the infamous gear actuators

[Fix]

47 minutes ago, Yetti said:

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

I know early Bravos might have Plessey around 1990..
Not sure then Ovations came around.

[Hank]

My old C has an ITT motor, so I'm good, right?

[1980Mooney]

16 minutes ago, Hank said:

My old C has an ITT motor, so I'm good, right?

ITT Actuators

Mooney SB M20-189A allowed for the substitution of the ITT actuator to replace the Dukes actuator. The ITT actuator is almost a carbon copy of a Dukes actuator.  Don Maxwell believes it is not as good. Both actuators have the same gears and that the ITT actuator is not addressed in the AD or SB M20-190. He inspects the ITT just as a Dukes, and have found several near failures that have never been inspected.

AD 75-23-04: SB M20-190 | Mysite (donmaxwell.com)

Edited February 1 by 1980Mooney

[Fix]

I got a quote from LASAR for a NEW Eaton actuator for $35000 !!!

Any other suppliers that might have have them for sale, at lower price ?

[Fritz1]

google salvage shops that have Mooney airframe parts and call them, 

[toto]

5 hours ago, Fix said:

I got a quote from LASAR for a NEW Eaton actuator for $35000 !!!

Any other suppliers that might have have them for sale, at lower price ?

I’ve seen Mooney actuators on eBay for $8-10k, hoping never to need one

ETA: There’s at least four on eBay right now, searching for “Mooney actuator.” No idea whether any of these are the part number you would need. 

[KSMooniac]

17 minutes ago, toto said:

I’ve seen Mooney actuators on eBay for $8-10k, hoping never to need one

ETA: There’s at least four on eBay right now, searching for “Mooney actuator.” No idea whether any of these are the part number you would need. 

I suspect they're perpetually listed just hoping to find a desperate buyer that hasn't put any effort into scrounging.

I have a Dukes (and am happy for that!) but I have a spare from my '81 salvage for future contingency options.  It would require quite a bit of effort to retrofit into my plane, but I'd rather do that than pay $xx,xxx for another option!  

[Ragsf15e]

17 minutes ago, KSMooniac said:

I suspect they're perpetually listed just hoping to find a desperate buyer that hasn't put any effort into scrounging.

I have a Dukes (and am happy for that!) but I have a spare from my '81 salvage for future contingency options.  It would require quite a bit of effort to retrofit into my plane, but I'd rather do that than pay $xx,xxx for another option!  

I have a dukes as well on my ‘68 F… any idea if there’s someone out there who can “rebuild” them?  Im also hoping never to need it, but the inability to get replacement gears or a new actuator if they’re needed is also spooky.

[DCarlton]

4 hours ago, Ragsf15e said:

I have a dukes as well on my ‘68 F… any idea if there’s someone out there who can “rebuild” them?  Im also hoping never to need it, but the inability to get replacement gears or a new actuator if they’re needed is also spooky.

I’m thinking….  how would you know you need one?  After you successfully landed by hand cranking your gear?  Or after you’ve bellied in?  Or ?  

[Ragsf15e]

22 minutes ago, DCarlton said:

I’m thinking….  how would you know you need one?  After you successfully landed by hand cranking your gear?  Or after you’ve bellied in?  Or ?  

Good question.  I guess if it started behaving erratically or caused me to crank down the gear? Or maybe the 40/1 gears failed the AD inspection one year?  They aren’t currently available?

[Yetti]

22 hours ago, 1980Mooney said:

ITT Actuators

Mooney SB M20-189A allowed for the substitution of the ITT actuator to replace the Dukes actuator. The ITT actuator is almost a carbon copy of a Dukes actuator.  Don Maxwell believes it is not as good. Both actuators have the same gears and that the ITT actuator is not addressed in the AD or SB M20-190. He inspects the ITT just as a Dukes, and have found several near failures that have never been inspected.

AD 75-23-04: SB M20-190 | Mysite (donmaxwell.com)

some bit of info.

