FAA Flags Loss-of-Control Risk From Flap Malfunctions In Bombardier Aircraft

The Federal Aviation Administration (FAA) is proposing a new airworthiness directive (AD) affecting a range of Bombardier CL-600 series aircraft after reports and analysis linked uncommanded flap movement to a potential loss-of-control risk during critical phases of flight.

The proposed rule, published in the Federal Register on Tuesday, would require operators of affected Challenger variants—including the 600, 601, 604, and related models—to incorporate updated procedures into the aircraft flight manual (AFM) to address abnormal flap behavior in flight.

According to the FAA, the unsafe condition stems from events in which flap systems transitioned without pilot command or failed to arrest unintended movement, generating “Flaps Fail” cautions and creating a scenario that could lead to significant pitch and speed changes. In worst-case conditions, the behavior could result in loss of control of the aircraft, according to the agency.

The proposed AD traces its root concern to an in-flight event involving a Challenger 604 where flaps extended unexpectedly during climb. In that case, investigators identified a malfunction in flap system components that prevented proper arrest of movement. While the aircraft was able to return safely, the FAA determined that similar latent failures could exist across the fleet.

The directive would require operators to revise the AFM to ensure flight crews are trained and briefed on how to respond to uncommanded flap deployment or “runaway” scenarios. In most cases, this centers on maintaining aircraft control through pitch and power management, retracting flaps in accordance with emergency procedures, and avoiding abrupt configuration changes that could exacerbate instability.

The FAA also ties the proposed action to previous Transport Canada findings, which identified flap control system interfaces and onboard monitoring systems as potential contributors to false fault indications or unintended system responses.

If adopted, the rule would formalize training and procedural requirements across all U.S.-registered affected aircraft, ensuring crews are prepared to recognize and respond to uncommanded flap movement events promptly and consistently.

The comment period remains open until July 10, 2026, as the FAA evaluates operator feedback and potential alternative compliance pathways before finalizing the directive.