ORIGINAL: aspectratio
Actually, I doubt that gyroscopic effects are very significant for our little models, but they would still exist. You acknowledge that they would exist if the AOA were changing, like when you rotate to take off, but gyroscopic effects could also be involved if even if the airplane at a high AOA is not changing pitch or yaw.
From the FAA's Pilot's Handbook of Aeronautical Knowlege (other aeronautical and physics texts make similar statements in principle): "The rotating propeller of an airplane makes a very good gyroscope and thus has similar properties. Any time a force is applied to deflect the propeller out of its plane of rotation, the resulting force is 90° ahead of and in the direction of rotation and in the direction of application, causing a pitching moment, a yawing moment, or a combination of the two depending upon the point at which the force was applied."
Emphasis added.
ORIGINAL: aspectratio
I know this seems counterintuitive, because you can move a gyroscope at a fixed AOA. As long as you do not try to change the direction of it’s axis, it will not precess. However, we are not talking about a simple gyroscope here. We are talking about the gyroscopic properties of a complex aerodynamic device known as a propeller, located at the front of a complex aeordynamic device known as an airplane.
A gyro is a gyro is a gyro regardless of shape. It doesn't even have to be symmetrical to exibit precession. Any rotating object can precess. Just because an airplane is more complex than a toy gyro doesn't mean it magically makes precession happen without a displacement. Just because P-Factor is acting doesn't mean precession is happening. You agreed with that above, multiflyer eloquently explained it, I explained it and it's in a lot of books that way and I demonstrated it to myself years ago with a bicycle wheel and toy gyros.
ORIGINAL: aspectratio
You wrote, "If a gyro's rotation plane is forced to displace, then a precessive force will occur in response." According to Sir Newton, force does not occur in response to displacement, but displacement occurs in response to force. “Objects at rest (or in motion) tend to remain that way until acted upon by a force.” A force to the plane of rotation of a gyroscope results in a force at 90 degrees. The result of these forces would be a precessing motion, assuming no other forces were at play.
You are missing the point that the force has to result in a displacement for precession to occur. If there is an equal and opposing force, then there is no displacement. If you hold a spinning bicycle wheel with an extended axle lightly by that axle, gravity will pull it down against its own "rigidity in space". As the far end of the axle rotates downward slowly, it also moves either to your left or your right, depending on which way you spun the tire. Now if you hold the axle rigidly, you are applying a force equal and opposite to gravity, and the wheel will not precess, i.e. it will not try to move left or right.
ORIGINAL: aspectratio
You go on to say, "If the gyro's rotation plane is not displaced then there is no precessive force." Well, now, wait a minute! You just said there can be equal but opposing forces without displacement. So, just because there is no displacement does not mean that there are no forces. This is my point. The gyroscopic forces are there whether you see them produce displacement or not. If they are exactly opposed, then they just cause wear at the engine bearings and stress the prop, even though there is no precessing motion to the prop’s plane of rotation.
There are two principle properties of a gyro: Rigidity in Space, and Precession. If a gyro's rigidity in space is overcome, the response is precession. They are related. Rigidity in space is not a force by itself; precession is. It's the rotating version of Newton's First Law. If you pitch an airplane up, for example, and ignore all the other turning forces, the propeller will apply a right yawing force to the airplane through the prop shaft, etc, because of precession. If this force is opposed with rudder application or other forces, the airplane will not yaw. The force is there, but it has been opposed so yaw does not occur. If on the other hand the airplane is not changing orientaion/attitude, THERE CAN BE NO PRECESSION. You can't have a reaction without an action!
ORIGINAL: aspectratio
A gyroscope does not create more force, it just redirects force, like the seesaw. So, to the extent that the yawing force is redirected to a pitching force, it is no longer available as yawing force (at the prop hub). In other words, gyroscopic forces reduce the yaw caused by the asymmetrical prop loading in a positive AOA. Gyroscopic forces, even if there is no precession to the plane of the prop, would not contribute to yaw caused by P Factor. In fact, they would decreases P Factor yaw to some extent, while reducing the need for elevator input. You have a gyroscope in the front of the aiplane trying to stabilize the AOA. Consequently, you need less rudder and less up elevator, or maybe some down. So, precession is not entirely irrelevant to a discussion of P Factor.
The above paragraph is almost entirely gibberish caused by your misunderstanding of precession. There is some truth mixed with nonsense.
ORIGINAL: aspectratio
The differential prop loading is often described conceptually as being equivalent to moving the center of engine thrust to the right, which would create a moment that would cause the plane to yaw left. Moving the center of thrust will cause a plane to yaw, but it is not very efficient way to do it. You do not get much leverage at the firewall, just like you do not get much leverage at the prop hub to pitch the plane, either. These are short lever arms way up in front of the CG.
What is your point? It still works and is well understood and documented. Even a relatively small force will eventually have a noticeable effect with no opposing force. And if you have ever done power on stalls with a high powered airplane, your right leg got tired. The force is so strong at high AOA, that even in a moderate left turn, you have to hold right rudder to keep the ball centered.
ORIGINAL: aspectratio
So, most of the above is really “academic” as far as I am concerned, although, it is interesting. I have read that a true Lomcevac Maneuver cannot be done with most model airplanes, because the pilots in full sized planes make use of the more significant gyroscopic precession of massive propellers, and that our models do not have enough rotating mass to actually do the maneuver. I don’t know this first hand.
Maybe the same guy that wrote that also wrote that a knife-edge loop is impossible. Actually you wrote MOST model planes, so I can probably agree with that. It's all relative--small spinning mass has a large effect on a light airplane. Try power-on flat spins left and right and see the difference.
ORIGINAL: aspectratio
What does this have to do with spiraling slipstream? Not much, except that they teach you in ground school that a spiraling slipstream is responsible for some of the left yaw you encounter when flying. I remain skeptical about how significant it really is.
The last sentence is meaningless unless quantified. Everyone knows Spiral Slipstream exists; no-one knows exactly how strong it is under all conditions. Countering well-established aeronautical principles with no proof, experimentation or quantification is merely a literary exercise.
Incidentally, the reaction to prop thrust is that the plane moves forward. If the plane also tries to roll left slightly due to torque (which it does), then we can infer that it MUST also be applying a right rolling motion to the air, hence Spiral Slipstream. If you acknowledge torque, then if you are a reasoning person, you MUST acknowledge that the spiral component of slipstream is in proportion to the torque force applied to the airplane through the prop shaft.
All the above discussion of course ignores the minute precession that occurs in a gyro whose plane of rotation is fixed relative to the surface of the revolving and orbiting earth/galaxy/universe/set of dimensions/multiverse/antiverse/plane of existence/etherial void/quantum iteration, etc. It also ignores time dilation effects between the observer and the spinning object, space-time distortions due to gravity, the small but existent travel time of light, and the offensive nature of halitosis.
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