Test on Aircraft Engine Ignition Systems

Question 1: Pressurized magnetos are used on most reciprocating-engine-powered aircraft that fly at high altitudes to prevent high voltage from arcing across to the wrong electrode.

A. Ano

B. Ne

Explanation: Pressurized magnetos are used on most reciprocating-engine-powered aircraft that fly at high altitudes because pressurized air is a better insulator than less dense air. This keeps the high voltage from arcing across to the wrong electrode and causing vibration and loss of engine power.

Question 2: Is the function of an impulse coupling to produce a hot and late spark during engine starting by rapidly spinning the rotating magnet after the piston passes its top center position?

A. Ano

B. Ne

Explanation: An impulse coupling is designed to hold the rotating magnet until the piston passes over its top center position, then releases it, allowing a spring to spin it fast to produce a hot and late spark for engine starting.

Question 3: What is the primary function of the capacitor in an aircraft magneto ignition system?

A. To minimize arcing at the breaker points.

B. To speed up the collapse of the primary current as the breaker points open.

C. To connect the primary circuit to ground when the ignition switch is placed in the OFF position.

D. To hold the rotating magnet until the piston passes its top center position during starting.

Explanation: The capacitor in a magneto serves two main functions: it minimizes arcing at the breaker points, and it speeds up the collapse of the primary current when the breaker points open.

Question 4: An aircraft reciprocating engine continues to run after the ignition switch is placed in the Off position. Based on this observation, what is the most likely malfunction in the ignition system?

A. The impulse coupling is stuck, preventing the magneto from stopping.

B. The magneto's primary circuit is not being grounded by the ignition switch.

C. The breaker points are not opening correctly in the E-gap position.

D. The capacitor is causing excessive arcing at the breaker points.

Explanation: The study materials state that 'What malfunction in the ignition system would cause an aircraft reciprocating engine to continue to run after the ignition switch is placed in the Off position? The ignition switch is not grounding the magneto primary circuit.' It also clarifies that when the ignition switch is placed in the OFF position, the primary circuit is connected to ground. Therefore, if the engine continues to run, the grounding action has failed.

Question 5: A hot spark plug has a short path for the heat to travel between the nose core insulator and the spark plug shell.

A. Ano

B. Ne

Explanation: A hot spark plug has a long path for the heat to travel between the nose core insulator and the spark plug shell. A cold spark plug has a shorter distance for heat to travel.