Discus 2 rudder stiff help please

[India November[_2_]]

The rudder on my D2b has become very stiff on its hinges during this season.. I disconnected the cables at the rudder horn, and it's clear the problem is in the rudder not elsewhere in the control circuit. Removed mylar seals without effect. No visible damage to the rudder, and no foreign objects visible between rudder and fin. Before I remove the rudder, has anyone out there encountered a similar problem? Glider has 650hrs TT, always hangared.

Thanks in advance for all suggestions!
Ian IN

[Tim Taylor]

On Monday, August 26, 2019 at 5:55:09 AM UTC-6, India November wrote:
> The rudder on my D2b has become very stiff on its hinges during this season. I disconnected the cables at the rudder horn, and it's clear the problem is in the rudder not elsewhere in the control circuit. Removed mylar seals without effect. No visible damage to the rudder, and no foreign objects visible between rudder and fin. Before I remove the rudder, has anyone out there encountered a similar problem? Glider has 650hrs TT, always hangared.
>
> Thanks in advance for all suggestions!
> Ian IN

The rudder rides on two surfaces that you could try to lube without removing the rudder. A lubricant with an extension nozzle should reach both. That said,
the rudder is relatively easy to remove (one nut). It is probably a good idea to remove it and clean the hinge points properly.

[Bravo 8]

On Monday, August 26, 2019 at 7:55:09 AM UTC-4, India November wrote:
> The rudder on my D2b has become very stiff on its hinges during this season. I disconnected the cables at the rudder horn, and it's clear the problem is in the rudder not elsewhere in the control circuit. Removed mylar seals without effect. No visible damage to the rudder, and no foreign objects visible between rudder and fin. Before I remove the rudder, has anyone out there encountered a similar problem? Glider has 650hrs TT, always hangared.
>
> Thanks in advance for all suggestions!
> Ian IN

I've got an ASW19B with a similar issue. I've adjusted the nut at the bottom of the rudder with no affect. I too would appreciate any suggestions. And thanks!

[[email protected]]

Is the gap between the rudder and fin skin OK? Check it by sliding 80 grit sandpaper in the gap with smooth side towards the rudder. Run it all the way up and down on both sides, all gaps should be free, sand till it is.Spray lube both hinge points.
JJ

[[email protected]]

Do you use an overboard type relief system?

[Eric Munk]

At 14:06 26 August 2019, wrote:
>Do you use an overboard type relief system?
>
If so, corrosion in the lower rudder hinge usually is the culprit.

[Mike the Strike]

Agree, hinges are the most likely problem. Definitely worth removal for an inspection of any possible damage from corrosion. If OK, clean and lube should fix.

Mike

[Craig Funston[_3_]]

On Monday, August 26, 2019 at 7:05:05 AM UTC-7, wrote:
> Is the gap between the rudder and fin skin OK? Check it by sliding 80 grit sandpaper in the gap with smooth side towards the rudder. Run it all the way up and down on both sides, all gaps should be free, sand till it is.Spray lube both hinge points.
> JJ

JJ, it's likely there are "V" seals in addition to the standard mylar seals.. Running sandpaper in the gap will likely destroy those seals.

Ian, the rudder comes off fairly easily with just removal of a single nut at the bottom of the rudder. I haven't looked specifically at the Discus, but if it's like all the other SH aircraft I've worked on, there's a castellated nut secured by a cotter pin. The cotter pin can be accessed by pushing the rudder to full deflection. Once the nut is off the rudder can be shifted upward and it will come off the hinge pins. It's helpful to remove the rudder cables first.

It may be time for new V-seals or cleaning and lubrication of the plain bearings. There's no mechanical reason why it should be stiff.

Hope all goes well. If there's any question, get it to an aircraft mechanic for some help.

