Yaw question
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Serious question, and I'd urge you to ponder it a bit. If we don't have a 90 degree banked turn, how can aircraft heading possibly change without rotating around it's yaw axis? I think you'll eventually come to the realization that it can't.
BTW. "normal" just means "at 90 degrees to". All three axes are normal to the other 2.
Last edited by A Squared; 26th Dec 2015 at 04:09.
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There seems to also be some confusion here about 'yawing', 'slipping' and 'balanced flight'. These are three different beasts that can occur completely independently of each other.
An aircraft flying straight and level is in balance, not yawing or slipping.
An aircraft in a traditional sideslip (constant heading) is slipping, out of balance but not yawing.
An aircraft in a balanced turn is in balance and yawing but not slipping.
An aircraft in a slipping turn is not in balance, but is slipping and yawing.
An aircraft in a rudder turn is out of balance, slipping and yawing.
A twin engine aircraft with one engine inoperative flying wings level is in balance, slipping but not yawing.
A twin engine aircraft with one engine inoperative flying at a zero slip bank angle is not in balance or yawing or slipping.
A twin engine aircraft with one engine inoperative in a balanced turn is in balance, slipping and yawing.
A twin engine aircraft with one engine inoperative flying with zero slip in a turn is yawing, but out of balance and not slipping.
9 permutations of three independent elements.
An aircraft flying straight and level is in balance, not yawing or slipping.
An aircraft in a traditional sideslip (constant heading) is slipping, out of balance but not yawing.
An aircraft in a balanced turn is in balance and yawing but not slipping.
An aircraft in a slipping turn is not in balance, but is slipping and yawing.
An aircraft in a rudder turn is out of balance, slipping and yawing.
A twin engine aircraft with one engine inoperative flying wings level is in balance, slipping but not yawing.
A twin engine aircraft with one engine inoperative flying at a zero slip bank angle is not in balance or yawing or slipping.
A twin engine aircraft with one engine inoperative in a balanced turn is in balance, slipping and yawing.
A twin engine aircraft with one engine inoperative flying with zero slip in a turn is yawing, but out of balance and not slipping.
9 permutations of three independent elements.
Last edited by Nomde plume; 25th Dec 2015 at 10:50.
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I am 98% sure, that if you asked any private or student pilot if the aircraft yaws when in a balanced turn, the answer would 99% of the time be no. Not saying that is the correct view, but i have never seen any educational literature that points toward it occurring when in balance. The description regarding it having to occur in order to change heading makes sense, but the general awareness isn't out there...
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Another item which might help an understanding of slip and skid is how the balance ball works.
It is influenced by gravity and centrifugal force. In a slip (as when starting a turn as mentioned above) it is gravity which causes the ball to be off centre towards the inside of the turn. In a skid, it is centrifugal force which takes it the other way.
I find it easy to imagine that anyone first learning about this could think that the ball should be on the opposite side i.e away from the direction that the aircraft is slipping or skidding.
It is influenced by gravity and centrifugal force. In a slip (as when starting a turn as mentioned above) it is gravity which causes the ball to be off centre towards the inside of the turn. In a skid, it is centrifugal force which takes it the other way.
I find it easy to imagine that anyone first learning about this could think that the ball should be on the opposite side i.e away from the direction that the aircraft is slipping or skidding.
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It's also useful to understand that the balance ball doesn't actually show yaw, it shows whether your current yaw rate matches your current angle of bank.
Skidding = too much yaw for the current angle of bank.
Slipping = not enough yaw for the current angle of bank.
Coordinated = correct amount of yaw for the current angle of bank (zero yaw and zero bank when flying in a straight line).
Most of the yaw in a turn comes from the natural stability of the aircraft which maintains alignment with the airflow i.e. the fin and other vertical surfaces. The rudder provides relatively small adjustments to yaw rate.
Skidding = too much yaw for the current angle of bank.
Slipping = not enough yaw for the current angle of bank.
Coordinated = correct amount of yaw for the current angle of bank (zero yaw and zero bank when flying in a straight line).
Most of the yaw in a turn comes from the natural stability of the aircraft which maintains alignment with the airflow i.e. the fin and other vertical surfaces. The rudder provides relatively small adjustments to yaw rate.
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Having the mistaken understanding of yaw being only slip/skid was the root of the OPs misunderstanding.
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I am 98% sure, that if you asked any private or student pilot if the aircraft yaws when in a balanced turn, the answer would 99% of the time be no.
jgray, pick up a model plane and go to one side of a room. Make the model follow a level, 180 turn (at about 30 degrees angle of bank). Look closely at the movements that you cause the model to make.
You will see the yaw, and the pitch. It may help to break the combined motions into separate ones.
Roll, pitch and yaw are some of the most fundamental things about how aeroplanes fly. When getting familiar with those, learn that each of those motions occurs about the centre of gravity. That is another fundamental.
I have encountered pilots that have been flying all their lives, without knowledge of some of these fundamentals.
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FGD, I get it. Without yaw, and with a constant bank angle - we are left with just pitch, leaving us unable to turn with gaining altitude. I just think that the general consensus amongst student and PPL pilots is that to have yaw, you need to have an out of balance condition on TC. Thanks to you and all other contributors for clarifying things for me
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You may be right about that. and I certainly wasn't intending to denigrate earlier you for holding that misconception, but rather I was attempting to explain to someone else how that misunderstanding of yaw was leading to your confusion in the first place. Nobody knows everything right off the bat, and something wasn't making sense to you so you asked. Nothing wrong with that at all.
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I think I remember yaw..it's what happens if you don't fly from ils to ils and if you try to turn before engaging yaw damper and autopilot ..tsk tsk...risky behaviour..are you trying to get a stunt role in a movie or something...
