AD 2013-26-13 Airworthiness Directives; Sikorsky Aircraft Corporation (Sikorsky) Helicopters

This AD becomes effective February 10, 2014.

Special flight permits will not be issued to allow flight in excess of life limits.

(1) The Manager, Boston Aircraft Certification Office, FAA, may approve AMOCs for this AD. Send your proposal to: Michael Davison, Flight Test Engineer, New England Regional Office, FAA, 12 New England Executive Park, Burlington, MA 01803; phone: (781) 238-7156; fax: (781) 238-7170; email: michael.davison@faa.gov. (2) For operations conducted under 14 CFR part 119 operating certificate or under 14 CFR part 91, subpart K, we suggest that you notify your principal inspector, or lacking a principal inspector, the manager of the local flight standards district office or certificate holding district office before operating any aircraft complying with this AD through an AMOC.

(1) Before further flight, insert into the airworthiness limitations section of the maintenance manual or instructions for continued airworthiness the low cycle fatigue (LCF) limit diagrams shown in Figures 2 through 7 (pages 9 through 14) of GE T700 Turboshaft Engine Service Bulletin T700 S/B 72-0041, Revision 1, dated March 12, 2010, for helicopters with the GE T700-GE-401C engine, or Figures 2 through 4 (pages 10 through 12) of GE T700 Turboshaft Engine Service Bulletin T700 S/B 72-0038, dated October 1, 2008, for helicopters with the GE T700-GE-701C engine. The diagonal line on each diagram represents the new cycle life limit (a combination of full low cycle fatigue events (LCF1) and partial low cycle fatigue events (LCF2) as those terms are defined in the Accomplishment Instructions, paragraphs 3.A.(1) and 3.A.(2) of each service bulletin) for each gas generator turbine (GGT) rotor part. A combination of LCF1 and LCF2, which results in a number below the diagonal line of the applicable diagram for each engine, indicates that the part has not reached its fatigue life limit. (2) Before further flight: (i) Obtain the actual LCF1 and LCF2 count from the engine “history recorder” (HR); (ii) Calculate the LCF1 and LCF2 fatigue retirement life for each GGT rotor part as follows: (A) Determine the actual LCF ratio by dividing the total actual LCF2 cycle count obtained from the HR by the total actual LCF1 cycle count obtained from the HR. Add to the actual counts from the HR any actual additional fatigue cycle incurred during any period in which the HR was inoperative. (B) Determine the LCF1 retirement life by dividing the maximum number of LCF2 events obtained from the applicable diagram for each engine by the sum of the actual LCF ratio obtained by following paragraph (e)(2)(ii)(A) of this AD plus the quotient of the maximum number of LCF2 events from the applicable diagram for each engine divided by the maximum number of LCF1 events from the applicable diagram for each engine. (C) Determine the LCF2 retirement life by multiplying the actual LCF ratio obtained by following paragraph (e)(2)(ii)(A) of this AD times the LCF1 retirement life determined by following paragraph (e)(2)(ii)(B) of this AD. (iii) Replace each GGT rotor part that has reached the new fatigue cycle life limit with an airworthy rotor part. (3) For helicopters with the GE T700-GE-401C engine, if you cannot determine the number of low cycle fatigue events manually from the HR or by combining both manual and HR counts, then the life limit for the GGT rotor part is the hours TIS for the part as shown in Table 1 of GE T700 Turboshaft Engine Service Bulletin T700 S/B 72-0041, dated August 21, 2009. (4) Before further flight, begin or continue to count the full and partial low fatigue cycle events and record on the component card or equivalent record that count at the end of each day for which the HR is inoperative.

This AD defines the unsafe condition as a critical engine part remaining in service beyond its fatigue life because the current life limit is based on hours time-in-service (TIS) instead of fatigue cycles. This condition could result in fatigue failure of an engine rotor part, engine failure, and subsequent loss of control of the helicopter.