Cheers,
Craig

[krasw]

On Monday, 26 August 2019 16:47:27 UTC+3, Bravo 8 wrote:
> On Monday, August 26, 2019 at 7:55:09 AM UTC-4, India November wrote:
> > The rudder on my D2b has become very stiff on its hinges during this season. I disconnected the cables at the rudder horn, and it's clear the problem is in the rudder not elsewhere in the control circuit. Removed mylar seals without effect. No visible damage to the rudder, and no foreign objects visible between rudder and fin. Before I remove the rudder, has anyone out there encountered a similar problem? Glider has 650hrs TT, always hangared.
> >
> > Thanks in advance for all suggestions!
> > Ian IN
>
> I've got an ASW19B with a similar issue. I've adjusted the nut at the bottom of the rudder with no affect. I too would appreciate any suggestions. And thanks!

There is a brass bushing inside lower hinge. This has worn short over time. You notice this by tightening the lower nut, rudder has no vertical play anymore and bolt is crushing the hinge. Replace brass bushing and you are good to go. Note, rudder must ALWAYS have vertical play, even when nut is tight. If there is no play, bushing is not doing it's job.

[Charlie M. (UH & 002 owner/pilot)]

Totally agree....
Minor bit....as swiping the coarse sandpaper between rudder and fin, move rudder maybe 20* and try again.
Do NOT assume the front radius on the rudder is constant....... may be fine in spots, my bind in others.
Yes, sounds like check binding between rudder and fin....if OK.....pull rudder, clean stuff (WD-40 can work here), lube and go from there...

[India November[_2_]]

On Monday, August 26, 2019 at 7:55:09 AM UTC-4, India November wrote:
> The rudder on my D2b has become very stiff on its hinges during this season. I disconnected the cables at the rudder horn, and it's clear the problem is in the rudder not elsewhere in the control circuit. Removed mylar seals without effect. No visible damage to the rudder, and no foreign objects visible between rudder and fin. Before I remove the rudder, has anyone out there encountered a similar problem? Glider has 650hrs TT, always hangared.
>
> Thanks in advance for all suggestions!
> Ian IN

Thanks to all for helpful comments. I did start using an overboard relief system this season using the factory-installed tube. This is #1 suspect. Next step...take the rudder off with my AME's help.
Ian IN

[Dave Nadler]

On Monday, August 26, 2019 at 8:55:09 PM UTC-4, India November wrote:
> On Monday, August 26, 2019 at 7:55:09 AM UTC-4, India November wrote:
> > The rudder on my D2b has become very stiff on its hinges...
> ...I did start using an overboard relief system this season using
> the factory-installed tube. This is #1 suspect.

Ian, Obviously, you need a Mark VIII:
https://www.youtube.com/watch?v=QEJJb_ufo8A

Make sure you pull rudder, deal with any corrosion and bushing wear,
and for heavens sake use proper grease and not WD-40 when re-installing.

[[email protected]]

On Monday, August 26, 2019 at 5:55:09 AM UTC-6, India November wrote:
> The rudder on my D2b has become very stiff on its hinges during this season. I disconnected the cables at the rudder horn, and it's clear the problem is in the rudder not elsewhere in the control circuit. Removed mylar seals without effect. No visible damage to the rudder, and no foreign objects visible between rudder and fin. Before I remove the rudder, has anyone out there encountered a similar problem? Glider has 650hrs TT, always hangared.
>
> Thanks in advance for all suggestions!
> Ian IN

If you are using the factory pee system, it will corrode the rudder horns. removing the rudder is easy as are the repairs and have been explained in other text. When you disconnect the rudder cables, be sure to attach a section of safety wire as the cables are spring loaded and may retract into the fus which will make retrieval of the cables difficult.

[India November[_2_]]

I had heard of corrosion issues from Dave Nadler et al and was closely watching the visible rudder horns and cable ends. I didn't imagine the internal parts could be affected first. We'll see when I get the rudder off. Good point about attaching safety wire. The cable ends retracted about 3 inches inside the fuselage when I removed the bolts.
Ian

[Dave Nadler]

On Tuesday, August 27, 2019 at 1:24:06 AM UTC-4, wrote:
> When you disconnect the rudder cables, be sure to attach a section
> of safety wire as the cables are spring loaded and may retract into
> the fus which will make retrieval of the cables difficult.

