- Sep 17, 2008
Finding the vertical location gives us nothing worth knowing. The airplane responds safely with the CG within its longitudinal limits, and the vertical location cannot change very much in any foreseeable loading situation. The manufacturer has already been through all that. Even in a high-wing airplane, with the extremes of full fuel and a light pilot, and low fuel and full people and cargo, the vertical CG movement won't be much because the loads aren't that far apart vertically to start with. The airplane's weight is the larger fraction and damps the displacement. Furthermore, the wing and tail both act in directions roughly perpendicular to the aircraft's longitudinal axis, and pitch changes don't change that much at all. The wing's center of pressure moves a bit with changes in angle of attack, but the response would be essentially the same wherever the vertical location of the CG might be.Got ya.
Not calculating the actual CG IS the Reason that dead level is important.
The actual acceptable center of gravity range is probably a football shaped three dimensional space with the long axis parallel to the wings axis.
I wasn’t thinking about large transports
More small aircraft not needing a type rating.
For them a relatively small scale would be enough to give you the gross weight
And of course once you put them on that platform it’s such a minor thing to get a vertical line of center gravity it just seemed like the thing to do.
Well of course not knowing the height of the center on that line is what causes the problem
So, see, the vertical CG, for our little airplanes, is irrelevant. Learning to fly involves enough difficulty without adding irrelevant stuff to the learning process. In fact, angle of attack (AoA) is a critical part of understanding flight, and yet students in recent decades haven't been getting it in flight training. Maybe ten minutes is spent on it in groundschool, and a few more in flight, and then it's ignored. That brevity in coverage gives the student the impression that it isn't important, and it kills some of them. They do buzz jobs and pull up hard to impress the folks, inadvertently getting the accelerated stall that they asked the airplane for, and it spins into the ground. They had been fed stall speed numbers without the crucial detail that stall speeds go up with wing loadings, and directional changes involve loading changes. Carb ice kills a few too, and wrecks a lot of airplanes, because they've come away with the impression that carb ice is a winter thing. More dysfunctional education.
There are a lot of subjects we need to enhance in training, but vertical CG isn't one of them.