EASA AD US-2022-21-05
Auto Flight - Auto-Throttle Computer - Built-in Test Equipment Tests
Summary
Airworthiness Directive 2022-21-05 is a final rule issued by the Federal Aviation Administration affecting certain Boeing 737-300, -400, and -500 series airplanes. It addresses a safety issue where a spoiler sensor failure may go undetected by the autothrottle computer, potentially leading to asymmetric thrust and uncommanded roll. The directive mandates repetitive built-in test equipment (BITE) tests of the autothrottle computer to detect and correct spoiler sensor failures.
What Changed
This new airworthiness directive introduces a requirement for repetitive BITE tests of the autothrottle computer on specified Boeing 737 models. It mandates corrective actions if the tests detect spoiler sensor failures. The directive also shortens the initial compliance time for the BITE test to within 250 flight hours or 2 months after the effective date, whichever occurs first.
Why It Matters
This directive is critical for aviation professionals as it addresses a latent failure mode that could compromise flight safety by causing asymmetric thrust and potential loss of airplane control. Operators and maintenance teams must ensure regular testing to detect spoiler sensor failures early, thereby maintaining safe autothrottle operation and preventing uncommanded roll events. Compliance reduces risk and enhances the reliability of flight control systems.
What To Do
Operators of affected Boeing 737-300, -400, and -500 series airplanes must perform the initial autothrottle computer BITE test within 250 flight hours or 2 months after November 10, 2022, whichever is sooner. If the test fails, corrective actions must be taken and the test repeated until it passes. These tests must then be performed repetitively as specified in Boeing Alert Requirements Bulletin 737-22A1411 RB.
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