Need help identifying part and purpose

[shawnd]

Hey folks, need some help identifying these parts behind the attitude indicator and where the two outgoing yellow wires lead to. Tried looking the part number painted on the aluminum but no luck in the service manual. The yellow wires are coming out of a resistor (?) on the far left side close to the skin of the body. We tried to take a pic of the resistor as best as we could. Any help appreciated!

[shawnd]

Some additional info: one of the yellow wires from the dimmer bus wraps under the panel and goes to one resistor. Another yellow wires comes out of the same slot and goes to the second resistor. Each resistor outputs one wire and that what we see coming out. 
 

 

[N201MKTurbo]

The yellow disk is your airspeed safety switch. I think the resistors are to dim your annunciator lights when the nav lights are on.

[N201MKTurbo]

There is no pitot line connected to your safety switch.

[PT20J]

No static line either. How did it pass a gear check?

[shawnd]

1 hour ago, N201MKTurbo said:

There is no pitot line connected to your safety switch.

 

4 minutes ago, PT20J said:

No static line either. How did it pass a gear check?

The plane is sitting in avionics shop undergoing avionics install. Hence it’s in this state. They will be installing new lines for pitot and static. 

[Fly Boomer]

1 hour ago, N201MKTurbo said:

The yellow disk is your airspeed safety switch. I think the resistors are to dim your annunciator lights when the nav lights are on.

I thought those things were usually stuck on the back of the airspeed indicator?

[N201MKTurbo]

22 minutes ago, Fly Boomer said:

I thought those things were usually stuck on the back of the airspeed indicator?

I haven't worked on every model Mooney. It looks like a Mooney Bracket its mounted on.

[PT20J]

46 minutes ago, Fly Boomer said:

I thought those things were usually stuck on the back of the airspeed indicator?

Early M20J's had them on the back of the airspeed indicator. Later Mooney moved it to a bracket behind the instruments. 

[KSMooniac]

Actually the earliest J's didn't even have them! Mine has a squat switch... Far simpler and more reliable IMO.

Sent from my motorola edge plus 2023 using Tapatalk

[EricJ]

40 minutes ago, KSMooniac said:

Actually the earliest J's didn't even have them! Mine has a squat switch... Far simpler and more reliable IMO.

Sent from my motorola edge plus 2023 using Tapatalk
 

Yeah, mine was converted from a squat switch to an airspeed switch within a few months of delivery.    They must have had a special on some simple upgrades or something, or maybe it was thrown in as part of the sale.    

[DCarlton]

6 hours ago, PT20J said:

Early M20J's had them on the back of the airspeed indicator. Later Mooney moved it to a bracket behind the instruments. 

My F is similar.  Clamped to a tube if I remember correctly.  Not attached to airspeed indicator.  My F is enjoying its third and hopefully last ridiculously expensive airspeed safety switch.  

[Shadrach]

1 hour ago, DCarlton said:

My F is similar.  Clamped to a tube if I remember correctly.  Not attached to airspeed indicator.  My F is enjoying its third and hopefully last ridiculously expensive airspeed safety switch.  

Was it retrofitted? I thought the early electric gear Mooneys had squat switches. Was your bird a manual gear that was converted later in life to electric.

[DCarlton]

10 hours ago, Shadrach said:

Was it retrofitted? I thought the early electric gear Mooneys had squat switches. Was your bird a manual gear that was converted later in life to electric.

I believe the electric gear was added in Kerrville right after production.  I saw the paperwork a few weeks ago going through the docs.  Seems like the Brittain autopilot was added using a similar post production process and paper trial.  Planning to take another look.  I have the original Dukes switch in a box. 

[Jetpilot86]

Not sure it helps, but they look a whole lot like resistors I bought at AutoZone when I put LED lights in my Jeep to prevent hyper flashing. 

[shawnd]

Based on eliminating wires from instruments they took out - the shop believes its from the old AI/HSI pins. Trouble is with the resistors, they would be stepping it down to 14V from 28V. The original person who started the work left the shop, hence all the fun. The shop will just have to test and figure it out.

The plane has gone through few rounds of avionics installations so it's definitely not in the original state when it comes to wiring.

[Shadrach]

21 hours ago, DCarlton said:

I believe the electric gear was added in Kerrville right after production.  I saw the paperwork a few weeks ago going through the docs.  Seems like the Brittain autopilot was added using a similar post production process and paper trial.  Planning to take another look.  I have the original Dukes switch in a box. 

Do you have the W&B revision? I’d be interested to know the net weight difference between the original manual system and electric.

[Aerodon]

14 hours ago, shawnd said:

Based on eliminating wires from instruments they took out - the shop believes its from the old AI/HSI pins. Trouble is with the resistors, they would be stepping it down to 14V from 28V. The original person who started the work left the shop, hence all the fun. The shop will just have to test and figure it out.

The plane has gone through few rounds of avionics installations so it's definitely not in the original state when it comes to wiring.

Those two wires are from the dimming bus to the BendixKing KI256 and KI525 indicators.  I guess the dimming circuit was still too bright or not balanced for these indicators.

The anodized device is the airspeed switch for the landing gear circuit, there is a spare CPC connector, I am using that to activate the airtime on my MD93 clock.

I have removed my Mooney dimmer circuit and replaced with a MaxDim dual dimmer.  Have a look at those 3 terminal trips in front of the airspeed switch.  Ground Bus #1 and Ground Bus #2.  Avionics Dimmer Bus.  With all the instruments you are removing, there are more than enough terminals on Ground Bus #1.  I have converted Ground Bus #2 into Panel Dimmer Bus.  This is a much more reliable and logical setup.

