How can you determine rate of roll on a turn coordinator?

tcco94

tcco94

Future GTA VI Pilot
I'm doing some CFII prep...came across a post 10 years ago and most said it's pretty useless. Since necroposting is a no-no, decided to ask again from a different perspective I guess....

Is it looking at the minature aircraft on the turn coordinator and "assuming" what rate of roll you have based on how drastic your plane's wing is dipped by that instrument?

Does this even matter? I just typically overthink and assume I'll be asked on a checkride. I'd rather understand why it's "pointless" or "inaccurate" than just saying... look at the instrument....
 
Ayork62493 said:
I guess all I use it for would be partial panel work for timed turns. Is that what you're referring to?
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Isn't timed turns your rate of turn and not the rate of roll?

I'm just asking what is "rate of roll" and how do you determine it on a turn coordinator?...and why it's important to know your rate of roll?
 
It isn't really as much a "rate of roll" as much as it is a prediction of heading change, if that makes sense. As in, it displays a rolling movement even before an actual heading change occurs, so it allows the pilot to more precisely fly headings with err... more of the smoothenesses and accuracies...
 
gotWXdagain said:
It isn't really as much a "rate of roll" as much as it is a prediction of heading change, if that makes sense. As in, it displays a rolling movement even before an actual heading change occurs, so it allows the pilot to more precisely fly headings with err... more of the smoothenesses and accuracies...
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So your turn coordinator will turn before the heading starts to move? Is there a reason for the delay then? Pretty much seems useless for determining rate of roll?
 
yes. Your turn coordinator starts moving even before your wings are banked enough to affect a heading change. So you can correct to wings level before a pronounced heading change occurs.
 
z987k said:
I can't think of when knowing your exact rate of roll is important in instrument flying. At no point does that matter.
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Well I can see that argument but when displaying key point differences in turn coordinators and turn and slip indicators a lot of people like to say "turn coordinators display rate of roll".....but being an instrument instructor I would like to be able to explain why it's irrelevant or what the rate of roll even is....rather than just saying "it's irrelevant".

When I try to find some research on how it's displayed, the whole conversation gets confusing.
 
tcco94 said:
Well I can see that argument but when displaying key point differences in turn coordinators and turn and slip indicators a lot of people like to say "turn coordinators display rate of roll".....but being an instrument instructor I would like to be able to explain why it's irrelevant or what the rate of roll even is....rather than just saying "it's irrelevant".

When I try to find some research on how it's displayed, the whole conversation gets confusing.
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The only thing relevant in a partial panel timed turn is the bank angle, time and airspeed. Rate of roll is not included in that. It gives you no useful information.
 
z987k said:
The only thing relevant in a partial panel timed turn is the bank angle, time and airspeed. Rate of roll is not included in that. It gives you no useful information.
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Okay thanks. And in reference to the partial panel timed turn, which instruments are you referring to being "covered" and which are your primary?

Guess it depends on what system you are simulating failing?
 
tcco94 said:
Okay thanks. And in reference to the partial panel timed turn, which instruments are you referring to being "covered" and which are your primary?

Guess it depends on what system you are simulating failing?
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I'm assuming the typical vacuum system failure where it takes out the DG and the AI.
 
z987k said:
I'm assuming the typical vacuum system failure where it takes out the DG and the AI.
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Okay well thanks. I will just note that then. I typically can overthink some things and study some stuff that's irrelevant and this was tough to find an answer. Glad I didn't waste too many hours.

Thanks again for the help.
 
tcco94 said:
Okay well thanks. I will just note that then. I typically can overthink some things and study some stuff that's irrelevant and this was tough to find an answer. Glad I didn't waste too many hours.

Thanks again for the help.
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I mean just sit there and think about it. Ask yourself what information roll rate gives you that you need.
 
z987k said:
I mean just sit there and think about it. Ask yourself what information roll rate gives you that you need.
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Yeah, I didn't even understand the practicality of in the first place.....or how to determine it, or what it even is .... It seemed to me like it'd be useful if you were in an airplane that you could roll but even then...what is a "rate of roll"? That assumption could be wrong as well.

I didn't wanna overthink it and have a stupid assumption in my head. Especially for IMC flying, just never thought of knowing what your "rate of roll" was and didn't know if this question was gonna pop up in an oral.
 
Your question is stuck in the way back of my mind from some old Gleim book I studied years ago. It's one of those gotcha questions. The correct answer is "you can't".

The turn coordinator doesn't provide any rate of Roll info. Only rate of Turn. And yes, rate of roll is a useless parameter for instrument flight. Don't confuse rate of roll versus rate of turn, two different things, only one matters IFR.
 
tcco94 said:
So your turn coordinator will turn before the heading starts to move? Is there a reason for the delay then? Pretty much seems useless for determining rate of roll?
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This seems to sort of suggest that you haven't yet studied the difference between a turn and slip indicator vs. turn coordinator. If you haven't, bone up. That will definitely be a CFII oral question.
 
Correct me if I'm wrong: rate of roll would be the rate of change of your bank angle; rate of turn would be the rate of change of your heading. (e.g. 2min for 360deg).

Hence the rate of turn indicator indications when taxiing through a turn.
 
adk said:
This seems to sort of suggest that you haven't yet studied the difference between a turn and slip indicator vs. turn coordinator. If you haven't, bone up. That will definitely be a CFII oral question.
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I'm not taking my double I checkride this month or anything...I've just started the study prep work so getting back into the thick of things with the instruments first. Don't worry. ;)
 
I actually have a theory now (god help us all).

How many large, fast aircraft have turn coordinators?

Rate of turn is dependent on angle of bank and true airspeed. A higher true airspeed requires a steeper bank angle to achieve a given rate of heading change than an aircraft travelling at a lower true airspeed.

It is more common for small aircraft to have turn coordinators, and large aircraft to not have them. I suspect this is because if you're shooting along in a skyhawk at 110 ktas, a 2 or 3 degree bank angle won't take very long to get you off course, whereas if you're shooting along in a Pilatipi at 260 ktas and you lean over into a 2 or 3 degree angle of bank, you are going to hear someone yell "hey knucklehead, straighten us out!" long before an actual heading change occurs.

So really by offsetting the gimball in the turn coordinator they just made it more sensitive so you could fix deviations more quickly.
 
gotWXdagain said:
I actually have a theory now (god help us all).

How many large, fast aircraft have turn coordinators?

Rate of turn is dependent on angle of bank and true airspeed. A higher true airspeed requires a steeper bank angle to achieve a given rate of heading change than an aircraft travelling at a lower true airspeed.

It is more common for small aircraft to have turn coordinators, and large aircraft to not have them. I suspect this is because if you're shooting along in a skyhawk at 110 ktas, a 2 or 3 degree bank angle won't take very long to get you off course, whereas if you're shooting along in a Pilatipi at 260 ktas and you lean over into a 2 or 3 degree angle of bank, you are going to hear someone yell "hey knucklehead, straighten us out!" long before an actual heading change occurs.

So really by offsetting the gimball in the turn coordinator they just made it more sensitive so you could fix deviations more quickly.
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:rolleyes: I like your theory.

OP, I promise, your examiner will not ask you the definition of Rate of Roll... He just wants you to know the difference btw a TC and TS Indicator... Explain what a canted gyro is, and you'll be fine.

P s. OP like some have said, its a great backup since most TC are electric driven gryos & due to 30 dgr cantation, its more sensitive to force acting on the longitudinal axis (roll) unlike a TS Indicator.

Simple as that.
 
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