FAA Powerplant Written Practice Test

What is the firing order of an aircraft engine with 9 cylinders?

1. 1-2-3-4-5-6-7-8-9

2. 1-3-5-7-9-2-4-6-8

3. 1-4-7-2-5-8-3-6-9

4. 1-5-3-7-9-6-4-2-8

The correct answer is: 1-3-5-7-9-2-4-6-8

In a nine-cylinder aircraft engine, the firing order is crucial for smooth operation and to maintain balance during engine cycles. The chosen order, which is 1-3-5-7-9-2-4-6-8, ensures that the engine runs efficiently and helps reduce vibrations. This specific firing order effectively distributes the power strokes across the engine's cycle, which is especially important in multi-cylinder engines to minimize the torque fluctuations and keep the engine balanced. By firing at these intervals, each cylinder contributes to the overall performance without overwhelming the engine or causing imbalances. Furthermore, the firing order impacts the overall design of the engine, including the layout of the ignition system and the timing of the valves. The provided order is indicative of a specific design that maximizes performance, ensuring that as one cylinder fires, there’s smooth continuity in the rotation of the crankshaft, leading to optimal power delivery and effective operation. Understanding firing orders is essential for maintenance and troubleshooting in aircraft engines, as deviations from these orders can lead to inefficient performance or potential engine failure. Hence, option B is the correct answer, as it accurately reflects the established firing sequence for a nine-cylinder aircraft engine.