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Landing Gear and Prop Question


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Alright new owner here. 1970 M20C with electric gear. After landing with gear down green and green indicated on the floorboard, I keep getting an intermittent horn during taxi. The gear down green light flickers on and off intermittently and when the light blinks off the horn sounds. It’s very intermittent so it’s been difficult to reproduce. I did pull the bottom panel off and mechanic and I cleaned the contacts on the limit switch but it hasn’t fixed it. Looking for any advice on that. 
 

Second thing I’d like to ask is after taking off the prop is having a hard time maintaining a constant RPM. It has a brand new prop and recently had the governer tested and according to the shop it isn’t the governer. It seems to be worse with full throttle, when I lower MP it seems to not be as bad. 
 

Any help/advice is appreciated. Thanks

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Alright new owner here. 1970 M20C with electric gear. After landing with gear down green and green indicated on the floorboard, I keep getting an intermittent horn during taxi. The gear down green light flickers on and off intermittently and when the light blinks off the horn sounds. It’s very intermittent so it’s been difficult to reproduce. I did pull the bottom panel off and mechanic and I cleaned the contacts on the limit switch but it hasn’t fixed it. Looking for any advice on that. 
 
Second thing I’d like to ask is after taking off the prop is having a hard time maintaining a constant RPM. It has a brand new prop and recently had the governer tested and according to the shop it isn’t the governer. It seems to be worse with full throttle, when I lower MP it seems to not be as bad. 
 
Any help/advice is appreciated. Thanks
In the manual gear version, the gear warning horn is armed by a simple switch that detects the presence of the handle on the lock socket.

The switch is adjustable in position, and very limited in throw - My IA had to adjust move at annual this year because it wasn't always closing when the handle was locked into the socket.

I would very there is a similar condition going on with yours.

Does anyone have a diagram showing the position of the gear alarm switch on the electric gear conversion?
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Following Shu’s advice is good...

the gear warning circuit is documented barely well... in the POH... (got a copy?, or find one in the download section...)

Horn, light, two switches, clean and check their connections... 

Might be as easy as the throttle position switch on the back side of the panel...

 

Now about that rpm control... got a pic, or video?

harder to solve problems through the internet... without a stream of data...

Got an engine monitor?

How many hours are on the gov? How long since it’s OH?

Lots of mechanical things to wear in a gov...

  • valve
  • fly weights
  • gear pump (there are two gear pumps on your engine)
  • internal oil leaks
  • external oil leaks

PP thoughts only, not a mechanic...

Best regards,

-a-

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9 minutes ago, ShuRugal said:

In the manual gear version, the gear warning horn is armed by a simple switch that detects the presence of the handle on the lock socket.

The switch is adjustable in position, and very limited in throw - My IA had to adjust move at annual this year because it wasn't always closing when the handle was locked into the socket.

I would very there is a similar condition going on with yours.

Does anyone have a diagram showing the position of the gear alarm switch on the electric gear conversion?

Do you think that would be the same switch under the belly? Basically the limit switch?
 

5 minutes ago, carusoam said:

Following Shu’s advice is good...

the gear warning circuit is documented barely well... in the POH... (got a copy?, or find one in the download section...)

Horn, light, two switches, clean and check their connections... 

Might be as easy as the throttle position switch on the back side of the panel...

 

Now about that rpm control... got a pic, or video?

harder to solve problems through the internet... without a stream of data...

Got an engine monitor?

How many hours are on the gov? How long since it’s OH?

Lots of mechanical things to wear in a gov...

  • valve
  • fly weights
  • gear pump (there are two gear pumps on your engine)
  • internal oil leaks
  • external oil leaks

PP thoughts only, not a mechanic...

Best regards,

-a-

I’ll attach the video. I’d have to double check the governer hours. I just called the shop that just worked on it and they said they couldn’t find anything wrong. But I’d assume there’s not much else to blame except the governer...?
 

 

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Yes, I would expect it to be a similar style of switch, relocated to the gear linkage where the J-bar attaches.

