91-06-12 BOEING: Amendment 39-6938. Docket No. 90-NM-194-AD. \n\n\tApplicability: Model 757 series airplanes listed in Boeing Alert Service Bulletin 757- 52A0049, dated July 5, 1990, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo ensure left and right passenger door Number 4 opening when required for emergency use, accomplish the following: \n\n\tA.\tPrior to the accumulation of 2,000 flight cycles, or within the next 100 flight cycles after the effective date of this AD, whichever occurs later, inspect the left and right Number 4 passenger door upper and lower hinge arm leaf springs for cracks and fractures, in accordance with Boeing Alert Service Bulletin 757-52A0049, dated July 5, 1990. \n\n\tB.\tIf cracked or fractured leaf springs are found as a result of the inspection required by paragraph A. of this AD, prior to further flight, accomplish either paragraph B.1. or B.2., below: \n\n\t\t1.\tReplace cracked or fracturedleaf springs in accordance with Section III. of the service bulletin; or \n\n\t\t2.\tReplace the cracked or fractured leaf springs with new steel leaf springs in accordance with an FAA-approved method, and reinspect those springs prior to the accumulation of an additional 2,000 flight cycles and thereafter at intervals not to exceed 500 flight cycles until the terminating action, required by paragraph D. of this AD, is accomplished. \n\n\tC.\tRepeat the inspection required by paragraph A. of this AD at the following intervals. \n\n\t\t1.\tFor airplanes with less than 5,000 flight cycles at the time of the last inspection: accomplish the next inspection within the next 500 flight cycles. \n\n\t\t2.\tFor airplanes with 5,000 or more flight cycles at the time of the last inspection: accomplish the next inspection within the next 150 flight cycles. \n\n\tD.\tWithin the next 18 months after the effective date of this AD, replace the upper and lower hinge arm steel leaf springs with titanium leaf springs for the left and right Number 4 passenger door, in accordance with Section III., of Boeing Alert Service Bulletin 757-52A0049, dated July 5, 1990. Such replacement constitutes terminating action for the repetitive inspections required by this AD. \n\n\tE.\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\tF.\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 (39-6938, AD 91-06-12) becomes effective on April 18, 1991.