Turn Coordinator

[Paul Sharp]

My turn coordinator is working sporadically.

If I understand things right, the type I have works together with my Cessna 300 Autopilot. Since the autopilot is working properly, even though the bank indicator needle freezes at times, I'm assuming that the problem is probably the indicator.

The plane goes in for annual inspection this weekend. I'm assuming the A&P guys can pull the Turn Coordinator and send it off for overhaul or exchange.

Any suggestions or input from others? Always appreciate opinions and past experiences which can save time and money...

[Bob Cook]

Paul

Double check and see if it in fact does drive the AP. Are you sure ?

1) is this a true turn and bank?
2) size and model ? 2 or 3 inch ?
3) It should run for at least 2 min after turning power off.. good test.
4) Some T&Bs are worth overhauling, others are not !

I believe the AI is driving the AP.

You should probably update with one that has a power flag as a warning the servo is non functional or is not up to speed.

Bob

[WebMaster]

If it is the Cessna AP, Bob is right, it is driven off the AI.
a working turn coordinator is required for Instrument Flight. I'd be afraid to fly IFR if the TC wasn't working.

Also, make, model information is always helpful in assisting in diagnosis.

[skymaster]

just finished repair and install my s-tec 65 ap. stec says 8000 hours mean time before failure on the tand b . its been broken for three years. looking forward to using the rate based unit. FYI finally got the last two cylinders on rear motor topped. GMAS was probably right recommending replacing all at once. but it took three years . the airplane had been sitting a couple years because previous owner was trying to get his medical returned. Looking at the cylinder valve condition i am not ever going to replace a cylinder with anythin but new. the old ones were o/h . lucky for me they did not spit metal. 73 p. j

[Paul Sharp]

I called Autopilot Central and after checking S/N's on Cessna 1967 models (year of my bird), that all before a S/N in the 700's (mine is 659) used a BLIND T&B. After that they used the actual Turn Coord. that was in the panel. (For 400 model A/P's they did use the AI instead of the TC, but not for the model 300 A/P).

So mine evidently doesn't use the TC in the panel anyway. That's why the darn thing was still working (the A/P, that is) even though the panel instrument went belly up.

An exchange TC is only $580 so I might just do that.

OTOH, couldn't I just get a cheaper T&B? The only reason I need it is for legalities, anyway, and I suspect that tellsl me which way the wings are tilted just as well, doesn't it? (I bought a second AI - electric model - for any real emergency should I ever need it.)

[Guy Paris]

Was out the other night in the bird and took another close look at the Turn and Bank, its one of those two and three quarter inch jobbies. I sure would hate like heck to have to do anything serious with it.... Wish I had placed the other A/I in a closer position. We had turn and bank indicators on the jets years ago, then they were removed. Might have been after the third attitude indicator was installed. Like my old boss would say, "its a risk intensive business". Guy, old72driver....

[Bob Cook]

FYI

The T&B is almost dead. There is a move afoot to replace a T&B with an electronic AI.

For those interested www.xbow.com (Crossbow) has a new approved (FAA) attitude sensor that will make the vacuum GYRO's disappear (mechanical).

It won't be long before there will be a whole new proliferation of Electronic AI's on the market for primary and backup use that we all can afford.

BTW this technology is at the heart of the drone and cruise missile guidance systems. Amazing technology... replaces lazer gyros and inertial nav systems costing 100k or more.

fyi

bob

[Paul Sharp]

I've read about the movement to replace TCs and T&Bs with AI's. Unfortunately, the archaic FAA we have so far has refused to allow that. So I bit the bullet a year ago and put in a separate, new, electrically-driven backup AI from R.C. Allen.

Meanwhile, you have to have a TC or T&B to be legal. So I pulled out the old one this morning - it is just the simple TC and doesn't interface to the autopilot. I am getting an exchange, which will pop right in and use the same connector.

Will be nice when we can use the newer stuff and dump some of the ancient technology...

Thanks to all for the input.

[skymaster]

wanted to share the photo of valve damage. J