🔍 Key Concepts

• Air start check valve function and purpose in an engine starting air system • Difference between mechanically operated valves (cams, rockers, followers) and pressure‑operated valves • How a pilot piston can transmit control air to a main valve element

💭 Think About

• Look closely at what parts in the illustration are in direct contact with the valve disc or spindle and ask: is anything riding on a cam or rocker arm? • Trace the path of the control air shown by the arrows: does it first act on a smaller component that then moves the main valve element? • Consider why a check valve in a starting air line must stay tightly shut if there is no control signal or pressure — what component in the drawing ensures this fail‑safe position?

✅ Before You Answer

• Identify whether you can actually see a cam, cam follower, or rocker arm anywhere in the figure • Locate the small piston-like piece above the main spring and spindle and determine what acts on its upper surface • Confirm which force must be present to overcome the main closing spring and move the spindle away from its seat