FAA Powerplant Written Practice Test

In a light sport aircraft with two carburetors, what is the correct sequence for carburetor synchronization?

1. Pneumatic synchronization first, then mechanical

2. Mechanical synchronization first, then pneumatic

3. Simultaneous synchronization

4. Visual inspection of carburetor settings only

The correct answer is: Mechanical synchronization first, then pneumatic

In the context of carburetor synchronization in a light sport aircraft with two carburetors, the correct sequence of mechanical synchronization followed by pneumatic synchronization is essential for ensuring that both carburetors operate in harmony. Mechanical synchronization involves adjusting the physical linkages and controls that connect the throttle and mixture levers to the carburetors. This step ensures that both carburetors are opening and closing at precisely the same time when the pilot operates the throttle. Achieving this alignment is crucial for balanced engine performance and to prevent issues such as uneven power output, which can lead to engine vibration or even loss of power in one engine, especially in multi-engine setups. Once the mechanical synchronization is confirmed, pneumatic synchronization is performed, which deals with the fuel-air mixture and ensuring both carburetors are delivering the same fuel flow to each engine cylinder. This step ensures that each carburetor is not only mechanically linked but also providing the proper air-fuel ratio, optimizing engine performance across the power range. The combination of these two synchronization methods is vital for the overall efficiency and performance of the aircraft's engine. Performing mechanical synchronization first allows for a solid foundational adjustment before fine-tuning with pneumatic synchronization, leading to an optimal operating condition for the engine.