NG to idle speed is greater than what percentage?

NG to idle speed is greater than what percentage?

• A. Greater than 50%
• B. Greater than 63%
• C. Greater than 70%
• D. Greater than 60%

Answer: (B)

Gas generator speed (NG) is the compressor turbine’s rotor speed expressed as a percent of its maximum. At idle, NG must stay above a minimum threshold to keep the engine stable, provide enough compressor airflow, and power the accessories and systems the helicopter relies on while the rotor is idle. For the UH-60S, the minimum NG for idle operation is greater than 63%. That’s why the best answer is the one stating “greater than 63%.” If NG were any lower, idle could become unstable or rough, and systems driven by the engine might not operate reliably. The other options aren’t the standard minimum: 50% or 60% would be too low to guarantee a stable idle, and 70% is higher than the usual idle target and isn’t the required minimum threshold.

Gas generator speed (NG) is the compressor turbine’s rotor speed expressed as a percent of its maximum. At idle, NG must stay above a minimum threshold to keep the engine stable, provide enough compressor airflow, and power the accessories and systems the helicopter relies on while the rotor is idle.

For the UH-60S, the minimum NG for idle operation is greater than 63%. That’s why the best answer is the one stating “greater than 63%.” If NG were any lower, idle could become unstable or rough, and systems driven by the engine might not operate reliably.

The other options aren’t the standard minimum: 50% or 60% would be too low to guarantee a stable idle, and 70% is higher than the usual idle target and isn’t the required minimum threshold.