The FAA has proposed an airworthiness directive for legacy Bombardier Challengers. The notice covers Models CL-600-1A11, CL-600-2A12 and CL-600-2B16. Those designations cover the Challenger 600, 601, 601-3A, 601-3R and 604.
The proposed rule was prompted by an in-flight event on a Model CL-600-2B16 airplane. The flaps extended from 0 to 45 degrees without crew command. A FLAPS FAIL caution message accompanied the movement. The flap-control system should have stopped the extension at 3 degrees. A failed retract relay prevented that arrest. The aircraft returned safely to its departure airport.
The FAA stated that uncommanded, unarrested flap movement could result in loss of control of the airplane. The proposed action is a revision of the existing aircraft flight manual. The revision would give the flightcrew procedures to follow during an uncommanded, unarrested flap-movement event. The change is procedural. It does not require hardware modification.
The notice was published in the Federal Register on 26 May 2026. The docket reference is FAA-2026-4642. The Federal Register document number is 2026-10382. Comments are due by 10 July 2026. The FAA's estimated cost of compliance is $85 per aircraft, as reported by AVweb.
The proposed rule is not yet binding. A final rule, with effective date and required compliance actions, follows once the FAA reviews comments. Transport Canada issued an airworthiness directive on the same condition in February 2023. Owners and flight departments of in-scope Challengers should track the docket. Operators wishing to influence the final text or the compliance timeline should respond within the comment window.
Source: FAA NPRM 2026-10382, Federal Register, 26 May 2026; GlobalAir, 26 May 2026; AVweb, 27 May 2026.