During lockout, which DEC function remains available?

During lockout, which DEC function remains available?

• A. NP overspeed protection
• B. NG limit
• C. Torque limit
• D. Rotor Speed Hold

Answer: (A)

The function that stays available during lockout is the NP overspeed protection. When the DEC is locked out, the engine’s electronic governor no longer actively limits fuel to meet NG or torque targets or to hold rotor speed. However, NP overspeed protection is tied to a dedicated overspeed monitor that continues to watch the power turbine rotor speed (Np) and will automatically trim fuel to prevent exceeding the maximum safe NP. This safety function operates independently of the DEC’s active controls, ensuring the rotor doesn’t overspeed even with lockout. The other protections—NG limit, Torque limit, and Rotor Speed Hold—depend on the DEC’s active control to enforce limits or maintain a commanded rotor speed. With the DEC locked out, those controls aren’t engaged, so they don’t remain available.

The function that stays available during lockout is the NP overspeed protection. When the DEC is locked out, the engine’s electronic governor no longer actively limits fuel to meet NG or torque targets or to hold rotor speed. However, NP overspeed protection is tied to a dedicated overspeed monitor that continues to watch the power turbine rotor speed (Np) and will automatically trim fuel to prevent exceeding the maximum safe NP. This safety function operates independently of the DEC’s active controls, ensuring the rotor doesn’t overspeed even with lockout.

The other protections—NG limit, Torque limit, and Rotor Speed Hold—depend on the DEC’s active control to enforce limits or maintain a commanded rotor speed. With the DEC locked out, those controls aren’t engaged, so they don’t remain available.