Nozzle setting at idle power on the ground is within which percentage range?

Nozzle setting at idle power on the ground is within which percentage range?

• A. 60-70%
• B. 70-80%
• C. 77-92%
• D. 90-100%

Answer: (C)

Idle nozzle setting controls how open the exhaust nozzle is at ground idle, which directly affects exhaust back pressure and engine stability. At idle on the ground, the engine doesn’t need full nozzle opening; the nozzle must be partially closed to maintain the proper pressure ratio across the turbine and to prevent surging while still providing enough idle thrust. The typical range for this condition is about 77 to 92 percent of maximum nozzle opening, reflecting normal variations with engine wear, ambient conditions, and temperature. If the nozzle were set much lower, back pressure would become excessive and idle could become unstable; if it were set much higher, the engine could run inefficiently and idle stability could suffer. So 77–92% best matches the operational balance required for a stable idle on the ground.

Idle nozzle setting controls how open the exhaust nozzle is at ground idle, which directly affects exhaust back pressure and engine stability. At idle on the ground, the engine doesn’t need full nozzle opening; the nozzle must be partially closed to maintain the proper pressure ratio across the turbine and to prevent surging while still providing enough idle thrust. The typical range for this condition is about 77 to 92 percent of maximum nozzle opening, reflecting normal variations with engine wear, ambient conditions, and temperature. If the nozzle were set much lower, back pressure would become excessive and idle could become unstable; if it were set much higher, the engine could run inefficiently and idle stability could suffer. So 77–92% best matches the operational balance required for a stable idle on the ground.