Abstract: A hangar door assembly for passing the vertical stabilizer of an airplane tail, includes a main door frame fitted into a wall of an aircraft hangar building, a main door pivotally mounted within the main door frame, an auxiliary door frame having a vertical edge, and fitted into the hangar building wall above the main door frame, an auxiliary door pivotally mounted on the vertical edge and biased with a spring to swing to an open position, a bearing assembly attached to the main door bearing against the auxiliary door, to oppose the biasing of the spring to close the auxiliary door when the main door is slid closed. A method for opening an auxiliary door as described above includes the steps of sliding the main door to an open position, thereby gradually moving the bearing assembly toward the vertical edge, keeping the auxiliary door in contact with the bearing assembly as the bearing assembly moves toward the vertical edge with the spring, thereby gradually opening the auxiliary door.

Abstract: A motorized drive unit for a horizontally sliding door section comprising a unitary housing assembly holding a drive motor and a floor-engaging wheel driven from the motor. A vertical lead screw fixedly positioned vertically on this housing assembly threadedly engages a nut fixedly positioned on the door section, so that the wheel can be raised from engagement with the floor. The housing assembly is slidable vertically on a support plate attached to the door section. A support member for the nut is attached to the same support plate.

Abstract: A horizontally sliding door section with a floor-engaging wheel driven from a motor. The wheel and its drive are located within the front-to-back extent of the door section in a housing hinged at one end on the bottom of the frame of the door section. A lead screw operated by a manual crank can be used to pivot the housing up about its hinge to raise the wheel from engagement with the floor of the building. The housing for the wheel has a removable front wall which carries the front bearing for the axle of the wheel, so that removal of this front wall disengages this bearing from the wheel axle.