89-14-09: Auxiliary Power Electrical Control Unit

89-14-09 EMPRESA BRASILEIRA DE AERONAUTICA, S.A. (EMBRAER): Amendment 39-6258. Applicability: EMBRAER Model EMB-120 and EMB-120RT series airplanes, equipped with Garrett auxiliary power units (APU) models GTCP36-150(A) or GTCP36-150(AA), certificated in any category. Compliance: Required within 25 hours time in service, or prior to the next APU start, whichever occurs later, after the effective date of this AD, unless previously accomplished. To prevent an uncontrolled APU overspeed, accomplish the following: A. Inspect the APU electrical control unit (ECU), Part No. 2118052-1/2118596-2, for water contamination, as follows: 1. Gain access to and remove the APU ECU from the airplane. 2. Install plastic covers on J1 and J2 connectors on the ECU. 3. In a suitable workshop area, cut the two tamper proof seals along the box/lid split line. 4. Remove the 14 screws that secure the ECU lid to the box. 5. Remove the ECU lid. 6. Use special attention to ensure that no foreign objects or material are allowed to enter the ECU, and that nothing inside the ECU is either touched or removed. 7. Using a bright light, inspect inside the ECU for moisture or water. 8. Turn the ECU slowly upside down and determine if water can be drained from the ECU. 9. If water is seen inside the ECU or if water can be drained out of the ECU, remove the ECU from service and replace it with a serviceable unit. 10. If the inside of the ECU is dry, carefully realign the ECU lid and packing with ECU box, and reinstall the 14 screws using an alternating fashion around the circumference until there is metal to metal contact between the ECU lid and the ECU box around the entire circumference. 11. Have a Quality Assurance person re-seal the ECU using new tamper- proof seals. 12. Reinstall the ECU. B. Prior to pressurized cleaning, install a suitable cover over the vent screen, to prevent exposing the APU ECU area to water contamination. Remove this temporary cover following completion of the pressurized cleaning procedure. C. An 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, Atlanta Aircraft Certification Office, FAA, Central Region. NOTE: 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, Atlanta Aircraft Certification Office. D. Special 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. All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to EMBRAER, 276 S.W. 34th Street, Fort Lauderdale, Florida 33315. These documents may be examined at the FAA Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or the FAA, Central Region, Atlanta Aircraft Certification Office, 1669 Phoenix Parkway, Suite 210C, Atlanta, Georgia. This amendment (39-6258, AD 89-14-09) becomes effective on July 18, 1989.