FAA Proposes Directive for Bombardier CL-600 Flap Control Safety

This article is based on an official notice from the Federal Aviation Administration (FAA).

The Federal Aviation Administration (FAA) has officially proposed a new Airworthiness Directive (AD) affecting all Bombardier, Inc. CL-600 series airplanes. Published in the Federal Register on May 26, 2026, under document number 2026-10382, the Notice of Proposed Rulemaking (NPRM) addresses a critical safety vulnerability involving the aircraft’s flap control system.

According to the FAA notice, the proposed rule was prompted by a concerning in-flight incident where an aircraft experienced an uncommanded and unarrested movement of its flaps. If left unaddressed, aviation regulators warn that this mechanical anomaly could lead to a complete loss of control of the airplane.

At AirPro News, we are closely monitoring this regulatory action. The FAA is currently seeking public comments on the proposal, which mandates specific updates to the Aircraft Flight Manual (AFM) to ensure flight crews are equipped with the proper emergency procedures to handle this specific failure.

Understanding the In-Flight Incident

The FAA’s proposed directive stems from a specific mid-air event involving a Bombardier Model CL-600-2B16 airplane. During the flight, the crew experienced an uncommanded flap extension from 0 to 45 degrees. This sudden movement was accompanied by a “FLAPS FAIL” caution message in the cockpit. Fortunately, the flight crew managed to stabilize the aircraft and return safely to their departure airport.

To understand the severity of this incident, it is helpful to understand the function of aircraft flaps. Flaps are aerodynamic devices located on the trailing edge of the wings. They are primarily deployed during takeoff and landing to increase lift and drag, allowing the aircraft to fly safely at slower speeds. An unexpected deployment to 45 degrees during standard flight operations drastically alters the aerodynamic profile of the aircraft, creating a severe safety hazard.

The Role of the Retract Relay

According to the FAA’s investigation detailed in the NPRM, the Bombardier CL-600’s flap control system is engineered with built-in safeguards. Specifically, the system is designed to automatically halt flap movement at 3 degrees if an anomaly is detected.

However, investigators identified a specific component failure that bypassed this safeguard.

“A failed ‘retract relay’ prevented the system from arresting the uncommanded movement, allowing the flaps to extend fully to 45 degrees,” the FAA research report noted.

Because the retract relay failed, the system could not arrest the uncommanded movement, resulting in the full 45-degree extension. The FAA explicitly identified this as an unsafe condition that requires immediate regulatory intervention to prevent future occurrences from resulting in a loss of aircraft control.

FAA’s Proposed Regulatory Action

To mitigate the safety risks associated with a retract relay failure, the FAA is taking a procedural approach rather than a mechanical one. According to the published docket (FAA-2026-4642), the agency is not currently proposing physical mechanical alterations or parts replacements for the affected aircraft.

Instead, the proposed AD requires owners and operators of the affected Bombardier models to revise their existing Aircraft Flight Manuals (AFM). These revisions will provide flight crews with standardized, specific procedures to execute in the event of an uncommanded, unarrested flap movement. By updating the AFM, the FAA aims to ensure that pilots know exactly how to stabilize the aircraft and execute a safe landing if the hardware fails.

Affected Aircraft Models

The FAA notice specifies that the proposed rule applies to all Bombardier, Inc. CL-600 series airplanes. This includes the following specific variants:

• Model CL-600-1A11 (600)
• Model CL-600-2A12 (601)
• Model CL-600-2B16 (601-3A, 601-3R, and 604 Variants)

Industry and Financial Impact

Because the FAA’s proposed directive relies on a manual update rather than heavy maintenance or physical parts replacement, the financial burden on aircraft operators is expected to be minimal. The primary costs will involve the administrative time required to physically update the flight manuals and the operational time needed to brief flight crews on the new emergency procedures.

Public Comment Period and Next Steps

As with all Notices of Proposed Rulemaking, the FAA has opened a public comment period before the directive becomes a final, enforceable rule. The agency is inviting written data, views, or arguments from aviation industry experts, aircraft operators, and the general public.

Comments must be submitted to Docket No. FAA-2026-4642 by July 10, 2026, which is exactly 45 days from the NPRM’s publication date. For technical clarification, the FAA has designated Aviation Safety Engineer Christopher Spencer at the FAA’s Westbury, NY office as the official contact for this directive.

AirPro News analysis

The FAA’s decision to mandate an Aircraft Flight Manual (AFM) revision rather than an immediate hardware redesign highlights a common regulatory strategy in aviation safety: relying on Crew Resource Management (CRM) and standardized emergency procedures to mitigate single-point hardware failures. While a failed retract relay presents a severe aerodynamic threat, the FAA’s assessment suggests that a properly trained crew with the right procedural checklist can safely manage the anomaly. This approach allows regulators to address the unsafe condition swiftly without grounding the entire CL-600 fleet or imposing crippling supply chain demands for new mechanical relays. However, we expect operators to closely monitor their fleets for any recurring relay issues, which could prompt the FAA to escalate this directive to require physical hardware inspections in the future.

Frequently Asked Questions

What is the deadline to submit public comments on this FAA proposal?
The public comment period closes on July 10, 2026.

Will this proposed rule ground the Bombardier CL-600 fleet?
No. The proposed Airworthiness Directive does not require grounding the aircraft. It mandates an update to the Aircraft Flight Manuals to provide crews with emergency procedures.

What exactly caused the flaps to deploy mid-flight?
According to the FAA, a failed “retract relay” prevented the aircraft’s safety systems from stopping an uncommanded flap movement, allowing the flaps to extend fully to 45 degrees.

Sources: Federal Aviation Administration (Federal Register)