Stall warning and protection systems exist to keep crews informed and, in some cases, to physically intervene before the airplane approaches its aerodynamic limits. But what happens when the system itself triggers incorrectly, firing the stick shaker and stick pusher at the wrong moment, during approach, when the crew's hands are already full? A Pilatus PC-12/47E test flight led to the discovery of the issue. After performing specific maneuvers near zero-g loads, the stall warning protection system (SWPS) mistakenly triggered during landing with 40-degree flaps at a higher-than-expected airspeed. This activation fired the aural warning, stick shaker, and stick pusher simultaneously. Because this flawed software version is currently active across the delivered fleet, it creates a hazardous condition that can drastically increase pilot workload, slash safety margins, and lead to a critical loss of aircraft control.

‍Field Notes: The fix is a Honeywell Primus APEX software update and a temporary POH revision (TR No. 32). Pilots with at least a private certificate can make the POH update and logbook entry themselves.

Why It Matters: An unexpected stick‑pusher on approach is one of the most startling, destabilizing events a crew can face. The FAA has issued several ADs for inappropriate SWPS activation, underscoring how false or premature stall‑protection cues have become a recurring safety focus.

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