FAA Powerplant Written Practice Test

Why are exhaust systems on turbocharged engines susceptible to damage at high altitude?

1. Lower external pressure.

2. Higher fuel temperatures.

3. Increased vibration levels.

4. Higher oxygen levels.

The correct answer is: Lower external pressure.

The reason why exhaust systems on turbocharged engines are susceptible to damage at high altitude primarily involves the concept of lower external pressure. As an aircraft climbs to higher altitudes, the atmospheric pressure decreases. This reduction in external pressure can lead to an increase in the exhaust gas temperature as the engine operates under different conditions than it does at lower elevations. In turbocharged engines, the turbocharger relies on exhaust gases to function effectively; however, with the surrounding atmosphere being less dense, there can be issues such as insufficient cooling for the exhaust system components. The materials used in the exhaust system may be more prone to thermal stress and could potentially be damaged by the higher temperatures that can arise due to the decreased pressure. This leads to a greater risk of failure in exhaust system components, as they may not be designed to handle these extreme operational conditions. Thus, the susceptibility of exhaust systems at high altitude is directly related to the effects of lower external pressure on engine performance and component durability.