Blanik L23 Pneumatic Strut Part Needed

[Six-Seven]

This is a long shot.

Our nitrogen filled pneumatic gear strut (shock absorber) on a Blanik L23 is flat. It appears that the fill valve is defective. Blanik America says that the factory is on summer vacation and it will be weeks to get the part we need.

Here is a picture of the part in question ==> https://dl.dropboxusercontent.com/u/238872560/2014-07-24%2012.56.59.jpg. FYI - What appears to be a schrader valve in the assembly is not.

Does anyone have a replacement fill valve or the entire strut assembly for sale?

Please contact me at 847-844-8776 or via email jhderosa <at> yahoo.com.

Thanks, John

[Bill D]

On Friday, July 25, 2014 11:28:34 AM UTC-6, Six-Seven wrote:
> This is a long shot.
>
>
>
> Our nitrogen filled pneumatic gear strut (shock absorber) on a Blanik L23 is flat. It appears that the fill valve is defective. Blanik America says that the factory is on summer vacation and it will be weeks to get the part we need.
>
>
>
> Here is a picture of the part in question ==> https://dl.dropboxusercontent.com/u/238872560/2014-07-24%2012.56.59.jpg. FYI - What appears to be a schrader valve in the assembly is not.
>
>
>
> Does anyone have a replacement fill valve or the entire strut assembly for sale?
>
>
>
> Please contact me at 847-844-8776 or via email jhderosa <at> yahoo.com.
>
>
>
> Thanks, John

IIRC, that's a standard US made Schrader valve. (Looks like a tire valve core on steroids.) Try unscrewing the valve, photographing it and emailing the photo to a supplier to see if they can match it. Start with:
https://www.schraderinternational.com/Products/Valves?sc_lang=en-us-e

[Six-Seven]

> IIRC, that's a standard US made Schrader valve. (Looks like a tire valve core on steroids.) Try unscrewing the valve, photographing it and emailing the photo to a supplier to see if they can match it. Start with:
>
> https://www.schraderinternational.com/Products/Valves?sc_lang=en-us-e

Thanks for the comments. I am unsure if this is a "standard" (i.e. car/bicycle tire) schrader valve. I looked at two L23's and there is no central "pin" in the middle. The central pin and spring is what holds a standard shrader valve shut as there is seldom much pressure on the other side. However, in this strut the pressure is 100's of pounds (3.3MPa = 460PSI) so the pressure itself holds the valve closed.

In the working L23 I can put a screw driver on the valve and unscrew the valve from the housing. On the broken L23 the valve just spins. My thinking is that the valve housing was stripped by someone applying too much mechanical pressure to it. So I believe I need the entire valve assembly (valve and housing) replaced.

[Boise Pilot]

Pretty sure this is the same part that was used on the Blanik L-13. I know there are a few of them around that are hangar queens due to the AD. Try that resource.





On Friday, July 25, 2014 11:28:34 AM UTC-6, Six-Seven wrote:
> This is a long shot.
>
>
>
> Our nitrogen filled pneumatic gear strut (shock absorber) on a Blanik L23 is flat. It appears that the fill valve is defective. Blanik America says that the factory is on summer vacation and it will be weeks to get the part we need.
>
>
>
> Here is a picture of the part in question ==> https://dl.dropboxusercontent.com/u/238872560/2014-07-24%2012.56.59.jpg. FYI - What appears to be a schrader valve in the assembly is not.
>
>
>
> Does anyone have a replacement fill valve or the entire strut assembly for sale?
>
>
>
> Please contact me at 847-844-8776 or via email jhderosa <at> yahoo.com.
>
>
>
> Thanks, John

[Six-Seven]

Here is an update and questions on the original thread about needing a strut part - the fill valve. We now have not one but two different (used) parts from an L13 I am working with at this point. Pictures and Blanik manual documentation can be found at http://aviation.derosaweb.net/Blanik

One replacement part is the original Blanik type that connects to the Blanik T-handle fill apparatus (and then to a nitrogen bottle) via a sort of ball and socket affair. The internal valve itself is held in check inside the fitting by a spring that is part of the assembly and depressed by the T-handle. There appears to not be any rubber seal of any sort in the fitting or the adapter, just a metal on metal seal. The original fitting leaked big time at this ball/socket joint while the new one leaks just a little. We tried to fill the strut to ~450PSI but no joy with this assembly.

Now onto valve style #2. This uses a standard Schrader valve insert like on a car/cycle/bike. I heard from a couple of quarters that this is a US adaptation so that they didn't have to buy the Blanik fill adapter. The question is how to marry this with our nitrogen bottle. I was able to locate the correct brass fitting for the bottle's hose end (flare) that gives me 1/8" NPT which I can adapt that to most anything. But what do I do at the Schrader valve end? The idea of holding a standard chuck against the valve at 450 psi doesn't seem quite rational. Is there such a thing as a screw on chuck? Can't find one from any of several sources (Napa, Grainger, McMaster, etc).

