COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bell Helicopter Textron 212 Series Helicopters AD/BELL 212/25 Amdt 4 Main Rotor Yoke 9/91 Applicability: All helicopters fitted with main rotor yoke P/N 204-011-102- (all dash numbers). Requirement: 1. Inspect the main rotor yoke in-situ in accordance with the Accomplishment Instructions in Bell Alert SB No 212-90-60, Revision A, dated 31 August 1990. 2. Remove the yoke assembly from the main rotor hub assembly and inspect the yoke in accordance with FAA AD 79-20-05, Amendment 39-3662. Compliance: As detailed in the Requirement Documents. Background: Amendment 3 implemented the additional inspections of ASB 212-87-48, which was issued as a result of fatigue cracks being found in service. It required that visual inspections of the main rotor yoke be performed daily and every 1200 hours/24 months. These are additional to the more detailed 2400 hourly inspection specified in FAA AD 79-20-05. Amendment 4 specifies Bell Alert SB 212-90-60, which supersedes ASB 212-87-48, and adds a yoke spindle inspection to Part III, required at 1200 hours/24 month intervals. Inspections done to earlier amendments may be considered for the purposes of determining when amendment 4 inspections are due.