Definition
A system on a reciprocating aircraft engine that increases the pressure of the air or fuel-air mixture entering the cylinders above what the engine could draw in by natural aspiration alone. Boost systems include superchargers (driven mechanically by the engine) and turbochargers (driven by exhaust gases), and they allow the engine to maintain rated power at higher altitudes where ambient air pressure is lower.
Plain English
A pump-like setup that forces extra air into the engine so it can keep making full power, even when flying high where the air is thin.
Context Anchor
Seen in discussions of flight control systems, especially on larger or faster airplanes where aerodynamic forces can make the controls heavy.
Derivation
From the everyday word 'boost,' meaning to push something up or increase it. The system 'boosts' the pressure of the air going into the engine.
Why Pilots Care
Maintains engine power output as altitude increases, improving climb rate and allowing safe takeoff weights at high-density-altitude airports.
Analogy
It is similar to power steering in a car. You still turn the wheel, but the system helps you apply the force needed to move the wheels.
Intuition Check
Do not assume “boost system” means an engine power-boosting system. Here, it means a system that helps move the flight controls by adding force to the pilot’s input.
Example Sentence 1
At 14,000 feet, the boost system kept the engine producing full rated power despite the thin air.
Example Sentence 2
At 8,000 feet the engine lost power until the boost system was engaged to restore manifold pressure.