Turn Coordinator flaked out during IPC

[FloridaMan]

This is a bit odd; the tiny airplane in my turn coordinator stopped turning during an IPC. I have the PC TC with the gyro flag. The flag didn't flag, just the tiny airplane stayed "wings level." After a few minutes it came back to life. I've never seen this before and have a redundant AI/TC and I moved to that. I kindof wish it'd stayed broken so the failure could be diagnosed. I don't know how the thing works and whether the device requires power to make the airplane do its thing (could a bad connection outside of the TC caused the issue), or if it's mechanically coupled. 

[Marauder]

1 hour ago, Antares said:

This is a bit odd; the tiny airplane in my turn coordinator stopped turning during an IPC. I have the PC TC with the gyro flag. The flag didn't flag, just the tiny airplane stayed "wings level." After a few minutes it came back to life. I've never seen this before and have a redundant AI/TC and I moved to that. I kindof wish it'd stayed broken so the failure could be diagnosed. I don't know how the thing works and whether the device requires power to make the airplane do its thing (could a bad connection outside of the TC caused the issue), or if it's mechanically coupled. 

The TC is a gyro based unit. If the wings are staying fixed, my guess it is something mechanical with the way the wings are attached to the gyro or something obstructing the movement. If you had no power to the TC and moved the plane around, the wings should move.

[kortopates]

Sounds like an excellent opportunity for you and your CFII to discuss your equipment dependency's and failures. As @Marauder points out above these are a electrically driven gyro. To the best of my knowledge, the red flag only indicates its getting power. Most commonly the TC gets lazy from the bearing getting worn or dry. I have not noticed one entirely stop and come back to life as you describe, but a simple test is to perform some timed 360's at standard rate and see how close you are to 2 minutes in both directions. If its not even (between left and right) and not close to 2 min yours will likely need new bearings or overhaul. These aren't very expensive.

Sounds like this happened while you were doing partial panel work? Your statement about "redundant AI/TC" struck my curiosity. Is this a back up instrument? Perhaps a AI with ball Slip indicator at the bottom?  

[N201MKTurbo]

The Britten Turn Coordinator has a grease filled dashpot as a damper behind its shaft bearing. Behind that is a brass disk with two spring wires that engage with a peg on the front of the gyro frame. The gyro movement is quite active especially in turbulence. The combination of the damper and spring wires decouples and filters the motion of the little airplane so it gives a steady indication. The back of the gyro frame is coupled to the PC valve through another set of spring wires without a damper.

If the airplane stopped moving and then started to work again the bearing for the little airplane needs to be serviced.

I helped (annoyed) an instrument shop while they overhauled mine once.

[Yetti]

I thought the Brittian one was vacuum operated with electric back up....

[markejackson02]

12 hours ago, Yetti said:

I thought the Brittian one was vacuum operated with electric back up....

I thought it was an electrically powered gyro that operated pneumatic values that controlled the P/C or autopilot?  I'm curious.  Probably will have mine overhauled at the annual as it is starting to get a little wobbly.

[Marauder]

14 hours ago, Yetti said:

I thought the Brittian one was vacuum operated with electric back up....

 

1 hour ago, markejackson02 said:

I thought it was an electrically powered gyro that operated pneumatic values that controlled the P/C or autopilot?  I'm curious.  Probably will have mine overhauled at the annual as it is starting to get a little wobbly.

It is an electric gyro that as Mark stated, operates pneumatics (at least mine worked this way).

[Yetti]

Seems to depend on the year of it

The PC system was upgraded in 1967 to utilize the Brittain TC100EVS autopilot turn coordinator gyro. The TC100EVS provides visual indication of wing leveling in addition to operating as the gyro sense element for the PC system.  Roll trim capabilities exist on the gyro unit but all other facets of the install remain the same.  The TC100EVS turn coordinator gyro operates from vacuum or electric power sources, either or both, for an added measure of safety.

http://www.brittainautopilots.com/mooney-pc-systems.html

Otherwise I would have to go have a talk with my transition instructor.   See I was paying attention.

 

[Yetti]

I put this one under the important things to know like when I lose my electrical system.  What happens when I lose my vacuum system , what happen when I lose both.

[RobertGary1]

A friend and I give each other IPCs every 6 months. Last year when it was my turn my vac pump died. I really wanted to do the entire IPC with the dead pump but he was against it. I've had the attitude indicator roll over and die in IMC but never had a pump die in IMC. Luckily I caught the dead pump very quickly because I've been watching these gauges for 20 years and they just didn't seem to be reacting right. It also reminded me to repair the vac sensor on my voice annunciator (which I did the next week). 

-Robert