Summary
The FAA is revising an earlier NPRM for an airworthiness directive (AD) that applies to certain EMBRAER airplane models as identified above. The original NPRM would have required modifying the total air temperature (TAT) sensor heating system. The original NPRM was prompted by a report indicating that the fully automated digital electronic control (FADEC) unit failed to compensate for ice accretion on the engine fan blades due to a false temperature signal from the TAT sensor to the FADEC. This action revises the original NPRM by requiring modification of additional electrical connections for the TAT sensor heating system. This action also would expand the applicability of the original NPRM because the additional electrical connections must be modified on airplanes that had the TAT sensor heating system modified previously (e.g., in production). This action also adds replacing the FADEC assemblies with new or modified assemblies as an additional means of compliance. We are proposing this supplemental NPRM to prevent failure of the TAT sensor, which could result in insufficient thrust to take off or (if coupled with the loss of an engine during takeoff) to abort the takeoff in a safe manner, and consequent reduced controllability of the airplane.