40:1 landing gear question

[charlesual]

Does anyone happen to know when Mooney switched from 20:1 to 40:1 gear ratio on the landing gear?

TIA

 

 

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[vorlon1]

10 hours ago, charlesual said:

 

Does anyone happen to know when Mooney switched from 20:1 to 40:1 gear ratio on the landing gear?

TIA

 

 

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And, (hopefully with the originators ok):

what was the purpose?

[Hank]

11 hours ago, charlesual said:

Does anyone happen to know when Mooney switched from 20:1 to 40:1 gear ratio on the landing gear?

Not yet on my 1970 . . . .

34 minutes ago, vorlon1 said:

And, (hopefully with the originators ok):

what was the purpose?

I think it had to do with the backspring replacement (also N/A to my C).

[tony]

I didn't think Mooney switched at all.  I thought the 40:1 gears were a LASAR STC.  

[charlesual]

I talked to Lasar and Dan told they’ve seen numerous 20:1 actuators come back with worn gears and scared me by stating that what’s at risk is the gears binding and not being able to put the gear down normally or by alternate gear extension. They sell the 40:1 gear mod for $1500. I elected to inspect and regrease my 20:1 actuator and found the gears to be in perfect condition so I’m sticking with the 20:1 and I’ll do the SB requirement until I either source a 40:1 gear that’s not so expensive or my gears show wear.


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[Guest]

10 minutes ago, tony said:

I didn't think Mooney switched at all.  I thought the 40:1 gears were a LASAR STC.  

Introduced as S/I M20-112.

https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_instructions/sim20-112_Rev_A.pdf

Clarence

[tony]

Thank you Clarence.  Always a great wealth if information  Now I know.  

[Mooneymite]

I would speculate that a mis-rigged landing gear is the culprit behind the failure of the original design 20:1 gears.  Properly rigged, neither the manual nor electric gear puts stress on the retraction mechanism.

[Guest]

The 20:1 gears are highly loaded and subject to wear if not properly lubricated.  They are subject to an AD and an SB.

The 40:1 gears lower the load on the gears improving life expectancy, but they too need regular greasing.

Part of the poor design of the gear actuators chosen by Mooney way back through to modern production is a single point of failure with no backup redundancy.  The back up extension system uses the same actuator and gears as the main system.

In a Piper Comanche if the actuator fails, you disconnect it from the mechanical system and lower the gear with a lever similar to the Mooney Johnson bar.

Clarence

[Marauder]

The 20:1 gears are highly loaded and subject to wear if not properly lubricated.  They are subject to an AD and an SB.
The 40:1 gears lower the load on the gears improving life expectancy, but they too need regular greasing.
Part of the poor design of the gear actuators chosen by Mooney way back through to modern production is a single point of failure with no backup redundancy.  The back up extension system uses the same actuator and gears as the main system.
In a Piper Comanche if the actuator fails, you disconnect it from the mechanical system and lower the gear with a lever similar to the Mooney Johnson bar.
Clarence

Clarence - what modifications did Mooney make to increase the gear VLo & VLe speeds? I’m sure I speak for a number of 104 KIAS owners who would love to drop the gear at a higher speed. Heck, I even take 120 KIAS!


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[PT20J]

13 minutes ago, Marauder said:

 

Clarence - what modifications did Mooney make to increase the gear VLo & VLe speeds? I’m sure I speak for a number of 104 KIAS owners who would love to drop the gear at a higher speed. Heck, I even take 120 KIAS!


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It was only an approved change to the operating limitations starting with M20J S/N 24-0378. SB M20-209 allows you to change the placard for earlier M20Js. I'm not aware that Mooney ever extended the change to the F or earlier. I think the real strain of the gear actuator is during retraction and the lower the airspeed the better. I know that the manual gear certainly takes more force to retract as the speed increases.

Skip

[N201MKTurbo]

10 hours ago, M20Doc said:

The 20:1 gears are highly loaded and subject to wear if not properly lubricated.  They are subject to an AD and an SB.

