FAA Powerplant Written Practice Test

To what altitude will a turbocharged engine maintain sea level pressure?

1. 1000 feet

2. 5000 feet

3. Critical altitude

4. Sea level only

The correct answer is: Critical altitude

A turbocharged engine is designed to maintain optimal performance and efficiency by using a turbocharger to compress the intake air, effectively allowing the engine to perform better at higher altitudes. The term "critical altitude" refers to the maximum altitude at which the turbocharger can maintain sea level pressure in the intake manifold. Above this altitude, the engine will not be able to achieve the same performance levels because atmospheric pressure decreases with altitude, but the turbocharger will still be working to compress the intake air up to the critical altitude. This critical altitude provides a point where the engine can operate as if it were still at sea level, allowing for more power and performance than normally achievable in naturally aspirated engines at higher altitudes. In contrast, options like just sea level or any specific altitude like 1000 or 5000 feet do not accurately reflect the operational characteristics of turbocharged engines, which are specifically designed to overcome altitude effects to a certain extent. Thus, the correct choice reflects the capabilities of the turbocharger in maintaining pressure and performance characteristics relative to altitude.