AD 75-17-27

75-17-27 MESSERSCHMITT-BOLKOW-BLOHM: Amendment 39-2332. Applies to Messerschmitt-Bolkow-Blohm (MBB) Models BO-105A and BO-105C helicopters, certificated in all categories, incorporating Main Rotor Head Assembly No. 105-14101. Compliance is required within the next 100 hours time in service after the effective date of this AD, unless already accomplished in accordance with MBB BO-105 Alert Service Bulletin No. 4 and Service Bulletin No. 10-11. To prevent development of incipient cracks, corrosion, and excessive wear on bolts of the main rotor head, accomplish the following: (a) For all Main Rotor Head Assemblies, P/N 105-14101, determine part number of Blade Mounting Bolts. If bolt P/N 105-14101.31 is found, replace with serviceable bolt of P/N 105-14101.29. (b) For Main Rotor Head Assemblies 105-14101 having Serial Number 50 or lower, determine part number revision letter of Main Rotor Bolts P/N 105-14101.22 and .23. If any bolt with revision letter "a" through "f" is found, replace with serviceable bolt of the same part number having revision letter "g" or subsequent. This amendment becomes effective August 20, 1975.