Definition
On a two-speed supercharged engine, the gear setting that drives the supercharger impeller at its higher speed, producing greater manifold pressure to maintain rated power at higher altitudes where the air is thinner.
Plain English
The faster gear for the engine's air-compressing fan, switched on at higher altitudes so the engine can keep producing full power in thinner air.
Context Anchor
Seen in discussions of supercharged aircraft engines and engine power management at altitude.
Derivation
Blower' is a long-standing mechanic's nickname for a supercharger, because it blows extra air into the engine. 'High' refers to the higher of the two available gear ratios driving the blower. So 'high blower' simply means the supercharger running in its high-speed gear.
Why Pilots Care
It allows the engine to produce rated power above the altitude where the low blower setting alone is no longer sufficient.
Grounding Statement
As the airplane climbs and the air gets thinner, the high blower setting helps push enough air into the engine to keep power from falling off too quickly.
Intuition Check
Do not read blower as a cabin fan or ventilation control here. In this engine context, blower means the supercharger that forces air into the engine.
Example Sentence 1
Climbing through the published shift altitude, the pilot moved the supercharger control to high blower setting and watched the manifold pressure recover.
Example Sentence 2
With the high blower setting engaged, manifold pressure remained steady even as the airplane climbed into thinner air.