Trim Jackscrew Binding

[jetdriven]

55 minutes ago, Piloto said:

Boat owners buy WD-40 by the boxes. During my college days I used to work part time on cargo ships and WD-40 was used extensively. I guess boat operators know a little bit more about rusty environments than pilots.

José 

You do what you want. My family will never get in your airplane beicause it’s not maintained to airworthy standards. 

. I’m advising people to follow the service manual lubrication requirements. An MD80 crashed and killed everyone because they used the wrong grease on a trim jackscrew.  WD-40 IS NOT A LUBRICANT. 

[jamesm]

5 hours ago, jetdriven said:

WD-40 IS NOT A LUBRICANT

That is what one things that my A&P instructor  emphasis to me in school years ago.  Some of the other stuff I learned from A&P school  I have probably  have  forgotten  but that is  one thing that stuck "WD-40 IS NOT A LUBRICANT and should be banned from being around airplanes" I can still see his face.

[Piloto]

8 hours ago, jetdriven said:

You do what you want. My family will never get in your airplane beicause it’s not maintained to airworthy standards. 

. I’m advising people to follow the service manual lubrication requirements. An MD80 crashed and killed everyone because they used the wrong grease on a trim jackscrew.  WD-40 IS NOT A LUBRICANT. 

Well I wouldn't fly on yours either because it has no pilot relief tube.

[Piloto]

WD-40 has a freezing temp of -81F ASTM D97 which is ideal for tight tolerance assemblies such as jackscrews in very cold weather. After I lubricated with WD-40 I could move the trim wheel much easier at -27F (12,000ft). 

https://www.wd40company.com/files/pdf/wd_40tec16952473.pdf

Lithium grease freeze at -15F ASTM D97

https://sinclairoil.com/sites/default/files/SL AF LITHIUM PLUS MULTI-PURPOSE EP2 GREASE.pdf

 

Edited February 3, 2018 by Piloto

[jetdriven]

1 hour ago, Piloto said:

WD-40 has a freezing temp of -81F ASTM D97 which is ideal for tight tolerance assemblies such as jackscrews in very cold weather. After I lubricated with WD-40 I could move the trim wheel much easier at -27F (12,000ft). 

https://www.wd40company.com/files/pdf/wd_40tec16952473.pdf

Lithium grease freeze at -15F ASTM D97

https://sinclairoil.com/sites/default/files/SL AF LITHIUM PLUS MULTI-PURPOSE EP2 GREASE.pdf

 

Further proof you don’t know what you’re talking about. Freezing temp is about one of 30 different properties that really matter for an aircraft.   And aeroshell 7 is called for in the SMM, it’s not lithium grease  but you didn’t know that. From the mfr:

”Aeroshell 7 is a Microgel thickened, synthetic diester oil base. Aeroshell 7 Grease is corrosion inhibited and fortified to resist oxidation, it combines excellent load-carrying capacity with a useful temperature range of -73°C to + 149°C”

Like I said, you shouldn’t be working on planes. And you’re smug and you think you know more than the people that design grease, oils, anti-icing fluids, corrosion properties of metals when exposed to urine, relying primarily on cell phone signals at altitude to avoid weather (which you end up flying through),  Boeing flight displays freezing up, amsafe airbags going off and killing pilots, even saying you should tie a pen to the sunvisor clip and keep it straight up and down when your gyros fail.

Maybe you’re born that way You’re so smart you found an alternate method of doing everything. And for everything there’s always a single instance or no instance at all but basing your operations and maintenance decisions on that.  Or maybe they taught you that at your Puerto Rican engineering school if you even have a degree.   I’m married to an engineer and I’m  partners wirh an engineer on an airplane and none of them are that stupid .   When it comes to supporting your positions with facts or evidence you’re  like a little kid,  stick your tongue out and go maaaaa.

But I’ll be here to call bullshit on everyone of them when i see it,  Lest somebody doesn’t know any better and takes your advice and get themselves  killed. 

Call me an asshole. Ok I get that. But at least I’m a factual and logical asshole and I’ve never deviated from accepted and standard practices and techniques unless I have a compelling and overwhelming reason to do so. Usually to be more accurate or to take into account things we have learned since it was printed. You, you get a feeling and go searching for supporting evidence, ignoring the vast majority. You sir, are a fool. I’m done with you and your amateur advice. 

Edited February 3, 2018 by jetdriven

[Piloto]

11 hours ago, jetdriven said:

 

Byron my observations and comments are not to be taken as rule, that would be a mistake. But as an old man I learned not to bash others, specially in public. It projects an immature image of you.

José

Edited February 3, 2018 by Piloto

[MB65E]

Geez! Take it easy guys! You both bring a lot to this site and to GA. I've enjoyed both of your comments over the years!!

We all get what we pay for from this site! It's still great tool! 

Relax!

-Matt

[Guest]

Try to be factual in what you write and post.  There are many people who come here looking for advise and information to take better care of their airplanes, or resolve issues they have.  

Presenting incorrect and erroneous information is just plain wrong.  If you want to do something different or contrary to the maintenance manual keep it to yourself unless you have some form of approval which you’re willing to publicize.

Just my opinion of course,

Clarence

 

 

[Hector]

Folks, if you are here often enough you inevitably will read stuff you don’t agree with. That being said, let’s keep it civil. Rants that develop into personal attacks just because you don’t agree with someone diminishes the experience for all.


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[Emmet]

On 2.2.2017 at 9:00 PM, PeytonM said:

We just got the jackscrew assembly back from a cleaning and relubing. We will put it back in the airplane early next week and we will take pics. 

Can u move the trim wheel manually? Try it from full nose up; that was the real test for me. I could not budge it. 

