90-20-06 BOEING: Amendment 39-6748. Docket No. 90-NM-89-AD. \n\n\tApplicability: Model 757 series airplanes, equipped with Arkwin Industries Incorporated part number (P/N) 1211233-005 ram air turbine deployment actuators with serial numbers 213 through 285, certificated in any category. \n\n\tCompliance: Required within the next 3,000 hours time-in-service after the effective date of this AD, unless previously accomplished. \n\n\tTo prevent loss of hydraulic power due to failure of the ram air turbine to deploy in the event of dual engine failure, accomplish the following: \n\n\tA.\tReplace the ram air turbine deployment actuator in accordance with Arkwin Industries Incorporated Service Bulletin 1211233-29-02, dated July 25, 1989. \n\n\tB.\tAn alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\tNOTE: The request should be submitted directly to the Manager, Seattle ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Seattle ACO. \n\n\tC.\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD. \n\n\tAll persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington. \n\n\tThis amendment (39-6748, AD 90-20-06) becomes effective on October 29, 1990.