Landing Gear Question

[alextstone]

During the pre landing check at the end of my last flight, I noticed that the Gear Down annunciator light was not illuminated. The great indicator was roughly aligned though, see photo. After landing, the annunciator lit up.

 

 

What are your thoughts?

 

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[Yetti]

What happens when you use the test button?

 

[alextstone]

What happens when you use the test button?
 

During the flight, no change your pressing the test button. Now, the Gear Down light is illuminated.

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[DVA]

Loose bulb or wiring issue. The lamp is simply there to illuminate the mechanical indicator.

 

Try tapping on the plastic cover (with purpose) when you lower the gear and it’s not on. If it flickers or illuminates when you do that you’ve found the easy to solve problem. If not, you’ll have to start to trouble shoot.

 

Your plane is safe to fly without a working lamp there. Your concern is the mechanical indicator is aligned.

 

 

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[alextstone]

50 minutes ago, DVA said:

Loose bulb or wiring issue. The lamp is simply there to illuminate the mechanical indicator.

 

Try tapping on the plastic cover (with purpose) when you lower the gear and it’s not on. If it flickers or illuminates when you do that you’ve found the easy to solve problem. If not, you’ll have to start to trouble shoot.

 

Your plane is safe to fly without a working lamp there. Your concern is the mechanical indicator is aligned.

 

 

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Hi DVA,

 

 My post was not clear.  The light that was not illuminated was the Gear Down light on the panel mounted annunciator panel, not the one for the indicator on the floor.  I posted that photo to show that the green bar is not quite lined up with the center bar of the indicator.  I am thinking that the gear is just a bit out of alignment, explaining the intermittent outage of the panel annunciator.  Thoughts?

 

Alex

 

[DVA]

Hi DVA,
 
 My post was not clear.  The light that was not illuminated was the Gear Down light on the panel mounted annunciator panel, not the one for the indicator on the floor. Thoughts?
 

As they say “that changes everything!”

We’ve found that many shops do not have special tools needed to accurately set the gear tensions per Mooney’s recommendations, and as such just swing the gear during an annual and consider things to be ok. Please make sure that the correct procedure has been done recently on your aircraft. That said, the indicator is imprecise, hence the “donut” of confidence. By rigging the gear correctly you’ll be sure to know it’s all lining up correctly underneath and as long as the indicator is in the zone, you’re good.

On to the panel lamp. Could just be an out of aligned microswitch, or a slew of other things electrical. My gut says your gear is likely ok from a travel standpoint, but that doesn’t mean it’s optimally rigged.

Let us know!
DVA


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[alextstone]

1 minute ago, DVA said:

 

As they say “that changes everything!”

We’ve found that many shops do not have special tools needed to accurately set the gear tensions per Mooney’s recommendations, and as such just swing the gear during an annual and consider things to be ok. Please make sure that the correct procedure has been done recently on your aircraft. That said, the indicator is imprecise, hence the “donut” of confidence. By rigging the gear correctly you’ll be sure to know it’s all lining up correctly underneath and as long as the indicator is in the zone, you’re good.

On to the panel lamp. Could just be an out of aligned microswitch, or a slew of other things electrical. My gut says your gear is likely ok from a travel standpoint, but that doesn’t mean it’s optimally rigged.

Let us know!
DVA


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I hear you about attention to detail.  This airplane is new to me as of September of this year.  I have encountered many more issues than I had hoped (see my other posts).  I recently scoured my logbooks line by line and recorded the last maintenance interval on every component to generate a list of overdue or suspect items.  So many discrepancies were found that I have learned to be much more involved going forward.  The shock donuts are at the top of the list.  They were last changed in 2007.  I plan to have the gear thoroughly checked and tensioned, etc. when I have the donuts replaced.  What questions should I ask of the shop in your view?

 

BTW, I used Pilot Partner app to organize the Maintenance items.  Pretty cool.  See attached PDF.

 

N1084U MX Status Report (1).pdf

[PT20J]

I think you are saying that the gear down light on the annunciator panel did not illuminate, but the floor indicator was in alignment and the floor indicator light was on.

I don't have a wiring diagram for an M, but the gear system is likely the same as my J. The down limit switch in the belly is a double pole switch. One pole shuts off the actuator motor when the gear is down and the other pole controls the light. It could be a loose connection between the switch and the annunciator panel, or a bad switch. It's probably not a switch adjustment since the motor apparently shuts off OK. Also, the annunciator light dims when the NAV lights are on and this can make it hard to see in the daytime.

