AD 74-08-02

74-08-02 BELL: Amendment 39-1805 as amended by Amendment 39-1873. Applies to Bell Model 47 Series helicopters equipped with Mast Control Stabilizer Bar Assemblies, P/N 47- 140-248, certificated in all categories.

Compliance required as indicated.

To detect possible failures of a stabilizer bar tube assembly and prevent possible loss of a stabilizer bar tube and weight, accomplish the following inspections:

(a) Before the first flight of each day after the effective date of this A.D., check the stabilizer bar tube assembly for looseness and cracks in accordance with the following procedures.

(1) Move each stabilizer tube assembly fore and aft in the horizontal plane by hand and visually check the tube assembly for cracks in area extending outboard six inches from the tube retaining nut, P/N 47-140-114-1.

(2) If looseness is found between a stabilizer bar tube assembly and the stabilizer bar frame, or if a crack is found in a tube, remove the loose or cracked tube assembly prior to flight and install a replacement tube assembly in accordance with (c)(2) and (c)(3) of this A.D.

(3) Looseness between the stabilizer bar frame and main rotor mast is a normal occurrence and is not an indication of a failed tube and is not cause for replacement of the bar tube assembly.

(4) The checks in (a)(1) may be performed by the pilot.

NOTE: For the requirements regarding the listing of compliance and method of compliance with this A.D. in the aircraft permanent maintenance record, see FAR 91.173.

(b) Within 10 hours time in service after the effective date of this A.D., unless already accomplished, and thereafter at intervals not to exceed 100 hours from the last inspection, inspect the rod assembly nut, P/N 47-140-119-1, for looseness as follows:

(1) Push up the inboard end of each tie rod and nut and determine that they move freely or readily.

(2) If the tie rod and nut do not move freely or readily, remove the stabilizer bar assembly before further flight and inspect each tie rod and tube assembly in accordance with the 1200 hour inspection procedures in Section I, of the appropriate Model 47 maintenance and overhaul instruction manual, and

(3) Assemble and install a serviceable stabilizer bar assembly as specified in paragraph (c)(2) and (c)(3) of this A.D.

(c) Inspect the gap between the face of each nut, P/N 47-140-119-1, and the inboard end of each stabilizer bar tube at intervals not to exceed 1200 hours time in service from the last inspection, after compliance with paragraph (b), in accordance with the following procedures:

(1) Remove the mast control stabilizer bar assembly from the helicopter and remove both tube and weight assemblies from the stabilizer bar assembly in accordance with Section III of the appropriate Model 47 maintenance and overhaul instruction manual.

(2) Assemble the stabilizer bar weight and taper pin on the tube assembly and adjust the gap, ifnecessary, between the face of each nut, P/N 47-140-119-1, and its mating tube assembly end to measure .0l0 to .024 inches clearance.

(3) Assemble and install the mast control stabilizer bar assembly on the helicopter in accordance with Section III of the appropriate Model 47 maintenance and overhaul instruction manual. In addition adjust the stabilizer core bearing as specified in item 1, Bell Helicopter Co. Technical Bulletin No. 47-(04-2)-73-2, or Service Bulletin No. 47-(04-2)-74-1 or later FAA approved revision.

(d) Inspect the fore and aft and lateral control power cylinders for proper alignment within 100 hours time in service after compliance with paragraph (b), and thereafter at intervals not to exceed 1200 hours time in service from the last inspection, in accordance with Section VII of the appropriate Model 47 maintenance and overhaul instruction manual.

(e) Within 10 hours time in service after the effective date of this A.D. inspect each tube assembly to determine that P/N 47-140-124-1, 47-140-125-1 or 47-140-125-3 is installed. If tube assembly, P/N 204-010-380-1 is installed, replace this tube before further flight in accordance with paragraph (c)(2) and (c)(3) of this A.D. The 204-010-380-1 tube is identified as a one piece swaged tube with a uniform wall thickness (that is, different inside diameters) and machine cut threads. In addition, this tube does not have Bell factory applied serial numbers.

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, andat 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 Region Office in Fort Worth, Texas.

(Bell Technical Bulletin No. 47-(04-2)-73-2, pertains to this adjustment of the bearing and alignment of power cylinders and Service Bulletin No. 47-(04-2)-73-1 pertains to stabilizer bar tube and tie rod. Service Bulletin No. 47-(04-2)-74-1 also pertains to the adjustment of the bearing.)

Amendment 39-1805 became effective May 6, 1974. This Amendment 39-1873 becomes effective June 14, 1974.