Steep Turns

Fly_Unity

Fly_Unity

Well-Known Member
So one of my instructors was talking to me about him teaching a student steep turns (CFI applicant). He said that the he was trying to explain to the student about the gyroscopic precession during a steep turn, and how that on a left turn the nose will lower, and on a right turn the nose will rise. I argued with him saying that this is no gyroscopic precession, but its just an illusion due to sitting in the left seat and its in reverse when sitting in the right seat. I explained that its identical sight picture if you sat in the middle of the airplane (I actually never heard of anyone using gyroscopic precession in with a steep turn). He seemed very insistent that I was wrong (or more that gyroscopic precession was another factor) and I dropped the matter because maybe I dont know what Im talking about.

Later I went up in a 152 and did a steep turn on my own, It took EXACTLY 2 full trim ups to maintain level flight both ways. But this was during a steady state turn so it really does not answer the question.

My questions is, Is this really a factor to initially start the turn? Would it be more of a factor in a high performance airplane?
 
I have never heard gyroscopic precesion referenced in relation to steep turns. I can't see how it would have any affect on a steep turn as there is very little pitch change involved, and (theoretically) no yaw.
 
Is there a large gyroscope spinning in front of the plane? Is the direction of said gyro changing during the turn? I would say your student is right, but the change would not be as noticeable as when slow and pitching up or down, or turning. But, yet there is a gyro spinning and you are changing the direction of the spinning gyro, so yes, there is gyroscopic precession. It may not be taught as such, but there is a force there.
 
You have the prop spinning and you are changing the plane in which it is spinning, so there will be some gyroscopic effect. If it will be large enough to be measurable is a completely different question.
 
Fly_Unity said:
I argued with him saying that this is no gyroscopic precession, but its just an illusion due to sitting in the left seat and its in reverse when sitting in the right seat. I explained that its identical sight picture if you sat in the middle of the airplane (I actually never heard of anyone using gyroscopic precession in with a steep turn).
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^^This is what I was taught to teach (if that makes sense). It was even one of the "ground lessons" I taught during my CFI initial ck ride as one of the common errors made when executing steep turns.
 
ShortField said:
^^This is what I was taught to teach (if that makes sense). It was even one of the "ground lessons" I taught during my CFI initial ck ride as one of the common errors made when executing steep turns.
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You might have been taught to teach it, but does that make it right? Sit back and think about gyroscopic precession. Now, is there a gyro spinning and changing direction during a turn, especially a steep turn with a quicker turn radius? If the answer is yes, then there HAS to be some gyro precession. Whether it is measurable or not is another story, but it is there...
 
Stone Cold said:
You might have been taught to teach it, but does that make it right? Sit back and think about gyroscopic precession. Now, is there a gyro spinning and changing direction during a turn, especially a steep turn with a quicker turn radius? If the answer is yes, then there HAS to be some gyro precession. Whether it is measurable or not is another story, but it is there...
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Agreed, however the assertion that pilot perspective (parallax error) plays a role is not incorrect.
 
I would say as others already have that the spinning fan in front of you does act like a gyro (re- left turning tendencies blah blah, I played angry birds in ground school...) and is subject to some precession force while turning.

However, I would Suggest that the phenomena (finally got to use this word in a sentence... YAY) that the CFI is explaining is due to his position in the cockpit, or the parallax error. Back in the baby days flying the 152 (crawl before you walk people...) I had a rivet on the left side of the engine for my left turns, and the rivet on the right side for right turns was the next one forward (or back, can't remember, not important, just the fact it's a different position)

My opinion is that the OP is correct by saying if you sat in the middle you would get the same view per turn, or in my case, use the equal screw on either side. Someone with access to a decathlon or something similar test this out please?
 
It's there but it really doesn't make a difference.

Rolling into a steep turn to the right, (assuming the engine turns clock-wise) some times not enough rudder is used to coordinate the roll and adverse yaw will prop the nose up. If left unattended it can cause slight gain in altitude.
 
There is a tendency for the nose to rise in a right turn and lower in a left turn.

Because of P-Factor.

Anytime you pull on the elevator, you increase P-Factor, so the nose will pull left, which is seen as up when in a steep right turn, and down when in a step left turn.

To stay coordinated in a steep turn whilst holding back pressure (increased angle of attack) you will need to hold some slight right rudder in the right steep turn, as in a climbing right turn; and none in the left stabilized steep turn, as in a left climbing turn, but if additional back pressure is aplied to gain lost altitude, some right rudder will be needed to stay coordinated.

