J/K model speed brake cable replacement

[airmocha]

My '85 K model (ModWorks 262 conversion) needs new cables for the speed brakes I hope I never need.

Can't find them. Anyone know where to get them?

Thanks!

[shawnd]

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/

[carusoam]

Electric doesn’t have cables....

But, there are manual speed brakes that probably do...

Best regards,

-a-

[tmo]

Won't McMaster make them as OPP the same way they do throttle / prop / mixture?

[shawnd]

@carusoam is correct, electric one, well is electric and doesn't have cables. The vacuum one does have cable from the bellows assembly to actuate the speedbrakes. Both 14V and 28V kits are made by precise flight.

[kortopates]

As Shawn mentioned above, the cable and cable housing (just like bicycle cables) is available from Precise and not expensive at all. It should really be the outer cable housing that disintegrates over the plus 30 years of use, but of course you can't replace the housing without replacing the cables. Your installer will also have to swage on the ends. Probably long over due at 35 years!

[airmocha]

Many thanks for the replies, guys. I did manage to learn that PreciseFlight was the source of the parts, but don't yet understand exactly what I have here. I consider myself fairly well-educated about aircraft systems and components (for a non-mechanic), with a degree in aviation technology, a career in the airlines, many type ratings, blah, blah, blah, and by my understanding, electrically powered (or hydraulic, or pneumatic)  speed brakes could easily employ cables to merely transfer force generated by a motor rather than a hydraulic or air pump or vacuum source. Electricity would be said to "power" them, but the cables and linkage mechanism, likely involving springs or some other opposing force provider that would retract them absent the application of that power, would be said to "actuate" them. The cables are just the errand boys (girls). They are, regardless of power source, electrically controlled via the deployment switch on my lower panel.

It's been over a year since I test-swooned my little heart-throb, but I could have sworn we tested the little buggers (which I have yet to need, but I know the day will come) on the ground with the engine not yet started, and that they deployed and retracted. But we could have already started it or even been airborne - I just don't recall. It's also entirely possible, though seems very unlikely, that a vacuum accumulator could be installed to store enough force to deploy them once in the event of an engine failure/fire where you'd be way up high and wanting to get on the ground ASAP. That accumulator, if working as designed, would allow at least one deployment without the engine running. But like I said, I only know of these things being used in non-transport category aircraft for one or two things - emergency gear extension, unfeathering propellers, or possibly a really high-end parking brake. In all of those cases, they're hydraulic, not pneumatic (or vacuum).

PreciseFlight's tech told me they have no record of ever having produced an electrically-powered set for Mooneys; that it pretty much has to be the vacuum (pneumatic) version. I'm going to do some more research and, absent anything to support my fuzzy memory of them deploying on the ground with the engine not yet running, I'm going to just order the set for the vacuum-actuated kind.

 

It sure would be nice if the manuals would get a little more nutsy-boltsy for us systems geeks, but oh well.

 

I do appreciate the help! Merry Christmas!

Edited December 23, 2020 by airmocha

[ArtVandelay]

PreciseFlight's tech told me they have no record of ever having produced an electrically-powered set for Mooneys; that it pretty much has to be the vacuum (pneumatic) version. I'm going to do some more research and, absent anything to support my fuzzy memory of them deploying on the ground with the engine not yet running, I'm going to just order the set for the vacuum-actuated kind.

That makes no sense, I have electric SB on my 78, model 100 IIRC.
And yes I have used them with the engine off.

[airmocha]

Hmmm....well, maybe my memory's not so bad, then?

[kortopates]

So why did you start off asking for where to get cables if you’re not sure what kind of Speed brakes you have? Or are you questioning that based on some early post suggesting they were electric; which might of confused your memory.
Let us know what you have and we can be more helpful!

If your not sure, there are 3 kinds. Perhaps easiest way to tell is too look in your POH for the AFMS for the speed brakes - which will be there if your documentation is in order as required.
If not, you can see the cables housing in gear wells if you have the earlier vacuum version. Electric don’t have cables and will have a placard on the wing not to pull them up manually; plus only require the master on to deploy. Vacuum need the engine running or electric standby vacuum on to deploy. A third very rare version, hydraulic, lay flat on the wing till deployed hydraulically - but very rare and look very different.
Lastly, part of your checklist should be to deploy them on the ground before flight.

There is no vacuum accumulator - they are not required for flight or airworthiness. Just a nice to have.


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[PT20J]

I have a '94 M20J that came from the factory with electric Precise Flight speed brake installed.

The electric ones have a motor in each cartridge and don't need any external cables.

Skip

[airmocha]

Well, simple-minded me, I just assumed there was only one type in use. It's on my list to investigate further. They are not the "lay-flat" type. They deploy vertically from within slots in the top of the wing. There are both placards on the tops of the wings near them AND cables running through the gear wells, and I could have sworn it only took electric power to extend them when I test flew my airplane before buying it, which led me to believe they were simply electric, not pneumatic/vacuum actuated. Having seen how rusted the cables are, I'm very hesitant to deploy them again for fear they may not retract. Obviously you mean the checklist would call for them to be deployed and then subsequently retracted before flight, but that doesn't speak to what power source is being used to deploy/retract them.