Really now, don't go spoiling the entertainment value for onlookers...

[Dave Nadler]

On Tuesday, August 27, 2019 at 8:17:45 AM UTC-4, India November wrote:
> I had heard of corrosion issues from Dave Nadler et al...
> I didn't imagine the internal parts could be affected...

Ian, internal corrosion is shown in the video:
https://www.youtube.com/watch?v=QEJJb_ufo8A

[[email protected]]

Better than that, bungee the rudder pedals back and relieve spring pressure and way easier to remove and replace the bolts holding the cables.

[[email protected][_2_]]

Better
Use string on the cable, when installing, pull string to position cable...drop in bolt....razor knife string.
No untying, unwinding, wires in the way.
Attach string first before removing bolt.
R

[rudolph stutzmann]

On Tuesday, August 27, 2019 at 8:41:54 AM UTC-4, Dave Nadler wrote:
> On Tuesday, August 27, 2019 at 8:17:45 AM UTC-4, India November wrote:
> > I had heard of corrosion issues from Dave Nadler et al...
> > I didn't imagine the internal parts could be affected...
>
> Ian, internal corrosion is shown in the video:
> https://www.youtube.com/watch?v=QEJJb_ufo8A

With our ships relief tube system, we have the tube that extends approx. 18" out the bottom of the ship; when using I bank and try to keep about 30 degrees of slip on the yaw string, hoping to keep everything clear of the fuselage....

[Karl Striedieck[_2_]]

Situations like this can be avoided if the annual inspections are done properly. Both the rudder and the seat pan must be removed to catch problems. When I was the dealer for a German company years ago I and the company were sued for a fatal crash where the flight controls under the seat pan were compromised. This happened because water had puddled under the seat pan and the ship was parked in a hangar with the tail elevated. The seat pan had never been removed.

Regarding rudder hinges, they are prone to corrosion from wing water dumping, flying through rain, tail ballast dumping and, especially, urine contamination. A friend had to replace the lower rudder hinge in his D2 due to corrosion.

Removing the rudder and seat pan annually is a must.

KS

[India November[_2_]]

On Tuesday, August 27, 2019 at 8:41:54 AM UTC-4, Dave Nadler wrote:
> On Tuesday, August 27, 2019 at 8:17:45 AM UTC-4, India November wrote:
> > I had heard of corrosion issues from Dave Nadler et al...
> > I didn't imagine the internal parts could be affected...
>
> Ian, internal corrosion is shown in the video:
> https://www.youtube.com/watch?v=QEJJb_ufo8A

Thanks Dave, yes I see you holding what looks suspiciously like a S-H rudder horn. :(

[Frank Whiteley]

On Tuesday, August 27, 2019 at 6:40:25 AM UTC-6, Dave Nadler wrote:
> On Tuesday, August 27, 2019 at 1:24:06 AM UTC-4, wrote:
> > When you disconnect the rudder cables, be sure to attach a section
> > of safety wire as the cables are spring loaded and may retract into
> > the fus which will make retrieval of the cables difficult.
>
> Really now, don't go spoiling the entertainment value for onlookers...

Dang, ran out of popcorn, but put it on the shopping list. Doesn't look like Amazon.com has one day delivery yet.

[[email protected]]

I’ll second Karl’s remarks. I remember a pilot at a Nationals that had a tow hook that was jammed........wouldn’t budge! I told him to pull the seat and we found a tow pulley that was sitting in water from a leaky wing bag..........he said the bag had always leaked. The problem comes from situation known as dissimilar metal corrosion. Usually, the brass bushing and steel bolt + water will set up an electrolytic action..........aka a little battery! Our little battery needs water to make it work and it works even better if it finds salt water or urine. The little battery hates lubrication, so inspect and lube everything you can git to, every year!
JJ

[India November[_2_]]

Thanks to everyone who posted suggestions. I appreciate your help.