The conversion to electric was available for the C as a kit - there should be a service instruction for the kit which details where the switch goes.

We also just had another MS member convert beck to J-bar from an electric gear - I don't recall who to link him, but the these was posted recently "Coronavirus Jbared me" or something similar.

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Josh,

Without knowing your mechanic...

How did he know there wasn’t a problem with the gov?

was he able to test the gear pump, valve and flyweights?

The other part that can wear is the in the prop itself... a cylinder there...

Essentially, it looks like the prop is altering its blade angle and the rpm is changing along with it...

or your tach is wandering unrelated to the prop...

Have you proven that the tach is working properly? (There’s an app for that...)

We have a really good prop guy around here... @Cody Stallings he might be familiar with what you have...

PP thoughts only, not mechanically inclined at all...

Best regards,

-a-

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Josh, the warning switch for the electric gear Mooneys is very different from the Johnson Bar system.

In the electric gear airplanes, there are limit switches attached to a mount.  Striker plates activate these switches which then serve multiple functions: stop the motor, switch on/off the appropriate light, and sound the warning horn through the switch on the throttle.

These switches get old over time, and will not activate at the same throw.  Unfortunately, this is the first warning that the switch is starting to go bad.  The switch can be adjusted in its mount so that it works properly, but if you do this you should probably budget for a new one sooner rather than later.  It is also possible that the locking adjustment nuts might have simply come loose, in which case you'd simply tighten the nuts and check gear rigging.

The biggest issue with your gear right now is that when the down lock switch intermittently clicks and you get the flicker and the horn, your electric gear motor is likely also being energized which puts a lot of strain on the system.

Before you fly the airplane again, I strongly suggest you get the airplane up on jacks and have the whole system checked for switch security and gear rigging before any significant damage is done to the motor or drive gears.

 

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1 hour ago, ShuRugal said:

In the manual gear version, the gear warning horn is armed by a simple switch that detects the presence of the handle on the lock socket.

The switch is adjustable in position, and very limited in throw - My IA had to adjust move at annual this year because it wasn't always closing when the handle was locked into the socket.

I would very there is a similar condition going on with yours.

Does anyone have a diagram showing the position of the gear alarm switch on the electric gear conversion?

Doesn't the switch on the Down Lock Block control the Red/Green light on the panel and switch on the throttle cable control the Horn? 

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4 hours ago, josh019 said:

But I’d assume there’s not much else to blame except the governer...?

first, check engine tach (noise & optic), second, recheck that governor just in case, as Anthony mentioned load of stuff there so more likely to go wrong  
The other bits are internal oil leaks in the spinner and blade pitch frictions, these are noticeable when you recycle the prop on power checks 

Also, just guessing: do you see erratic RPM only on high power? or worsen in low power? prop balance? on specific pitch/rpm ranges?  
on fine pitch (24MP & 27RPM) then probably spinner issues? on coarse pitch (27MP & 24RPM) then probably governor issues?

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How recently was the prop installed?  How much flight time since?  Did you exercise the prop well before the flight?  Was the oil warm?  Sometimes when installing a fresh prop it has air trapped in it.  It can be difficult to get the air out and it may take a bit of working the prop through its cycles to do it.  Has the prop been properly greased?  There is a procedure for that.  Don't just start pumping grease into it or you will get to have it resealed.  

 

Mark

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One really important thing...

For the flickering gear down light...

That could be one of two things...

  • the gear isn’t locked in place... or
  • the sensor is out of adjustment...

Best to find out before the gear collapses for some known reason...

Often with the mechanical J-bar system... the down lock block wears. The wear makes the pilot believe he has clicked the gear in place... but the wear causes an edge to grow... the gear feels like it is in place, but it isn’t... the click doesn’t happen... so it is down, but not locked...

Make sure your gear is locking... don’t fly it if it isn’t...

Using caution while moving the plane around... side loads could be hazardous...

PP thoughts only, not a mechanic...

Best regards,

-a-

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