quote:

ORIGINAL: otrcman

I hesitate to write this, because I don't want to "take the bait" from those who have questioned the use of gyros in model airplanes. But there is a perfectly valid argument for the use of stability augmentation (gyros) in models, just as there is a valid argument for the same use in some full scale airplanes.

First off, let me establish that I am fully qualified to make this argument. I am a retired flight test engineer, having been involved in testing airplanes from X-15 and Space Shuttle, down to simple light airplanes. A great portion of my career has been in studying the man-machine interface of a pilot flying an airplane. I have a bachelor's degree in Aero Engineering (Cal Poly 1964) and a Masters in Systems Engineering (USC, 1989). In addition, I am a commercial pilot and flight instructor, specializing in training pilots to fly full scale vintage tailwheel airplanes. I have made approximately 15,000 takeoffs and landings in various tailwheel airplanes.

1. Here is the bottom line reason why gyros can be useful to us in our scale models:

Model airplanes are not real airplanes. But we modelers want our planes to behave in flight like their full sized counterparts. We work hard to make them look real statically and we want them to look real in flight. Gyros help us do that.


2. Why can't we just fly them like a full sized pilot flies his plane ?

Scale models have the same shape as their real counterparts, but they do not have the same mass or size and therefore they move differently and look different when they move. Essentially, they have higher angular rates (less inertia, less damping) and they respond much more quickly to upsets such as atmospheric turbulence.

3. We model pilots are human beings just like the pilots of the real airplanes. We have pretty much the exact same response rates, accuracy, and lag times. Controls engineers call this "the human transfer function". Transfer function describes the way we respond to a task and how quickly we begin to lag in our responses as the task speeds up. The argument raged between test pilots and engineers for a long time that some pilots are more skilled than others. But today it's pretty much universally agreed that a human being who is trained for a task exhibits responses which can be mathematically modeled and are readily predictable.

4. The task of the model pilot is further hampered by the poorer visual cues. We can't look straight down the nose like a pilot of a full sized airplane. Visually, flying a model is more like shooting from the hip as opposed to sighting down the barrel of a rifle.

5. And the task of the model pilot is still further hampered by our lack of "feel" in the seat of our pants when the model airplane moves.



So we model pilots are the same sort of human beings as full scale pilots, but the task is different. Therefore, the outcomes can't be matched.

The gyro simply adds apparent size to the model in terms of body motions. The airplane swings more slowly, responds to gusts less, and doesn't overshoot in its response to our inputs. In short, the model becomes closer to the real airplane in its behavior. This enables us to interact with the model in a more realistic fashion and pleases us because the visual appearance in flight more closely matches the realistic static appearance.


Are there folks who still don't get it ? Sure. I wrote this for those who appreciate what the gyros are doing for them and to help them understand WHY it helps. Can't help the others.

Dick Fischer

quote:

ORIGINAL: Silverexpress

The speed and torque of the servo also makes a difference. As does the location of the control rod ends in regards to their locations relative to the center of rotation - servo horn, and rotating axis of controlled surface.

These are just two items that can easily affect the response time and strength of the gyro controlled item.