J/K model speed brake cable replacement

[Guest]

1 hour ago, airmocha said:

Ok so I just read the supplement in my POH, and they ARE vacuum actuated with suction from the vacuum system (no discussion of whether the standby would work or not), and NOT engine vacuum.

Sorry for the wasted time. Didn't have the POH handy earlier and, like I said, when I'd read the description before it just didn't strike me as odd enough to recall, at least not for a year. Curious to me that the system is termed DRC, for Descent Rate Control, by PreciseFlight. Almost made me skip that supplement because I was searching for the term "Speed Brakes."

The supplement mentions using 20" and 2200 rpm as a good power setting for descents, "to keep the engine warm." I've occasionally used lower MP settings than that for slow cruise, but the lower airspeeds and closed cowl flaps keep the jugs around 270-280, so I wouldn't think that could be harmful.

Any info to the contrary?

Onward and downward!

I believe that either the engine driven vacuum pump or the standby pump will power the speed brakes.

Clarence

[jetdriven]

Yes but according to Precise flight you can’t remove the engine-driven vacuum pump.  They must work when actuated and the standby vacuum is not approved for continuous duty 

[carusoam]

9 hours ago, airmocha said:

Carusoam, apologies if I'm wasting any of your time or seeming to be trying to come off as overqualified. I'd been under the impression I could relax and would be among friends here. I was actually trying to save others' time explaining basics to me by summarizing my background.

I will try to post a pic soon. Holidays are upon us now, no time at the moment.

I do dispute the idea that vacuum might be ever-available in all or even most gotta-get-down-fast scenarios, particularly when/if avoiding shock-cooling is a/the goal. it sure sounds like the vacuum-powered kind are what I have. Shocker, I know, but I'll admit I'm not educated enough to know, but I feel like I can sanely envision a couple ways in which a turbocharged engine with a still-functioning exhaust/intake system but severe issues in another area (such as a busted fuel line, for example, which could be feeding a fire at FL240, etc.) could still, perhaps even unavoidably, develop super-atmospheric pressure - particularly up where atmospheric is down in the teens of inches Hg. My understanding is that a closed or partially-closed throttle AND an engine spinning fast enough to create vacuum downstream of the throttle would be necessary, but I'm not even pretending to know.

Again, Merry Christmas.

Mocha,

Trust me when I say this... you are amongst friends...

My ability to write in a friendly manner has been disrupted... so, I am continuously working on this writing skill...

 

There isn’t any time wasted...

It is all about getting you the information that you want/need...

... and to do that, often requires a bunch of input from the user...

 

I’m the front line kinda guy... trying to point people in the proper direction...

Often collecting enough info so that when the big cannons like doc and Paul arrive, they have enough info to work with...

I’m retired, I have plenty of time...

The big cannons seem to be working full time still... before coming to work here too...  

 

MS is an amazing community...

Go MS!

Best regards, happy holidays, and Merry Christmas too...

-a-

[airmocha]

Thanks and Merry Christmas, M20Doc! If I'm reading that diagram correctly (miracles DO occasionally happen), pneumatic lines may be carrying carrying the force (vacuum) out to a separate actuator in each wing, then, and the cables would then be relatively small/short, running only between each wing's pair of brakes and their dedicated actuator? So they wouldn't be exposed to much and only very slowly, if ever, rust.

Part #26 on that diagram seems to bear a similarity to the rusty, stringy thingies I'm seeing in my gear wells. Could you perhaps post or send me a key to this diagram, or at least the name of that particular part?

Only things out there beyond them are flap and aileron linkages, nav and strobe lights, and probably a magnetic flux gate, judging by the age of my slaved HSI. None of those things would seem to have any need for a ferric cable, but I think I took Aircraft Systems and Components, which I loved, the same semester as Basic Drafting, which I despised, so it's a wonder I can recall any of what actually mattered...

[kortopates]

Merry Christmas Mocha. The cables originate under the rear seat in a vacuum canister/bellows, activated by a solenoid, that when activated, pulls the pair of cables that run all the way to each brake through the painted conduits in your wheel wells to extend them.
The conduits brakes down with age becoming brittle and then cracks. Feeling the conduits will show if yours are okay or not. If there good that leaves the brake bearing and a spring - used only to retract them. The spring is easily replaced but the entire brake assembly is riveted around the bearings.
Extremely simple system.


