90-06-04 BOEING: Amendment 39-6522. Docket No. 90-NM-18-AD. \n\n\tApplicability: All Model 737 series airplanes, equipped with Walter Kidde APU fire detection systems that either have not yet had an initial "C" check performed or that have had an APU replaced since performing the last "C" check, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent an undetected APU fire, accomplish the following: \n\n\tA.\tWithin 3 days after the effective date of this AD, placard the APU as inoperative until the inspection required by paragraph B., below, has been accomplished. \n\n\tB.\tWithin 5 days after installation of the placard required by paragraph A., above, inspect to determine whether a Walter Kidde APU fire detector is installed in the APU compartment. This inspection can be performed by viewing through the APU cooling air exhaust outlet (ref: Model 737 Maintenance Manual 49-11-00). The Walter Kidde element is protected by a perforated shield surrounding the length of the element. If the perforated shield is not seen, open the lower APU shroud and verify that the fire detector element installed is Boeing Part Number 10-61096-316/Walter Kidde part number 894481. \n\n\tNOTE: Boeing Model 737-300 and 737-400 series airplanes inspected in accordance with Boeing Telex M-7272-90-0735, dated January 31, 1990, comply with the inspection requirements of this AD. \n\n\tC.\tIf configuration discrepancies are discovered while accomplishing the inspection required by paragraph B., above, within 5 days, remove and replace the detector with the appropriate Walter Kidde detector that has been approved for installation on the airplane. Upon completion of the inspection required by paragraph B. and this modification, if required, the placard required by paragraph A., above, may be removed. \n\n\tD.\tWithin 10 days after the inspection required by paragraph B., above, if configuration discrepancies are discovered, submit areport of findings to the Manager, Seattle Manufacturing Inspection District Office, ANM-108S, FAA, Transport Airplane Directorate, 7300 Perimeter Road South, Seattle, Washington 98108. The report must include the airplane serial number. \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, FAA, Northwest Mountain Region. \n\n\tNOTE: The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), who will either concur or comment and then send it to the Manager, Seattle Aircraft Certification Office. \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 information from the manufacturer may obtain copies upon request to Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or Seattle Aircraft Certification Office, 9010 East Marginal Way South, Seattle, Washington.\n \n\tThis amendment (39-6522, AD 90-06-04) becomes effective on March 19, 1990.