Final rule · 2026-05264

Special Conditions: Textron Aviation Inc. (Textron) Model MU-300-10, 400, 400A Airplanes; Rechargeable Lithium Batteries and Battery System Installations

These special conditions are issued for the Textron Model MU- 300-10, 400, and 400A airplanes. These airplanes will have a novel or unusual design feature when compared to the state of technology envisioned in the airworthiness standards for transport-category airplanes. This design feature is an emergency lighting power supply containing rechargeable lithium batteries. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for this design feature. These special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to those established by the existing airworthiness standards.