Panel Dimmer Bus - post lights, console, clock, compass, glareshield

Avionics Dimmer bus - dang - as I write this I can't think of any avionics that will need a dimmer.  Maybe I will rethink this and put the glareshield on #2.

 

(Edit, yes the G500, GTN750, GI-275, SL30 can use a dimmer input)

 

This frees up one CB / power wire (Glareshield Dimmer), and its in the right location for a GSB15 instead of the Cigar Aux Per.

I will be doing a drawing of this for my records, will share when ready.  I think this is a good modification for all Mooneys.

 

Aerodon

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Aerodon]

Shawn, another 'gotcha' that you are going to run into if you are removing the vacuum system and / or annunciator panel.  This SB had the ACU 'Rem Sense' removed from the Field CB and spliced into the annunciator power (Alt #1) and the vacuum Hi/Lo switch (Alt#2).  I tried to figure out why, best I can think of is that if the field circuit breaker trips, then you won't get an over/under volt warning.

I looked at the later M20K's and they revised the wiring diagram to take this wire directly to the Annunciator and Vac Warning CB's.  I don't know why the SB just didn't call for that in the first place - you had to change the CB's from 1A to 2A anyway, so it would be easier to move these wires from the Field CB's right there instead of splicing behind the annunciator.

 

Aerodon

 

 

 

 

 

SBM20-245A-4.pdf

[shawnd]

23 hours ago, Aerodon said:

Those two wires are from the dimming bus to the BendixKing KI256 and KI525 indicators.  I guess the dimming circuit was still too bright or not balanced for these indicators.

The anodized device is the airspeed switch for the landing gear circuit, there is a spare CPC connector, I am using that to activate the airtime on my MD93 clock.

Thanks Don - looks like elimination logic matches up with your finding. The trick with the airtime is interesting. I installed a MidContinent Chronos digital clock in prep for IFR - https://www.mcico.com/clocks/6420093-5 decided to start timing when battery power comes on.  Is the actual flight time useful in the US?

[shawnd]

23 hours ago, Aerodon said:

I have removed my Mooney dimmer circuit and replaced with a MaxDim dual dimmer.  Have a look at those 3 terminal trips in front of the airspeed switch.  Ground Bus #1 and Ground Bus #2.  Avionics Dimmer Bus.  With all the instruments you are removing, there are more than enough terminals on Ground Bus #1.  I have converted Ground Bus #2 into Panel Dimmer Bus.  This is a much more reliable and logical setup.

Panel Dimmer Bus - post lights, console, clock, compass, glareshield

Avionics Dimmer bus - dang - as I write this I can't think of any avionics that will need a dimmer.  Maybe I will rethink this and put the glareshield on #2.

(Edit, yes the G500, GTN750, GI-275, SL30 can use a dimmer input)

This frees up one CB / power wire (Glareshield Dimmer), and its in the right location for a GSB15 instead of the Cigar Aux Per.

I will be doing a drawing of this for my records, will share when ready.  I think this is a good modification for all Mooneys.

I am swapping out the AI, HSI and the Nav2 CDI with 275s so will keep the wiring as is for now. Also, don't want the airplane to sit for another 2-3 months! But this is really good info - will save it for when I do redo the panel down the road. Thanks!

[shawnd]

22 hours ago, Aerodon said:

Shawn, another 'gotcha' that you are going to run into if you are removing the vacuum system and / or annunciator panel.  This SB had the ACU 'Rem Sense' removed from the Field CB and spliced into the annunciator power (Alt #1) and the vacuum Hi/Lo switch (Alt#2).  I tried to figure out why, best I can think of is that if the field circuit breaker trips, then you won't get an over/under volt warning.

I looked at the later M20K's and they revised the wiring diagram to take this wire directly to the Annunciator and Vac Warning CB's.  I don't know why the SB just didn't call for that in the first place - you had to change the CB's from 1A to 2A anyway, so it would be easier to move these wires from the Field CB's right there instead of splicing behind the annunciator.

I am not doing a complete redo of the panel like you are :-) but this is good information and great insights! You have the two-alternator version?

[PT20J]

4 hours ago, shawnd said:

Thanks Don - looks like elimination logic matches up with your finding. The trick with the airtime is interesting. I installed a MidContinent Chronos digital clock in prep for IFR - https://www.mcico.com/clocks/6420093-5 decided to start timing when battery power comes on.  Is the actual flight time useful in the US?

FAR Part 1 Definitions:

Flight time means pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing.

Time in service, with respect to maintenance time records, means the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing.

[shawnd]

3 minutes ago, PT20J said:

FAR Part 1 Definitions:

Flight time means pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing.

Time in service, with respect to maintenance time records, means the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing.

Thanks but I don't think its that easy. Here's an article that sheds more light and that the FAR isn't the most clear cut answer:

https://pilotinstitute.com/pilot-logbook-time/#what-counts-as-flight-time

FAA links I found for fun reading:

https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/data/interps/2016/Johnson-ALPA_2016_Legal_Interpretation.pdf

https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/Data/interps/2004/Kania_2004_Legal_Interpretation.pdf

I would interpret this as me as a pilot turning on the master switch to prepare for flight with the intention of going flying and landing is flight time :-) (ducks and hides)

 

[shawnd]

If you are tracking actual flight time, i.e., take off to a full stop landing, where do you find this information being useful?