59-17-05 HELIO: Applies to All Model H-391B Aircraft Except Serial Numbers 093, 094, and 098; and Model H-395, Serial Numbers 502 Through 510.
Compliance required as indicated.
Within the next 10 hours unless already accomplished inspect the horizontal tail front spar splice plate, P/N 391-020-305, for cracks around all bolt holes and the 2.0-inches diameter lightening hole. If cracks are found, the fitting should be replaced with an identically dimensioned part 0.063-inch 4130 steel. If no cracks are found the original aluminum fitting shall be inspected at each 25 hours thereafter until the next 100-hour inspection or October 1, 1959, whichever occurs first, when it must be replaced with a steel part.
(Helio Service Bulletin No. 21 covers this subject.)