AV8B Control Stick Column and Pilot Force Sensor Design
Simple design problem requiring a lot of work. The control column for the Harrier aircraft is what the pilots hold to control the flight of the plane. See the cockpit image to the right.
In developing a flight control system it became necessary to measure the force applied to the control column by the pilots. Sounds easy? Go into a 5 G turn out of a roll and try to distinguish dynamic flight loadings from pilot inputs. Plus we had to work within the allotted limited space between the pilot's legs. All while passing a ton of cabling from the fire and flight controls of the handle to the plane. And the column was labeled an air worthiness critical structural component, which means that a pilot diving straight down can brace his legs, and pull on the stick with all his force, seeing the ground rising at him, and we can not break.
I came up with an innovative, counter balanced, 3 axis differential LVDT sensor that would measure relatively accurate loads. Design featured BeCu machined spring design with machined ceramic induction paths. I was working on Mu metal induction path design for cost and impact resistance when the money ran out.
On the weak side, the design required calibration and I never did find out how stable the circuit was over time.
In hindsight, since the sensor design was completely my own, I still wonder how this junior engineer ended up third on the patent. :-)
View of Harrier cockpit with control column pointed out.
My 3 axis LVDT design.