No back spring in landing gear actuators

[philip_g]

I don't even know which one this is? Who is consolidated or avionics products corp? Came after dukes but before Eaton? 

 

Forum reduced the quality significantly. Here's a link.

https://ibb.co/JBwgtLc

 

 

 

Edited November 7, 2021 by philip_g

[PT20J]

Thanks to @1980Mooney for the link to the Shop Talk article -- I always enjoy Kerry's clear explanations.

So, after reading this and reviewing the M20J IPC and SMM, I think  the following is true:

1. Mooney used Dukes through 1977 (through S/N 24-0377). It has the hand crank emergency retraction system and came with 20:1 gears and doesn't have a no back spring.

2. In 1978 (S/N 24-0378) Mooney switched to Avionics Products actuators which use the pull chord emergency retraction system, have 40:1 gears and a no back spring. Avionics Products and Eaton actuators are the same. Mooney describes them in the IPC as Eaton/Avionics Products actuators. Most likely, Eaton acquired Avionics Products at some point.

3. At some point Mooney also used Plessey actuators which appear to be functionally and dimensionally equivalent to the Eaton/.Avionics Products actuators though they have different internals including a different no back spring. Apparently the Plessey actuators are no longer supported.

4. The M20J IPC lists the Eaton part numbers. They are all 100000 series numbers. A web search turned up this document on Eaton's website: https://www.eaton.com/ecm/groups/public/@pub/@eaton/@aero/documents/content/ct_156830.pdf

Apparently, Eaton makes 100000 series actuators for a number of applications for various airframe manufacturers. The document lists these as being repairable by Eaton. It would be interesting to call Eaton and find out if they can repair a Mooney actuator, and what the cost and turnaround time would be.

Skip

[Alan Fox]

I would suggest someone finds a vendor to make these , Mooney is pretty much done , if a couple break , it will go AD , and ground the fleet .... Time to get moving

[Sabremech]

9 hours ago, Alan Fox said:

I would suggest someone finds a vendor to make these , Mooney is pretty much done , if a couple break , it will go AD , and ground the fleet .... Time to get moving

If anyone has even a broken spring, I can look into having a PMA spring made. 
David

[A64Pilot]

18 hours ago, philip_g said:

I don't even know which one this is? Who is consolidated or avionics products corp? Came after dukes but before Eaton? 

 

Forum reduced the quality significantly. Here's a link.

https://ibb.co/JBwgtLc

 

 

 

Read PT20J’s post, functionally it’s an Eaton, even though it says Avionic on it, mine is the same (81 J model)

Edited November 8, 2021 by A64Pilot

[A64Pilot]

42 minutes ago, Sabremech said:

If anyone has even a broken spring, I can look into having a PMA spring made. 
David

That is what it will take I believe, you have a PMA? I’m surprised no one has, there has to be money in it, especially for the Plessey guys, their only solution currently is a 14K or so overhauled Eaton?

Edited November 8, 2021 by A64Pilot

[1980Mooney]

15 hours ago, PT20J said:

Thanks to @1980Mooney for the link to the Shop Talk article -- I always enjoy Kerry's clear explanations.

So, after reading this and reviewing the M20J IPC and SMM, I think  the following is true:

1. Mooney used Dukes through 1977 (through S/N 24-0377). It has the hand crank emergency retraction system and came with 20:1 gears and doesn't have a no back spring.

2. In 1978 (S/N 24-0378) Mooney switched to Avionics Products actuators which use the pull chord emergency retraction system, have 40:1 gears and a no back spring. Avionics Products and Eaton actuators are the same. Mooney describes them in the IPC as Eaton/Avionics Products actuators. Most likely, Eaton acquired Avionics Products at some point.

3. At some point Mooney also used Plessey actuators which appear to be functionally and dimensionally equivalent to the Eaton/.Avionics Products actuators though they have different internals including a different no back spring. Apparently the Plessey actuators are no longer supported.

4. The M20J IPC lists the Eaton part numbers. They are all 100000 series numbers. A web search turned up this document on Eaton's website: https://www.eaton.com/ecm/groups/public/@pub/@eaton/@aero/documents/content/ct_156830.pdf

Apparently, Eaton makes 100000 series actuators for a number of applications for various airframe manufacturers. The document lists these as being repairable by Eaton. It would be interesting to call Eaton and find out if they can repair a Mooney actuator, and what the cost and turnaround time would be.

