the infamous gear actuators

[PT20J]

The M20J SMM calls for 1000 hr replacement of the spring in both Plessey and EATON actuators. Note that Plessey called it a torsion spring and EATON calls it a no-back spring. Mooney service documents are SIM20-92 for Plessey and SBM20-282A for EATON.

I don’t believe there are any parts available for Plessey actuators and Mooney’s solution is to replace with an EATON. 

[Alan Fox]

If I order a dozen , so they make them , will you guys pay 20% over list ???  I did it last year , I can do it again... Let me know , and I will make calls

[larryb]

My shop suggested I order, and pay for, a spring at my 2021 annual so it would be ready a year later in 2022 when I needed it. It took 10 months but it did eventually arrive.

How much would it be, per spring, to order 100, or 1000, vs 12? Usually the cost is in the manufacturing setup and not the material. I’d bet a long term order of 1000 springs would return a lot better than the stock market these days for a savvy investor.

[A64Pilot]

6 hours ago, Will.iam said:

As discussed before mooney has no spare cash for inventory. Can only sell what they order and one off’s or 2 or three more expensive so when they get about 10 orders or so pre paid they get an oder put through. I think last order they had arrive were already spoken for. 

Yeah, I was supposed to be on Lasar’s list for that order, but no call. That’s why I pre-paid with Top Gun, I figure then hopefully one will actually have my name on it when and if there is a next batch.

But things like this aren’t hard to forecast demand, if it’s 10 per year then buy 20 and when you’re down to 5 reorder. I can’t image Mooney is paying $500 a spring, I hope a fraction of that. I bet most Mooney heavy shops would keep one or two in stock if able. At $1,000 a spring surely there is room for profit for everybody.

‘So long as they keep coming is all I care about, I’m past 2500 hours on original spring.

[A64Pilot]

33 minutes ago, larryb said:

My shop suggested I order, and pay for, a spring at my 2021 annual so it would be ready a year later in 2022 when I needed it. It took 10 months but it did eventually arrive.

How much would it be, per spring, to order 100, or 1000, vs 12? Usually the cost is in the manufacturing setup and not the material. I’d bet a long term order of 1000 springs would return a lot better than the stock market these days for a savvy investor.

I’m thinking if the yearly use is 100, then order 100, if you sell 10 a month and it takes 3 months to get them in, reorder when you get to 30 left.

But it’s not smart to sit on several years worth

Surely though whoever makes these things doesn’t take a year to make them, 

[PT20J]

2 hours ago, Alan Fox said:

If I order a dozen , so they make them , will you guys pay 20% over list ???  I did it last year , I can do it again... Let me know , and I will make calls

I assume this is for Eaton springs, yes? Just out of curiosity, are you ordering from Mooney or Eaton?

[A64Pilot]

3 hours ago, Alan Fox said:

If I order a dozen , so they make them , will you guys pay 20% over list ???  I did it last year , I can do it again... Let me know , and I will make calls

I would if I hadn’t already paid for one six months ago that I hope will arrive soon.

[Pinecone]

Can you even order them directly from Eaton?

Many parts, the supplier will not sell direct.

We just had to replace the cowl flap motor.  It seems Globe will not sell you one, but will "overhaul" the one you have.  But the overhauled part is a new one.

Again, there was a thread, that I cannot find, about someone with a PMA that was willing to make these, but needed a broen one to determine what steel was used.

But if there is a group buy to order a batch from Eaton, count me in.

[A64Pilot]

On 12/19/2022 at 8:16 AM, Pinecone said:

Can you even order them directly from Eaton?

Possibly if Eaton has PMA, no if they don’t. But I bet they won’t sell direct.

Then there is the possibility that they would for a min order?

I think though they attach a lot of liability if they do, that they may avoid by selling to Mooney.

[BlueDun]

What is the result of a broken backspring?

[toto]

Just now, BlueDun said:

What is the result of a broken backspring?

If the spring is actually broken, then it will not be possible to extend or retract gear using either the electric actuator or emergency backup.

Anecdotally, my understanding is that this happens more often on retraction than on extension - so it may be more likely that your gear are stuck down than stuck up.

[A64Pilot]

How many broken NBS’s have there been though? 

I’ve been on this forum for 2 yrs I guess and while there have been  dozens of gear up landings, I don’t remember any from broken springs.

Although my insurence person mentioned a Mooney geared up at Daytona and couldn’t get them down either electrically or mechanically, but they didn’t know why.

