Definition
The high-speed setting of a two-speed internal supercharger fitted to certain reciprocating aircraft engines. In high blower, the supercharger's impeller is driven through a higher gear ratio, spinning faster relative to the crankshaft to produce greater manifold pressure at high altitude where the air is thin.
Plain English
The faster of two gear settings on an engine's built-in air pump. Switching to high blower spins the pump harder so the engine can keep making power when the air gets thin at altitude.
Context Anchor
Seen in operating instructions and checklists for older or high-performance piston aircraft engines with two-speed superchargers.
Derivation
Called a 'blower' because the supercharger blows compressed air into the engine's intake. 'High' refers to the higher gear ratio used at high altitude, not to high power or high speed of the aircraft.
Why Pilots Care
Enables the engine to maintain rated power above the critical altitude, improving climb rate and cruise performance in supercharged aircraft.
Intuition Check
Do not read “blower” as a cabin fan or ventilation control. In this term, it means the engine’s supercharger. “High” means the higher-speed supercharger setting, usually used for higher-altitude operation.
Example Sentence 1
Climbing through 12,000 feet, the pilot shifted the supercharger into high blower as called for in the engine operating instructions.
Example Sentence 2
In high blower the engine maintained 30 inches of manifold pressure at 15,000 feet.