Why are side sticks unpopular in sailplanes

On Sun, 19 Feb 2017 05:08:07 -0800, Tango Eight wrote:

On Sunday, February 19, 2017 at 7:14:48 AM UTC-5, J. Nieuwenhuize wrote:
Side sticks seem pretty popular in powered aircraft. Personally like
them.
In sailplanes they have the additional advantage of allowing either a
smaller cockpit (less drag) or more room. Diana, HP18 and several older
designs have them.

Yet, they seem highly unpopular. Why would a well-designed sidesticks
not be liked, just because it's different, or are there reasons I'm
missing?

Had a side stick for a decade. Center stick is just better.

Can you expand a bit, please?

I wondered if the short grip-pivot lever might raise stick forces in roll
and/or coarsen aileron control, but I've flown a DG-300, which has a
similarly short grip-pivot distance on the roll axis as well as the same
sliding pitch motion and don't recall that I found the control feel a lot
different from a centre stick.

The only thing I recall that's comment-worthy is that the DG-300's
'automatic trim' system has a more friction in it than the Libelle's
system, but that has nothing to do with side sticks.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Sunday, February 19, 2017 at 9:59:27 AM UTC-5, Martin Gregorie wrote:
On Sun, 19 Feb 2017 05:08:07 -0800, Tango Eight wrote:

Had a side stick for a decade. Center stick is just better.

Can you expand a bit, please?

Sure. I think the irreducible issue is simply one of leverage and limited motion options. There's only one way to grip the stick, there's only one way to interact with it.

All of the side stick designs I've seen for direct mechanical actuation of controls require a sliding fore/aft motion for elevator (elbow + shoulder) and a rolling motion of the wrist for aileron. Blending those motions with finesse is just more work (more fatigue) than a conventional gimballed stick. I landed out a couple of times in my side stick glider simply because I got tired and sloppy after 4+ hours and couldn't climb well. Coordination never became unconscious in that ship.

The other things that I don't like about side stick equipped gliders tend to be the *reasons* designers opted for side sticks, not the sticks themselves: supine seating position, lousy forward visibility, tiny instrument pods, cockpits with no extra space for anything.

That said, I have always had a desire to fly (but not own!) a Diana2, just because the thing was so radical.

Evan Ludeman / T8

On 2/19/2017 9:02 AM, Tango Eight wrote:
On Sunday, February 19, 2017 at 9:59:27 AM UTC-5, Martin Gregorie wrote:
On Sun, 19 Feb 2017 05:08:07 -0800, Tango Eight wrote:

Had a side stick for a decade. Center stick is just better.

Can you expand a bit, please?

Sure...
(Snip...)

All of the side stick designs I've seen for direct mechanical actuation of
controls require a sliding fore/aft motion for elevator (elbow + shoulder)
and a rolling motion of the wrist for aileron. Blending those motions with
finesse is just more work (more fatigue) than a conventional gimballed
stick. I landed out a couple of times in my side stick glider simply
because I got tired and sloppy after 4+ hours and couldn't climb well.
Coordination never became unconscious in that ship.

"Mercy!" he exclaims about having to landout. I never suffered that particular
fate as a result of my side stick (longest single-flight time 9 hours), but I
concur with the sentiment of that last sentence. Coordinating my Zuni is
another of those things that's "different" about the ship...as was
coordinating my (similarly high-in-roll w. light pitch forces) HP-14 before
it. Not dangerous or difficult, just "not unconscious," as in always on the
fringes of my awareness. But, from my perspective, simultaneously never a
problem, just "different."

FWIW - for readers unfamiliar with the HP-14, HP-18, Zuni designs - Evan's
HP-18 (side stick) and my HP-14 (center stick) are both fully supine designs,
while the (original side-stick-design) Zuni has a "standard semi-reclined"
seating position...with a normally-sized cockpit and instrument pod and view
outside.

I transitioned into my HP-14 with ~200 total hours and put ~200 hours on it
before transitioning into the Zuni. No "German quality" optics on either, the
HP-14 having more distortion thanks to looking though its flat-wrapped forward
canopy section at very shallow in-flight angles. I always found that more of a
"mental nuisance" than I did anything about the fully-reclined seating (*very*
comfortable IMO). Ditto its quite narrow - even for thin, small-framed me -
cockpit with limited sandwich space...though it had eNORmous space atop/after
the spars for water (sucked via tube), multiple O2 tanks, a tent (aerotowed to
a camp once), etc. Of course all visual complaints vanished upon use of
landing flaps (I always used 90-degrees in the HP). So its supine pilot
position may well have been somewhat problematic for old-style,
visually-acquired turnpoints, in contest flying when the HP-14 was designed...

Bob W.

It's probably worth adding that there were a number of factors that made the HP-18 a lot of work to fly well, among them irreducible play in the stick aileron motion, no aileron differential(!!), small tail volume, no hands off stability at all. It wasn't really my intention to blame the wear out factor on the stick location, but it probably came out that way.

-Evan

On Sun, 19 Feb 2017 08:02:38 -0800, Tango Eight wrote:

On Sunday, February 19, 2017 at 9:59:27 AM UTC-5, Martin Gregorie wrote:
On Sun, 19 Feb 2017 05:08:07 -0800, Tango Eight wrote:

Had a side stick for a decade. Center stick is just better.

Can you expand a bit, please?

Sure. I think the irreducible issue is simply one of leverage and
limited motion options. There's only one way to grip the stick, there's
only one way to interact with it.

All of the side stick designs I've seen for direct mechanical actuation
of controls require a sliding fore/aft motion for elevator (elbow +
shoulder) and a rolling motion of the wrist for aileron. Blending those
motions with finesse is just more work (more fatigue) than a
conventional gimballed stick. I landed out a couple of times in my side
stick glider simply because I got tired and sloppy after 4+ hours and
couldn't climb well. Coordination never became unconscious in that
ship.

The other things that I don't like about side stick equipped gliders
tend to be the *reasons* designers opted for side sticks, not the sticks
themselves: supine seating position, lousy forward visibility, tiny
instrument pods, cockpits with no extra space for anything.

That said, I have always had a desire to fly (but not own!) a Diana2,
just because the thing was so radical.

Thanks for the additional detail. Like you I'd like to check out a Diana
2 for comfort and forward visibility and wonder if cricked necks could be
a problem. I entirely understand your point about about panel space.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |