What is happening in Kerrville?

[201Mooniac]

56 minutes ago, A64Pilot said:

That’s what the girl at Top Gun told me when I called and asked if she had an update. I don’t know her name but she seems to know what she’s talking about.

That would be Rachel and she definitely knows what she is talking about.

[kortopates]

On 7/4/2023 at 2:52 PM, Danb said:

And here’s a broken cable revealed when changing the NBS  A nick in the brass ring messed up the cable. The plane only had about 900+ hours 

Great example of why its a bad idea to practice a manual gear extension in the air! Who would ever think a newer Acclaim would have a bad cable, they're protected by a plastic sheath. Must have been missed somehow at earlier annual(s); although not all of the cable is viewable while doing the manual extension..

[A64Pilot]

2 hours ago, 201Mooniac said:

That would be Rachel and she definitely knows what she is talking about.

I came to that opinion quickly myself, and from her demeanor she didn’t seem to be making this up about the No back spring.

‘What she couldn’t tell me though was if there is going to be another order or not, I can only hope that Eaton agrees thst there is a problem with the springs and will replace them, but it’s been several months since then.

Called for an update, Annika I think she said her name was? Anyway she is supposed to call me back when she knows something, I assume she’s going to call Mooney, but that’s my assumption she didn’t say that.

Edited July 7, 2023 by A64Pilot

[PT20J]

I did some research on no-back springs a while back. It's confusing to sort out because Mooney used two different actuators with "no-back" springs; one manufactured by Plessey, and one manufactured by Eaton. There were a couple of early spring failures in Plessey actuators with TT > 1000 hours, and I believe this is where the 1000 hour replacement recommendation came from. There was another recent failure of a Plessey NBS bringing the total Plessey failures to 4 or 5. There was one reported failure of an Eaton NBS that led to Eaton recalling a batch of actuators for inspection. Don Maxwell told me that this was due to a bad batch of springs. Don also told me that the spring was supposed to be rated for 20K operations. Mooney seems to have just carried over the 1000 hour limit from the Plessey to the Eaton.

Personally, I have an Eaton with a spring that was replaced about 700 hours ago by the previous owner and I don't plan to ever replace it. The Eaton actuator seems pretty robust. It's weak point is the brass clutch for the emergency gear extension that can get cobbled up if the emergency gear extension lever isn't fully engaged and the motor is activated.

If I had a Plessey actuator, I would be looking to replace it with an Eaton because I don't believe there are parts available for these and they have had several failures. It's an expensive replacement, however.

Skip

[toto]

5 hours ago, A64Pilot said:

I want one because I think after 2200 hours and 42 years it’s time to have the actuator disassembled, cleaned and re-lubricated and while you’re there it makes sense to me to replace the spring. In fact I think disassembling, cleaning and re-lubing the actuator every 10 years or so is prudent, that’s why I think replacing the spring every 1,000 hours isn’t a bad idea, because I think you should be there anyway.

The tough question is whether the original NBS is more or less likely to suffer premature failure than a new one. Depending on the failure rate of new springs vs old ones, you might actually be better off having the actuator serviced and keeping the old spring. 

Really wish we had more data on this - but as you said, the fact that we haven’t heard about failures here on MS is a good sign that they’re rare. 

[A64Pilot]

35 minutes ago, toto said:

The tough question is whether the original NBS is more or less likely to suffer premature failure than a new one. Depending on the failure rate of new springs vs old ones, you might actually be better off having the actuator serviced and keeping the old spring. 

Really wish we had more data on this - but as you said, the fact that we haven’t heard about failures here on MS is a good sign that they’re rare. 

Yeah, I wish I had better data too, but nobody is collecting data, so you have to go with what data you can get.

So far as it being robust, I think it is, it’s designed for a max load of 2,000 lbs and to pull 55 amps. Without looking I’m not sure what our CB is, maybe 15 amps? Whatever it is it’s not 55 amps, so it’s not even possible to come anywhere near its max allowable load the CB will trip way before.

I’d assume highest load is retract and that it’s not but a couple hundred lbs max? I think gear extension is actually pulling against it, just the opposite of retract and I guess could be higher based on A/S but an opposite load.

Personally I don’t drop gear until the white arc because I really, really want to baby the thing. I think there are NO new ones at any cost?

I have a hard time justifying testing the manual extension myself as testing could cause damage and does it guarantee anything as far as continued operation?

 

Edited July 7, 2023 by A64Pilot

[PT20J]

Manual extension should be tested at annual inspection when the airplane is on jacks  

There’s not much data on the springs because out of thousands of airplanes and countless gear cycles there has only been a handful of documented failures. It’s statistically insignificant and the 1000 hour limit seems completely made up. 

[1980Mooney]

6 hours ago, A64Pilot said:

But then hours isn’t a good way to track as it’s more likely cycles are what causes the fatigue, but who tracks landing cycles? ..Then throw in how many failures of NBS springs have there been? I don’t know but suspect not many ….that’s why I think replacing the spring every 1,000 hours isn’t a bad idea, because I think you should be there anyway.

If the spring costs $1,000 it is a bad idea to change something that doesn’t need changing. Making us spend a $1,000/each as a precaution to replace all the springs in the fleet with electric landing gear because a) some boneheads forgot how to manufacture and b) more boneheads did not trace the handful of bad NB springs that got installed is insanity. 

They don’t fail at 1,000 hours  And as you have proven they don’t fail at 2,200 hours and 42 years.

BTW - I predict that the price of the properly manufactured springs will go up once they get them into inventory. 

My 2 cents…

[Echo]

Putting the R in ridiculous.  I will pass on this maintenance induced failure...testing emergency gear extension and replacing back spring.  $1000 spring? f#$& that.

[PT20J]

47 minutes ago, 1980Mooney said:

If the spring costs $1,000 it is a bad idea to change something that doesn’t need changing. Making us spend a $1,000/each as a precaution to replace all the springs in the fleet with electric landing gear because a) some boneheads forgot how to manufacture and b) more boneheads did not trace the handful of bad NB springs that got installed is insanity. 

They don’t fail at 1,000 hours  And as you have proven they don’t fail at 2,200 hours and 42 years.

BTW - I predict that the price of the properly manufactured springs will go up once they get them into inventory. 

My 2 cents…

Well, as I said, the 1000 hrs comes from the two early Plessey failures. It’s not a airworthiness limitation so there is nothing that requires you to adhere to it. 

Eaton apparently did have traceability and recalled a certain lot of actuators, but since it was a Mooney service bulletin rather than an AD, there is nothing that required owners to comply. 

If you have the Eaton actuator you should be fine. 

[ArtVandelay]

Do these not require any maintenance? No grease, just testing during annual?

[Fly Boomer]

8 minutes ago, bluehighwayflyer said:

If it makes you guys feel any better the NBC spring on my previous 1978 M20J (with an Avionics Products actuator) was replaced by Top Gun at the behest of a previous owner at 3500 TTAF and my IA and I replaced it again at 10000 TTAF, so the second one had 6500 hours on it at replacement.

I now believe the “bad batch” theory, personally, and would only be concerned about the NBC spring if the one I had installed was manufactured in the years just before 2004 when the SB was issued.  Disassembling, cleaning, inspecting, and lubricating the actuator every decade or so, per the SB, is a very good idea, though.  Mine was pretty dry and chattering a bit when we took it apart but was nice and quiet thereafter.

 

When you opened it up, did you use the mixture of grease and molybdenum powder?

[A64Pilot]

12 hours ago, PT20J said:

Manual extension should be tested at annual inspection when the airplane is on jacks  

There’s not much data on the springs because out of thousands of airplanes and countless gear cycles there has only been a handful of documented failures. It’s statistically insignificant and the 1000 hour limit seems completely made up. 

I’m not saying do or do not do, but testing during Annual only determines it will work that one time it was tested.

Now if for some reason the emergency system accumulated any wear then yes it’s a pretty easy case to make that it should be tested at some interval, but what interval?

It would seem maybe that the time to test could be if you ever found the manual lever released or tried to actuate the gear with it released?

So far as never replacing something until it “needs” it, does anyone wait until the tire busts before replacing it?

Tire comment not meant towards the quote, just thrown out there.