Skip

A couple more articles to add for your summary analysis and then some confusion on the Plessey:

• See Tom Rouch's review of Actuators (MooneyFlyer Aug 2017) on pages 17-19. He states that the Plessey is obsolete and that the springs are no longer available.  

Present Position (themooneyflyer.com)

• See Damon Trimble, Pascual Puetrolas (LASAR) and Paul Loewen's comments on Actuators (MooneyFlyer Sept 2020) pages 12-13.  They highlight the problem of relating gear cycles to hours and note that the actual life is longer for most planes.

Present Position (themooneyflyer.com)

• And last although Rouch and @donkaye state that Plessey springs are no longer available, @adverseyaw posted a thread in January saying that the factory and MSC's received Plessey torsion springs in November of last year.

 

 

On 11/5/2021 at 7:10 PM, donkaye said:

I knew this was a problem at least 5 years ago.  I spoke with Tom Bowen, then Chief Engineer at Mooney at the time about it.  At  the time they said they were looking into it.  The Plessey springs were no longer being manufactured.  That is why I have recommended that a buyer of any Bravo or other Mooney adjust the price of the plane if it had a Plessey Actuator because they were likely to have to replace it--minimum $10,000 for a rebuilt Eaton one to much more ($15,000?) for a new one.

 

On 11/4/2021 at 9:05 PM, donkaye said:

Sorry, they were gone long go.  If a rebuilt actuator is even available, I think they used to run about $10K.  Laser had them.  Tom Rouch from Top Gun is not refurbishing them any more.  I knew that Tom was getting ready to retire, so I bit the bullet and had him rebuild one while I still could.

 

[Sabremech]

50 minutes ago, A64Pilot said:

That is what it will take I believe, you have a PMA? I’m surprised no one has, there has to be money in it, especially for the Plessey guys, their only solution currently is a 14K or so overhauled Eaton?

I do have PMA and am willing to support the Mooney fleet in those parts that it makes sense to get PMA on. I’m also willing to help as far as owner produced parts where it doesn’t make sense to go as far as PMA.

Thanks,

David

[Ragsf15e]

20 hours ago, PT20J said:

Thanks to @1980Mooney for the link to the Shop Talk article -- I always enjoy Kerry's clear explanations.

So, after reading this and reviewing the M20J IPC and SMM, I think  the following is true:

1. Mooney used Dukes through 1977 (through S/N 24-0377). It has the hand crank emergency retraction system and came with 20:1 gears and doesn't have a no back spring.

2. In 1978 (S/N 24-0378) Mooney switched to Avionics Products actuators which use the pull chord emergency retraction system, have 40:1 gears and a no back spring. Avionics Products and Eaton actuators are the same. Mooney describes them in the IPC as Eaton/Avionics Products actuators. Most likely, Eaton acquired Avionics Products at some point.

3. At some point Mooney also used Plessey actuators which appear to be functionally and dimensionally equivalent to the Eaton/.Avionics Products actuators though they have different internals including a different no back spring. Apparently the Plessey actuators are no longer supported.

4. The M20J IPC lists the Eaton part numbers. They are all 100000 series numbers. A web search turned up this document on Eaton's website: https://www.eaton.com/ecm/groups/public/@pub/@eaton/@aero/documents/content/ct_156830.pdf

Apparently, Eaton makes 100000 series actuators for a number of applications for various airframe manufacturers. The document lists these as being repairable by Eaton. It would be interesting to call Eaton and find out if they can repair a Mooney actuator, and what the cost and turnaround time would be.

Skip

Now Skip, I know you meant emergency “extension”, not “retraction”!  If the gear is stuck down (and locked), I’m much happier (and it’s not an emergency) than if it’s stuck up!  

[A64Pilot]

7 hours ago, Sabremech said:

I do have PMA and am willing to support the Mooney fleet in those parts that it makes sense to get PMA on. I’m also willing to help as far as owner produced parts where it doesn’t make sense to go as far as PMA.

Thanks,

David

Hopefully someone will send you a spring, I don’t have one or I would.

OPP is of course one at a time and if a whole slew of them is done in my opinion it weakens your case should the FAA object, especially for a holder of a PMA  (my opinion only) worth what you paid for it.