I think if you drop gear as soon as you hit gear speed, dropping them is much harder on the actuator than retraction. I don’t know that but if you look at the lower doors they seem to be mounted such that they would have a very significant load pulling the gear towards the open position, and the actuator has to fight that.

It has to fight it on retraction too, but at roughly half the airspeed.

[PT20J]

1 hour ago, A64Pilot said:

How many broken NBS’s have there been though? 

I’ve been on this forum for 2 yrs I guess and while there have been  dozens of gear up landings, I don’t remember any from broken springs.

Although my insurence person mentioned a Mooney geared up at Daytona and couldn’t get them down either electrically or mechanically, but they didn’t know why.

I think if you drop gear as soon as you hit gear speed, dropping them is much harder on the actuator than retraction. I don’t know that but if you look at the lower doors they seem to be mounted such that they would have a very significant load pulling the gear towards the open position, and the actuator has to fight that.

It has to fight it on retraction too, but at roughly half the airspeed.

I doubt anyone knows. The FAA would only know if SDRs were filed. Mooney would only know if incidents were reported back to the factory. The NTSB would only know in the rare case it caused an accident.

For the Eaton, SBM20-282A mentions a single failure which precipitated a recall of specific serial numbers by Eaton.

For Plessey, SIM20-92 mentions two failures. The recent accident I referenced earlier in this thread makes three.

The Plessey springs failed at approximately, 400 hrs., 1200 hrs., and 1500 hrs. Time on the Eaton failure is unknown.

As near as I can tell from reading all the Mooney service literature, the 1000 hour replacement interval originated with a Plessey service instruction and Mooney carried it over to the Eaton actuator.

Skip

[A64Pilot]

Do they wear, or is it fatigue?

If fatigue like I think there really isn’t any point in inspection, crack growth once it begins is so rapid that even with frequent inspections you won’t find it before it fails.

Many springs are subjected to extremely high cycles before failure, think valve springs for instance, others like tailwheel springs not so much before they break.

If this spring does what I think it does and works like I suppose, chattering is likely to cause failure, but I doubt we would hear it.

Just wondered if crankshafts or connecting rods broke more often than NBS ?

I would think if it wasn’t very rare at least one person on this forum would have had one break?

[toto]

2 hours ago, A64Pilot said:

I think if you drop gear as soon as you hit gear speed, dropping them is much harder on the actuator than retraction. I don’t know that but if you look at the lower doors they seem to be mounted such that they would have a very significant load pulling the gear towards the open position, and the actuator has to fight that.

My understanding is that the spring isn't taking much abuse in normal operation - it has something to do with preventing the mechanism from turning backwards.  

There used to be a really fantastic photo essay on @Hyett6420's website, and @donkaye had a great blog post about the NBS, but both of those posts seem to be offline now.

The definitive thread here on MS is below.  Bring your popcorn - it's ten years long

https://mooneyspace.com/topic/10747-no-back-spring-in-landing-gear-actuators/

There was also a recent Mooney Flyer article about the NBS, nothing particularly new though:

https://themooneyflyer.com/issues/2020-SepTMF.pdf#page=12

[A64Pilot]

I think I know how it works.

I think it works by one side being fixed so it can’t turn and the other fixed to something that will turn if the gear weight tries to back drive the mechanism, I think the spring is over a shaft that’s turned by the motor and while the motor is doing the turning, nothing happens, but if the system is being back driven one end of the spring is rotated and it tightens up on the shaft stopping rotation.

But that’s all theory, I’ve never taken one apart nor have I seen any parts diagrams etc., so I could be WAY off.

If it works like I think  if it were to chatter from lack of lubrication or whatever, that would be putting lots of stress on a bent over tang that it would have to have and could break that tang off.

But the way I envision the spring working would mean if it broke it would only lose its ability to prevent the system from being back driven, so I’m missing something.

Either way it doesn’t matter how it works, I’m wondering on how often there are gear ups that are caused by this spring.

Not that I’ve met a large number of Mooney drivers, but out in the wild I’ve not yet met one that has ever heard of a no back spring and I think most if they had paid for one would have remembered it?

It would seem based on what I think is a min order quantity for Mooney to procure them that there aren’t many being replaced.

How many have heard of this thing prior to hearing about it here? I think the answer is not many, pretty sure the IA that took care of my aircraft before I bought it never had as it wasn’t replaced. Previous owner if he knew would have replaced it.

