Airworthiness Directive · Amendment 39-17709 · Main rotor hub, 6230 main rotor mast/swashplate, 6320 main rotor gearbox, 6310 engine/transmission coupling, 6510 tail rotor drive shaft
Sikorsky Aircraft Corporation (Sikorsky) Helicopters
This AD applies to Model S-70, S-70A, and S-70C helicopters, certificated in any category, with the following parts installed:
(1) Spindle and liner assembly, part number (P/N) 38023-10374-041;
(2) Main Rotor Hub, P/N 70070-10046-055 and -056;
(3) Main Rotor Spindle nut, P/N 70102-08105-102;
(4) Main Rotor Control Horn, P/N 70102-08111-047;
(5) Main Rotor Hub, P/N 70103-08112-041 and -047;
(6) Rotating Swashplate, P/N 70104-08001-044 and -045;
(7) Main Rotor Shaft Extension, P/N 70351-08186-043;
(8) Main Rotor Gear Box Housing, P/N 70351-38110-043, -044, and -045;
(9) Main Rotor Shaft, P/N 70351-38131-042;
(10) Output Bevel Gear and Shaft, P/N 70358-06620-101 and -102;
(11) Left Tie Rod Assembly, P/N 70400-08115-043, -045, -046, and -047;
(12) Forward Bellcrank Support Assembly, P/N 70400-08162-042;
(13) Lateral Servo Bellcrank, P/N 70400-08166-041; or
(14) Tail Rotor Servo Assembly, P/N 70410-06520-044 through -046.
We are adopting a new airworthiness directive (AD) for Sikorsky Model S-70, S-70A, and S-70C helicopters. This AD establishes a new life limit based on a prorated formula for certain identified components (parts) installed on Model S-70, S-70A, and S-70C helicopters after being previously installed on certain military model helicopters. This AD was prompted by the discovery that certain parts have been interchanged between military helicopter models with different life limits and the possibility that these same parts can be interchanged with civilian models with different life limits. The actions are intended to establish a pro-rated in service life limit for each identified part to prevent fatigue failure of a part and subsequent loss of control of the helicopter.
You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.
(1) Within 25 hours time-in-service (TIS):
(i) Insert into the airworthiness limitation section of the maintenance manual or instructions for continued airworthiness the component life prorating formula in Section 1.1.3, Component Life Prorating, pages 1-25 and 1-26, of Sikorsky Technical Manual TM 1-70-23AW-2, Change 3, dated April 15, 2012.
(ii) Using the service life limits in Table 1 to Paragraph (e) of this AD, apply the component life prorating formula and calculate the new life limit for each specified part. If the number of hours of a part is unknown, that part cannot be installed on a Sikorsky Model S-70, S-70A, or S-70C helicopter. Do not calculate a new life limit for the part where the Model SH-60 life limit is higher than the life limit on Models S-70, S-70A, and S-70C.
| P/N | Part description | S-70, S-70A, S-70C service life | UH-60M service life | SH-60B/F service life |
|---|---|---|---|---|
| 38023-10374-041 | Spindle and Liner Assembly | 8,000 | 6,400 | 10,000 |
| 70070-10046-055 and -056 | Main Rotor Hub | 5,100 | 3,100 | 1 N/A |
| 70102-08105-102 | Main Rotor Spindle Nut | 8,000 | 6,400 | 10,000 |
| 70102-08111-047 | Main Rotor Control Horn | 20,000/1,300 2 /2,500 2 | 10,000 | 1 N/A |
| 70103-08112-041 and -047 | Main Rotor Hub | 5,100 | 3,100 | 1 N/A |
| 70104-08001-044-045 | Rotating Swashplate | 11,000 | 4,600 | 9,600 |
| 70351-08186-043 | Main Rotor Shaft Extension | 14,000 | 4,900 | 16,000 |
| 70351-38110-043, -044, and -045 | Main Rotor Gear Box Housing | 11,000 | 4,000 | 9,000 |
| 70351-38131-042 | Main Rotor Shaft | 17,000 | 5,200 | 19,000 |
| 70358-06620-101 and -102 | Output Bevel Gear and Shaft | 5,000 | 1,800 | 1 N/A |
| 70400-08115-043, -045, -046, and -047 | Left Tie Rod Assembly | 14,000 | 4,600 | 6,300 |
| 70400-08162-042 | Forward Bellcrank Support Assembly | 14,000/2,500 3 | 5,600 | 7,600 |
| 70400-08166-041 | Lateral Servo Bellcrank | 20,000 | 11,000 | 14,000 |
| 70410-06520-044 through -046 | Tail Rotor Servo Assembly | 15,000 | 11,000 | 1 N/A |
(iii) Record the newly-established life limit of each part on the part's component log card or equivalent record.
(2) After establishing the new life limit, replace each part that has reached or exceeded its new life limit with an airworthy part before further flight.
(3) Do not install the following parts on a Model S-70, S-70A, or S-70C helicopter if they have been previously installed on a Model UH-60M helicopter:
(i) Bolt, self retaining, P/N 70103-08801-102;
(ii) Bifilar, P/N 70107-08400-046;
(iii) Aft Bellcrank, P/N 70400-08102-045;
(iv) Aft Walking Beam Assembly, P/N 70400-08104-048; or
(v) Close Tolerance Bolt, P/N 70400-26802-102 and -103.
