Definition
Two physical characteristics of a runway that affect takeoff and landing performance: the surface (the material the runway is made of and its current condition, such as dry asphalt, grass, gravel, or a wet or contaminated surface) and the gradient (the slope of the runway, expressed as a percentage representing the change in elevation from one end to the other). Both factors alter the distance an aircraft needs to take off or land and must be considered during performance planning.
Plain English
What the runway is made of and how it slopes. A soft, wet, or rough surface makes the aircraft accelerate or stop differently than a smooth dry one. A runway that tilts uphill or downhill also changes how much room the aircraft needs.
Context Anchor
Seen in takeoff and landing performance planning, especially when using runway data, airport information, or performance charts.
Derivation
Gradient comes from the Latin gradus, meaning a step or a degree of incline. In aviation it refers to the steepness of the runway expressed as a percentage. A 2 percent gradient means the runway rises or falls 2 feet for every 100 feet of length.
Why Pilots Care
Surface type affects tire friction and braking effectiveness while gradient alters the effective takeoff or landing distance required.
Grounding Statement
Picture the difference between running on dry pavement and running uphill through wet grass; the airplane also needs more room when the runway surface or slope works against it.
Intuition Check
Do not read surface as just the runway material, or gradient as just a general steepness idea. In performance planning, surface means the runway condition the wheels actually roll on, and gradient means the runway’s uphill or downhill slope.
Example Sentence 1
Before departing the short grass strip, the pilot reviewed the runway surface and gradient and added a safety margin to the calculated takeoff distance.
Example Sentence 2
A grass runway surface combined with an uphill gradient increased the required rollout length for landing.