Which of the following describes an advantage of FADEC over a hydromechanical fuel control?

• A. Requires no engine trimming; improved engine starts; saves fuel; provides engine limit protection; constant idle speed with changes in conditions; fully modulates active clearance control; repeatable engine transients.
• B. Increases maintenance requirements.
• C. Lowers reliability in extreme conditions.
• D. Eliminates fuel control entirely.

Answer: (A)

FADEC provides precise, automated control of fuel and ignition through sensors and software, delivering consistent and safe engine performance across a wide range of conditions. Because it uses closed-loop scheduling and digital logic, it can adapt in real time to changes in ambient conditions, engine speed, and load.

That is why this option stands out. It highlights several real advantages: automatic trimming means the engine is continually optimized without manual adjustments; smoother, more reliable starts come from carefully timed fuel and ignition sequences; fuel savings come from optimizing metering over the entire operating envelope; engine limit protection keeps parameters like ITT and speed within safe bounds; maintaining a constant idle speed despite changes in altitude or temperature is achievable with feedback control; active clearance control can be modulated continuously for efficiency and reduced wear; and the overall transients are repeatable because the digital controller produces deterministic responses.

Other choices describe effects that don’t match how FADEC works—for example, signaling more maintenance, reduced reliability in harsh conditions, or eliminating fuel control altogether. FADEC actually enhances control fidelity, relies on electronic metering rather than purely mechanical means, and typically reduces manual maintenance through built-in diagnostics and fewer trim adjustments.