AD 77-11-02 ACTIVE

77-11-02 MESSERSCHMITT-BOLKOW-BLOHM GmbH: Amendment 39-2912. Applies to Model BO-105 helicopters, certificated in all categories.

Compliance is required as indicated.

To prevent the possible failure of the main rotor hub quadruple nuts and the consequent loss of the main rotor, accomplish the following:

(a) For main rotor hub quadruple nuts, P/N's 105-14101.19 and 105-14101.20 and associated bolts, P/N's 105-14101.22 and 105-14101.23, with more than 1,400 hours total time in service, within the next 100 hours time in service after the effective date of this AD, unless already accomplished within the last 200 hours time in service, and thereafter at intervals not to exceed 300 hours time in service from the last inspection, remove the quadruple nuts and associated bolts and inspect them for cracks using a magnaflux process, or an FAA-approved equivalent.

(b) If a crack is found in a nut or bolt during any of the inspections required by this AD, before further flight, replace the cracked part with a serviceable part of the same part number. For parts installed as replacements, before the accumulation of 1,500 hours total time in service on the replacement parts and thereafter at intervals not to exceed 300 hours time in service from the last inspection, remove the replacement quadruple nuts and associated bolts and inspect them for cracks using a magnaflux process or an FAA-approved equivalent.

(c) Before the accumulation of 2,400 hours total time in service on a quadruple nut or bolt specified in paragraph (a) of this AD, replace the quadruple nuts and associated bolts with serviceable nuts and bolts of the same part numbers and comply with paragraphs (a) and (b) of this AD for the replacement parts.

(MBB Service Bulletin No. 10-18 dated July 18, 1975, covers this same subject.)

This amendment becomes effective June 14, 1977.