Cessna also used this actuator as a flap actuator.   I never figured out the cross reference number.   I have been through the disconnect gears and they are well made.   The biggest thing that would fail would be the motor and probably could be fixed with a set of brushes.  It's basically a side window motor and could probably find it on an old ford.

[PT20J]

On 2/1/2024 at 6:26 AM, Fix said:

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 ?

Everything you need to know is in this thread. Of the four known failures, Three have been Plessey actuators. One torsion (no-back) spring failed recently in less than 1000 hours. The company is defunct and, unless there is some new-old stock sitting on a shelf somewhere, there are no more springs available. The Eaton unit seems much more reliable. Personally, I would not buy an aircraft with a Plessey actuator unless I had a way to replace it, but that's a personal decision you'll have to make.

[1980Mooney]

12 hours ago, DCarlton said:

I’m thinking….  how would you know you need one?  After you successfully landed by hand cranking your gear?  Or after you’ve bellied in?  Or ?  

 

1 hour ago, Yetti said:

some bit of info.

Cessna also used this actuator as a flap actuator.   I never figured out the cross reference number.   I have been through the disconnect gears and they are well made.   The biggest thing that would fail would be the motor and probably could be fixed with a set of brushes.  It's basically a side window motor and could probably find it on an old ford.

 

11 hours ago, Ragsf15e said:

Good question.  I guess if it started behaving erratically or caused me to crank down the gear? Or maybe the 40/1 gears failed the AD inspection one year?  They aren’t currently available?

 

16 hours ago, Ragsf15e said:

I have a dukes as well on my ‘68 F… any idea if there’s someone out there who can “rebuild” them?  Im also hoping never to need it, but the inability to get replacement gears or a new actuator if they’re needed is also spooky.

 

This is from 2017 but Tom Raush at Top Gun talks about how they rebuild the Dukes.  He also indicates that the 40/1 gears are available but the disengage unit is a high wear item which they have to scrounge from salvage.  See page 18 in the attached Mooney Flyer

• " The early Mooneys have Dukes and ITT actuators. These are a real problem today, since we can't get parts, except for the updated gear kits (40:1). Most commonly, the disengage unit that allows the manual extension crank to engage, happens to be a high wear item, and we have no parts available. We have had to retrofit newer gear actuators to older models because of lack of parts and have almost used everything in the salvage yards."
• 2017-AugTMF.pdf (themooneyflyer.com)

Don Maxwell's site makes it sound like they rebuild the Dukes and ITT actuators.  His post shows the wear patterns on the gears that precede failure.

• AD 75-23-04: SB M20-190 | Mysite (donmaxwell.com)

As @Yetti said, if it is the electric motor issue that should be reparable. 

Edited February 2 by 1980Mooney

[DCarlton]

Does it make sense to reduce wear and tear on the gear actuator by changing your flying habits?  Reduce speed an extra 10-15 mph before you drop the gear?  Get the gear up 30 mph before you hit max gear extension speed?  Is that good piloting or an overreaction?  

These discussions make me feel better about my F.  Signifiant numbers were produced; better chance of finding parts perhaps.  So far so good.  

[1980Mooney]

On 2/1/2024 at 8:26 AM, Fix said:

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 ?

There is no reason to replace the Plessey gear actuator in 350 hours when it reaches 1,000 hours.  It is not an AD.

1,000 flying hours may not have a good relationship to actuator cycles. - consider a family flyer vs one used for rental or training.

That said, if you buy a plane with a Plessey and it does fail for any reason you are looking at a high cost for the actuator. The labor to swap it out does not sound too bad.  Per Tom Raush at Top Gun from the same Mooney Flyer

• "Since 1977, Mooney has used a linear jack screw actuator, which is a much more reliable system. 
  While there are several manufacturers, all are interchangeable. Later models are 24 volt, but the 
  motor is easy to change so you can put a newer actuator in an older model, just by changing the 
  motor. "

As @PT20J says that only buy it if you have a way to replace the Plessey.  That means there needs to be a substantial discount in the purchase price, or like @KSMooniac have a spare in hand.

