The place for technical discussions about GA and flying.
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By Corsican
We have an electric turn coordinator in our PtF aircraft. The aeroplane image which indicates the direction of bank bounces around with no constraint so effectively useless. The red indicator flag indicates an electrical fault .

I am wondering if the cause of the fault is :
1) electrical failure, need to check the connections in the first instance;
2) failure of the springs which should control the movement of the wings?;
3) gyro failure (possibly due to electrical failure?).

I appreciate that it could be any or none of the above, but curious if there are any ideas/someone has seen this before we either send it off to be fixed, replaced or just leave as is. Practically, as a day VFR aircraft, I only ever glance at the ball (which works). Thanks in advance for your thoughts.
As you say it can be anything but most older TCs are loud when the gyro is spinning.

So if it does then that rules out a connection problem but it can still be the bearings/brushes/or the springs.
By riverrock
Eventually the brushes on the DC motor which turns the gyro wear out - but could also be any sort of electrical issue.
Check the electrics, if not that - its off for repair / overhaul / replacement.
By Corsican
Thank you both, I will try and check out the electrics in the first instance. The DI and AI make quite a racket, but given the red flag on the TC, I assume that the gyro is not spinning on that as no power to spin it. If the electrics don't work (who knows, it may just be a bad connection), then I may try and promote a panel rebuild without the AI and DI and just the slip ball as none are really useful or accurate (whiskey compass works) and better to fly with head up and out anyways. She would never get signed off as an IMC capable PtF anyways!

Vaguely irritating to have instruments which don't work, even if I do not really use them; we should either fix them or get rid of them, but getting rid of them means unsightly empty holes hence the panel rebuild aspiration/daydream.

Will report back if I get to the bottom of this (and won't hold my breath on a panel rebuild!). Thank you again for your quick and helpful responses.
By Nick
If the power supply is ok the other thing that quite often happens is the commutator becomes dirty. Polish it up with very fine abrasive paper or better still a fine glass fibre brush. (Thistle brush). This normally does the trick.

Corsican liked this
Be careful what you wish for.

I'm about half way through a complete rebuild of everything forward of the door-post on my PtF vintage aircraft. It started out as new radios and a rewire. Passed via new panel and a repaint of the footwell to a total strip down, new fuel pipes (the old ones were leaking) new windscreen and more. It's turned into a six-month job...
Not just the fuel pipes... The 70 year old wiring was not up to much and the numerous modifications carried out along the way since, not much better. Every inch of electrical cable in the entire aircraft went in the bin.

Anyone who has worked on vintage aircraft will be familiar with the scenario whereby you remove on thing and the part behind falls off. Frustrating as it is, better to know what needs doing.

By the time I'm finished it will be like the farmer's axe - three new heads and two new shafts and as good as the day it was bought.
By Corsican
Thanks for your replies, sorry for the delayed response.

Agree that trying to fix one thing on the panel could open a can of worms; this is also a PtF (1946 although a full rebuild 12 years ago).

Interesting thing happened the other day when I flew. To my mild surprise, as I started taxing, the red inop flag on the TC went "black" and it started working?!? The wings were still bobbing about somewhat, but this does suggest that there is a loose connection so will have a look at that. Not sure what to do about the bobbing wings. Of course, I got airborne and promptly forgot to check if it was still working, being now conditioned to never pay attention to it (and arguably, should not need it in VMC anyway, but it is just the minor irritation factor of knowing it is not working or only intermittently so).

Tail feathers coming off in February so will investigate more fully then, but mindful of your advice on where that could lead.
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By Lockhaven
Sounds to me as though the gyro is not achieving the correct rotational speed therefore has reduced rigidity.

As you suggest check the wiring connections first and also its resistance, check the instrument label to ensure you are supplying the correct voltage i.e the instrument is not a 24v one and you are giving it 12v.