Droop
Droop turns up in 2 fields: lighting, aviation. Here is what it means to the people in each one.
Droop in lighting
The fall in an LED's efficiency as drive current or temperature rises, so extra power yields proportionally less light.
Efficiency droop is the drop in LED efficacy at high current density, caused by carrier losses inside the chip; thermal droop is the drop in output as junction temperature rises. Together they explain why luminaire makers often use many LEDs run gently instead of a few run hard, and why a fixture tested cold on the bench delivers less in a hot ceiling. The hot-to-cold factor in datasheets quantifies the thermal part.
"Running those chips at 700 milliamps puts us deep into droop, use twice as many boards at 350 and the efficacy jumps."
Droop in aviation
A hinged section on the leading edge of a wing that tilts downward to increase lift at low speeds.
An aerodynamic control surface located on the front edge of a wing that pivots downward to increase the wing's camber. Unlike slats, which create a physical gap for airflow, a droop leading edge remains sealed against the main wing structure, delaying stalls during high-angle-of-attack maneuvers like takeoff and landing.
"Check the leading edge droop mechanisms during the walkaround to ensure there's no hydraulic fluid leaking."