Last week FAA issued a Notice of Proposed Rulemaking [NPRM] that would amend FAR Part 23 certification standards for light jet aircraft to standardize and codify the myriad one-off special conditions, exemptions and equivalent levels of safety [ELOS] currently needed to issue type certificates for this burgeoning class of aircraft. FAA also said that the current system of one-off exemptions leads to inconsistencies and "misinterpretations," implying that various aircraft certification offices don't have sufficient regulatory guidance to achieve uniform certification standards.

One-off type certifications of Part 23 turbofan aircraft were practical when manufacturers were attempting to certify only a few models under the regulation. However, the current system is creating an onerous workload for FAA, now that several manufacturers are seeking or intend to seek FAR Part 23 approval for their turbofan aircraft. As a result, FAA believes it's time to streamline the certification rules for those models to expedite the approval process.

The proposed rule essentially requires turbofan-powered aircraft to meet the design, performance and certification standards of piston- and turboprop-powered aircraft in the next higher weight class. Thus very light jets (VLJs) with maximum takeoff weights (MTOW) under 6,000 lb would have to meet the performance requirements for piston twins weighing 6,000 lb to 12,499 lb. Light jets between 6,000 lb and 12,499 lb w0uld have to meet most of the requirements of FAR Part 23 Commuter Category aircraft with MTOWs between 12,500 lb and 19,000 lb, currently the upper limit for Part 23 aircraft. The changes will bring multiengine FAR Part 23 turbofan aircraft into closer alignment with the heavier FAR Part 25 jets.

The proposed changes to FAR Part 23 will specify new structural integrity and stability standards in light of the high-altitude, high-Mach performance capabilities of many new light jets, recognize the capabilities of integrated, large-format, flat-panel display avionics systems, codify special safety considerations for single-engine turbofan aircraft with power plants embedded in their fuselages, and formalize the use of certain FAR Part 25 transport category certification requirements for FAR Part 23 turbofan aircraft. It also will require than all FADEC-controlled engines used in FAR Part 23 aircraft meet the electrical power autonomy requirements of the Part 33 engine certification rules.

For more information, see Federal Register Vol 74 Num 157, pages 41,521 through 41,556.

PiperJet photo credit: Piper Aircraft