Updated Part 23 Rules To Revive Four-Seat GA Market

By John Croft
Source: Aviation Week & Space Technology

Terrafugia chief executive Carl Dietrich, a member of the ARC, says the new certification rules will be much more agile when it comes to embracing advanced technologies, a requirement for the TF-X.

“By 2020, when all aircraft have [Automatic Dependent Surveillance-Broadcast] and the certification pathways are in place, it will become a question of what we can physically do,” says Dietrich. “The TF-X is entirely computer-controlled to provide flight-envelope protection and prevent loss of control or controlled flight into terrain, the two biggest causes of general aviation accidents. Fly-by-wire technology will also simplify pilot training.” He adds, “They will be able to update ASTM standards much more quickly than federal regulations. It is working very well with light sport aircraft.”

The final form of the revamped Part 23 rules—which include certification requirements for structure, design and construction, engine and avionics, and can cover propeller and jet aircraft in some cases weighing up to 19,000 lb.—are likely to be different from the LSA model in that the FAA will remain fully involved in the process. “We're not changing what the FAA does,” says Bowles. “We're changing what the applicant does to meet the threshold.”

A new bill moving through the U.S. Congress aims to force the FAA to implement the updated regulations before 2016. According to Congress, the average small aircraft is now 40 years old, and over the past decade the sector has lost about 10,000 active private pilots annually. Supporters of the bill say the decline can be mitigated or reversed by the new Part 23 rules.

While the FAA says the legacy rules have produced safe airplanes “for decades,” technological advances have changed the original assumptions of the Part 23 divisions, which were based on weight and engine type. “The new small-turbine engines, composite airframes and lightweight digital electronics offer Part 23 airplanes the operational capability and performance of traditionally larger Part 25 airplanes,” the FAA says in a 2009 study on Part 23 certification processes, work the Part 23 reorganization ARC used as its starting point. “Part 23 standards have evolved beyond their original intent to address the increasing performance and complexity,” the FAA says. “Unfortunately, the slow, simple Part 23 airplanes have suffered as the standards have shifted toward more complex airplanes.”

GAMA's Bowles says ARC's recommendations represent an evolution of the rules rather than a revolution. “The things you do to certify [an aircraft or component] will continue to evolve, but this change lets us do that much more quickly and flexibly,” he says. Under today's rules, for example, when “someone comes along with a really good idea,” he says, they have to work with the FAA for 2-3 years to develop special conditions to allow the technology to be used in a one-off application.

“For the new Part 23, someone would say, 'I have a new idea for a new way to deal with an issue,' and industry would sit down and develop a standard in 6-12 months,” says Bowles. The FAA would review and, ideally, accept the new standards, which would then be available for anyone in the U.S. to use, as well as regulators in countries with an aviation bilateral agreement with the FAA.

Bowles says “any of the standards bodies” could develop the consensus standards, including ASTM, SAE and RTCA, but that efforts will not be duplicated. ASTM has formed a new international committee, F44, to specifically target general aviation improvements.

A different ASTM group, F39, is finishing standards for angle-of-attack (AOA) indicators as part of an FAA and industry effort that is a prelude to the Part 23 rule change. An AOA indicator gives a pilot a direct measurement of an aircraft's margin with respect to a stall, rather than the indirect readings of airspeed and attitude generally used today.

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