How to Determine the Rate of Roll on the turn coordinator???

Flight_Watch

Flight_Watch

New Member
Anyone know a way to determine the "rate of roll" using the Turn Coordinator?

It was a question asked by a Chief Instructor to a CFI candidate. He didn't know the answer and the Chief Instr. told him to look it up. None of the other instructors seem to know the answer.

I know there is no direct way to measure from the instrument but is there a calculation or rule that would work? For example we know that it can show us a standard rate turn and that 10% of our airspeed (+) 7 will also give us a standard rate turn.

I thought that if anyone knows the answer it is probably someone on here.

Interested to hear your responses.


turn.jpg
 
Are you kidding me? I think you're making more of the question than what he was really asking.
smile.gif


The answer is simple: look at the instrument. A turn coordinater indicates rate of roll as it happens. A turn indicator, does not.

I can't imagine he's looking for anything more technical than that. I think it's a trick question.


Edited to add: If he's really got a stick up his ass and is seriously looking for a technical answer...

You would calculate how many degrees of bank a standard rate turn is for that given speed (divide airspeed by 10 and add 50% of that...or something like that). You'd then calculate the time it takes to roll into said standard rate turn. Divide the number of degrees for standard rate by the time it took to roll in, and viola- rate of roll in degrees per second. Absolutely useless knowledge.

rolleyes.gif
 
Hmmm...perhaps you are right. It might be a trick question given that he would not give the CFI the answer. The whole thing still confuses me.
 
Rate of roll? You mean can you calculate how fast you're rolling into a bank with the instrument?

Can't do it, doesn't matter, and who cares.

Now, rate of turn can be calculated in time, which can be interpolated to degrees per second. Partial panel stuff for when you're really screwed in IMC...........you know, those times when you're partial panel with nothing but a tachometer, a hobbs meter, a turn coordinator, an altimeter, and a suction gauge.........
grin.gif
 
You mean like:

Standard rate turn
45 degrees= 15 sec.
90 degrees= 30 sec.
180 degrees= 60 sec.

180/60=3

So the "rate of roll" using the Turn coordinator is 3 degrees per second?
 
[ QUOTE ]
Anyone know a way to determine the "rate of roll" using the Turn Coordinator?

[/ QUOTE ]

Sure; when the TC's wings are level, the roll rate is zero.
grin.gif


Comical, yes; but really, that's the only roll rate the TC will accurately indicate.
 
[ QUOTE ]
You mean like:

Standard rate turn
45 degrees= 15 sec.
90 degrees= 30 sec.
180 degrees= 60 sec.

180/60=3

So the "rate of roll" using the Turn coordinator is 3 degrees per second?


[/ QUOTE ]
No that is rate of turn. I think it was a trick question. Rate of roll meaning how fast you are rolling into the turn? Ummmm, just look at it I guess. You can see how fast you are rolling by looking at how fast the wings on the turn coordinator are rocking back and forth.
 
[ QUOTE ]
[ QUOTE ]
Anyone know a way to determine the "rate of roll" using the Turn Coordinator?

[/ QUOTE ]

Sure; when the TC's wings are level, the roll rate is zero.
grin.gif


Comical, yes; but really, that's the only roll rate the TC will accurately indicate.

[/ QUOTE ]
That's not the only way. When the wings are steady on standard rate your rate of roll is zero. When they are steady anywhere your rate of roll is zero. As long as they are not moving your rate of roll is zero. When they are moving however, as aloft said you can't accurately deturmine rate of roll, but if the wings are moving fast, you have a high rate of roll. If they are moving slowly, you have a low rate of roll.
 
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Anyone know a way to determine the "rate of roll" using the Turn Coordinator?

[/ QUOTE ]

Sure; when the TC's wings are level, the roll rate is zero.
grin.gif


Comical, yes; but really, that's the only roll rate the TC will accurately indicate.

[/ QUOTE ]
That's not the only way. When the wings are steady on standard rate your rate of roll is zero. When they are steady anywhere your rate of roll is zero. As long as they are not moving your rate of roll is zero. When they are moving however, as aloft said you can't accurately deturmine rate of roll, but if the wings are moving fast, you have a high rate of roll. If they are moving slowly, you have a low rate of roll.

[/ QUOTE ]

Just like what I was saying. Can't determine rate of roll, but can determine rate of turn (degrees per second) as the formulas up top showed.
 
Rate of Turn in degrees per second= (1091 * Tan of bank angle) / TAS.

Estimate for a 3 degree/second turn rate= .10 of TAS + 7.

Radius of Turn in feet= TAS squared/ (11.26 * tan of bank angle).
 
[ QUOTE ]
Rate of Turn in degrees per second= (1091 * Tan of bank angle) / TAS.

Estimate for a 3 degree/second turn rate= .10 of TAS + 7.

Radius of Turn in feet= TAS squared/ (11.26 * tan of bank angle).

[/ QUOTE ]

I'm impressed you know that, but man..how did those formulas get left off of my kneeboard!?!
tongue.gif
 
[ QUOTE ]
Rate of Turn in degrees per second= (1091 * Tan of bank angle) / TAS.

Estimate for a 3 degree/second turn rate= .10 of TAS + 7.

Radius of Turn in feet= TAS squared/ (11.26 * tan of bank angle).

[/ QUOTE ]

Keep the public math to a minimum in the cockpit......and no algebra.
 
It's really just a general indication of roll rate; nothing direct. Agreed that it's a pretty useless question (it's also a pretty useless feature as far as I can tell).
 
The TC responds both to motion about the vertical axis and motion about the longitudinal axis. When you initiate your normal turn, you are going to have motion about both of these axes followed by just motion about the veritcal axis as the turn is established. Therefore, observing the TC in normal flight does not directly address your question due to the yawing involved. Roll rate information would somehow have to be extrapolated from how fast the TC reaches its steady state position, as others have mentioned.

My idea:
If you really want to direclty observe roll rate from the TC, you will have to do some side slips. Bank the aircraft while keeping the nose on a constant heading, and the TC will move as a result of rolling alone. The incline of the miniature airplane will directly correspond to your roll rate and could be calibrated by monitoring the attitude indicator with a stop watch.
 
MikeD your the only one who is really worried about rate of roll ie 360* per second would mean you can make a full alieron roll in one second.


TRICK QUESTION
Rate of turn - same thing, you need to put your turn (change in heading), over time. ie. Standard rate of turn (hash marks) = 360 in 2 min
Half standard rate (half way to hash marks) 180 in 2 min

The turn coordinator is a direct indication of the rate of turn, and quality of turn (slip or skid inclonimeter) but you cannot tell rate of roll, bank angle, without taking too much time to figure it out and get out your calculator.
 
[ QUOTE ]
Impressive. Thanks Chris!

What does "Tan of bank angle" mean?

[/ QUOTE ]
Cessna_Flyer,

You'll need to know that formula for instrument groundschool. But again that's for rate of turn not rate of roll.
 
You must log in or register to reply here.
Back
Top