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7 Answers

Turn & Slip Indicator Vs. Turn Coordinator

Asked by: 53400 views Aircraft Systems

Can someone explain the exact difference between the older "TS-Indicator" and  "TC"?

I do know all the detailed differences as far as how both the instruments are setup and the principles on which they work,

but it still doesnt make any sense to me, what the real difference is, or if there is a main different at all.

Books always say, that the TS only shows rate of bank and the TC shows rate of roll & turn. What's the difference there?

I have also flown planes with either of them, and to me, they just seem the same. Except maybe, that the older version is established a tiny bit later than the newer one.

Thanks

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7 Answers



  1. Nathan Parker on Oct 28, 2012

    “Books always say, that the TS only shows rate of bank and the TC shows rate of roll & turn. What’s the difference there?”

    Rate of bank and rate of roll are the same thing. Rate of turn really means rate of yaw. The TS only shows rate of yaw, but the TC initially shows rate of roll, but once the bank is established, it shows the rate of yaw too.

    Yaw rate is a stand-in for knowing what your bank angle is, which neither device can show you. A bank (when coordinated) will produce a turn which is measured by how fast the nose moves across the horizon (yaw rate). Since it’s an indirect measure of the bank angle, it’s a bit sluggish; the TC was designed to address this, by measuring the roll rate, since you have to roll to get into a bank. Most people find that this device didn’t accomplish its goal, since it makes the device twitchy compared with the TS.

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  2. John D. Collins on Oct 28, 2012

    The TC indicator provides both bank rate and turn rate, whereas the TS only provides turn rate. Because the TC is affected simultaneously by turn and yaw, it can be difficult to use it to recover from an upset. The old TS has the advantage that it only indicates turn rate, and if you are partial panel, this can save your life.

    Back in the mid 1920’s it was fatal if you flew into a cloud. A pilot named Howard Stark worked out a method using the newly developed Turn and Slip Indicator by Sperry to safely fly in the clouds with this instrument. If an upset occurred, he employed what came to be known as the Stark 1-2-3 method to recover control. First, stop the turn with the rudder so the turn needle is in the center, second center the ball by using the ailerons to level the wings and third control the dive with use of the airspeed indicator and the stick to control the elevators. This method is foolproof and is still used by many experienced pilots today. Unfortunately, it doesn’t work with the Turn Coordinator because the indicator shows both rate of turn and rate of bank. There are many old and not so bold pilots who either replace the turn coordinator with a turn and slip indicator or install a spare turn and slip in their aircraft when it is equipped with a turn coordinator that is required for the autopilot operation.

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  3. Dave on Nov 01, 2012

    Hi!

    Thanks for the very comprehensive answers.

    It honestly is still confusing to me. Nathan, you saying “rate of turn” really means “rate of yaw”. How should i understand that, if you a constant turn rate is usually the result of a constant bank angle, and yaw is not really making an aircraft turn.
    Now what i still do not understand, both instrument show the same reactions. By that i mean, If i pushed the rudder (yawing left/right) on an airplane carrying a TS, it makes the needle deflect in the exact same way as the miniature airplane does in a TC. If i banked in any direction on an aircraft carrying a TS, it also does the exact same thing (needle defl.) as on a TC. That again, is what i ment in my previous question, about “what is the difference between the two”, as they both show yawing and rolling (and const. ). And when i compared the bank angle on the attitude indicator for a “standard rate” turn, they are also the same with both instruments on the same model of airplane at the same TAS.
    The only difference i see, is that the TC, is established a little bit quicker than the TS. Or am i missing something here?

    Thanks a lot.

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  4. Nathan Parker on Nov 02, 2012

    “yaw is not really making an aircraft turn.”

    Yaw is strictly a measure of the angle between the longitudinal axis of the airplane and a particular direction. If that angle changes, regardless of how, then there is a yaw rate. This doesn’t mean that there is ever any “slip” angle, or lack of coordination.

    Is is possible, of course, to produce a yaw by using the rudder, but the yaw rate is low after the rudder hits the stops. The resulting turn, if we keep the wings level, is very slow and is what we call a “boat turn”. The yaw rate is low in this instance.

    We normally turn by banking the airplane. The vertical stabilizer will yaw the airplane into the relative wind as the airplane direction changes. As long as the airplane is banked, the aircraft will keep yawing into the relative wind until the airplane has yawed completely around in a circle. Therefore, if we measure the yaw rate, we measure the turn rate.

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  5. Jarek on Nov 30, 2012

    I am not going to answer the question, but rather ask my own hoping to receive an aswer from either John or Nathan. I once decided to fly in a sailplane into a small cloud (late in the evening when I knew all the other sailplanes were already in the hangar). My turn indicator was not on (no battery) so I only had the ball in the tube. Sure enough after about 20 seconds things got out of hand and I was glad to fly (entirely by accident) out of the cloud. The earth came into my view from the last direction I expected it to be. MY QUESTION: is it really possible to recover control of the aircraft even when say already belly up with the use of a (powered) turn indicator and Stark 1-2-3 method? I tried to find some instruction flights addressing this issue on Youtube, but to no avail. Are you aware of any? Cloud flights are not encouraged in my soaring club, hence my complete ignorance. To my mind stopping at cloudbase is only half the fun 🙂

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  6. Jarek on Nov 30, 2012

    Hi, I am not going to answer the question but rather ask my own hoping to receive an answer from either John or Nathan. I once tried to fly my glider into a small cloud (late in the evening when all the other aircraft were already in the hangar). Things got out of hand in about 20 seconds and I was glad to fly out the cloud with the earth coming into my view from the last direction I expected it to be! I only had the ball-in-the-tube (no turn indicator, nor TC). MY QUESTION: is it really possible to recover control with TS and Stark 1-2-3 method, even if already in, say, belly up configuration? My soaring club does not encourage cloud flights, hence my complete ignorance. I tried to find something on this issue on YouTube, but to no avail. Are you aware of any such vids? Have you ever tried to fly IFR without AH, but with TS only?
    To my mind, stopping at cloud base is only half the fun 🙂

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  7. CFI on Oct 18, 2018

    John, thanks for your details but sorry I may be a little dense. I get that when the TC is banked and the little airplane is aligned with the hash mark showing a standard rate turn, that means 3 deg turn per sec. But how do we read the bank(roll) rate from the TC? What is the roll rate?

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