MOSAIC Moves Beyond Two Seats—and Beyond Aircraft Certification

MOSAIC’s practical implications are becoming clearer as manufacturers outline larger aircraft and the FAA explains expanded inspection privileges. Reporting this week highlights four-seat and twin-engine designs pursuing the new framework, while FAA guidance updated October 15 addresses a less conspicuous but important ownership issue: who may perform an experimental amateur-built aircraft’s annual condition inspection.

The developments reflect two different effects of the FAA’s Modernization of Special Airworthiness Certification final rule, published in July 2025. It broadens the possibilities for light-sport aircraft certification, but also changes aspects of aircraft ownership and maintenance. Neither should be confused with an unrestricted expansion of sport-pilot privileges.

More aircraft possibilities, distinct pilot privileges

An October 12 AvBrief review examines four-seat aircraft that could reach the U.S. market through MOSAIC’s expanded certification framework. The rule allows airplanes with up to four seats, including twins, to pursue special light-sport aircraft certification through compliance with ASTM standards.

The review points to Brazil, which adopted its own comparable framework in 2022, as an indication of what manufacturers might bring to the United States. It identifies the Van’s RV-10, Sling TSi and Montaer MC-04 as aircraft already certificated through ASTM standards. The RV-10 was the first four-seat S-LSA certificated in Brazil.

That experience is relevant to prospective American buyers, but it is not confirmation of U.S. certification or availability. AvBrief presents these aircraft as likely market entrants, not as a completed U.S. delivery lineup. Buyers should distinguish an established overseas program from a manufacturer’s U.S. certification plans and actual delivery commitments.

Another example emerged in AVweb’s October 15 report on Utah-based Wasatch Aero. The developer has outlined a four-seat, twin-turboprop aircraft intended for multiengine training and personal flying under MOSAIC. The report says the expanded framework accommodates multiple engines and turbine propulsion, but Wasatch has not established a timeline for its proposed twin.

For sport pilots, the crucial qualification is straightforward: a light-sport airworthiness category does not automatically confer permission to operate the aircraft. Sport pilots cannot fly twins. As AVweb reports, operating Wasatch’s proposed aircraft would require the appropriate higher-level pilot certificate and multiengine rating.

AvBrief also highlights the appeal of qualifying single-engine airplanes with clean stall speeds below 59 knots for flying without a medical certificate. That should not be treated as a complete eligibility checklist. Prospective owners need to establish both the aircraft’s eligibility and their own applicable pilot privileges, rather than infer either from an S-LSA label or seat count.

A meaningful change for homebuilt owners

The FAA’s repairman guidance provides a more immediate ownership takeaway. It states that MOSAIC expanded light-sport repairman privileges to include experimental amateur-built aircraft, with those changes effective October 22, 2025. Certificates issued before that date remain valid and equivalent.

For an appropriately trained owner, this can create a condition-inspection route even when that owner did not build the aircraft. But the limits matter: a repairman holding an inspection rating may inspect only aircraft they own, wholly or partly, and the aircraft must match the category and class, as applicable, covered by their training.

The aircraft’s operating limitations also require attention. The FAA warns that existing limitations may restrict who can perform the annual condition inspection; owners or authorized agents may request amendments. Limitations issued after January 30, 2026, include a light-sport repairman among those authorized to perform it.

This is not an abandonment of the amateur-built “51 percent” rule. An October 16 MiGFlug explanation reports that the FAA declined a request to eliminate or modify that requirement because it was outside the rulemaking proposal. The major-portion requirement and education-or-recreation purpose remain intact.

For pilots weighing their next aircraft, MOSAIC therefore calls for three separate checks: the aircraft’s certification status, the pilot’s operating privileges, and the owner’s inspection arrangements. This week’s developments suggest a broader market ahead, but the strongest purchasing decisions will rest on documented approvals and aircraft-specific limitations—not anticipated capabilities alone.