FAA Private Pilot Airplane (PAR)Aerodynamics and Aircraft SystemsMedium
A pilot is comparing two otherwise identical piston engines: one normally aspirated and one turbocharged. Both are climbing to 14,000 feet density altitude. Which statement correctly describes the primary advantage of the turbocharged engine at this altitude?
- AIt compresses intake air using exhaust gas energy, allowing it to maintain sea-level manifold pressure at altitude
- BIt burns less fuel per horsepower produced than the normally aspirated engine
- CIt uses a supercharger driven directly by the crankshaft to increase manifold pressure
- DIt eliminates the possibility of carburetor icing at high altitude
Show answer & explanationAnswer & explanation
Correct answer: A. It compresses intake air using exhaust gas energy, allowing it to maintain sea-level manifold pressure at altitude
A turbocharger uses a turbine driven by exhaust gases to compress incoming intake air, allowing the engine to maintain sea-level (or higher) manifold pressure at altitudes where a normally aspirated engine's power output would be significantly reduced due to lower ambient air density.
Why the other options are wrong
- B. Turbocharging does not inherently improve fuel efficiency per horsepower; it restores power lost to altitude.
- C. This describes a supercharger, which is mechanically driven, not exhaust-driven like a turbocharger.
- D. Turbocharging does not eliminate carburetor icing risk; that depends on the induction system, not boost source.
Turbocharging
A method of increasing engine power at altitude by using exhaust gas energy to drive a turbine that compresses intake air, maintaining higher manifold pressure than ambient conditions would otherwise allow.
- Turbocharger is driven by exhaust gases; supercharger is driven mechanically by the engine
- Allows engines to maintain sea-level power to higher altitudes ('critical altitude')
- Does not by itself prevent carburetor icing
Memory trick: Turbo turns exhaust into extra oomph.