Rudder and aileron inputs during steep turns are like climbing turns and all the P-Factor, gyroscopic precession, spiraling slipstream, and engine torque act the same on the airplane in high power/high angle of attack whether it is climbing or turning.
 
I would also like to add the mechanics of your arm play into the climb to the right and decent to the left (if you sitting in the left seat) when you use a yoke. The more you fly the more you train yourself to account for this. But to new students it will happen every time, also to CFI's new to the right seat. Just my observations.
 
I agree with what everyone has written, and for whatever it is worth, there is zero reference to gyroscopic precession related to steep turns in any government aviation publication. In a situation such as this, if someone suggested I should include that in my teaching of the maneuver I'd ask if they could provide a reference for it so I could ensure I was teaching it properly. If anyone finds one, I'd be most interested in seeing it.
 
nosehair said:
There is a tendency for the nose to rise in a right turn and lower in a left turn.

Because of P-Factor.

Anytime you pull on the elevator, you increase P-Factor, so the nose will pull left, which is seen as up when in a steep right turn, and down when in a step left turn.

To stay coordinated in a steep turn whilst holding back pressure (increased angle of attack) you will need to hold some slight right rudder in the right steep turn, as in a climbing right turn; and none in the left stabilized steep turn, as in a left climbing turn, but if additional back pressure is aplied to gain lost altitude, some right rudder will be needed to stay coordinated.

Rudder and aileron inputs during steep turns are like climbing turns and all the P-Factor, gyroscopic precession, spiraling slipstream, and engine torque act the same on the airplane in high power/high angle of attack whether it is climbing or turning.
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The issue is the WHEN the gain in altitude occurs. If not enough rudder is used to coordinate, the slight climb always happens while rolling right to establish the turn. This this slight "pitch up" happens before 30dg of bank is even reached. During the first part of the roll, let's say the first 30dg, there really should be no AOA increase. In this case, Torque, P-Factor, and Slip Stream, really only affecting the roll rate of the airplane.

With aerobatic style steep turns, 60-80 dg bank, there is very little p-factor or gyroscopic precession to deal with. These are done at full throttle right on the edge of the buffett. The most common errors are coordinating the hard roll in and setting the pull.

To the OP:

To achieve the same roll rate to the right as you would to the left, more aileron deflection is needed. When rolling left, P-Factor and slip-stream dampen out the adverse yaw & torque helps the roll rate. When rolling right, P-factor and slip-stream exacerbate the the adverse yaw and the you're rolling against the torque. So to achieve equal roll-rates Left & Right, more aileron to the right must be used. More aileron deflection means more adverse yaw. More adverse yaw means more rudder is needed... The most common error with a roll to the right is not using enough rudder.

Yaw is always an ear-to-ear motion relative to the pilot. As you roll uncoordinated into a turn, that adverse yaw actually turns into pitch. That pitch, coupled with power (usually added during a steep turn) and airspeed will lead to an initial climb. I know this works because it's how I cheat the start of my slow roll....;)

To better understand the steep turn. Don't just think of it one 360dg turn right or left.

Break it down into 3 parts: The roll in, the pull (turn), the roll out, and focus on each part individually.
 
To the CFI in question w.r.t. to Gyro Precession, there is no mention of gyroscopic precession in the Airplane Flying Handbook in any part of the steep turns discussion (roll-in, established, or roll-out) so, if this CFI is teaching an Initial CFI candidate to teach his private students using material that is NOT included in any FAA publications, he should be able to provide a reference for where his info comes from (or a VERY VERY good argument that he might someday include in his OWN book lol). Regardless of personal feelings, I would not teach a pre-private student anything that does not have a citation somewhere in an FAA handbook or manual, but that’s just me.

With that being said, even though there is no mention of Gyroscopic Precession during steep turns, the physical principle of gyroscopic precession is still present.
Torque-Induced Precession (gyroscopic precession) occurs anytime a "torque" (rotational force) is applied to a rigid spinning body (ex. propeller).
So, to put it simply, GP happens anytime we have...
1. A rotational force and...
2. A spinning thing.