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[kortopates]

Yes but according to Precise flight you can’t remove the engine-driven vacuum pump.  They must work when actuated and the standby vacuum is not approved for continuous duty 

One of our Savvy clients did exactly this, removed the engine driven vacuum pump, that weighs hardly anything, and left the (very heavy) electric standby pump installation to activate speed brakes and didn’t learn until we managed their annual that it wasn’t approved.
Much better to get the useful load back by removing the standby pump but this client IIRC had a standby alternator installed on the vacuum pad instead.


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[airmocha]

1 hour ago, kortopates said:

Merry Christmas Mocha. The cables originate under the rear seat in a vacuum canister/bellows, activated by a solenoid, that when activated, pulls the pair of cables that run all the way to each brake through the painted conduits in your wheel wells to extend them..


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So any clue what the rusty cables could be? The painted conduits are nicely intact, and the "DRC"/speed brakes worked fine last time I tried them. 

[airmocha]

Eureka?

What about a bonding wire for my static wicks?

[PT20J]

20 hours ago, airmocha said:

Eureka?

What about a bonding wire for my static wicks?

By golly, I think you’ve figured it out! I never would have thought of that.
 

Edit: Sorry, too much eggnog 

[Guest]

10 hours ago, airmocha said:

Thanks and Merry Christmas, M20Doc! If I'm reading that diagram correctly (miracles DO occasionally happen), pneumatic lines may be carrying carrying the force (vacuum) out to a separate actuator in each wing, then, and the cables would then be relatively small/short, running only between each wing's pair of brakes and their dedicated actuator? So they wouldn't be exposed to much and only very slowly, if ever, rust.

Part #26 on that diagram seems to bear a similarity to the rusty, stringy thingies I'm seeing in my gear wells. Could you perhaps post or send me a key to this diagram, or at least the name of that particular part?

Only things out there beyond them are flap and aileron linkages, nav and strobe lights, and probably a magnetic flux gate, judging by the age of my slaved HSI. None of those things would seem to have any need for a ferric cable, but I think I took Aircraft Systems and Components, which I loved, the same semester as Basic Drafting, which I despised, so it's a wonder I can recall any of what actually mattered...

Here’s the drawing and parts list for the speed brakes.  The vacuum servo pot is under the back seat, with cables routed to the s left and right speed brakes.

Clarence

Edited December 26, 2020 by M20Doc

[Guest]

13 hours ago, airmocha said:

Eureka?

What about a bonding wire for my static wicks?

Never heard of that one?  Can you follow it through the wing to see where it goes?

Clarence

[ArtVandelay]

By golly, I think you’ve figured it out! I never would have thought of that.

Aren’t they bonded by being attached to the aluminum skin?

[PT20J]

2 hours ago, ArtVandelay said:

Aren’t they bonded by being attached to the aluminum skin?

Yes 

[airmocha]

So no other J/K model owners who've read this out there have these ferric, uninsulated cables in their gear wells, then?

[airmocha]

Ok so finally got some time, light, and heat in the same place. It's definitely the DRC cable. Thing's so old the conduit's mostly gone. Thing I thought was the intact, healthy cable's just the brake line. Can't believe I couldn't tell before, but it was dark, I was cold, and had Christmas bearing down on me...

 ..over which we enjoyed having one of our house's two sewer lines back up into the master bathroom.

 

What a year. Hope 2020 DOES let the door hit it on the way out.

Truly appreciate the help, y'all.

Edited December 27, 2020 by airmocha
punctuation

[carusoam]

Many people on the same page...

See ya 2020!

And there was one plumbing challenge mentioned earlier in the week...

Parker mentioned....   “...I'm not sure if the recentplumbing  disaster at our house kicked this to 2022.”

He didn’t share much detail... 

Best regards,

-a-

 

[airmocha]

Going to attempt to feather the edge on this topic a little by referring any interested to a "howdy" in the General section, since I'm new and have heretofore only sought to "take" from this community.