Questions
======
- Is it possible to safely hand-hold 450 psi at the valve?
- We assume the strut should be filled without having to raise the fuselage to unload the strut. Yes? We tried it both ways and it didn't matter.
- The manual (see http://aviation.derosaweb.net/Blanik) alludes to filling the strut with liquid "only in the vertical position". Has anyone done this? Is the strut X% hydralic fluid and Y% nitrogen? How much is X and Y?
- The manual says at fully inflated the distance X (Fig 301) on the strut should be 13mm (about 1/2"). This location is conveniently located under the strut boot. Sigh.
- Does it appear that the strut is just BAD? Can it be rebuilt?
- How have you filled the strut?
- Anyone know of a back issue of Soaring mag. that deals with all this?

Any advice is welcome.

Thanks, John

[Mark628CA]

Some Oxygen fill systems use Schrader valves, and an adapter from the CGA-540 fitting on O2 cylinders to Schrader fittings (with a screw-on nut) is available from Mountain High Equipment & Supply. And since 2,000 psi is fairly standard with O2, you should be OK.

I can't find the part number on the website, but you could call Eric at 800 468-8185 and ask him. I think they are around $95. Not cheap, but it is an idea.

[Tim Taylor]

Most aircraft shops have a nitrogen tank with the correct fitting. Same fittings are used on aircraft struts.

[Bob Kuykendall]

On Sunday, August 10, 2014 8:10:41 PM UTC-7, Six-Seven wrote:
> ...Is there such a thing as a screw on chuck?...

Aircraft Spruce and Specialty part number 06-11700.
http://www.aircraftspruce.com/catalog/lgpages/gooseneck.php?clickkey=342208

Thanks, Bob K.
https://www.facebook.com/pages/HP-24-Sailplane-Project/200931354951

[Frank Whiteley]

On Sunday, August 10, 2014 9:10:41 PM UTC-6, Six-Seven wrote:
> Here is an update and questions on the original thread about needing a strut part - the fill valve. We now have not one but two different (used) parts from an L13 I am working with at this point. Pictures and Blanik manual documentation can be found at http://aviation.derosaweb.net/Blanik
>
>
>
> One replacement part is the original Blanik type that connects to the Blanik T-handle fill apparatus (and then to a nitrogen bottle) via a sort of ball and socket affair. The internal valve itself is held in check inside the fitting by a spring that is part of the assembly and depressed by the T-handle. There appears to not be any rubber seal of any sort in the fitting or the adapter, just a metal on metal seal. The original fitting leaked big time at this ball/socket joint while the new one leaks just a little. We tried to fill the strut to ~450PSI but no joy with this assembly.
>
>
>
> Now onto valve style #2. This uses a standard Schrader valve insert like on a car/cycle/bike. I heard from a couple of quarters that this is a US adaptation so that they didn't have to buy the Blanik fill adapter. The question is how to marry this with our nitrogen bottle. I was able to locate the correct brass fitting for the bottle's hose end (flare) that gives me 1/8" NPT which I can adapt that to most anything. But what do I do at the Schrader valve end? The idea of holding a standard chuck against the valve at 450 psi doesn't seem quite rational. Is there such a thing as a screw on chuck? Can't find one from any of several sources (Napa, Grainger, McMaster, etc).
>
>
>
> Questions
>
> ======
>
> - Is it possible to safely hand-hold 450 psi at the valve?
>
> - We assume the strut should be filled without having to raise the fuselage to unload the strut. Yes? We tried it both ways and it didn't matter.
>
> - The manual (see http://aviation.derosaweb.net/Blanik) alludes to filling the strut with liquid "only in the vertical position". Has anyone done this? Is the strut X% hydralic fluid and Y% nitrogen? How much is X and Y?
>
> - The manual says at fully inflated the distance X (Fig 301) on the strut should be 13mm (about 1/2"). This location is conveniently located under the strut boot. Sigh.
>
> - Does it appear that the strut is just BAD? Can it be rebuilt?
>
> - How have you filled the strut?
>
> - Anyone know of a back issue of Soaring mag. that deals with all this?
>
>
>
> Any advice is welcome.
>
>
>
> Thanks, John

Perhaps others can confirm. I seem to recall an anecdote about there being a bleed hole that the seal passes if the strut is fully collapsed. Thus you need to extend the strut while elevating the tail before filling because if you do it when filling it may be possible for the strut to expand fast enough under high pressure to launch the glider several feet into the air once the seal moves past the bleed hole.

Frank Whiteley

[Six-Seven]

We just bought the following item which is similar. but fancier, than the Aircraft Spruce unit mentioned by Bob K.

http://www.skygeek.com/ats-556.html

The saga continues.

- John

[[email protected]]

On Monday, August 11, 2014 at 7:29:04 PM UTC-6, Oscar-Hotel-Mike wrote:
> We just bought the following item which is similar. but fancier, than the Aircraft Spruce unit mentioned by Bob K.
>
> http://www.skygeek.com/ats-556.html
>
> The saga continues.
>
> - John

John,

Considering a similar solution for our L-23. Did that part work for you?

[Stephen Damon]

Frank is correct on the strut being able to make the glider jump like a low rider. Pressure should be between 750 and 950 lbs.