FAA Powerplant Written Practice Test

Why is the exhaust system on a turbocharged engine more susceptible to damage at high altitude?

1. High temperature variations

2. Lower external pressure

3. Increased moisture content

4. Higher fuel consumption

The correct answer is: Lower external pressure

The correct response highlights that turbocharged engines rely on their exhaust systems to function optimally at high altitudes. As altitude increases, the external atmospheric pressure decreases. This lower pressure means that the exhaust gases expand more than they typically would at sea level. The design of the exhaust system must accommodate this expansion, and if not properly managed, it can lead to increased stress and potential structural failures within the exhaust components. Additionally, at high altitudes, the turbocharger's effectiveness can be impacted due to reduced air density. This can result in excessive temperatures in the exhaust system, exacerbating any structural weaknesses. Therefore, the combination of reduced external pressure and the resulting thermal conditions makes turbocharged engines' exhaust systems particularly vulnerable at high altitudes. While factors such as temperature variations, moisture content, and fuel consumption are indeed important considerations in engine operations, they do not specifically address the unique challenges faced by the exhaust systems of turbocharged engines at high altitude as effectively as the issue of lower external pressure.