How does the engine compensate for variable power demands from collective inputs?

How does the engine compensate for variable power demands from collective inputs?

• A. The HMU automatically adjusts to maintain constant RPM
• B. The LDS increases/decreases fuel flow through the HMU
• C. The PCLs auto-feather
• D. The oil cooler modulates flow

Answer: (B)

When you change the collective, the rotor load on the engine changes and the engine must adjust fuel to keep the rotor speed and power steady. The Load Demand System senses that collective demand and modulates fuel flow through the Hydromechanical Unit. Increasing collective prompts the LDS to raise fuel flow; decreasing collective lowers fuel flow. The HMU meters the precise amount of fuel to match that commanded flow, maintaining the desired engine speed and power output in response to the pilot’s input. Other mechanisms don’t continuously adjust fuel delivery to match collective demand in the same way, so the LDS-driven fuel flow through the HMU is the correct answer.

When you change the collective, the rotor load on the engine changes and the engine must adjust fuel to keep the rotor speed and power steady. The Load Demand System senses that collective demand and modulates fuel flow through the Hydromechanical Unit. Increasing collective prompts the LDS to raise fuel flow; decreasing collective lowers fuel flow. The HMU meters the precise amount of fuel to match that commanded flow, maintaining the desired engine speed and power output in response to the pilot’s input. Other mechanisms don’t continuously adjust fuel delivery to match collective demand in the same way, so the LDS-driven fuel flow through the HMU is the correct answer.