Seems like a nice bunch here, just taking a quick survey of the thread titles...refreshing if true, if indeed possible, in this time. I quit all my other social media earlier in 2020 because of the constant, draining rancor. Looking for other outlets.

 

With that, I'll say "ttyl" here and hope to see more of you elsewhere in 2021. Safe travels, high groundspeeds (however you may achieve them), and greasy landings, all!

 

Here's a link to my howdy post:

 

Edited December 27, 2020 by airmocha
link added

[Carsten Gott]

I have the same problem: The cables -those on the previous pics posted by Airmocha- are rotten. And I don´t want to take everything apart to install new ones without having the parts. And here it comes, I just received a mail from preciseflight:

Quote: "Unfortunately, the Vacuum series SpeedBrakes are obsolete and we no longer support them. I have attached an installation manual that may be helpful for you. I am sorry we can't be of more help."

They made me an offer to change everything to electrical and would even give me a discount of 500$...

I am intending to turn that offer down and ask the forum, who has the drawings or dimensions etc. of those cables? That is no rocket science, but mine are rotten so much, I cannot even use them as a sample... Who can help?

Thanks a lot in advance

Carsten

[carusoam]

13 hours ago, Carsten Gott said:

I have the same problem: The cables -those on the previous pics posted by Airmocha- are rotten. And I don´t want to take everything apart to install new ones without having the parts. And here it comes, I just received a mail from preciseflight:

Quote: "Unfortunately, the Vacuum series SpeedBrakes are obsolete and we no longer support them. I have attached an installation manual that may be helpful for you. I am sorry we can't be of more help."

They made me an offer to change everything to electrical and would even give me a discount of 500$...

I am intending to turn that offer down and ask the forum, who has the drawings or dimensions etc. of those cables? That is no rocket science, but mine are rotten so much, I cannot even use them as a sample... Who can help?

Thanks a lot in advance

Carsten

Carsten,

This thread is a bit older than most memories last…

 

Do you want to describe what you have?

Or hope somebody goes back and reads dozens of posts to exercise the memory?

It’s possible that somebody has great memory…

 

Most often,  people purchase new parts for their existing speed brakes direct form the speed brake company…

It is near impossible to change from one series to the next without major work involved…

Best regards,

-a-

 

[Pinecone]

From other threads, I recall the switching from vacuum to electric  speed brakes is not that difficult.  Remove the two SB cartridges and the associated lines and bellows (actuator), install the electric ones and run some wires.

An of course, the hard part, paying for them.

 

[Fly Boomer]

On 8/23/2022 at 1:04 PM, Carsten Gott said:

I have the same problem: The cables -those on the previous pics posted by Airmocha- are rotten. And I don´t want to take everything apart to install new ones without having the parts. And here it comes, I just received a mail from preciseflight:

Quote: "Unfortunately, the Vacuum series SpeedBrakes are obsolete and we no longer support them. I have attached an installation manual that may be helpful for you. I am sorry we can't be of more help."

They made me an offer to change everything to electrical and would even give me a discount of 500$...

I am intending to turn that offer down and ask the forum, who has the drawings or dimensions etc. of those cables? That is no rocket science, but mine are rotten so much, I cannot even use them as a sample... Who can help?

Thanks a lot in advance

Carsten

I don’t know the model number, but these PreciseFlight speed brakes are activated by mechanical cable that runs through the MLG wheel well on both sides.  I believe there is a diaphragm or bellows in the fuselage that converts from air power to mechanical power via the mechanical cables.  I too am interested in documentation of any kind and, given the response the OP got from PreciseFlight, specifications and source for the rusted out cables.

[MisfitSELF]

On 12/16/2020 at 3:30 PM, shawnd said:

If they are precise flite speedbrakes - there's two version: vacuum powered & electrical. Not sure which cables you are looking for. Have you tried calling them?  https://www.preciseflight.com/

Mine uses cables as well.  1984 M20J but the speed brakes were installed in 1990 or 1991.  They are precise flite and they are totally mechanical.  No vacuum and no electric required.  I'd also be interested in a source for the cables. 

I've contacted preciseflight a couple of years ago and was told "well pass the message to our expert on those and get back with you" -- of course I never heard back.  I should nag them again...

Edited August 27, 2022 by MisfitSELF