AD/B737/99 - Main Rudder Power Control Unit (PCU)
1AD/B737/99 - Main Rudder Power Control Unit (PCU)
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COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
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Boeing 737 Series Aeroplanes
AD/B737/99 Main Rudder Power Control Unit (PCU) 1/97
Applicability: All Boeing 737 models.
Requirement: 1. Perform a test on the main rudder power control unit (PCU) in accordance with Boeing Alert Service Bulletin (ASB) 737-27A-1202 dated 01 November 1996 to verify proper operation.
- If, as a result of Requirement 1, the test gives unusual results as described in the referenced ASB, replace the main rudder PCU and perform the test of Requirement 1.
Note: FAA AD T96-23-51 refers.
Compliance: 1. For Requirement 1, prior to 14 November 1996 and there after at intervals not to exceed 250 hours time in service.
- For Requirement 2, before further flight.
Background: Recent tests on the main rudder PCU conducted by Boeing demonstrated a potential failure scenario that was previously unknown. These tests revealed that rudder pedal can cause deformation in the linkage leading to the primary and secondary slides of the servo valve of the main rudder PCU if the secondary slide of the PCU jams in certain positions. This situation could result in rudder motion in the opposite direction of the rudder command.