EASA AD US-2022-10-02: Engine Controls - Reduction Gearbox Assembly - Vibration Tests

What to do

Affected operators must perform initial and repetitive special vibration tests on the reduction gearbox assembly or engine as specified in the AD. If vibration levels exceed the prescribed limits, the reduction gearbox assembly or the entire engine must be replaced with a serviceable unit before further flight. The AD becomes effective on June 28, 2022, and compliance must be achieved by that date or within the specified flight hours detailed in the directive.

Summary

The document titled "Engine Controls - Reduction Gearbox Assembly - Vibration Tests" is a Federal Aviation Administration (FAA) Airworthiness Directive (AD 2022-10-02) that applies to certain Honeywell International, Inc. T53 model turboshaft engines, including T5311A, T5311B, T5313B, T5317A, T5317B, T5317A-1, T5317BCV, and various former military T53 models. This AD mandates initial and repetitive special vibration tests of the engine's reduction gearbox assembly and requires replacement of the gearbox or engine if vibration limits are exceeded. The directive addresses unsafe conditions caused by tachometer drive spur gear failures that could lead to engine overspeed and loss of power turbine speed indication.

What changed

This AD supersedes AD 2002-03-01 by expanding the applicability to include Honeywell T5317A-1 and T5317BCV engine models, which were previously not covered. It revises the required actions by removing certain definitions and clarifying that special vibration tests must be performed before further flight on newly installed engines or reduction gearbox assemblies. The AD continues to require initial and repetitive vibration testing and replacement actions based on test results.

Why it matters

This AD is critical for aviation professionals because it ensures the continued airworthiness and safety of affected Honeywell T53 turboshaft engines by preventing failures of the tachometer drive spur gear. Operators, maintenance organizations, and compliance teams must adhere to these requirements to avoid potential engine overspeed events, loss of critical engine instrumentation, and subsequent hard landings. Compliance helps maintain operational safety and regulatory conformity.