Does gyroscopic precession happen during a steep turn?
I will use only the "Established" Steep Turn example (NO rotation about the longitudinal axis ie. changing in bank angle. Bank angle is at a constant whatever angle)
In a steady state turn (steep or not so much), our direction (heading) is the only thing changing. Since our airplane is changing direction (heading), our airplane is rotating about the vertical (straight up - straight down) axis. When our airplane rotates about an axis, it applies a "torque" to any spinning things we have on board and since we have a giant spinning propeller on the front (or back lol) of our airplane, our airplane will be under the influence of gyroscopic procession during a turn (steep or not so much).

Steep Turn Induced Gyroscopic Precession is a "Control Pressure" problem, not a "Pitch Attitude" problem.
In any movement about any axis of flight in an airplane, we use a certain amount of “control pressure” to induce said movement. It is actually one of the most simple ideas in aviation (no 3 letter acronyms required lol), more control pressure = more movement. When we perform a steep turn, we are adding back-pressure on the yoke to account for the amount of vertical lift lost in such a high bank angle. Therefore, we can infer that if we had NOT SPINNING BODIES on our airplane, we would require the same amount of back elevator pressure, regardless of turn direction, during a steep turn. When we throw in a big spinning gyro on the front of our airplane we must factor in its affect on our back elevator pressure requirement.

Consider an airplane perfectly trimmed for straight and level flight at 90 kts. If someone else was to rotate the trim wheel forward without you knowing, how would you know? You would know because you would need to add back pressure in order to maintain the same pitch attitude thus remaining in straight and level flight. The same idea is true in a steep turn with regards to “felt” gyroscopic forces. When you rotate (change direction/heading) in a steep turn, you are going to feel a “nose-up force” or a “nose-down force” depending on which way you are turning (Left = Down, Right = Up). If left uncorrected, this gyroscopic force will cause the airplane to pitch down or up. In order to counteract this felt force in the control yoke, you are simply going to pull back more or less until you regain the pitch attitude you desire. It will require slightly more elevator-back pressure in a left turn and slightly less elevator back pressure in a right to maintain the level turning pitch attitude. That’s it. Your “SIGHT PICTURE” (what physical placement the nose of the airplane must be in in order to maintain a level turn) is not going to change DUE TO GYROSCOPIC PRECESSION because the only thing different in a left or right turn (WITH RESPECT TO GP) is the amount of control pressure required. All you will notice is a tendency for the airplane to pitch down or up and if you correct accordingly, your sight picture should remain unchanged. It is for this reason that, I believe, the FAA does not mention Gyroscopic Precession in the Steep Turn Discussion.

As for the reason why your sight picture DOES appear to be different in a left or right steep turn, I refer you to the FAA Airplane Flying Handbook (No gyroscopic precession required lol).
 
TwoTwoLeft said:
Break it down into 3 parts: The roll in, the pull (turn), the roll out, and focus on each part individually.
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^That's how I teach it. I even break down the roll in to the turn, where I find most students mess up. Ie when to add in the trim, power, and back pressure. But the best thing I have found is cover up every instrument and just have them focus on the number on reference point and say keep it on the horizon and the airplane will do the rest. most are dumbfounded how we did a 360deg turn with out looking at our altitude and maintained our altitude spot on...
 
I too have never heard or read about gyroscopic precession during a steep turn , I usually just go into basic aerodynamics to give the SP a basic understanding of the maneuver in itself and then I stop it right there unless its one of those rare students that are very inquiring. I wonder if your IP was maybe thinking about the precession on the A.I? hmmm
 
It is true that the specific details of the steep turn maneuver, as described in the trusty FAA Airplane Flying Handbook, do not include gyroscopic precession as a force acting during the turn, and I don't think they include P-Factor or the other forces that have changed due to a change in angle of attack. Nor is a deep understanding necessary for the execution by a practicing pilot. Although it helps, sometimes, for a student to understand why.

But, as a CFI, the explanation of these forces, and the reference in the Handbook to basic forces acting on the airplane in a climb, in the rotation of the nose: up, down, left, and right, all are affected by the changing forces created by the prop, are necessary knowledge. The Book does teach these forces, and the CFI can reference these basic forces in the book.
 
Actually, it's the demonstration of control these single-prop forces which make it necessary to "add-on" a single engine rating if you get a multi first.
 
Um, a twin has the exact same "prop forces" that a single has. The reasons for a single engine add-on (as reflected by the PTS) are: Systems, performance, takeoff/landings (no soft field in a multi) and emergency procedures. (Last I checked there is no accel-go for a single...)
 
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