PMA if your willing is the way to go go, I can’t imagine any A&P blink an eye on a PMA part, but some may give pause to an OPP one as the airworthiness determination is on them, and how would Joe Average A&P determine the airworthiness of a spring?

Side benefit is I believe you could make a decent amount of money on them.

[toto]

I think this has already been asked (more or less) in this thread, but if a person just wants to get in line for a spring and is willing to wait, where’s the best place to send the order? Go to a friendly neighborhood MSC, or directly to Mooney, or .. ?

If you pull your actuator and ship it off to LASAR, I assume you’ve got the same wait time for a spring as if you submit the order yourself to Mooney?

[Sabremech]

I would go with a PMA on this part due to the critical function of it and knowing that an AP would be skeptical of installing it. Owner produced is more in line with what I’ve done on the gear up and down lock blocks. 
Thanks,

David

[toto]

2 minutes ago, 1980Mooney said:

I wonder that the attitude of the insurance companies might be regarding an OPP in a critical application even if a local A&P signed it off as airworthy.

Per Tom Rauch, Top Gun, in MooneyFlyer Aug 2017 "If the no-back clutch spring breaks while retracting the gear, the gear will not go down for landing. ..... The main defect in this gear system is that the emergency extension depends on an intact no-back clutch spring. "

If an OPP no-back spring turns out to be weak and fails prematurely resulting in a gear-up, might an insurance company refuse to cover the repair?  Perhaps this is what will cause A&P's to be very cautious.

I always thought that the NBS failure was much more likely in retraction than extension simply because it’s much more stress on the actuator. So in many cases, the spring snaps when the switch is flipped and the gear remain down. I guess the worst-case scenario is that the spring fails when the gear are halfway up, and you’re just stuck.

All that being said, I suspect that NBS failures are a trivially small portion of the gear-up incidents. Humans forgetting to flip the switch causes the vast majority of these. I don’t know anything about insurance, but it seems unlikely that they would even pursue the investigation of an OPP spring. 

Parker would have an interesting take on the OPP question. 

[Alan Fox]

1 hour ago, Sabremech said:

I would go with a PMA on this part due to the critical function of it and knowing that an AP would be skeptical of installing it. Owner produced is more in line with what I’ve done on the gear up and down lock blocks. 
Thanks,

David

I believe one of my MSC vendors , may have a used one , You are welcome to it , as long as I can have it back , when you are done...

 

[Sabremech]

48 minutes ago, Alan Fox said:

I believe one of my MSC vendors , may have a used one , You are welcome to it , as long as I can have it back , when you are done...

 

Hi Alan, I might need several old ones just to confirm sizing. I’m also going to have to destroy one for the metal analysis. I do have someone willing to send me one to start the process and I may take you up on your offer just to confirm measurements so that I can return it. 
Thann you,

David

[PT20J]

I've never disassembled one of these, so I don't fully understand all the details of the design, but it is clear from the descriptions in M20-282-A that the spring serves primarily as a brake to keep the gear in the up position. This is necessary because the actuator uses a ball screw (recirculating ball bearings between the nut and threaded jackscrew), likely to reduce friction under load, and ball screws can back drive the actuator. The Mooney landing gear has no up locks, so the weight of the retracted gear could back drive the actuator unless it had some sort of locking mechanism. This is not a problem in the down position because the gear is locked down by an over-center mechanism in the linkages. Thus, only a one-way brake is needed.

The spring is a form of what is known as a wrap spring. It fits over the input hub driven by the motor and the output hub that drives the screw. This whole assembly fits inside a cylindrical housing with the spring having a slight interference fit in the bore. The spring can be thought of as "brake shoes" and the housing a "brake drum" in analogy with old style automotive drum brakes. Any attempt to back drive the actuator unwinds the spring slightly and cinches it in the housing stopping rotation of the ball screw.

I found online a company that manufactures these springs. https://reell.com/products/clutch-torsion-spring-manufacturers.

EDIT: Just to be clear: I don't mean to suggest that Reell manufactures the exact springs used by Eaton or Plessey but rather that Reell is one of several manufacturers that produce this particular type of spring. I don't know if Eaton or Plessey used an "off the self" spring, or if their actuators required a custom spring design. 

