What is the start air pressure?

What is the start air pressure?

• A. 40 psig
• B. 50 psig
• C. 45 psig
• D. 60 psig

Answer: (C)

Start air pressure is the regulated pressure that drives the pneumatic starter to spin the engine up to light-off. It must be high enough to overcome internal friction and provide the starter enough torque, but not so high that it overspeeds the compressor or stresses the starter valves. In this system, the nominal start air pressure is set at 45 psig, which sits in a practical middle range that reliably starts the engine under different temperatures and tolerances. Pressures much lower than this can fail to start, while higher pressures can risk overspeed and equipment wear, so 45 psig is the best-fit value.

Start air pressure is the regulated pressure that drives the pneumatic starter to spin the engine up to light-off. It must be high enough to overcome internal friction and provide the starter enough torque, but not so high that it overspeeds the compressor or stresses the starter valves. In this system, the nominal start air pressure is set at 45 psig, which sits in a practical middle range that reliably starts the engine under different temperatures and tolerances. Pressures much lower than this can fail to start, while higher pressures can risk overspeed and equipment wear, so 45 psig is the best-fit value.