What does the term 'thrust excess' refer to?

Thrust excess is a crucial concept in understanding aircraft performance, particularly in evaluating how much thrust is available relative to what is needed for a given flight condition. The term specifically refers to the difference between the available thrust from the aircraft's engines and the thrust required to maintain level flight, climb, or perform a particular maneuver.

When considering this definition, thrust excess indicates the surplus capability of the engines to produce thrust beyond what is necessary to sustain flight, which can impact climb rate, acceleration, and overall aircraft performance. When the thrust available exceeds the thrust required, the aircraft will accelerate, allowing for greater maneuverability or a climb.

This differentiation is vital when pilots assess situations such as takeoff, climbing to altitude, and recovering from stalls, as it informs them about the performance margins they have on hand. A positive thrust excess means the aircraft can increase its speed or altitude, while a negative thrust excess indicates a potential struggle to maintain flight conditions.

In essence, "thrust available minus thrust required" captures the concept of thrust excess succinctly, making it clear why this definition is the most accurate representation among the choices.