gopher Offline
Senior Member

Registered: 01/06/09
Posts: 3459
Loc: London
To you pilots out there, when you're flying the plane, can you "feel" any gimballing system in the stick? (Probably not quite as applicable to yoke flyers.)

To elaborate, with the original Cougar, it had a straight forward gimbal system, whereby you can very clearly (especially with the stock springs) feel when you've crossed over from one axis to the other because the spring tension would go right to zero when passing through the centre before increasing again as you cross the axis.
In modding one of my Suncom sticks, it doesn't have a traditional gimbal but a centre spring, which means that the spring tension is uniform throughout the entire throw of the stick, but also that you can't feel "where" the stick is because you don't have the spring tension going to zero when it lies along an axis. Upshot of that is that is that an aileron roll can slowly turn into a barrel roll if I'm not paying attention.

What's it like in a real tube with engines, wings and a tail? Are there any stick force changes when crossing axes, or is it quite possible for your stick to "drift" if you're not paying attention? (Not that I'm calling you lot bad pilots neaner )


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#3520130 - 02/16/12 04:01 PM Re: Q for Pilots on 'Sticks and Gimbals [Re: Gopher]
Paul Rix Offline
Member

Registered: 07/06/00
Posts: 1983
Loc: NW of Austin, Tx
It all depends on how the aircraft is trimmed. The stick or yoke will naturally want to settle where the resistance is zero. That may not be at the central position though (depending on the trim settings). The Challenger has taken me a bit to get used to because the trim forces felt at the yoke are artificial (it is much more like flying a sim than anything else I have flown so far). The yoke on the Challenger does have a noticeable central position that you can feel as you pass through it, but all the airplanes I flew prior to this one had no such thing . Also bear in mind that trim forces are proportional to airspeed. Hope that helps.
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#3520135 - 02/16/12 04:08 PM Re: Q for Pilots on 'Sticks and Gimbals [Re: Gopher]
BeachAV8R Offline
Lifer

Registered: 01/22/01
Posts: 22684
Loc: KCLT
Indeed. The flight controls will seek the position that results in neutral forces on the stick. If you are sitting on the ramp in something like the Citation the yoke is very heavy if you try to pull it back. At 120 knots the same yoke with the same trim setting is light as a feather as aerodynamic forces "fly" the control surface to the neutral setting.

There is no center "hump" or detent in any of the planes I fly. That might be different in something like the Airbus that has a set center position (?)...
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#3520139 - 02/16/12 04:10 PM Re: Q for Pilots on 'Sticks and Gimbals [Re: Gopher]
BeachAV8R Offline
Lifer

Registered: 01/22/01
Posts: 22684
Loc: KCLT
Oh..and one oddity to the Citation at least is the aileron/rudder interlink. So as you add rudder the yoke is biased to move toward the rudder pedal. The reason for this (partially - adverse yaw is another) is to aid in lifting the wing as you apply rudder if you have an engine failure.

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#3520159 - 02/16/12 04:40 PM Re: Q for Pilots on 'Sticks and Gimbals [Re: Gopher]
Billzilla Offline
Member

Registered: 12/12/99
Posts: 2369
Loc: Brisbane, QLD, Australia
You may not want to know this but ...

On 747's, they are purely a hydraulic flight control system that moves the control surfaces, but the control valves to move the hydraulic rams are positioned by conventional wires that run along the top of the inside of the fuselage down to the tail & wings. The controls, because they would otherwise have no feel at all, are centred by means of springs under the floor and when you move the trim the neutral point of the centring action of those springs is mechanically moved to follow the change.
So wind some nose-down trim in and the big aeroplane accelerates and the hydraulics move the entire stabiliser for you and also move the springs for the elevator under the floor a little so the control columns also move forward a little.]
Feels reasonably natural.

The FBW Airbus's though have a joystick similar to a gaming one, though a very smooth feel to them. They don't don't have the neutral point move at all with trim change and indeed the pilots do not have to make any trim changes for speed or power anyway.

Anyway that's why I've never bothered with artificial feel for gaming sticks as you really don't get any with most real aeroplanes.
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#3520160 - 02/16/12 04:41 PM Re: Q for Pilots on 'Sticks and Gimbals [Re: Gopher]
Gopher Offline
Senior Member

Registered: 01/06/09
Posts: 3459
Loc: London
Thanks for the input guys. It's interesting to hear that a/c sticks don't "centre" the way it does in sims, even in artificial feedback systems, although from an aerodynamic point of view it makes sense.
Thanks again!

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#3520173 - 02/16/12 04:58 PM Re: Q for Pilots on 'Sticks and Gimbals [Re: Gopher]
bogusheadbox Offline
Opinionated Aussie Bloke
Member

Registered: 03/14/06
Posts: 1432
Airbus is just like your couger. Fly by wire systems so all we have is the spring tension in the sidestick.

The stick will always sit in neutral position and with control checks, you can definitely feel when passing the neutral point in both axis (or is it axises?)

As bill said, no stick neutral position change with trim. Though we do have a trim wheel, unless in manual reversion (mechanical backup), we never touch it.

Fly by wire does take out a lot of the feel, but with some clever programming that is made better. For instance, when entering the flare, a conventional aircraft will feel the increased force on the stick. Not so in the airbus, it has (for best intentional purposes) a couger as a contoller. So when approching close to ground, the airbus will give you a small nose down trim to make you pull back a little more on the stick and give you that flare sensation.





Edited by bogusheadbox (02/16/12 05:11 PM)
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#3520296 - 02/16/12 07:30 PM Re: Q for Pilots on 'Sticks and Gimbals [Re: Gopher]
tomcat Offline
Senior Member

Registered: 10/27/99
Posts: 2623
Loc: Halifax, NS, Canada
Cue the "This is why SimHQ is great" comments... Great thread!

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#3520453 - 02/17/12 02:10 AM Re: Q for Pilots on 'Sticks and Gimbals [Re: tomcat]
wheelsup_cavu Offline
Lifer

Registered: 12/03/08
Posts: 20404
Loc: Corona, California
Originally Posted By: tomcat
Cue the "This is why SimHQ is great" comments... Great thread!

+1


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