My airplane is an '85 M20K with a ModWorks 262 mod. I believe the speed brakes came as part of that mod, and the manual appears complete, but I haven't yet found a section describing the speed brakes' power source for actuation.

Edited December 23, 2020 by airmocha

[carusoam]

Mocha...

Lets cut to the chase scene...

Got a pic?

There are at least two manufacturers of speed brakes on Mooneys... they look and operate completely differently...

Then there are three different eras of the preciseflight  version... mechanical, vacuum, electric...

Oddly, hydraulic isn’t on the list...

 

And... if I were to guess... no matter how dead your engine is... you still have vacuum if the prop is spinning... so an accumulator isn’t needed 99.999+% of the time...

If the prop stops... you probably won’t be as interested in deploying the speed brakes... 

 

As far as the bits and pieces go... the most modern speed brakes were built in a cartridge style... they are easily removed from the airframe with all their bits and pieces...

Do you want to post a pic?

The speed brakes are an awesome tool... they do kill off some efficiency... but, many MSers don’t live in the middle of no-where, in the flat lands....

One of the coolest parts of Transition Training... is performing E-descents... Speed brakes are awesome for this... with proper training, you can be on the ground in a couple of minutes...

Yes, I read you are Uber educated, highly experienced, and mechanically inclined... Transition Training is perfect for people like you...  

PP thoughts only, not a mechanic or CFI...

Best regards,

-a-

[airmocha]

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.

Edited December 24, 2020 by airmocha
mistake in verbiage

[airmocha]

It occurred to me right after I stood up from the computer that perhaps the source of said vacuum could be the same pump that's driving the gyros, and not the intake side of the engine.

Seems plausible since the gyros would be unaffected by a momentary drop in suction, but again, a more detailed systems description in the manual would really be nice. Been a while since I looked for it - maybe it's hiding in there somewhere.

[Aerodon]

On 12/16/2020 at 12:49 PM, airmocha said:

My '85 K model (ModWorks 262 conversion) needs new cables for the speed brakes I hope I never need.

Can't find them. Anyone know where to get them?

Thanks!

Hi 'Mocha  

I have some documentation and knowledge on the speedbrakes. I have seen the 100 series OEM vacuum brakes on a 252 and the only difference between the 14 and 28V is a resistor to the solenoid turning the vacuum solenoid on.   I have seen an 'electric' cable version on a friend's Lancair.  A small electric motor winds the cable up on a capstan.  I have heard that Precise Flight made a certified version of this, but not many copies were sold.  (I have not verified this).  You have a 262 which is an aftermarket version of the 252, you may well have an electric motor version of the 100 series speed brakes?

Then the 2000 series came along which are completely different and have no cables.

Take some pictures, including the actuator button and warning annunciator on the panel.  Look for documentation in you POH, W&B, 337's etc.

Aerodon

 

 

[RJBrown]

picture #1 is of a 1980 M-20K with speed brakes deployed. They were installed by Mod Works in the early 90s.

pictures #2 & 3 are of a 1988 M-20J in my hangar. They are exactly like the ones in picture 1 and are the most common used on your plane. They are fully electric.

An electric motor runs them up and down. If they lose electrical signal (like master switch turned off) a spring pulls them down immediately. They are held in by the 18 screws seen from the top. They are removed through the cover on the bottom.

If they are not operating properly they can be removed and sent in to Precise Flight for repair. 
I was told by them that with covers on and wiring secure the airplane can still be flown.

When new one side was returned for warranty repairs. 
part of the certification involved making sure that if only one were deployed the handling characteristics were not negatively affected. I have tested that premise. I found very little difference in how the plane handled. Speed brakes are not a go no-go item. 
At low speed/high angle of attack they make very little difference. Take off performance is not significantly degraded with them up. I left them up through landing they make the plane feel more solid and reduce the Mooney “float”
 

New style introduced in 2000 are the currently sold product pictured in the fourth picture. They have a rounded profile making them easy to tell the difference from the earlier style.

[RJBrown]

On 12/16/2020 at 1:49 PM, airmocha said:

My '85 K model (ModWorks 262 conversion) needs new cables for the speed brakes I hope I never need.

Can't find them. Anyone know where to get them?

Thanks!

“I hope I never need”?

I don’t understand your statement. The speed brakes are a wonderful addition to your plane and are very useful. I use them on almost every cross country flight.

My Rocket could climb to 24k at 1500fpm. Without speed brakes I could only descend at 500 fpm and could not always comply with center instructions. With speed brakes there were no problems getting down. Coming across the front range where MEAs exceed 16,000’ to land at Centennial airport south of Denver is much easier and safer with speed brakes.  I can remember being slam dunked by center without speed brakes, not fun. On the ILS too high and still pushing VNE. Had to call a missed approach and go around just to get slowed down. 

 

 

[airmocha]

Pics of what I have...

