FAA Powerplant Written Practice Test

On many turbine powered aircraft, which valve works with the start valve to supply air to the pneumatic starter?

1. Compressor outlet valve

2. Pressure-regulating and shutoff valve

3. Throttle valve

4. Fuel control valve

The correct answer is: Pressure-regulating and shutoff valve

The pressure-regulating and shutoff valve plays a critical role in managing the airflow for the pneumatic starter system in turbine-powered aircraft. This valve regulates the pressure of the compressed air that is supplied to the starter, ensuring that the right amounts are delivered to start the engine. When the pneumatic starter is engaged, the pressure-regulating and shutoff valve allows high-pressure air from the engine's compressor to flow through the start valve to the starter. By controlling the airflow and maintaining the appropriate pressure, this valve ensures that the starter operates efficiently and effectively, enabling successful engine starts. In the context of turbine engine starting, the other options do not directly manage the flow or pressure of air required by the pneumatic starter. The compressor outlet valve controls the air flow at a different stage of operation, the throttle valve primarily manages fuel-air mixture and engine power output, and the fuel control valve is focused on regulating fuel flow rather than pneumatic functions. Thus, the pressure-regulating and shutoff valve is essential for supplying the right pneumatic pressure for starting the engine.