Skip

[gsxrpilot]

4 hours ago, alextstone said:

BTW, I used Pilot Partner app to organize the Maintenance items.  Pretty cool.  See attached PDF.

N1084U MX Status Report (1).pdf

A good friend of mine, has created that app. It's very good.

[hypertech]

Were your nav lights on?  Mine dims with the nav lights. No other indicator - only the gear down indicator. It can be so dim in the day that it looks off. 

[alextstone]

10 hours ago, hypertech said:

Were your nav lights on?  Mine dims with the nav lights. No other indicator - only the gear down indicator. It can be so dim in the day that it looks off. 

No, that was the first thing I checked.  I flew again today.  Upon departure, the "Gear Down" panel annunciator was brightly lit.  Upon gear extension, my wife swore she could see a dimly lit annunciation; I could not.  The floor indicator was "in the green" so we landed without further consideration.   

On a related topic, my shock donuts are quite old (11 years!) and even though they have passed annual inspection, I feel I should replaced them per the Mooney service instructions of 3-5 years for long body (heavier) aircraft.  I figure when that's done, it would be a good time to have the whole gear system re evaluated and serviced / adjusted as necessary.  Anyone have further input on this? What should I expect to budget for this?

[gsxrpilot]

The pucks are about $110 each and you need 11 of them, if I remember correctly. The gear pre-load and over center should be checked at annual.

[alextstone]

9 minutes ago, gsxrpilot said:

The pucks are about $110 each and you need 11 of them, if I remember correctly. The gear pre-load and over center should be checked at annual.

Thanks, Paul.  What is your opinion on the replacement interval?  3-5 yrs as per the Mooney Service Instruction or on condition?

[PaulM]

Donuts are done per the maint spec. (I sent you a link to the manual).. 

A. Main gear shock discs. (Fig. 32-28).

(1) Remove dust shield. Check gap between re- taining collar (A) and top retaining plate (B). Allowable gap is 0.00 to 0.85 inches.

I'm looking at the wiring diagram for your SN..  It seems that if the down limit switch is good the floor lamp will illuminate and trigger the annunciator lamp. If the display lamp isn't correct then it would be either in the wiring or internal to the indicators..

Now: how is the "test" button?.  does the gear down illuminate with the test button?.. if not, it is internal to the annunciator panel.   flaky lamp or something else. 

Looked further at the wiring diagram, the other side of that bulb goes to the NAV light switch, and  a dimmer resistor so a problem there will also affect the indicator. 

Edited December 29, 2018 by PaulM

[LANCECASPER]

[gsxrpilot]

37 minutes ago, alextstone said:

Thanks, Paul.  What is your opinion on the replacement interval?  3-5 yrs as per the Mooney Service Instruction or on condition?

I would say on condition. But then I don't fly a long body. 5 years might be just about right for the long bodies.

[carusoam]

Expect on condition...

They compress continuously, slowly, over time... Crosslinked rubber experiences cold flow...

Fresh donuts are enjoyable...

Completely flat ones, not so much...

The maintenance manual makes it easy to measure, go/nogo...

Leaving the tanks full all the time probably doesn’t help the cause.

M20Cs go a decade...

M20Rs might go 5 years...

All based on time, temp, weight, over time...

PP thoughts only, not a mechanic.

Best regards,

-a-

[Guest]

Once your gear rigging is checked/confirmed you can have the floor position indicator ( item 37)adjusted so that the lines are aligned.  Removed the plastic trim, loosen the screws on the plastic lens, adjust until aligned and secure the screws.

Clarence

Edited December 29, 2018 by M20Doc

[alextstone]

Thanks, All, for the great info.  I’ll inspect.

 

Alex

[Zack EA]

11 hours ago, alextstone said:

Thanks, Paul.  What is your opinion on the replacement interval?  3-5 yrs as per the Mooney Service Instruction or on condition

Mine were changed last month, there were 12 years old and were still in OK shape. It all depends on the specs. 

[hypertech]

My pucks are about the same age and I decided to have them changed at this years annual.  You do need 11 of them and the cheapest price I could find was on sky geek.  They list at $106 there and if you wait around on the page for a while it gave me another 5% off to complete my order so I paid $100 each.  They are slow to ship though so order early.