Skip

[EricJ]

24 minutes ago, PT20J said:

I've never disassembled one of these, so I don't fully understand all the details of the design, but it is clear from the descriptions in M20-282-A that the spring serves primarily as a brake to keep the gear in the up position. This is necessary because the actuator uses a ball screw (recirculating ball bearings between the nut and threaded jackscrew), likely to reduce friction under load, and ball screws can back drive the actuator. The Mooney landing gear has no up locks, so the weight of the retracted gear could back drive the actuator unless it had some sort of locking mechanism. This is not a problem in the down position because the gear is locked down by an over-center mechanism in the linkages. Thus, only a one-way brake is needed.

The spring is a form of what is known as a wrap spring. It fits over the input hub driven by the motor and the output hub that drives the screw. This whole assembly fits inside a cylindrical housing with the spring having a slight interference fit in the bore. The spring can be thought of as "brake shoes" and the housing a "brake drum" in analogy with old style automotive drum brakes. Any attempt to back drive the actuator unwinds the spring slightly and cinches it in the housing stopping rotation of the ball screw.

I found online a company that manufactures these springs. https://reell.com/products/clutch-torsion-spring-manufacturers.

Skip

That's a good resource, even as a potential OPP source.

 

[PT20J]

7 minutes ago, EricJ said:

That's a good resource, even as a potential OPP source.

 

Agreed. Now that I understand that these types of springs are common in linear motion control actuators, and that there are likely multiple producers, it wouldn't seem too hard to source. Problem is that if it isn't an off the shelf part, it might require a hefty setup charge and a minimum order. Hence, someone going the PMA route might make sense. Another thought is that Mooney is probably really short staffed and overloaded right now and someone doing the legwork to find a vendor might be a path forward.

Skip

[EricJ]

8 minutes ago, PT20J said:

Agreed. Now that I understand that these types of springs are common in linear motion control actuators, and that there are likely multiple producers, it wouldn't seem too hard to source. Problem is that if it isn't an off the shelf part, it might require a hefty setup charge and a minimum order. Hence, someone going the PMA route might make sense. Another thought is that Mooney is probably really short staffed and overloaded right now and someone doing the legwork to find a vendor might be a path forward.

Skip

In my admittedly limited experience with custom springs, many spring shops make one-off stuff all the time and setup isn't that big of a deal once the dimensions, etc., are sorted out.   It's not like a complex CNC part, spring winding is more straightforward.   Basically, I wouldn't assume setup would be a bigger barrier than waiting a long time or paying crazy prices, anyway.    Again, it's not like I've checked for this, but once in a while somebody gets custom springs wound here for a racing application or something and it seems like it's never really that bad.   There is a story among the local Mooney veterans at DVT of a guy with a J-bar C model that got a field approval to put lower gear doors on.   The added aero load required different return springs, so he had a set custom wound at a local shop to his new spec.   Anyway, just a thought, but this resource you found sounds like a good first stop for such a thing.

 

 

[N201MKTurbo]

http://www.crossoverdrives.com/Media/crossover_drives_catalogs/crossover drives psi clutch series.pdf
 

Perhaps these guys have a comparable Spring? I would think they have the expertise to make them.

https://reell.com/products/clutch-torsion-spring-manufacturers

Edited November 15, 2021 by N201MKTurbo

[N201MKTurbo]

Obviously, these springs can be made inexpensively.

https://www.amazon.com/Cutex-Clutch-Spring-R10393000-Machine/dp/B08PKGG1VB/ref=asc_df_B08PKGG1VB/?tag=hyprod-20&linkCode=df0&hvadid=527817862462&hvpos=&hvnetw=g&hvrand=17035189875460459296&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9030049&hvtargid=pla-1580726309432&psc=1

 

The magic words to search on are “Spring Wrap Clutch”

[N231BN]

This is the spring that came out of my 231 after 2350 hrs of use. The gear did chatter when cycling on jacks, that went away with the new spring.

[N201MKTurbo]

42 minutes ago, N231BN said:

This is the spring that came out of my 231 after 2350 hrs of use. The gear did chatter when cycling on jacks, that went away with the new spring.

Any chance you could take a calipers and measure the ID, OD, height and the wire height and width?

[N231BN]

Any chance you could take a calipers and measure the ID, OD, height and the wire height and width?

In order of request:
0.710
0.852
0.285
0.047
0.066

[Guest]

I can’t imagine many companies wanting to produce these springs.  The first lawsuit after a gear up landing would seal their fate.

Clarence