The Federal Aviation Administration (FAA) has issued the airworthiness criteria that Archer Aviation will need to meet for its M001 air taxi to be certified for use.
The Archer Model M001 powered-lift has a maximum gross takeoff weight of 6,500 lbs. and is capable of carrying a pilot and four passengers and uses 12 electric engines powered by onboard batteries for propulsion.
According to the regulator:
“Because the FAA has not yet established powered-lift airworthiness standards in 14 CFR, the FAA type certificates powered-lift as special class aircraft. Under the procedures in 14 CFR 21.17(b), the airworthiness requirements for special class aircraft are the portions of the requirements in 14 CFR parts 23, 25, 27, 29, 31, 33, and 35 found by the FAA to be appropriate and applicable to the specific type design and any other airworthiness criteria found by the FAA to provide an equivalent level of safety to the existing standards. This notice announces the applicable regulations and other airworthiness criteria developed, under § 21.17(b), for type certification of the Archer Model M001 powered-lift.
“The Archer Model M001 powered-lift has characteristics of both a rotorcraft and an airplane. It is designed to function as a helicopter for takeoff and landing and as an airplane cruising at higher speeds than a helicopter during the en-route portion of flight operations. Accordingly, the Archer Model M001 powered-lift proposed airworthiness criteria contain standards from parts 23, 33, and 35 as well as other proposed airworthiness criteria specific for a powered-lift with electric engines.
Some key points:
- In the event of a loss of engine power, airplanes and rotorcraft inherently have the ability to glide or autorotate, respectively. Although the aircraft may sustain damage, the ability to glide or autorotate allows the aircraft to reasonably protect the occupants. However, not all powered-lift have these capabilities. To address this, the FAA proposes a definition for “continued safe flight and landing,” unique for the Archer Model M001 powered-lift, that modifies language from the existing definition in § 23.2000; the FAA also proposes a new definition for “controlled emergency landing” to capture the level of performance the Archer Model M001 powered-lift must meet, equivalent to a glide or autorotation.
- While the FAA has experience certifying indirect flight-control systems such as fly-by-wire systems, Archer’s design uses a unique, integrated flight- and propulsion-control system that requires new airworthiness criteria. In addition, the FAA proposes a new AM1.2105, which incorporates all of § 23.2105 and adds criteria in new paragraphs (f) and (g). Proposed AM1.2105(f) and (g) would ensure the pilot is capable of executing a controlled emergency landing in the event of a loss of power or thrust, whether by the aircraft’s ability to glide or autorotate, or through an equivalent means that reasonably protects occupants.
- Archer’s new and novel design uses a distributed propulsion system to provide forward thrust, lift, and control. While some of these design features can be addressed by existing airworthiness standards in parts 23 and 27, other features require the development of new airworthiness criteria. The proposed airworthiness criteria address the following unique and novel powerplant installation features: multi-engine isolation in a distributed propulsion system, simplified control of distributed propulsion, integration of a propulsion system into aircraft flight controls, and energy-system crashworthiness associated with vertical takeoff and landing capability.
- Traditional existing airworthiness standards do not adequately represent the aerodynamic loads, used for structural design, of a powered-lift. Therefore, the FAA finds that additional airworthiness criteria are necessary for structural design. The FAA created AM1.2200 and AM1.2225 by revising §§ 23.2200 and 23.2225 to address the powered-lift structural design envelope. The FAA created AM1.2240 by revising § 23.2240 to remove level 4 airplane requirements, because the Archer Model M001 powered-lift is not a level 4 airplane. In addition, the FAA proposes a new AM1.2320, which incorporates all of § 23.2320 except for § 23.2320(b). Proposed AM1.2320(b) contains a new bird strike requirement specific for the applicant’s design. The FAA recognizes the threat from bird strikes in the environment in which these aircraft are intended to operate is more severe than the environment that rotorcraft or part 23 fixed-wing aircraft operate in today. The Archer Model M001 powered-lift has inherent design features and expected operations that potentially expose the aircraft to a higher probability of impact with birds.
- The FAA proposes a more comprehensive bird strike requirement for the Archer Model M001 powered-lift. As cited in the Aviation Rulemaking Advisory Committee (ARAC) Rotorcraft Bird Strike Working Group (RBSWG) report, an analysis of bird strike threats against rotorcraft showed the median bird size for birds involved in damaging strikes was 1.125 kg (2.5 lb). Based on that research, the FAA proposes a bird impact size of 1.0 kg (2.2-lb), consistent with rotorcraft industry testing. The applicant must perform an evaluation at the aircraft level to determine what parts of the aircraft are exposed to potential bird strikes. The FAA also proposes a requirement for bird deterrence devices to reduce the potential for bird strikes.
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