Having now disassembled the rudder with my AME, the answer seems to be that the retaining nut was too tight.

The rudder on this ship is kept in place by an M8 metal locknut and washer on the lower pivot pin. On disassembly, the nut was hard to turn at first. After loosening by 1/2-turn the rudder moved freely. Upon removing the rudder the bronze bushing and washer on the lower pivot had bright mating faces showing sliding contact.

Not so clear is why the nut had become overtight. The rudder never been taken off. One theory is that the nut worked itself tighter through friction as the rudder moved.

No significant corrosion was seen on the rudder horn, bearing or mounts.

On reassembly after cleaning and lubrication and with a new metal locknut my AME could reproduce the issue by tightening the nut against the bearing. After backing off the nut slightly to give slight clearance the rudder moves freely.

Some pics here if anyone wishes to take a look. https://1drv.ms/u/s!Al9GDrAowZRAi59DtaN_UVgdwaIqCA?e=jhOKn8

Ian IN

[Nyal Williams[_3_]]

On Monday, August 26, 2019 at 7:55:09 AM UTC-4, India November wrote:
> The rudder on my D2b has become very stiff on its hinges during this season. I disconnected the cables at the rudder horn, and it's clear the problem is in the rudder not elsewhere in the control circuit. Removed mylar seals without effect. No visible damage to the rudder, and no foreign objects visible between rudder and fin. Before I remove the rudder, has anyone out there encountered a similar problem? Glider has 650hrs TT, always hangared.
>
> Thanks in advance for all suggestions!
> Ian IN

Do you have a bladder relief exit on the fuselage behind the gear? Urine can run backward and up to the first hinge point and cause problems there. If that is the case, move the exit from where it is and to one side of the landing gear structure and have the tube clear the ground a couple of inches. This means you must lower the gear before urinating.

[Bob Kuykendall]

On Sunday, September 8, 2019 at 6:51:03 PM UTC-7, India November wrote:

> ...The rudder on this ship is kept in place by an M8 metal locknut and washer on the lower pivot pin. On disassembly, the nut was hard to turn at first. After loosening by 1/2-turn the rudder moved freely...

> ...On reassembly after cleaning and lubrication and with a new metal locknut my AME could reproduce the issue by tightening the nut against the bearing. After backing off the nut slightly to give slight clearance the rudder moves freely...

Very interesting. In the US, that arrangement would probably never pass muster for 14CFR Part 23 certification. AC43.13 requires that a nut on a pivot bolt subject to rotation must be secured with a cotter pin.

Relying on the self-locking feature of a nut to prevent overtightening or loss of the nut (and failure of a primary flight control system) is quite suboptimal. As you have already observed, relatively little deterioration of the nut or the pivot bolt is required to result in failure of this connection.

--Bob K.

[[email protected]]

As delivered, the ship came with Schempp-Hirth standard brass bushing and brass washer which allows the self-locking nut to be tightened up completely and the rudder will still move freely. Not uncommon to find the brass washer installed upside-down or missing and replaced with a standard washer. In either case, tightening the nut will produce a stiff rudder.
JJ

[krasw]

On Tuesday, September 10, 2019 at 10:07:23 PM UTC+3, wrote:
> As delivered, the ship came with Schempp-Hirth standard brass bushing and brass washer which allows the self-locking nut to be tightened up completely and the rudder will still move freely. Not uncommon to find the brass washer installed upside-down or missing and replaced with a standard washer. In either case, tightening the nut will produce a stiff rudder.
> JJ

I was a bit amazed that op, provided with necessary knowledge about lower hinge bushing, managed to not get it replaced by proper part, and still get it signed off by AME.