The transfer of air travelers with disabilities between a mobility aid and an aircraft seat is a major source of injury for both the travelers and the airline personnel assisting in the transfer. The risk to both parties might be reduced through the biomechanical study of the transfer task. Such study requires that the contact forces acting on the body of the rear transferor be known, including the contact force between the rear transferor and the seat-back. A seat-back mounted force plate was designed and constructed to accurately measure the magnitude and the center of pressure location of normal forces applied to the seat-back. This force plate collects data from four preloaded single component force transducers. The force transducers are mechanically isolated from shear forces to protect them from damage. Testing of the force plate found a normal force magnitude accuracy of 0.19 %FS over the 890 Newton (200 lbf) calibrated range. The force plate was shown to have a horizontal and vertical center of pressure location accuracy of 2.66 and 1.58 millimeters (0.105 and 0.062 inches) RMS respectively over its 343 by 293 millimeter (13.5 by 11.5 inches) measurement range. By measuring forces that may have otherwise been ignored, the seat-back mounted force plate can improve the quality of the biomechanical analysis of aircraft transfers. / Graduation date: 2005