FAA Special Conditions are tailored regulatory requirements issued for novel or unusual aircraft designs where existing regulations do not provide adequate safety standards. For electric vertical take-off and landing (eVTOL) and hybrid-electric aircraft, the FAA has issued Special Conditions covering battery energy storage systems, thermal runaway prevention and high-power electric propulsion systems.
This approach has since evolved. Rather than certifying eVTOL designs as Part 23 airplanes carrying bolt-on Special Conditions, the FAA now type-certificates them as powered-lift aircraft under the “special class” process in 14 CFR 21.17(b), drawing airworthiness criteria from Part 25 and other existing parts as appropriate to each design. Joby Aviation’s JAS4-1 and Archer Aviation’s Midnight have both received final airworthiness criteria under this route, and the FAA published Advisory Circular AC 21.17-4 in 2025 to give applicants consolidated guidance on the process. Battery-specific requirements — energy and power ratings, thermal runaway containment, crew warning, and installation safety — are addressed within each aircraft’s individual certification basis rather than through a single standing Special Condition.
References: Joby JAS4-1 Airworthiness Criteria (Federal Register), FAA AC 21.17-4
See also: 14 CFR Part 25, CS-25