No Back Clutch Spring M20-282-0001 Eaton Kit Update Good News

[Pinecone]

3 hours ago, cliffy said:

The failure mode of the spring was one of the "ears" breaking off due to minute cracks in the bend area in a production run of springs. It had something to do with the heat treatment. 

The new springs SEEM to be exact clones of the historical design. Once the failure mode was determined subsequent production runs didn't seem to have any failures IIRC.

Historically, as noted, very few springs failed but if it does you have a real problem in flight. 

From what I have read, they bent the ears after they heat treated the spring.  That is bassackwards.  

Bend THEN heat treat.

Not sure of what the failure mode of the few failures of the springs in the production aircraft was.

[Pinecone]

4 hours ago, Slick Nick said:

But do you buy it to have a spare on the shelf? Or do you have it installed and keep your original as a spare?

What is the failure mode of this spring? Is this design any better / more durable? Is there something about the new spring that precludes the likelihood of failure compared to my stock one? Or is it the exact same design, and it should be more durable simply by the fact that it's got fewer cycles on it?

From all the reading I have done.  I would NOT replace my spring unless there was some indication that there was an issue.  Don Maxwell says you can tell when doing the gear swing during annual that it is having issues.

For the right price, I would buy one and put it on the shelf, just in case mine started making noise.

[MikeOH]

@Pinecone

I'm guessing that $3,000 isn't the 'right price'

Oh, and might I suggest a safety deposit box vs. 'on the shelf' as a secure storage location

[cliffy]

On 10/28/2024 at 10:32 AM, 1980Mooney said:

You just made the case for Lasar to raise the price even more.  Heck it would still be a bargain at $6,000 or even $12,000 for the spring given the price to repair or replace the geared up Mooney. 

But that logic and reality is exactly what is driving Private Equity to buy up general aviation suppliers. and raise prices. Hartzell/Arcline Investment acquisition and price increase has been discussed here.  Vance Street Capital Partners bought McFarlane, Tempest, Marvel-Schebler, AirForms, PMA Parts, Precision Airmotive, Alcor, CFS Fuel Systems, etc and call is VS Victor Sierra Aviation Holdings.  Lesser know is Warburg Pincus's early move to acquire and consolidate aviation avionics suppliers primarily to the Department of Defense  - it is called Extant Aerospace and now owned by TransDigm.  They bought the old Goodrich/L3 Harris line for instance.  They are not shy about jacking prices and screwing everyone including the DOD.  If you have a WX-500 for instance, they are now selling it for $23,000. 

 

No different than the guy who "reserved"  all the short N numbers and now sells them online

One of those "why didn't I think of that" moments

[GeeBee]

I must say, last week I called Lasar and bought a toothbrush.

 

[hammdo]

Got this email today from Lasar:

 

[toto]

5 minutes ago, hammdo said:

Got this email today from Lasar:

 

Interesting 

[1980Mooney]

19 minutes ago, hammdo said:

Got this email today from Lasar:

 

What is the price?

[hammdo]

https://lasar.us16.list-manage.com/track/click?u=418263be1d9c7a7f755f64da3&id=a9c67e4e18&e=0a44abd565

got this email an hour ago…

[toto]

5 minutes ago, hammdo said:

https://lasar.us16.list-manage.com/track/click?u=418263be1d9c7a7f755f64da3&id=a9c67e4e18&e=0a44abd565

got this email an hour ago…

Oh right okay, um nvm 

[N201MKTurbo]

That’s an awful lot for a$10 spring.

[ArtVandelay]

That’s an awful lot for a$10 spring.

That’s about a 120% inflation rate. But if you need it…although I don’t think many are going to do the 1000 hour service just because.

[A64Pilot]

On 10/28/2024 at 3:46 PM, Pinecone said:

From what I have read, they bent the ears after they heat treated the spring.  That is bassackwards.  

Bend THEN heat treat.

Not sure of what the failure mode of the few failures of the springs in the production aircraft was.

It is backass wards, but it is very often done.

For instance the balance control springs we used in Thrush flight controls looked a lot like screen door springs. When we ordered them they were cut to length and then a section of the wrap bent 90 degrees so you could attach a cable to them.

Of course they broke every so often, every spring eventually does and of course they always broke at the bend. They really weren’t a safety of flight issue when they broke

Edited Saturday at 07:00 PM by A64Pilot

[PT20J]

As near as I can determine there was a catastrophic failure of an Eaton no-back spring about 25 years ago. Eaton recalled a bunch of actuators in 2002. I have never been able to find any documentation regarding the findings of the recall but there is a general belief (unsupported by evidence, but perhaps still true) that some springs may have been improperly manufactured. If any of those springs have never been replaced, they are probably not going to fail catastrophically or they would have by now.

The spring acts a brake to prevent back driving (hence the descriptive name) the ball screw actuator and thus hold the retracted landing gear in the up position. Since it is a friction device, there will be some wear on it. Presumably when it completely wears out it will slip and the gear won't stay fully retracted, but that's conjecture. According to Don Maxwell, when the spring is wearing out it makes a distinctive chattering sound. This makes sense as it is probably beginning slip a bit. Anyway, Don's advice to me was that if it's not chattering, don't mess with it.

There have been several catastrophic failures of the spring in the Plessey actuators (Plessey calls it a torsion spring, but Mooney tends to call the spring in both brands a no-back). The first two occurred at a little over 1000 hours and I believe that is likely the origin of the 1000 hr replacement interval. There are no parts available for the Plessey actuators and they seem be the units that fail and cause the gear ups.

[A64Pilot]

When you say chattering is it during retraction or extension? I assume retraction?

Is this something that can be heard in flight or just during retraction ground tests?

[PT20J]

1 hour ago, A64Pilot said:

When you say chattering is it during retraction or extension? I assume retraction?

Is this something that can be heard in flight or just during retraction ground tests?

You'll have to ask Don - I've never heard one make a noise. 

[A64Pilot]

There is more to this spring than it merely keeping the gear from unwinding if you will when retracted.

If that was all it did then it wouldn’t prevent extension if it was broken, but apparently it does.

I think I’d have to see an actuator disassembled for me to understand this spring. I’m thinking it functions as a sort of clutch if you will and if it doesn’t engage then there is no drive. But if it did that then the motor would just spin, but apparently a broken spring locks something up?

 

 

 

[PT20J]

57 minutes ago, A64Pilot said:

There is more to this spring than it merely keeping the gear from unwinding if you will when retracted.

If that was all it did then it wouldn’t prevent extension if it was broken, but apparently it does.

I think I’d have to see an actuator disassembled for me to understand this spring. I’m thinking it functions as a sort of clutch if you will and if it doesn’t engage then there is no drive. But if it did that then the motor would just spin, but apparently a broken spring locks something up?

 

 

 

I've never had one apart either. What I know comes from talking to people that have worked on them, reading articles about them and studying the service literature. There also used to be some good pictures on MS which were lost when we moved to the new server. I believe it is a wrap spring brake in one direction and a wrap spring clutch in the other. From the accident report descriptions, the failure mode that causes the gear not to extend is when one of the tangs breaks off and  jams the actuator gear train so that it cannot rotate.