Challenger 300, 350 and 3500 operators will need to plan ahead in order to secure the necessary parts kits to address AD 2025-02-01.

The MCAI states that during several in-service events, following a STAB TRIM FAULT advisory message and an autopilot disconnect, both pilot and co-pilot commands to trim the horizontal stabilizer nose-up resulted in a nose-down movement of the horizontal stabilizer.

In some events, the horizontal stabilizer reached the full travel nose-down position before the crew recognized the nature of the problem and quickly recovered control of the airplane for safe landing.

An issue with the trim switch wiring installation was identified as the main cause of the in-service unintended horizontal stabilizer motion events. The current wiring of the system is such that if trim is enabled via the copilot-side trim switch and the pilot-side trim switch malfunctions, it is possible for trim to move uncommanded or opposite to the intended direction.

The resulting AD 2025-02-01 requires installing pitch/roll trim switch relays and is covered by a dedicated schedule. Dedicated schedules are used to reserve and manage inventory due to limited availability of rotable stock, parts, and/or kits. Parts are limited; therefore, advanced part scheduling is highly recommended prior to a maintenance visit.

The bottom line is operators need to pre-plan in order to secure Kit 350K27-012, which is required for this AD.

Rest assured that West Star Aviation has the experience and resources to help. Having completed more than 20 of these ADs across our four full-service locations, we can guide you through the process of securing the necessary parts kit and scheduling the installation.