60-08-04 LOCKHEED: Amdt. 132 Federal Register April 14, 1960. Applies to All Models 1049 Series and 1649A Aircraft.
Compliance required as indicated.
As a result of several cases of rudder torque tube failure (P/N 306525-2 and P/N 306525- 3), attributed to stress corrosion, the following inspection must be accomplished:
Within the next 300 hours' time in service on all aircraft which have accumulated 5,000 hours' time in service, visually inspect for cracks, using a 10-power magnifying glass, the lower attachment portion of the upper rudder torque tube and the upper attachment portion of the lower rudder torque tube. If cracks or crack indications are found, reinspect the above area using dye penetrant or equivalent. (The cracks progress along the longitudinal direction from the edge of the tube to the first row of bolt holes and beyond. The cracks may also emanate from the second row of bolt holes.)
Replace the torque tube prior to further flight if the tube is cracked beyond the first 3/8- inch bolt attachment hole or if the tube is cracked at the second row of 5/16-inch bolt attachment holes.
If the tube is cracked from the edge to the first 3/8-inch bolt hole a repair may be used provided the repaired tube is reinspected in the above manner every 300 hours until replaced. The repair must be made prior to further flight and consists of the addition of two 1/4-inch blind lockbolts or Jobolts, located one on each side of the crack, spaced halfway between the existing 3/8-inch bolt holes and in line with these bolts. The maximum number of cracks permitted is two. If the crack progresses beyond the 3/8-inch bolt attachment hole, with the repair installed, replace the torque tube prior to further flight.
If no cracks are found, reinspect visually every 1,300 hours' time in service. If torque tubes are replaced with new parts (P/N 306525-5 or P/N 306525-7), no further special inspections are required. (Lockheed Service Letter FS/237201 coversthis same subject.)
Revised August 19, 1960.