The 40:1 gears lower the load on the gears improving life expectancy, but they too need regular greasing.

Part of the poor design of the gear actuators chosen by Mooney way back through to modern production is a single point of failure with no backup redundancy.  The back up extension system uses the same actuator and gears as the main system.

In a Piper Comanche if the actuator fails, you disconnect it from the mechanical system and lower the gear with a lever similar to the Mooney Johnson bar.

Clarence

I had a brush fall out of my actuator once. The emergency extension system worked. My ex partner once didn't notice the alternator quit and killed the battery. It worked for him.

So it isn't completely worthless.

[Guest]

1 hour ago, N201MKTurbo said:

I had a brush fall out of my actuator once. The emergency extension system worked. My ex partner once didn't notice the alternator quit and killed the battery. It worked for him.

So it isn't completely worthless.

It’s not entirely worthless, it’s a deficient design when both the main system and back up system use the same gears in the actuator.  There is no means of disconnecting a failed actuator from the retraction mechanism.  

Clarence

Edited July 29, 2020 by M20Doc

[MikeOH]

16 hours ago, charlesual said:

I talked to Lasar and Dan told they’ve seen numerous 20:1 actuators come back with worn gears and scared me by stating that what’s at risk is the gears binding and not being able to put the gear down normally or by alternate gear extension. They sell the 40:1 gear mod for $1500. I elected to inspect and regrease my 20:1 actuator and found the gears to be in perfect condition so I’m sticking with the 20:1 and I’ll do the SB requirement until I either source a 40:1 gear that’s not so expensive or my gears show wear.


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Same plan for me.  Just had the expensive Part II inspection done and all looked good.  What I've never figured out is if these 20:1 gears are so HORRIBLE, how do mine have over 5600 hours on them and still look good?  My guess is they've been properly maintained!

Personally, I rather LIKE the 3 second cycle time. Frankly, when (if?) mine need replacement, I'm going to look for a set of 20:1s!  The present ones have made it 50 years, so I figure I'm not too worried about having to replace them again!

[Mooneymite]

6 hours ago, MikeOH said:

Same plan for me.  Just had the expensive Part II inspection done and all looked good.  What I've never figured out is if these 20:1 gears are so HORRIBLE, how do mine have over 5600 hours on them and still look good?  My guess is they've been properly maintained!

Personally, I rather LIKE the 3 second cycle time. Frankly, when (if?) mine need replacement, I'm going to look for a set of 20:1s!  The present ones have made it 50 years, so I figure I'm not too worried about having to replace them again!

I agree.  Properly rigged and lubricated, the 20:1 gear set will go at least 4400 hours with very little wear.  Nothing lasts forever, but with a condition inspection every 200 hours, an impending failure should be detected ahead of time.

[David Lloyd]

"It’s not entirely worthless, it’s a deficient design when both the main system and back up system use the same gears in the actuator.  There is no means of disconnecting a failed actuator from the retraction mechanism. " 

Still, it is a reliable system used not only by Mooney but by Beech on all Bonanzas and Barons.  A part breaking and disabling both means of actuation on an otherwise working system is a 1% kind of problem.  More realistic is bent actuation rods, frozen rod ends and improper downlock tensions due to lack of maintenance. The biggest problem will always be failure of the PIC to put the landing gear down.

[PTK]

1 hour ago, Mooneymite said:

Properly rigged and lubricated, the 20:1 gear set will go at least 4400 hours with very little wear. 

This is wisdom! The key is properly rigged. Also it is important to respect the VLO speeds. The system sees the most stress in retraction. This also applies to the 40:1 gear as well. 

[Hank]

42 minutes ago, PTK said:

This is wisdom! The key is properly rigged. Also it is important to respect the VLO speeds. The system sees the most stress in retraction. This also applies to the 40:1 gear as well. 

Every takeoff is like a touch and go or missed approach:  positive rate, gear up.

It not only gives me better initial climb for safety (speed is life, altitude is life insurance), but it apparently protects my gear motor, too.  

