FAA Powerplant Written Practice Test

What is the function of a blast tube in aircraft reciprocating engines?

1. A device to direct fuel flow

2. A device to cool an engine accessory

3. A device to enhance overall engine performance

4. A device to monitor exhaust emissions

The correct answer is: A device to cool an engine accessory

The function of a blast tube in aircraft reciprocating engines is to facilitate the cooling of engine accessories. Specifically, a blast tube directs a flow of air from a source, often from the propeller's slipstream or another airflow, to various components that require cooling. This is crucial because certain engine accessories, such as magnetos, alternators, or other accessories located near the engine may generate significant heat during operation. Proper cooling ensures these components function efficiently and do not overheat, which could lead to failure or diminished performance. Thus, the blast tube plays an essential role in maintaining the health and efficiency of the engine by ensuring that critical components remain within their optimal temperature ranges.