AD 78-08-04

78-08-04 BOEING: Amendment 39-3187. Applies to Model 747 series airplanes certificated in all categories and equipped with pressurization system outflow valve assemblies, Boeing P/N 60B00025-3, -11, -12, and -17 (Hamilton Standard P/N 719201-2, -3, -4, -5, -6, -7, - 8, and -9). Compliance required as indicated. To prevent rapid loss of pressurization in flight accomplish the following:

A. Within 350 hours time in service after the effective date of this airworthiness directive, unless already accomplished, and thereafter at intervals not to exceed 900 hours time in service until modified in accordance with part B of this airworthiness directive, inspect forward and aft gates of each outflow valve assembly in accordance with the instructions contained in Boeing Service Bulletin No. 747-21-2139, Revision 1 dated April 7, 1978, or later FAA approved revisions, or in a manner approved by the Chief, Engineering and Manufacturing Branch, FAA Northwest Region. Gates found with delamination or cracks in the hinge-to-gate bonds must be removed and replaced with a part free of delamination or cracks. Removed gates may be forwarded to Hamilton Standard for further evaluation or modified in accordance with part B of this airworthiness directive, as applicable, prior to being returned to service. B. Within 4000 hours time in service after the effective date of this airworthiness directive, modify the outflow valve assemblies in accordance with the instructions contained in Hamilton Standard Service Bulletin H.S. Code 747 AC-114, Revision 1 dated March 15, 1978, or later FAA approved revision, or by an equivalent method approved by the Chief, Engineering and Manufacturing Branch, FAA Northwest Region. C. Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Engineering and Manufacturing Branch, FAA Northwest Region, may adjust the inspection compliance time and/or modification compliance time specified in this airworthiness directive to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for that operator. The manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1).

AD 77-25-06, Amendment 39-3098 (42 FR 63637) is hereby superseded. This amendment becomes effective May 10, 1978.