[EricJ]

2 hours ago, David Lloyd said:

It’s not entirely worthless, it’s a deficient design when both the main system and back up system use the same gears in the actuator.  There is no means of disconnecting a failed actuator from the retraction mechanism.  

Still, it is a reliable system used not only by Mooney but by Beech on all Bonanzas and Barons.  A part breaking and disabling both means of actuation on an otherwise working system is a 1% kind of problem.  More realistic is bent actuation rods, frozen rod ends and improper downlock tensions due to lack of maintenance. The biggest problem will always be failure of the PIC to put the landing gear down.

Cessna twins use a similar system, too.   Cessna singles with the 'impaired duck' retractable gear have a similar issue where the emergency hydraulic hand pump is useless if the hydraulics have failed and won't hold pressure.   It really only backs up the electric motor, pretty much like the Mooney system.   It's often not practical to design a fully redundant or fail-safe backup for something like a small single-engine aircraft due to the complexity, cost, and weight it might add.

Comanches have a really good backup for electrically operated gear.  Arrows and Seminoles and others that have hydraulic gear that will free fall when the pressure is released are great, too.   Those kinds of systems seem to be in the minority, though, and they don't always work, either.

There is no perfect system. 

[Marauder]

17 hours ago, PT20J said:

It was only an approved change to the operating limitations starting with M20J S/N 24-0378. SB M20-209 allows you to change the placard for earlier M20Js. I'm not aware that Mooney ever extended the change to the F or earlier. I think the real strain of the gear actuator is during retraction and the lower the airspeed the better. I know that the manual gear certainly takes more force to retract as the speed increases.

Skip

If this is nothing more than a paper exercise, I wonder if the SB could be applied to earlier models with the same gear motor / gear ratios as the early Js? Would a FSDO even entertain the conversation?

http://www.mooney201.de/files/M20-209.pdf

[Hank]

27 minutes ago, Marauder said:

If this is nothing more than a paper exercise, I wonder if the SB could be applied to earlier models with the same gear motor / gear ratios as the early Js? Would a FSDO even entertain the conversation?

http://www.mooney201.de/files/M20-209.pdf

You can pay your A&P to do whatever you want. Why involve the FSDO???

[PT20J]

1 hour ago, Hank said:

You can pay your A&P to do whatever you want. Why involve the FSDO???

Because it's a change to an operating limitation which has to be approved by the FAA.

[Hank]

13 minutes ago, PT20J said:

Because it's a change to an operating limitation which has to be approved by the FAA.

That's my question:  why change a limitation, unless you want longer time between inspections. Just do it. 

It's just a Service Bulletin, which are not mandatory for us in Part 91 anyway.

Edited July 29, 2020 by Hank

[PT20J]

The SB is indeed optional under part 91. Unless you have an included serial number and wish to change the gear speed limitation, you can ignore it.

If you have a model earlier than a M20J, the SB does not apply and there is no way to change the gear speed without getting the FAA involved because the gear speed is a limitation listed in the TCDS. If you look at the TCDS for the M20J, you will note that the SB is referenced. Note also that the SB is marked FAA Approved. That's because in order to get FAA approval of the TCDS change, you can bet that Mooney sent a raft of engineering backup to the FAA.

Skip

[Hank]

1 hour ago, PT20J said:

The SB is indeed optional under part 91. Unless you have an included serial number and wish to change the gear speed limitation, you can ignore it.

If you have a model earlier than a M20J, the SB does not apply and there is no way to change the gear speed without getting the FAA involved because the gear speed is a limitation listed in the TCDS. If you look at the TCDS for the M20J, you will note that the SB is referenced. Note also that the SB is marked FAA Approved. That's because in order to get FAA approval of the TCDS change, you can bet that Mooney sent a raft of engineering backup to the FAA.

Skip

Sorry, I was still thinking this thread was about the speed that the landing gear moves using one of two gear sets. Suddenly you are talking about Vg, the speed that the airplane is moving with the landing gear hanging out in the wind regardless of the speed that the landing gear moves up and down . . . .

Please pardon my confusion . . . .