Airworthiness Directive · Amendment 39-17269 · -13-p
Sikorsky Aircraft Corporation (Sikorsky) Model Helicopters
This AD applies to Model S-70, S-70A, and S-70C helicopters, certificated in any category.
We are adopting a new airworthiness directive (AD) for Sikorsky Model S-70, S-70A, and S-70C helicopters, which are restricted category helicopters derived from the military Model UH-60 helicopter. This AD would require reducing or establishing life limits for certain listed helicopter parts. This AD is prompted by a review of the United States Army's analysis of their Model UH-60 fleet, which determined it necessary to establish or reduce the life limits of certain parts. The actions are intended 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.
Before further flight:
(1) Establish or reduce the retirement life of the following parts listed in Table 1-1 of the Sikorsky Technical Manual TM 1-70-23AW-2, change 3, section 1.1, Airworthiness Limitations, by inserting a copy of Table 1-1 into the Airworthiness Limitations section of TM 1-70-23AW-2 or by making the following pen and ink changes to the Airworthiness Limitations of the maintenance manual:
(i) For each dowel pin on the main transmission housing, part number (P/N) NAS607-10-12P, NAS607-12-14P, and NAS607-12-18P, establish a life limit of 3,000 hours time-in-service (TIS).
(ii) For elastomeric sleeve bearing, P/N SB5203-202, establish a life limit of 720 hours TIS.
(iii) For right tie rod attach bolt, P/N SS5025-04H010, establish a life limit of 3,500 hours TIS.
(iv) For right tie rod attach bolt, P/N SS5025-04H10, establish a life limit of 5,000 hours TIS.
(v) For oil cooler axial fan ball bearing, P/N 210SFFC, installed in oil cooler axial fans, P/N 70361-03005-103 through -106, establish a life limit of 2,000 hours TIS; and for bearings installed in oil cooler axial fan, P/N 70361-03005-107, establish a life limit of 2,500 hours TIS.
(vi) For oil cooler axial fan ball bearing, P/N 210SFFC-0129, installed in oil cooler axial fan, 70361-03005-103 through -106, establish a life limit of 2,000 hours TIS; and for bearings installed in oil cooler axial fan, P/N 70361-03005-107, establish a life limit of 2,500 hours TIS.
(vii) For main rotor hub, P/N 70070-10046-055, establish a life limit of 5,100 hours TIS.
(viii) For main rotor blade, P/N 70080-15001-041, establish a life limit of 5,000 hours TIS.
(ix) For tail rotor blade, P/N 70080-15002-041, establish a life limit of 5,000 hours TIS.
(x) For main rotor blade, P/N 70080-15003-041, establish a life limit of 5,000 hours TIS.
(xi) For tail rotor blades, P/N 70080-15004-041 and P/N 70080-15005-041, establish a life limit of 5,000 hours TIS.
(xii) For main landing gear shock strut piston assembly, P/N 70250-12067-102, establish a life limit of 9,000 hours TIS.
(xiii) For Number 2 crossfeed breakaway valve, P/N 70307-03600-103, establish a life limit of 1,500 hours TIS;
(xiv) For main module planetary carrier assembly, P/N 70351-08175-043, -044, and -045, establish a life limit of 1,400 hours TIS; and for P/N 70351-08175-046 establish a life limit of 12,000 hours TIS.
(xv) For dowel pins, P/N 70351-08404-101, -102, and -103 on main transmission housings, P/N 70351-08110-044 and -045, establish a life limit of 3,000 hours TIS; for dowel pins, P/N 70351-08404-101, -102, -103, and -104 on main transmission housings, P/N 70351-28110-043 and -044, establish a life limit of 7,300 hours TIS; for dowel pins, P/N 70351-08404-101, -103, and -104, on main transmission housings, P/N 70351-38110-043, -044, and -045, establish a life limit of 11,000 hours TIS.
(xvi) For dowel pin, flight control support mounting to main transmission housing, P/N 70531-04805-101, 70531-04805-102, and 70531-08405-103, establish a life limit of 3,000 hours TIS.
(xvii) For dowel pin, flight control support mounting to transmission case, P/N 70351-28404-101, on main transmission housings, P/N 70351-08110-044 and -045, reduce the life limit from 4,300 hours TIS to 3,000 hours TIS.
(xviii) For main module planetary carrier assembly, P/N 70351-38175-041, establish a life limit of 6,500 hours TIS.
(xvix) For dowel pin, flight control support mounting to transmission case, P/N 70351-38404-101, on main transmission housings, P/N 70351-38110-043, -044, and -045, reduce the life limit from 20,000 hours TIS to 11,000 hours TIS.
(xx) For the tail rotor servo, P/N 70410-06520-044, -045, and -046, establish a life limit of 15,000 hours TIS.
(2) Remove from service any part with a number of hours time-in-service equal to or greater than the part's retirement life as stated in paragraph (e)(1) of this AD.
