Experimental tools: a clamp to hold a light airplane's control yoke in a fixed position in the pitch axis
February 22, 2006 edition
steve at aeroexperiments.org
When a pilot has a means of holding an airplane’s control yoke in a completely fixed position in the pitch axis, this permits some very interesting explorations into flight dynamics.
To fix the control yoke in a particular position in the pitch axis, I lightly clamped this special tool (photo #1, #2, #3, #4) to the control yoke torque tube. This provided an artificial limit to the control yoke's forward travel: when the tool touched the face of the instrument panel, the control yoke could not be moved any further forward. This allowed the control yoke to be easily held in a completely fixed position in the pitch axis, without any restriction of motion of the yoke in the roll axis.
The tool is essentially a set of vice grips (about 18 cm, or 7 inches, in length) with two flat pieces of metal (8 cm by 3 cm, or 3 inches by 1.25 inches) welded to the jaws. This item as sold in hardware stores as a “Locking Sheet Metal Tool”; my particular version was made by the Irwin company, part #23EL5. To each of the flat faces, I glued a sheet of firm (non-foam) rubber (about 4 mm, or 3/16 inches, in thickness). This cushioned the interface between the flat metal surfaces and the control yoke torque tube, and provided a no-slip surface.
The tool worked extremely well—when locked in place on the control yoke torque tube with light pressure, it stayed firmly in place with no tendency to slip, and left no marks of any kind on the torque tube.
(Here is an earlier version of the tool: a small set of ordinary vice grips, with the jaws padded with wraps of electrical tape. This version didn’t work nearly as well as the later version—it was prone to slipping out of place on the torque tube.)
Of course, when experimenting with a tool like this, only light pressure should be used to clamp the tool to the control yoke torque tube, so that there is zero risk of damaging or distorting the torque tube in any way.
For notes on some interesting experiments that can be carried out with this tool, see the related articles on this website entitled "Flying with a fixed elevator position--creating a pitch "phugoid" oscillation", Flying with a fixed elevator position--exploring relationships between roll and pitch", and "Flying without using the rudder -- looking at adverse yaw (sideslip)".
The in-flight yoke clamp photos are courtesy of Jim Norton.