[toto]

1 minute ago, 1980Mooney said:

There is no reason to replace the Plessey gear actuator in 350 hours when it reaches 1,000 hours.  It is not an AD.

I had the same thought but I wasn't sure if it was true for Sweden?  Maybe @Fix can advise on Swedish aviation regs

[EricJ]

5 minutes ago, DCarlton said:

Does it make sense to reduce wear and tear on the gear actuator by changing your flying habits?  Reduce speed an extra 10-15 mph before you drop the gear?  Get the gear up 30 mph before you hit max gear extension speed?  Is that good piloting or an overreaction?  

These discussions make me feel better about my F.  Signifiant numbers were produced; better chance of finding parts perhaps.  So far so good.  

The aero forces seem to help pull the gear down, at least on my J with the lower gear doors.   I have to get the gear up before 90-95 kts or it'll blow the breaker, but I can put them down at any speed below gear transit speed (134 kts on my airplane) with no issue.    There seems to be more stress on the system pulling the gear up than putting it down.    The rigging has been well within spec the entire time I've owned it.

 

[DCarlton]

15 minutes ago, EricJ said:

The aero forces seem to help pull the gear down, at least on my J with the lower gear doors.   I have to get the gear up before 90-95 kts or it'll blow the breaker, but I can put them down at any speed below gear transit speed (134 kts on my airplane) with no issue.    There seems to be more stress on the system pulling the gear up than putting it down.    The rigging has been well within spec the entire time I've owned it.

 

I've been surprised at how much you feel the floor flex when you drop the gear when the plane is on the jacks during annual.  I've wondered about the load on the gear motor.  Don't notice it so much in flight but you're busy doing other things.  I'm going to pay more attention to gear movement when the plane is at speed.  

The biggest problem with Mooney's is there's nothing else I'd rather own and fly that's not $700K and up.  :>. Maybe an experimental if well built and scrutinized.  

[Skyland]

Regarding the Dukes, back in 2003 in our 1977J partnership, I had the actuator fail on take off - at night, nonetheless. It resulted in failure of the gear to retract and the inability of the emergency extension system to operate.

Here's what led up to this event.  Mooney SB M20-190B calls for checking the backlash of the actuator worm and pinion gears every 100 hours.  In our IA's estimation he felt there was excessive play, and since a new pinion gear was available we sent the actuator to a well known West Coast facility who specializes in actuator repairs.  A new gear was installed and after installation back into the plane, the gear swing operated at twice the speed.  Wham up, wham down.  Didn't feel right at all.  Come to find out there are 40:1 and 20:1 gears.  Apparently, a new 20:1 gear was installed and the shop insisted all is fine.

Well, slow forward a mere one month later and the system failed.  Upon selecting gear up, a terrible grinding sound was heard.  Immediately put the gear switch to the down position and more continuous grinding.  I know, instantly reversing the motor is no doubt a big no no but it was somewhat instinctual trying to save the actuator.  Pulled the gear motor C/B this time to stop the grinding.  Continued climbing to a safe altitude and reported to the tower my issue.  Circled in the area attempting to troubleshoot.  Fortunately, the gear indicator in the floor was lined up indicating it failed in the down position.  Don't recall the annunciator light status.  Upon activating the emergency extension system, the handle just freewheeled.  Oh oh, couldn't confirm gear was actually locked.  Tower didn't seem too concerned and no equipment was called.  Came in and made a nice soft landing and gently taxied to the hanger.  Looking at the gear over center mechanism the next morning it was floppy loose.  Couldn't believe the gear held.

Called that shop to report what happened and their response was they received replacement gears that were not heat treated.  Ya, thanks for letting us know.  Probably explains the stripped teeth on the new gear.  The original pinion gear was reinstalled and to my knowledge it still in the plane to this day, knowing the current owner.

[Fix]

2 hours ago, 1980Mooney said:

There is no reason to replace the Plessey gear actuator in 350 hours when it reaches 1,000 hours.  It is not an AD.

