Which instruments are classified as engine instruments?

• A. Horizon indicators and vertical speed indicators
• B. Gyroscopes and magnetic compasses
• C. Tachometers and oil pressure gauges
• D. Radio altimeters and transponders

Answer: (C)

The classification of engine instruments includes those that monitor the performance and operational status of the engine, which is essential for ensuring safe and efficient flight operations. Tachometers and oil pressure gauges fall squarely into this category.

Tachometers provide critical information regarding the rotational speed of the engine, often measured in revolutions per minute (RPM). This data is vital for preventing engine over-speed conditions, which could lead to catastrophic failures.

Oil pressure gauges, on the other hand, are crucial for monitoring the engine's lubrication system. Maintaining adequate oil pressure is necessary for engine longevity and functionality, as insufficient oil pressure can lead to engine seizure or damage due to lack of lubrication.

In contrast, instruments like horizon indicators, vertical speed indicators, gyroscopes, magnetic compasses, radio altimeters, and transponders serve different critical roles in flight monitoring and navigation, but do not directly provide information about engine performance. Hence, tachometers and oil pressure gauges are definitive examples of engine instruments.