VOLUME 1 May 1, 1948 NUMBER 8 MODEL 18 SERVICE NOTES AND CHANGES Elevator Tab Rheostat Modification An improved elevator tab rheostat drive has been incorporated in Model D18 airplanes in production.  This change was effective on D18S Serial A-402 and D18C Serial AA-27.  Model D18 airplanes delivered prior to A-402 and AA-27 may be […]