FAA Powerplant Written Practice Test

What is the correct sequence for synchronizing carburetors on a light sport aircraft with two carburetors?

1. Pneumatic synchronization first, then mechanical

2. Mechanical synchronization first, then pneumatic

3. Simultaneous synchronization of both

4. No synchronization is required

The correct answer is: Mechanical synchronization first, then pneumatic

The correct sequence for synchronizing carburetors in a light sport aircraft equipped with two carburetors is to perform mechanical synchronization first, followed by pneumatic synchronization. Mechanical synchronization is essential because it aligns the linkages and ensures that both carburetors operate in unison concerning throttle input from the pilot. This step includes ensuring that the throttle plates in both carburetors open and close at the same rate and angle, which is critical for balanced engine performance and smooth operation. After completing mechanical synchronization, pneumatic synchronization is conducted to fine-tune the fuel-air mixture and ensure that both carburetors are delivering the correct mixture under various operating conditions. This second step focuses on the performance of the engine during actual operation, allowing for adjustments that account for how the air and fuel mixture affects each cylinder's combustion. Synchronizing in this order ensures optimal engine performance and efficiency, avoiding issues related to uneven power delivery or engine roughness.