48-51-02: Horizontal Tail Surfaces

48-51-02 CONVAIR: Applies to All Model 240 Aircraft. Recently reported difficulties concerning the horizontal tail surfaces for Convair Model 240 aircraft have indicated the necessity of conducting thorough and frequent inspections of all critical items to detect any fatigue cracks and to minimize the development of hazardous conditions. The several reported difficulties appear to result from tail vibrations induced by the engines and/or propellers at certain r.p.m.'s. Pending completion of the necessary investigations and determination of adequate remedial measures, the following must be accomplished: A. To be accomplished daily on the left horizontal surfaces. (NOTE: Time limit may be extended to each No. 3 operation upon incorporation of AD 49-44-02 and CVAC Service Bulletins 240-219 and 240-247). Utilizing available inspection openings but without removing any surfaces, conduct a close, visual inspection of the following: 1. Horizontal stabilizer skin, rearspar and hinge brackets. 2. Elevator skin, leading edge ribs, spars, hinge brackets and balance weight installations. 3. Tab skin, spar, hinge brackets and balance weight installations. Particular care should be taken to detect any evidence of loose balance weights, sheared rivets or cracked hinge brackets. Any failed parts should be adequately repaired or replaced prior to the next flight. NOTE: Inspection procedures which have been satisfactorily demonstrated to the CAA Agent to provide equivalent safety may be accepted in lieu of the inspection procedures outlined above. NOTE: The following static balance tolerances about the respective hinge lines must be retained after rework of any surface: 1. Left elevator, including flight tab; 72-87 inch-pounds tail heavy with the seal curtain removed. 2. Right elevator, including trim tab: 0-15 inch-pounds nose heavy with the seal curtain removed. 3. Elevator flight tab: 6-8 inch-pounds nose heavy. B. To be accomplished at periods not to exceed 50 hours until close tolerance bolts and bushings have been installed in elevator tab hinges in accordance with CVAC Service Bulletin 240-205. Remove all elevator flight tab hinge pins and inspect the pins, bushings and bearings for sign of wear. Worn parts should be replaced. This supersedes AD 48-47-01.