Maintenance and replacement intervals are tough to determine, but very often preventative maintenance saves huge amounts of money, yes 1K for a spring is overpriced for the item I think, but compared to the expense of a gear up it’s nothing. Depending on the damage and insured amount of the airplane a gear up can well be the death knell of the airplane, but best case your out of an airplane for an extended period, and of course most often it’s not really “as good as new” when you do get it back.

So it’s tough to determine what’s the best course of action because there just isn’t any real repeatable data out there.

It’s similar to tail wheel springs on the Crop Duster I used to help build, some broke them every few hundred hours, some flew thousands of hours and never broke one. On that I believe how and where they were landed was the difference, but how do you recommend a replacement interval? We had data, so many springs were broken over the years we even fielded a rudder repair kit. But the data was all over the place from a couple hundred hours to probably over ten thousand.

[PT20J]

2 hours ago, Fly Boomer said:

When you opened it up, did you use the mixture of grease and molybdenum powder?

That’s only used for the Dukes actuators which do not have a no back spring.

[PT20J]

2 hours ago, bluehighwayflyer said:

If it makes you guys feel any better the NBC spring on my previous 1978 M20J (with an Avionics Products actuator) was replaced by Top Gun at the behest of a previous owner at 3500 TTAF and my IA and I replaced it again at 10000 TTAF, so the second one had 6500 hours on it at replacement.

I now believe the “bad batch” theory, personally, and would only be concerned about the NBC spring if the one I had installed was manufactured in the years just before 2004 when the SB was issued.  Disassembling, cleaning, inspecting, and lubricating the actuator every 1000 hours or so, per the SB, is still a very good idea, though.  Mine was pretty dry and chattering a bit when we took it apart but was nice and quiet thereafter.  FWIW, the 6500 hour NBC spring we removed looked fine, visually, under a magnifying glass.

 

You make my point. There is tons of data that Eaton springs go many thousands of hours since many (most?) owners and shops don’t even seem to know about the 1000 hr replacement interval and failures are extremely rare.

The last Plessey spring with a documented failure had been replaced only a few hundred hours before it broke. 

I agree that periodic inspection and lubrication is a good idea.

[A64Pilot]

I used to ask every Mooney driver I met out in the wild if they had changed their NBS and who did they got to do it, because of course I wanted to find out where to either take the airplane, or where to send the actuator.

I never met a single one who even knew what I was talking about. 

I’m going to guess that the majority of springs have never been changed.

I think a poll here of how many aircraft that were purchased that had their springs changed prior to purchase as well as was the prior owner a participant of this forum might give as good a data as there is.

Knowing how many NBS kits the factory sells a year might give an idea as well.

Data that I would like to have is other than pilot’s just forgetting the gear, what are the causes of failure?

I’ve heard of several failed actuator tubes and my guess most of those are from hard landings, but how many are from failed actuators of any kind of failure mode, and what’s the most common failure mode?

In other words what do we need to inspect for, what needs maintaining? I know follow the manual, not arguing against that, but what needs special attention? Saying everything does isn’t really an answer.

Soon after buying my airplane it developed a worrying habit, I would put the gear switch down and nothing would happen, that I could see how it could result in a gear up, and as it was intermittent and usually after some interval they would come down (I never had to manually drop the gear). I could also see how in the gear up landing how the actuator could activate causing damage, and how after the aircraft was recovered how the gear would seem to operate properly.

Just saying it’s possible that some of the story’s we hear of “I put the gear down” may be true, not every one of them is pride trying to cover a mistake.

FAA issued something not too long ago highlighting that we need to be more attentive to our gear maintenance, but as it wasn’t specific it wasn’t worth much, I couldn’t determine are the primarily worried about manual gear down locks, limit switches in electric gear, relays, gear switches or what?

Been nice if they came out and listed in order the top 5 causes of a gear up landing or something.

[PT20J]

When moving the gear switch either up or down, I keep my hand on the switch until the light confirms that it has completed the operation. When putting it down, I confirm the floor indicator. This habit helped immediately alert me when it failed to retract due to a bad relay recently.

[toto]

19 minutes ago, A64Pilot said:

I used to ask every Mooney driver I met out in the wild if they had changed their NBS and who did they got to do it, because of course I wanted to find out where to either take the airplane, or where to send the actuator.

I never met a single one who even knew what I was talking about. 

I’m going to guess that the majority of springs have never been changed.

