AD/B737/81 Amdt 1 - Thrust Reverser Control System Inspection and Modification

Overview

The Civil Aviation Regulations 1998, specifically Part 39, was enacted to establish safety standards and regulatory requirements for civil aviation in Australia. The Regulations, which were established under the Civil Aviation Act 1988, aim to ensure the safety and efficiency of civil aviation operations. Part 39, which includes the Airworthiness Directives (ADs), was introduced to address specific safety concerns and ensure that aircraft meet the required safety standards. The ADs are issued by the Civil Aviation Safety Authority (CASA) to mandate corrective actions for identified safety issues in specific aircraft models. The objective of AD/B737/81 is to address a safety concern related to the thrust reverser control system in Boeing 737 series aeroplanes, specifically the 737-300, -400, and -500 models, to prevent uncommanded in-flight deployment of the thrust reversers. The AD/B737/81 was issued to mandate inspections and modifications to the thrust reverser control system to ensure the safe operation of the affected aircraft. The directive requires operators to conduct a specific test of the thrust reverser Auto-Restow function, as outlined in the Boeing 737 Maintenance Manual, to verify proper operation. Additionally, the AD mandates the incorporation of thrust reverser sync-locks as per Boeing Service Bulletin 737-78-1053. These measures are intended to mitigate the risk of uncommanded thrust reverser deployment, which was identified as a safety concern following an accident. Compliance with this directive is mandatory, with specific timelines provided for the required inspections and modifications.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105 concerning the Civil Aviation Safety Authority's Schedule of Airworthiness Directives, addresses the Boeing 737 Series Aeroplanes through AD/B737/81 Amendment 1. This regulation applies to all Boeing 737-300, -400, and -500 series aircraft that do not incorporate the intent of Boeing Service Bulletin 737-78-1053. The directive mandates that these aircraft undergo a specific inspection and modification of the thrust reverser control system. The requirement is to carry out an auto-restow test of the thrust reverser as specified in the Boeing 737 Maintenance Manual, and if discrepancies are found, they must be rectified before further flight or the aircraft must be operated in accordance with an approved Minimum Equipment List (MEL). Additionally, the thrust reverser must be modified to include sync-locks as per Boeing Service Bulletin 737-78-1053. Compliance with these directives is mandatory, with inspections required before 31 March 1995 and at intervals not exceeding 4000 flight hours since the last inspection, and modifications must be completed by 31 December 1999. This directive was issued following an accident attributed to an uncommanded in-flight deployment of a thrust reverser, aiming to ensure the safety and airworthiness of the specified aircraft.

Key Provisions

The Civil Aviation Regulations 1998, Part 39 - 105, under the Civil Aviation Safety Authority, includes specific Airworthiness Directives for Boeing 737 Series Aeroplanes. One such directive, AD/B737/81 Amendment 1, pertains to the thrust reverser control system for Boeing 737-300, -400, and -500 series aircraft that do not incorporate the modifications specified in Boeing Service Bulletin 737-78-1053. This directive mandates that operators must carry out a specific test of the thrust reverser's Auto-Restow function as outlined in the Boeing 737 Maintenance Manual, Section 78-31-00. This test is crucial to verify that the thrust reverser operates correctly, and operators must select the appropriate procedure based on the thrust reverser modification standard and engine accessory unit configuration. If any discrepancies are found during this test, operators must rectify the defect before further flight or operate the aircraft in accordance with an approved MEL (Minimum Equipment List). The directive also requires operators to incorporate thrust reverser sync-locks as specified in Boeing Service Bulletin 737-78-1053, Revision 1, Revision 2, or Revision 3. Implementing these modifications is the terminating action for the requirement to test the Auto-Restow function. Once these modifications are completed, subsequent tests of the Auto-Restow function must comply with the requirements specified in the Boeing 737 Maintenance Planning Document (MPD). Compliance with these requirements is essential to ensure the safe operation of these aircraft and is directly linked to the safety measures in place following an accident attributed to an uncommanded in-flight deployment of a thrust reverser. Operators of the affected Boeing 737 series aircraft must adhere to the compliance schedule outlined in the directive. Specifically, operators must complete the thrust reverser inspection and modifications before 31 March 1995 and thereafter at intervals not exceeding 4000 flight hours since the last inspection. Additionally, all modifications must be completed by 31 December 1999. Failure to comply with these requirements could result in the aircraft being deemed unairworthy, which could lead to significant operational disruptions and safety risks. The directive is also supported by Boeing Message M-7272-94-6132 dated 7 December 1994, and FAA AD 94-21-05, which further underscores the importance of these safety measures. In the event of non-compliance with the provisions of this Airworthiness Directive, operators may face severe consequences. These could include fines, suspension or revocation of the aircraft's Certificate of Airworthiness, and potential criminal charges for operators who knowingly allow an unairworthy aircraft to fly. The specific penalties for breaches of these regulations can vary, but they may include substantial monetary fines and imprisonment for individuals found guilty of deliberate non-compliance. Ensuring strict adherence to these requirements is therefore critical to maintaining the safety and airworthiness of Boeing 737-300, -400, and -500 series aircraft.