Action
Final rule.
Summary
The FAA is superseding Airworthiness Directive (AD) 2021-14- 20, which applied to all The Boeing Company Model 737 airplanes. AD 2021-14-20 required repetitive functional tests of the cabin altitude pressure switches, and on-condition actions, including replacement, if necessary. AD 2021-14-20 also required reporting test results. This AD was prompted by data collected from the reports required by AD 2021-14- 20, which revealed that the switches were subject to false test failures due to lack of clear instructions for setup of the test adapters during the functional tests. This AD retains the repetitive functional tests and on-condition actions, and specifies certain adapter requirements for the functional tests. The FAA is issuing this AD to address the unsafe condition on these products.