I will do mine next week.

Would you mind to share the pics? Can you also explain which measurements you took before disassembly?

 

[Vance Harral]

45 minutes ago, Emmet said:

Would you mind to share the pics?

Not PeytonM, but we overhauled our jackscrew assembly (by which I mean we R&R'd it, and had LASAR actually do the overhaul) just about a month ago.  Here's what it looks like when first removed from the airplane.

The big block in the middle contains the "nut" and the bearings.  That's where you're going to find the old, dried up grease, as well as the (probably worn) shims.  The shaft on the right attaches to the trim control rods that go down into the belly.  The "screw" part on the left attaches to the tail, and is what's underneath this boot you can see when you remove the empennage fairing:

Note the hole at the far lower right of the above photo.  There are four of these, and that's how you get access to the bolts that go through the square block, and hold the jackscrew assembly in place.

[Vance Harral]

If you remove the bolts and nuts that hold the "block" together, you can slide it off the bearings that allow the screw to turn, as well as remove the shim(s) that take up the play in the system:

 

Here's the shim:

 

Here are the bearings after sliding the block off.  Note that the bearings are press-fit onto the shaft.  You need a puller of some sort to remove them:

 

This is as far as we got before we chickened out:

Edited March 29, 2018 by Vance Harral

[Vance Harral]

The problems that can occur when the system is neglected - which it often is for long periods of time due to the pain of disassembling it - are as follows:

• Old, dried up grease in the bearings - this wasn't as bad as I thought it might be in our airplane.  It is essentially sealed, after all.
• Wear in the bearings from normal, long-term use - this was our biggest problem.
• Shims worn, or not the right size in the first place.  You can see in the photos above we had only a single shim, and was allowing a fair amount of play.
• Wear in the "screw" itself.  In our case, there was almost no wear, and the folks at LASAR say it isn't unusual for it to actually be in quite good shape when inspected.

When we got things disassembled to the point of the last photo above, we realized the bearings were in fairly bad shape.  We hadn't yet ordered replacements, and when we realized it would require a puller to get them off the shaft, we chickened out and just overnighted the whole thing to LASAR.  Dan fixed us up and had the freshly overhauled unit back in our hands in less than a week.

[cliffy]

WD-40   Water Displacement Fluid Formula #40    'nuf said?

Look it up

 

[carusoam]

Great pics, Vance!

Thanks for sharing them.

Best regards,

-a-

[PTK]

On 2/3/2018 at 1:24 AM, jetdriven said:

... I’ve never deviated from accepted and standard practices and techniques...

Well, Byron...with all respect Sir, you have indeed deviated standard practices. You mounted your Aera 660 contrary to the standard and accepted practice of portrait orientation! You completely disregarded and ignored the aforementioned standards, as if they didn’t exist, and proceeded to mount it in landscape! 

[N201MKTurbo]

You can actually take the bearings apart by removing the snap rings that hold the shields on. The balls come out easily and you can compleatly clean the balls and races and re-assemble them with new grease.

[jetdriven]

I never could get the bearings clean enough to reuse. I even replaced them with new bearings and it still bound up in the housing. Evidently the bearings fitting absolutely square in there is critical and I couldn’t get it right. 

The bearing is a KP16A btw. Cheap and avaiable from eBay and Amazon. 

[Emmet]

Thanks for the pics, Vance!

They help a lot - hope we get it right next week ...

[Vance Harral]

2 hours ago, Emmet said:

Thanks for the pics, Vance!

They help a lot - hope we get it right next week ...

Glad they helped, good luck with your project!

For what it's worth, suggest you pay heed to jetdriven's troubles with binding after reassembly, which is part of the reason we sent our unit to LASAR for overhaul.  We spoke directly with Dan Reisland about this, and he said reassembly of the "guts" inside the block (bearings and shims) is critical, and if not done just right can lead to exactly the sort of binding jetdriven talks about.  My guess is it mostly has to do with selecting the right size shim(s) to minimize play without binding up.  The right size depends on detailed tolerances of the block and the bearings, and installing different bearings affect that, even if the new bearings are the same part number.  So something of an art, based on experience.  That's my impression, anyway.

If you're just going to clean and reassemble your existing parts, I'd guess odds are they will go back together fine.  If you're contemplating new bearings, or your shims are worn, or you just want a slightly bigger shim to tighten up play, you may want to let the pros do it.  At the risk of sounding like a shill for LASAR, Dan was extremely helpful to us with this, as well as our landing gear work, at our recent annual.  I'm sure the LASAR guys would be the first to tell you these are just mechanical parts and they're not some sort of mystical gurus.  But they do this sort of thing every day, and experience counts.

[N201MKTurbo]

FWIW

I have found when you overhaul the jackscrew it works pretty good when you put it back in. But after a few hundred hours it works even better.

[Emmet]

I would love to send it to Lasar, but as I am based in Europe it is more complicated. I do intend to install new bearings and will take a close look at the shims.

[nels]

In looking at the photos I’m wandering, what is the positive stop at the end of the stroke. Also, is the end of the stroke the position where it sometimes seizes?

[thinwing]

On 2/2/2018 at 9:06 PM, Piloto said:

Well I wouldn't fly on yours either because it has no pilot relief tube.

Have you tried "depends" adult diapers?

[N201MKTurbo]

19 minutes ago, nels said:

In looking at the photos I’m wandering, what is the positive stop at the end of the stroke. Also, is the end of the stroke the position where it sometimes seizes?

The limits are normally set by the stops on the trim wheel. At the jack screw end the limit is set by the hing thingy in the tail and the control rods binding up on the other end. A properly rigged screw will never get to those limits.

Edited March 30, 2018 by N201MKTurbo