I think a poll here of how many aircraft that were purchased that had their springs changed prior to purchase as well as was the prior owner a participant of this forum might give as good a data as there is.

Knowing how many NBS kits the factory sells a year might give an idea as well.

Data that I would like to have is other than pilot’s just forgetting the gear, what are the causes of failure?

I’ve heard of several failed actuator tubes and my guess most of those are from hard landings, but how many are from failed actuators of any kind of failure mode, and what’s the most common failure mode?

In other words what do we need to inspect for, what needs maintaining? I know follow the manual, not arguing against that, but what needs special attention? Saying everything does isn’t really an answer.

Soon after buying my airplane it developed a worrying habit, I would put the gear switch down and nothing would happen, that I could see how it could result in a gear up, and as it was intermittent and usually after some interval they would come down (I never had to manually drop the gear). I could also see how in the gear up landing how the actuator could activate causing damage, and how after the aircraft was recovered how the gear would seem to operate properly.

Just saying it’s possible that some of the story’s we hear of “I put the gear down” may be true, not every one of them is pride trying to cover a mistake.

FAA issued something not too long ago highlighting that we need to be more attentive to our gear maintenance, but as it wasn’t specific it wasn’t worth much, I couldn’t determine are the primarily worried about manual gear down locks, limit switches in electric gear, relays, gear switches or what?

Been nice if they came out and listed in order the top 5 causes of a gear up landing or something.

One of the distressing things I see with retract pilots generally is that they don’t do much preflight inspection of the gear. When I do a preflight, I’m lying on the ground with a flashlight and looking up into the gear wells, looking for anything unusual with the tires, gear, pucks, tubes or mechanism. I know that I can’t see everything, but the goal is to have a very very clear picture of how things normally look, so it’s obvious when there’s something unusual.

I have a suspicion that when someone has a problem with their gear, it didn’t just happen spontaneously, but that it was developing over a period of time, and their abbreviated “check the fuel, check the oil” preflight was inadequate to see the trend. 

[Fly Boomer]

9 hours ago, PT20J said:

That’s only used for the Dukes actuators which do not have a no back spring.

If it's an Eaton or Avionics Products actuator, what holds the gear up?

[A64Pilot]

7 minutes ago, Fly Boomer said:

If it's an Eaton or Avionics Products actuator, what holds the gear up?

I thought that was the purpose of the no back spring, to keep the actuator from being back driven in either direction?

Never seen a Dukes but assume it may be a worm gear as those can’t be back driven, a chain hoist is an example.

[Fly Boomer]

35 minutes ago, A64Pilot said:

I thought that was the purpose of the no back spring, to keep the actuator from being back driven in either direction?

Skip says the others don't have the NBS.  I thought they all did.  Mine (252) isn't Dukes but logs say "actuator clutch spring replaced".

[EricJ]

35 minutes ago, Fly Boomer said:

Skip says the others don't have the NBS.  I thought they all did.  Mine (252) isn't Dukes but logs say "actuator clutch spring replaced".

The systems with the lawnmower-pull-type emergency deployment have NBS.   The crank-handle type do not.

[Fly Boomer]

1 minute ago, EricJ said:

The systems with the lawnmower-pull-type emergency deployment have NBS.   The crank-handle type do not.

So, models later than the 252 have a crank instead of the recoil starter and, hence, don't have the NBS? 

[EricJ]

2 minutes ago, Fly Boomer said:

So, models later than the 252 have a crank instead of the recoil starter and, hence, don't have the NBS? 

No, aircraft before 1978 have a crank-handle emergency gear deployment system and no NBS.   The lawnmower-pull-type emergency deployment was introduced in 1978.

[PT20J]

1 hour ago, A64Pilot said:

I thought that was the purpose of the no back spring, to keep the actuator from being back driven in either direction?

Never seen a Dukes but assume it may be a worm gear as those can’t be back driven, a chain hoist is an example.

That's correct. The Dukes uses a wheel and worm gear train like the flap actuator. This is inherently locking. The Plessey and Eaton units use a ball screw driven by a spur gear chain that can be back driven and since there are no mechanical up locks on an electric gear Mooney, it needs a brake keep the weight of the gear from back driving the actuator. The spring acts as wrap spring brake in one direction and a wrap spring clutch in the other.