FAA Ground School Practice Test

What could indicate a fuel/air mixture that is too lean during flight?

1. Engine overheating

2. Loss of power

3. Excessive exhaust smoke

4. Engine backfiring

The correct answer is: Loss of power

The indication of a fuel/air mixture that is too lean during flight is often associated with a loss of power. When the mixture is lean, there is insufficient fuel relative to the amount of air being drawn into the engine. This lean condition can cause incomplete combustion, leading to reduced engine performance and a noticeable drop in power output. Pilots may experience a lack of thrust, particularly during operation in critical phases like climb or takeoff, where optimal power is crucial. In contrast, engine overheating, excessive exhaust smoke, and engine backfiring are symptoms generally linked to other conditions. For instance, engine overheating can occur with a rich mixture or due to cooling system deficiencies, while excessive exhaust smoke is more characteristic of a rich mixture or oil leaks. Engine backfiring typically indicates a timing issue or malfunction within the ignition system rather than a lean fuel condition. Understanding these distinctions helps in diagnosing engine performance issues accurately.