The actuator works fine as I know of.
Spring has ~1650h and as I know after 2000h it's time to change it.

But there are no springs available...
 

[toto]

9 hours ago, EricJ said:

The aero forces seem to help pull the gear down, at least on my J with the lower gear doors.   I have to get the gear up before 90-95 kts or it'll blow the breaker, but I can put them down at any speed below gear transit speed (134 kts on my airplane) with no issue.    There seems to be more stress on the system pulling the gear up than putting it down.    The rigging has been well within spec the entire time I've owned it.

 

This is interesting. I normally retract the gear well before ME speed and I extend well before ME speed. But if it’s actually easier on the actuator to lower the gear at a higher speed, then I’ll stop doing the slow speed extension. (Or, at least, I’ll stop worrying about it.)

[EricJ]

8 minutes ago, toto said:

This is interesting. I normally retract the gear well before ME speed and I extend well before ME speed. But if it’s actually easier on the actuator to lower the gear at a higher speed, then I’ll stop doing the slow speed extension. (Or, at least, I’ll stop worrying about it.)

I don't know that's it's easier on it to lower it at higher speed, or that it makes much difference, but at least on mine it's clearly harder to raise it.   So raising it as soon as possible probably makes more difference than lowering it early.   Maybe that's another reason why the factory guys tended to pop the gear up right away.

[DCarlton]

2 hours ago, EricJ said:

I don't know that's it's easier on it to lower it at higher speed, or that it makes much difference, but at least on mine it's clearly harder to raise it.   So raising it as soon as possible probably makes more difference than lowering it early.   Maybe that's another reason why the factory guys tended to pop the gear up right away.

Misaligning the gear doors to create intentional lift when raising or lowering the gear would have been contrary to reducing drag.  I’ll bet the main doors are supposed to be aligned with the flow.  What about the nose gear.  I could see higher speeds creating more load lowering but maybe not as high as dragging the weight of everything up. Those nose gear doors are weird.  Who knows about drag during the transition. Hum.. just rambling out loud.   I’m going with the slower is better philosophy.  

[EricJ]

7 minutes ago, DCarlton said:

Misaligning the gear doors to create intentional lift when raising or lowering the gear would have been contrary to reducing drag.  I’ll bet the main doors are supposed to be aligned with the flow.  What about the nose gear.  I could see higher speeds creating more load lowering but maybe not as high as dragging the weight of everything up. Those nose gear doors are weird.  Who knows about drag during the transition. Hum.. I’m going with the slower is better philosophy.  

It seems to be tribal wisdom with some reasonable evidence that the lower gear doors on J's and K's create more aero force on the gear than the older models that don't have them.    Some of the older Mooney drivers on my field told me about an engineer local that years ago added the lower doors to a J-bar C model and had to have different assist springs wound to make up for the difference in required force.   This was apparently done with a DER and a 337, but it did seem to confirm that there's a difference in force required to move the gear due to the lower doors.    Looking at them it makes sense to me that they'll try to pull the gear down somewhat.    I'm just speculating that it's the same thing that makes my gear seem to be a lot easier on the motor to put down than pull up.

[DCarlton]

49 minutes ago, EricJ said:

It seems to be tribal wisdom with some reasonable evidence that the lower gear doors on J's and K's create more aero force on the gear than the older models that don't have them.    Some of the older Mooney drivers on my field told me about an engineer local that years ago added the lower doors to a J-bar C model and had to have different assist springs wound to make up for the difference in required force.   This was apparently done with a DER and a 337, but it did seem to confirm that there's a difference in force required to move the gear due to the lower doors.    Looking at them it makes sense to me that they'll try to pull the gear down somewhat.    I'm just speculating that it's the same thing that makes my gear seem to be a lot easier on the motor to put down than pull up.

Lower doors are for drag reduction when retracted ?  Forgot about those.  I don’t have them.  Found the link with the tribal knowledge.