Definition
A propeller or engine thrust line that is positioned above the airplane's center of gravity. Because the thrust acts above the CG, an increase in power produces a nose-down pitching tendency, and a reduction in power produces a nose-up tendency.
Plain English
The line along which the engine pushes the airplane forward sits higher than the point the airplane balances around. So when you add power, the nose wants to drop, and when you reduce power, the nose wants to rise.
Context Anchor
Used in longitudinal stability and pitching discussions, especially when explaining why some aircraft pitch down when power is added.
Derivation
"Thrust line" is the imaginary straight line along which the engine's thrust acts. "High" here means high relative to the center of gravity, not high in the sky. Naming the line lets engineers and pilots talk about how thrust direction affects pitch.
Why Pilots Care
Pilots must anticipate and compensate for pitch changes with power adjustments to maintain control, especially during climbs, descents, or go-arounds.
Grounding Statement
Picture the engine pushing forward from a point above the airplane’s balance point; that off-center push tries to rotate the nose downward.
Intuition Check
“High” does not mean high power here. It means the engine’s line of push is physically above the aircraft’s balance point.
Example Sentence 1
Because the floatplane has a high thrust line, the instructor warned the student to expect the nose to drop when full power was applied for takeoff.
Example Sentence 2
During a go-around the pilot counters the high thrust line effect by applying slight back pressure to hold the desired pitch attitude.