[toto]

10 minutes ago, A64Pilot said:

How many have heard of this thing prior to hearing about it here?

I had never heard of it before MS. I’m also on the original spring. I would like to get it replaced whenever the replacements are available, but it’s not all that high on my list of concerns. 

[201Mooniac]

50 minutes ago, A64Pilot said:

How many have heard of this thing prior to hearing about it here? I think the answer is not many, pretty sure the IA that took care of my aircraft before I bought it never had as it wasn’t replaced.

I've replaced mine 3 times over 27 years.  My IA (at the time, Tom Rouch now Mark Rouch) made me aware of it when I bought the plane and always tracks it as a time limited item.

[Will.iam]

I only know about it because the previous owner was an A&P and has a nice list of items that are tracked. 

[PT20J]

1 hour ago, A64Pilot said:

I think I know how it works.

I think it works by one side being fixed so it can’t turn and the other fixed to something that will turn if the gear weight tries to back drive the mechanism, I think the spring is over a shaft that’s turned by the motor and while the motor is doing the turning, nothing happens, but if the system is being back driven one end of the spring is rotated and it tightens up on the shaft stopping rotation.

But that’s all theory, I’ve never taken one apart nor have I seen any parts diagrams etc., so I could be WAY off.

If it works like I think  if it were to chatter from lack of lubrication or whatever, that would be putting lots of stress on a bent over tang that it would have to have and could break that tang off.

But the way I envision the spring working would mean if it broke it would only lose its ability to prevent the system from being back driven, so I’m missing something.

Either way it doesn’t matter how it works, I’m wondering on how often there are gear ups that are caused by this spring.

Not that I’ve met a large number of Mooney drivers, but out in the wild I’ve not yet met one that has ever heard of a no back spring and I think most if they had paid for one would have remembered it?

It would seem based on what I think is a min order quantity for Mooney to procure them that there aren’t many being replaced.

How many have heard of this thing prior to hearing about it here? I think the answer is not many, pretty sure the IA that took care of my aircraft before I bought it never had as it wasn’t replaced. Previous owner if he knew would have replaced it.

It never became an AD, so the way to know about it is to read the service and maintenance manual and the Mooney service bulletins. But, apparently a lot of mechanics (and owners) don’t check these.

Skip

[A64Pilot]

18 hours ago, PT20J said:

It never became an AD, so the way to know about it is to read the service and maintenance manual and the Mooney service bulletins. But, apparently a lot of mechanics (and owners) don’t check these.

Skip

One argument that I think spurious is that it’s not a Safety issue is why no AD but that argument doesn’t hold water as people have been hurt in gear up’s and there are many AD’s for less serious issues. I wonder if there just isn’t enough evidence for an AD?

I wonder how much of it was Eaton wanting to shed liability, from what I can tell one failed that tripped the Eaton SB, Mooney pretty much had to adopt the Eaton SB or accept liability, and I think there was some concern about one production lot?

I’m sure this has been beaten to death, just I’ve never heard of a failure and you would think that some number of gear ups would be due to the spring if it was much of a problem at all. But it seems missed rigged is a much more serious concern.

[PT20J]

What I find interesting is that there have been at least three documented failures of Plessey springs, but Mooney only issued one service instruction for Plessey actuators. Mooney's service literature has only mentioned a single failure in Eaton actuators (and it may have been a bad lot because Eaton, in response, recalled a range of serial numbers) and yet Mooney has issued a service instruction and three service bulletins for the Eaton. It may just be that the Eaton was more widely used, or that Plessey is no longer supported, but  the service documentation makes it sound like the Eaton units are more problematic whereas I would be more concerned if I had a Plessey actuator based on the (sparsely) documented history of failures.

Skip

[A64Pilot]

I think it’s because the Plessey is gone, no parts, answer is replace it with an Eaton at I think $14,000?

What kind of service bulletin could you issue on something with no parts available?

I paid $1,000 six months ago for s spring so I’ll have it changed, figure actuator needs cleaning, inspection and relubing anyway, besides amortized out it’s only $1 an hour, and 1,000 hours will likely retire me.

[Fix]

If I buy an Mooney with Plessey gear actuator, and there is 350h left on the spring.

Is the only option today to replace whole gear actuator with Eaton.
Any estimated price for gear actuator and installation?

Can Eaton supply them without waiting 1 year ?

[Yetti]

Just curious is this an issue on say like an  Ovation?