EASA releases Special Condition for certification of small VTOL aircraft

Avatar for Oliver JohnsonBy Oliver Johnson | July 2, 2019

Estimated reading time 5 minutes, 12 seconds.

The European Union Aviation Safety Agency (EASA) has released a Special Condition to pave the way for type certification of small VTOL aircraft.

The CityAirbus VTOL aircraft, which is currently in development at Airbus. EASA said it hoped its newly-announced Special Condition would provide clarity for future manufacturers of VTOL aircraft. Airbus Photo

The Special Condition applies to people-carrying heavier-than-air VTOL aircraft in the small category (up to nine passengers and a maximum takeoff weight of 3,175 kilograms/7,000 pounds), with lift/thrust units used to generate powered lift and control.

In a press release announcing the release of the Special Condition, EASA called it “the first building block to enable the safe operation of hybrid and electrical VTOL aircraft.”

“We are actively engaging with the industry to develop the right technical requirements to take benefit of the new technologies bringing safety and environmental benefits to the community,” said Patrick Ky, executive director of EASA. “The establishment of a common set of conditions for the certification of these new concepts of vehicles will enable a fair competition on the European market as well as clarity for future manufacturers and their investors.”

The VTOL Special Condition is largely based on EASA’s Certification Standard (CS) for Normal, Utility, Aerobatic and Commuter Category Aeroplanes (CS-23 Amendment 5), along with elements of its rules for Small Rotorcraft certification (CS-27) “where deemed appropriate.”

The Special Condition introduces two certification categories — Basic and Enhanced — tied to the aircraft’s intended operations.

Aircraft that will be used for operations over congested areas (defined as any area substantially used for residential, commercial or recreational purposes) or for commercial transport of passengers, must be certified in the Enhanced category. To do so, they will have to meet requirements for continued safe flight and landing, and be able to continue to their original destination, or a suitable alternative vertiport, after a failure.

Aircraft in the Basic category need only demonstrate that they can perform a controlled emergency landing “in a similar manner to a controlled glide or autorotation,” the Special Condition states.

EASA said this step would provide greater scalability in setting safety objectives, with the high safety levels of the Enhanced category protecting both passengers and those below when flying over congested areas.

The Special Condition applies to small rotorcraft with a normal operating speed of up to 250 knots, and includes a requirement for a flight recorder, and in the event of a bird strike, stipulations for the aircraft to be able to continue safe flight (in the Enhanced category) or perform a controlled emergency landing (in the Basic category).

The July 2 publication of the Special Condition incorporates changes following industry feedback to the proposed version of the regulation, released in October.

Among the key areas of concern in the proposals for industry was a lack of clarity in some of the definitions, including the scope of the Special Condition, with several helicopter OEMs expressing concern that there wasn’t sufficient distinction between it and CS-27 “small rotorcraft.” As a result, EASA defined the Special Condition as applying to aircraft with distributed propulsion, specifically when more than two lift/thrust “units” are used to provide lift during a vertical takeoff or landing.

EASA said it has reviewed more than 150 VTOL project configurations at different stages of maturity.

The regulator is now consulting with its advisory bodies to determine whether it needs to develop new rules or amend existing ones “to address new technologies and operational air transport concepts.” It added that the experience gained through applying this Special Condition will inform that rulemaking process.

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1 Comment

  1. Special condition must include “Flockstrike” not solitary bird strike . Vulnerability to simultaneous multiple (or all) lifting and control rotors loss on encountering flocking birds is a paramount risk case and vastly exceeds anticipated time between failures of vehicle itself. Some configurations can stretch netting across ducts or framework to protect critical rotors ,some cannot . Failsafe configurations are rare in VTOL using rotorspeed control for stability and handling . Crashes will cruel it for all entrants or future players ,retrorocket and chute deploy are partial answers.

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