At 37,000 ft, the starter disengages at approximately what percent rpm?

At 37,000 ft, the starter disengages at approximately what percent rpm?

• A. 60%
• B. 46%
• C. 70%
• D. 80%

Answer: (A)

During a turbine engine start, the starter accelerates the compressor to a set speed, then fuel is introduced and the engine lights off. The starter is designed to disengage when the N2 spool reaches about sixty percent. This threshold provides a safe, reliable transition to self-sustaining operation: fast enough to light off and spin up the core, but not so high that the starter or gear train is overstressed. At 37,000 ft, the air is thinner, but the control limit remains around sixty percent because it’s a mechanical/electrical boundary built into the start system. The other options would either cut off the starter too early (leading to longer starter operation and heat) or too late (risking overspeed or unnecessary wear).

During a turbine engine start, the starter accelerates the compressor to a set speed, then fuel is introduced and the engine lights off. The starter is designed to disengage when the N2 spool reaches about sixty percent. This threshold provides a safe, reliable transition to self-sustaining operation: fast enough to light off and spin up the core, but not so high that the starter or gear train is overstressed. At 37,000 ft, the air is thinner, but the control limit remains around sixty percent because it’s a mechanical/electrical boundary built into the start system. The other options would either cut off the starter too early (leading to longer starter operation and heat) or too late (risking overspeed or unnecessary wear).