| AD Number | 74-15-06 | Status | Active |
| Effective Date | December 30, 1977 | Issue Date | Not specified |
| Docket Number | Unknown | Amendment | 39-3089 |
| Product Type | ["Aircraft"] | Product Subtype | ["Rotorcraft"] |
| CFR Part | --- - Part 39 | CFR Section | N/A |
| Citation | This information is not available. | ||
| Manufacturer(s) | Sikorsky Aircraft Corporation |
| Model(s) | S-58A S-58B S-58BT S-58C S-58D S-58DT S-58E S-58ET S-58F S-58FT S-58G S-58H S-58HT S-58J S-58JT |
74-15-06 SIKORSKY AIRCRAFT: Amendment 39-1890 as amended by Amendment 39-2134 and 39-2447 is further amended by Amendment 39-3089. Applies to all S-58 model series helicopters equipped with magnesium input and/or intermediate housings.
Compliance required as indicated unless already accomplished. To preclude possible failure of the magnesium input and/or intermediate housings of the tail rotor gearbox assembly, P/N S1635-64000 series, accomplish the following:
1. Within the next three hours time in service after the effective date of this AD, or whenever unusual vibration in the tail rotor system is experienced, accomplish the following in accordance with the instructions set forth in Section 2, Paragraphs A and C of Sikorsky Service Bulletin No. 58B35-17C, dated November 24, 1975 (hereinafter Bulletin No. 58B35-17C).
a. Inspect the nuts attaching the tail rotor gearbox assembly to the pylon fitting.
b. Inspect the input and intermediate housings of the gearbox.
c. Retorque the nuts that attach the input to intermediate housing.
2. After completion of the initial inspections required in Paragraph 1, conduct the repetitive inspections specified in a, b, and c below as applicable. Sections and paragraphs listed are part of Bulletin No. 58B35-17C.
a. Every ten hours time in service inspect in accordance with Section 2, Parargraphs A(2) and C(2), (a) thru (d), if both Sikorsky Service Bulletins listed below are not complied with or lightweight input and/or intermediate tail rotor gearbox housings are installed:
(1) 58B15-14B, Balance of Rotary Rudder Assembly.
(2) 58B20-14B, Strengthening of Pylon Carry-Thru Structure of Rotary Rudder Assembly.
b. Every 20 hours time in service, inspect in accordance with Section 2, Paragraphs C(2), (a) thru (d), if tail rotor gearbox S1635-64000-9 is installed and if both Sikorsky Service Bulletins 58B15-14B and 58B20-14B or their latest FAA approved revisions are compliedwith.
c. Every 50 hours time in service, inspect in accordance with Section 2, Paragraphs C(2), (a) thru (d), if tail rotor gearbox S1635-64000-10 is installed and if both Sikorsky Service Bulletins 58B15-14B and 58B20-14B or their latest FAA approved revisions are complied with.
3. Within the next 25 hours time in service after the effective date of this AD, remove the tail rotor gearbox assembly (P/N S1635-64000 series) from the aircraft and accomplish the one-time inspection set forth in Section 2, Paragraph B, of Bulletin No. 58B35-17C.
4. Every 50 hours time in service after the inspection required in Paragraph 1 above, inspect the nuts attaching the tail gearbox to the pylon fitting in accordance with Section 2, Paragraph A(1) of Bulletin No. 58B35-17C. If heavy weight input housing, P/N S1635-64009-3N, and heavyweight intermediate housing, P/N S1635-64074, are both installed, inspect in accordance with Section 2, Paragraph D(2), of Bulletin No. 58B35-17C.
5. Tail rotor gearbox assembly (P/N S1635-64000 series) input and intermediate housings and pylon fittings (S1620-64129) found to have evidence of cracks shall be replaced with an acceptable assembly prior to further flight. All other defects found as a result of the inspections required by Paragraphs 1, 2, 3, and 4 shall be repaired in accordance with instructions contained in Bulletin No. 58B35-17C prior to further flight.
6. Remove from service magnesium input and intermediate housings P/N's S1635-64009-3N, S1635-64074, S1635-64009, S1635-64010 as follows:
a. Prior to July 31, 1978, for all turbine engine powered S-58T helicopters.
b. Prior to December 31, 1978, for all piston engine powered S-58 helicopters.
Replace with aluminum input and intermediate housings S1635-64009-101 and S1635-64074-103 respectively.
NOTE: Sikorsky Service Bulletin No. 58B35-25 covers this subject.
7. Upon submittal of substantiating data through a Federal Aviation Administration inspector, the Chief, Engineering and Manufacturing Branch, Federal Aviation Administration, New England Region, may adjust the compliance time.
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 Sikorsky Aircraft, Division of United Aircraft Corporation, Stratford, Connecticut 06602. These documents may also be examined at the Office of the Regional Counsel, New England Region, Federal Aviation Administration, 12 New England Executive Park, Burlington, Massachusetts 01803 and at Federal Aviation Administration 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 Federal Aviation Administration at its headquarters in Washington, D.C., and at the New England Regional Office in Burlington, Massachusetts.
Amendment 39-1890 became effective July 27, 1974.
Amendment 39-2134 became effective April 3, 1975.
Amendment 39-2447 became effective December 10, 1975.
This amendment 39-3089 becomes effective December 30, 1977.