90-26-12: Main Rotor Blades

90-26-12 SIKORSKY AIRCRAFT: Amendment 39-6841. Docket No. 90-ASW-27. Applicability: All Model S-64E helicopters, certificated in any category. Compliance: Required as indicated, unless already accomplished. To prevent operation with a crack in the main rotor blade spar, which could result in possible loss of the helicopter, accomplish the following: (a) Within the next 3 hours' time in service after the effective date of this AD, visually check the BIM pressure indicators of the main rotor blades for black or red color indication. (b) Before further flight, replace any blade with black or red indication visible in the BIM pressure indicator with an airworthy part of the same part number unless the black or red indication is found to be the result of BIM system malfunction. NOTE: Sikorsky Service Bulletin 64B15-4C pertains to operation, maintenance, and check of the main rotor blade with BIM. (c) The checks required by this AD may be performedby the pilot and must be recorded in accordance with Section FAR 43.9. The record must be maintained as required by Section FAR 91.173, 121.380, or 135.439. (d) Repeat the check required by paragraph (a) of this AD prior to the first flight of each day and thereafter at intervals not to exceed either-- (1) Three hours' time in service from the last check for helicopters engaged in seven or more external lifts per hour; or (2) Five hours' time in service from the last check for helicopters engaged in either less than seven external lifts per hour or operation without external cargo. (e) Prior to the first flight of each day, check the BIM pressure indicator for proper functioning as follows: (1) Press in and hold the manual test lever (grenade-type handle) on the raised area of the handle over the pin-type actuation plunger. NOTE: The indicator glass bulb should not be handled since the heat of the hand may change the internal reference pressure and result in an erroneous indicator reading. (2) Depress the actuation plunger fully to shut off the pressure completely from the blade into the indicator. If necessary, press with the thumbs of both hands to overcome the plunger spring force. NOTE: If pressure is applied to the end of the lever on the flat area, the actuation plunger will not fully depress. (3) Verify proper operation of the indicator by observing that a full-black or full-red (unsafe) indication appears in not less than 10 or more than 30 seconds after depressing the plunger for a temperature of -6.7 degrees C (20 degrees F) or above. At lower temperatures, extend the upper limit to the corresponding time listed below: Temperature Time -7.2 to -17.8 degrees C ( 19 to 0 degrees F) 35 seconds -18.3 to -28.9 degrees C (- 1 to -20 degrees F) 40 seconds -29.4 to -40.0 degrees C (-21 to -40 degrees F) 50 seconds -40.5 to -51.1 degrees C (-41 to -60 degrees F) 60 seconds(4) Release the lever and observe that the black or red indication snaps back immediately, leaving an all-white or all-yellow (safe) indication. (5) If the indicator does not meet the specified requirements, then either identify and correct the malfunction or replace the suspect main rotor blade with an airworthy blade of the same part number prior to further flight. (f) Upon submission of substantiating data by an owner or operator through an FAA Airworthiness Inspector, an alternate method of compliance with the requirements of this AD or adjustments to the compliance (schedule) times specified in this AD may be approved by the Manager, Boston Aircraft Certification Office, Engine and Propeller Directorate, Aircraft Certification Service, Federal Aviation Administration, 12 New England Executive Park, Burlington, Massachusetts 01803. This amendment (39-6841, AD 90-26-12) becomes effective on January 18, 1991.