AD 99-08-03 Airworthiness Directives; Boeing Model 737-600, -700, and -800 Series Airplanes

Models named: 737-600, -700, -800 series. Read the applicability below — it usually turns on serial or part numbers too.

All Boeing Model 737-600, -700, and -800 series airplanes; certificated in any category. Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (c) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Required as indicated, unless accomplished previously. To prevent overheating, melting, and subsequent failure of the power feeder terminals, which could result in increased risk of fire and the loss of electrical power from the associated alternating current (AC) power source, accomplish the following: Initial Inspection (a) Within 90 days after the effective date of this AD: Perform a one-time general visual inspection to verify proper installation of the power feeder terminals and associated hardware located in power distribution panels (PDP) P91 and P92, in accordance with the following procedures. Using a flashlight, inspect each of the six power feeder terminals by looking into the access holes located in the plastic cover of the rigid bus assembly. The holes are located on the aft face of PDP's P91 and P92. [Refer to the Boeing 737-600, -700, -800, -900 Airplane Maintenance Manual (AMM), Section 24-21-71/401, Figure 401 (Sheet 1), for the location of PDP P91 and P92.] On PDP P91, the holes are adjacent to terminal blocks TB5001 and TB5002. On PDP P92, the holes are adjacent to terminal blocks TB5005 and TB5006. There are a total of six holes per PDP. [Refer to the Boeing 737-600, - 700, -800, -900 AMM, Section 24-21-71/401, Figure 401 (Sheet 2), for the location of the access holes on the PDP's.] Note that although each PDP has nine power feeder terminals, only the six terminals adjacent to the access holes require inspection. Verify that the power feeder terminal is properly installed and held in place on the busbar by the No. 8 socket head cap screw, and verify that the cap screw is inserted into the hole in the terminal. For the proper power feeder terminal and screw buildup, refer to the Boeing 737- 600, -700, -800, -900 AMM, Chapter 24-21-71/401, Figure 401 (Sheet 4). The subject power feeder terminal is identified as item [7] and the cap screw as item [12]. This visual inspection does not require loosening or removing any fasteners. The inspection may require looking through the access hole at a slight angle to see the terminal clearly. The terminal can be identified by its shiny metal finish; the current transformer behind the terminal block is made of plastic with a flat black finish. If the power feeder terminal and No. 8 socket head cap screw are not assembled as shown in Boeing 737-600, -700, -800, -900 AMM, Section 24-21-71/401, Figure 401 (Sheet 4): Prior to further flight, replace the rigid bus assembly with a new assembly, in accordance with the procedures specified in Boeing 737-600, -700, -800, -900 AMM, Section 24-21-22. [[Page 15922]] Repetitive Torque Check (b) Concurrent with the accomplishment of the requirements of paragraph (a) of this AD: Perform a torque check of the attachment screws of the power feeder terminals in accordance with the procedures specified in Boeing Maintenance Tip 737 MT 24-003, dated May 14, 1998. Repeat the torque check thereafter at intervals not to exceed 1,000 flight hours, in accordance with the maintenance tip. Alternative Methods of Compliance (c) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. Special Flight Permits (d) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. (e) This amendment becomes effective on April 19, 1999. Issued in Renton, Washington, on March 29, 1999. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 99-8133 Filed 4-1-99; 8:45 am] BILLING CODE 4910-13-P