A through-transmission ultrasonic (TTU) inspection system for ultrasonic inspection of a part, such as an aircraft component. The TTU inspection system may include a first end effector and/or a second end effector. The first end effector may be positioned on a first surface of the part and the second end effector may be positioned on a second surface of the part, opposite the first surface. The first and/or second end effector may also include an acoustic coupling medium encircled by a plurality of pins independently movable toward and away from a housing of the first and/or second end effector, such that the pins may follow local part contours along the first surface at all times, while retaining the acoustic coupling medium between the first surface and a transducer in the housing of the first and/or second end effector.