AD 74-07-01

74-07-01 BELL: Amendment 39-1801 as amended by Amendment 39-1864. Applies to all cyclic and collective main rotor control tube assemblies installed within a 30 degree angle of the vertical axis on Model 47 series helicopters, certificated in all categories.

Compliance required within the next 100 hours time in service after the effective date of this A.D., unless already accomplished, and thereafter at intervals not to exceed 1200 hours time in service from the last inspection.

To detect corrosion and prevent possible failure of the control tube assemblies, accomplish the following inspection.

(a) Remove the control tube assemblies from the helicopter and remove the rod end bearing and insert or clevis at each end of the tube assembly and clean the inside of the tube.

(b) Inspect each control tube for internal corrosion using a light and borescope or equivalent inspection means.

(c) Remove corroded control tubes from service prior to further flight, exceptas specified by paragraph (g) of this A.D. and submit a report of finding a corroded tube to Chief, Engineering and Manufacturing Branch, Flight Standards Division, Southwest Region, FAA, P.O. Box 1689, Fort Worth, Texas, 76101. The control tube assembly part number, degree of corrosion found and total time in service should be included in the report. FAA Form 8330-2 may be used for this report. (Reporting approved by the Bureau of the Budget under BOB No. 04- R0174.)

(d) Reinstall serviceable rod end bearings and inserts or clevis in the uncorroded and serviceable tubes using acceptable techniques, methods and practices as specified below.

(1) Tubes with double drilled rivet holes, sharp nicks or scratches and internal corrosion are considered unserviceable.

(2) Tubes must have internal corrosion protection using zinc chromate primer, hot linseed oil or other equivalent corrosion inhibitor. The tube ends must be sealed, air and water tight, as specified in Paragraphs 4 and 5, Part II, Bell Helicopter Company Service Bulletin No. 47-11-73-1, Rev. A, dated December 6, 1973 or later approved revision or as specified in an equivalent FAA approved procedure when the insert, rod end bearing or clevis and rivets are installed.

(e) Install control tube assemblies on the helicopter and check the controls rigging and check tracking of the main rotor blades in accordance with pertinent Model 47 maintenance and overhaul information manual.

(f) 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 the manufacturer 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 A.D. 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.

(Bell Helicopter Company Service Bulletin No. 47-11-73-1, Rev. A, dated 12-11-73 pertains to this subject.)

(g) Tubes with light corrosion over less than twenty-five percent of the area in any one-half inch length of the tube may be returned to service provided the tube is assembled and protected as noted in paragraph (d) of this A.D. and the tube is removed from service prior to accumulating 200 hours time in service after the initial inspection prescribed by this A.D. was conducted.

NOTE: Advisory Circular No. 43-4, page 47 defines light corrosion.

Amendment 39-1801 became effective April 22, 1974. This Amendment 39-1864 becomes effective May 30, 1974.