[airmocha]

So it would appear that I have all-electric speed brakes, as in the pics RJBrown kindly provided, but I also have some very sad, rusty cables running through the aft portions of my gear wells, and I can't imagine what those would be for, if not the speed brakes. The pic is badly focused, I realize, but they are textured, like cable, and not smooth like wiring insulation.

Next time I have it fired up, I will get someone out there with me to observe the cables' behavior and extend the brakes with the orange push-button I meant to photograph just now, but forgot, on the bottom of my panel. If the brakes move but the cables don't, I guess I have a mystery on my hands. It is comforting to hear that if they get stuck extended, or if one extends or retracts without the other, that the handling and performance won't be drastically compromised.

I'll also pore through the POH again and see if my memory's just failing me (it wouldn't have been "memorable" to me to have read that they were either vacuum- or electrically-actuated when I read through it the first time, since both seem completely plausible and conventional to me), and my mechanic only just mentioned the need to replace the cables on my first annual with this plane last November. The shop that did the pre-buy for me didn't even mention them.

 

As far as how I would hope/plan/intend to use them, I understand they're helpful/effective for making steep, unplanned, and/or less-shock-cooling-prone descents, and I understand, very, very well, that sometimes ATC asks the impossible of all pilots, and often relegates GA aircraft/pilots to last priority in favor of the airliners and corporate rigs. Many of those kinds of shenanigans happen "back east" and "out west" far more frequently than they seem to here in Flyover Country.

All of that said, however, a) I haven't even had my plane over 10,000 MSL yet because I'm still awaiting my ADS-B-out installation, b) I fly almost exclusively over flatlands and in/out of low-elevation-airports, and I rarely run it so hard that there isn't plenty of room to accrete speed in a powered descent (so long as it's not bumpy), c) I make power reductions extremely gradually, typically commencing a few minutes before descent and try to allow at least one minute per inch of MP I reduce, until bottoming out at the gear warning, around 15". I have yet to see my EI monitor give the first indication of any shock cooling at all in doing so, so I believe I'm being kind to my turbo/engine. If I'm wrong, feel free to correct me.

So I'm just not an adherent to the idea of using speed brakes as a replacement or mitigation for poor descent planning or as a normal part of every descent, and when I said I hope I "never" need the brakes, I was simply (trying to be) saying that I hope I literally never get faced with any dire need to land immediately (fire, heart attack, etc.) and figuratively only very rarely get so lazy and/or far behind the airplane that I need to use the speed brakes to facilitate what could have been a normal descent/landing at a low-cruise power setting, if I'd only just begun it sooner. By my training, doing so is sloppy flying and waste of gas, and I didn't buy a Mooney to allow myself to get away with either.

[airmocha]

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!

Edited December 24, 2020 by airmocha
additional info on vacuum source

[RJBrown]

I would pull the bottom panel and see for sure what I had. I still think it will be electric.

then I read your post. It must be one of the last of the vacuum ones.

descent from high altitudes is a math problem. When high but not IFR I would pull 1 inch per minute and figure descent up against vne if possible. As you get lower the descent rate goes up to maintain the same speed through the thicker air. This way you stay fast but regain the energy used to climb. If IFR you are stuck with what center gives you while still powering down slow.

Edited December 24, 2020 by RJBrown

[kortopates]

Good progress, some more good news perhaps is that the cables for the speed brakes is not the rust colored cable - the speed brakes cables are in the painted conduit that has the fitting. Which makes sense because they’ve been there longer than the paint job. I have no idea what the rust colored cable is though, other than being a more recent addition to your airframe. First thing I would check is if it’s on both sides like the speed brake cables are. Is it really a solid cable? Looks more like red sleeving over something like wires. But all electrical wires are routed through the leading edge of the wing.

On power, shock cooling is pretty much a myth. That said, with advance planning I always begin a descent early with ATC pilot discretion descents and come down very slowly at about 200’/min at cruise power till within 3 min of an IF or from the airport if VFR. My Brakes rarely get used except at every run up.

Those CHTs aren’t an issue in descents, but whenever they drop below 250F I teach just adding enough power to maintain level till they’re all at 250+. Same if the oil got too cold.


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[kortopates]

I would pull the bottom panel and see for sure what I had. I still think it will be electric.

His are clearly vacuum from the conduit in the wheel well.
Plus his AFMS shouldn’t lie!

But just gentle lifting of the brake up with a finger will also show it as the vacuum style with only resistance from the spring unlike the electric motor driven unit which will be obvious since it won’t move easily - thus time to stop.


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[Guest]

7 hours ago, airmocha said:

It occurred to me right after I stood up from the computer that perhaps the source of said vacuum could be the same pump that's driving the gyros, and not the intake side of the engine.

Seems plausible since the gyros would be unaffected by a momentary drop in suction, but again, a more detailed systems description in the manual would really be nice. Been a while since I looked for it - maybe it's hiding in there somewhere.

This may help.  Electrically controlled, vacuum powered, cable actuated.

Clarence