AD 76-04-09

76-04-09 BELL: Amendment 39-2528. Applies to Bell Models 206A, 206B, 206A-1, and 206B-1 helicopters certificated in all categories, except those having installed main rotor hub yokes delivered as replacement spare parts from Bell Helicopter Company after August 11, 1974, and Models 206A and 206B bearing serial numbers 1174, 1192, 1252, 1355, 1381, 1382, 1390, 1398, 1399, 1400, 1408 through 1411, 1444, 1464, 1466, and subsequent.

Compliance required within 200 hours' time in service after the effective date of this AD unless already accomplished.

To detect and prevent possible cracks in the main rotor hub yokes, accomplish the following:

(a) Remove the main rotor hub assembly form the helicopter and remove the pillow blocks and trunnion from the hub assembly in accordance with the pertinent model maintenance manual.

(b) Inspect the yoke for cracks in each trunnion bore and in each tooling hole in the yoke web section using a 10-power or higher magnifying glass or an equivalent inspection method.

(c) If a crack is found, remove and replace the discrepant yoke before further flight.

(d) Inspect each yoke trunnion bore edge for nicks, scratches, or tool marks using a 10-power or higher magnifying glass or an equivalent inspection method.

(e) If nicks, scratches, or tool marks are found on these edges, they must be removed, before further flight, as prescribed in Bell Helicopter Company Service Bulletin No. 206-04-1-74-1, Revision A, dated August 22, 1974, or later approved revision or in accordance with an equivalent FAA approved procedure.

(f) Assemble and install the main rotor hub on the helicopter in accordance with the pertinent model maintenance manual.

The manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive who have not already received these documents from themanufacturer may obtain copies upon request to the Service Manager, Bell Helicopter Company, P. O. Box 482, Fort Worth, Texas 76101. These documents may also be examined at the Office of the Regional Counsel, Southwest Region, FAA, 4400 Blue Mound Road, Fort Worth, Texas, and at FAA Headquarters, 800 Independence Avenue, S.W., Washington, D.C. A historical file on this AD which includes the incorporated material in full is maintained by the FAA at its headquarters in Washington, D.C., and at the Southwest Regional Office in Fort Worth, Texas.

This amendment becomes effective March 30, 1976.