48-51-01: Control Wheel Shaft Inspection

48-51-01 BEECH: Applies to AT-11, C18S, D17S Airplanes Equipped With Beech Half-Circle Type Control Wheels. To be accomplished as soon as possible, but not later than March 1, 1949. To preclude the possibility of failure of the control column wheel shaft due to too great a counterbore depth in the shaft, the following inspection should be accomplished: (Bow-tie type control wheels attached to the control shaft by three bolts through a flange on the shaft are satisfactory and need not be inspected). (1) Drill a 3/8-inch hole in the center of the hub of the control wheels. Do not allow the drill to go more than 1 inch into the hub or the pin securing the wheel will be damaged. (2) Place a narrow scale or straight wire through the 3/8-inch hole and obtain the distance from the bottom of the counterbore (not the peak of the counterbore cone) to the face of the hub. (3) Insert a small hook scale or bent wire in the hole and obtain the distance from the end of the shaft to the face of the hub. (4) Subtract the distance obtained in step No. 3 from the distance obtained in step No. 2 to obtain the depth of the counterbore in the end of the shaft. If this distance is over 1 7/16 inches, the shaft must be replaced. All shafts having a counterbore less than 1 7/16 inches deep are satisfactory. (Beech Service Bulletin No. C-18-9 dated November 22, 1948, covers this same subject.)