Definition
A pre-determined throttle (and, where applicable, propeller and mixture) setting used to establish a stabilized descent at a target airspeed and/or rate of descent. The specific value is taken from the aircraft's published performance data or developed by the pilot for that airframe, and is applied as part of the entry into a descent so that pitch and trim adjustments produce the intended descent profile.
Plain English
The power level you set on the engine when you want the aircraft to start going down in a controlled way. It's a known number for your aircraft that, combined with the right pitch attitude, gives you a smooth descent at the speed or rate you want.
Context Anchor
Seen in instrument flying when entering or maintaining straight descents, especially when the pilot is trying to hold a constant airspeed or a constant rate of descent.
Derivation
“Descent” comes from Latin words meaning “to climb down.” “Setting” means a selected position or value. Together, the phrase points to a selected engine-power value used while the airplane is going downward.
Why Pilots Care
Correct descent power settings maintain airspeed limits, produce the planned descent rate, and keep the aircraft stable during instrument approaches.
Intuition Check
Do not assume a descent power setting is simply “power idle” or “less power.” It is the specific power choice that produces the desired descent for that aircraft, weight, configuration, and target speed.
Example Sentence 1
Approaching the initial fix, the pilot reduced to the briefed descent power setting and lowered the nose slightly to begin a 500-foot-per-minute descent.
Example Sentence 2
During the approach, the instructor called for the descent power setting to maintain 90 knots at 500 feet per minute.