Takeoff and landing performance is effected by a number of factors. The runway, the pilot, the condition of the airplane, and the atmospheric conditions all effect how the airplane will perform during its takeoff, climb, approach, and landing.
Runway Slope
If the runway has an upslope, the airplane will have to climb that slope during its takeoff roll. This slows acceleration during the takeoff roll, resulting in an increased takeoff distance. A landing on an upsloping runway, however, aids in deceleration of the airplane, producing a shorter landing distance.
The effects are reversed for a downsloping runway. A takeoff performed on a downhill slope aids in acceleration during the takeoff roll, decreasing the takeoff distance. The airplane is more difficult to stop after a landing on a downsloping runway, however, and a greater landing distance is required.
Runway slope is stated in terms of gradient, which is a percentage. For example, a runway with a +2% gradient will rise 2 feet vertically for every 100 feet of runway distance. If an pilot performs a 1,500 foot long takeoff roll on a runway with a +2% gradient, the airplane will have to raise itself 30 feet before it leaves the ground. A downslope is stated as a negative gradient, such as -2%.
Runway Surface
Takeoff or landing on a hard, smooth runway surface, such as concrete or asphalt, results in little friction being generated between the airplane's wheels and the runway. This low friction translates to better acceleration during the takeoff roll and a shorter takeoff distance. A gravel, dirt, or grass runway is softer and rougher. The airplane accelerates slower on such a runway, resulting in a longer takeoff roll.
Runway Contamination
Runway contamination refers to an other than dry runway condition, such as a snowy, icy, or wet runway. During the takeoff roll, the tires have to plow through this contamination, slowing acceleration and lengthening the takeoff roll. While this is more clearly true of snow on the runway, is it also true of standing water, even if it is only a thin layer or water or small puddles on the runway. Rain can dramatically affect the airplane's performance on soft runways that may become muddy.
Contamination greatly affects landing performance, as well. An airplane's tires are made to be as small and light as possible. If there is snow or ice on the runway, the runway will become slick. The brakes will become much less effective.
Standing water on the runway causes hydroplaning. An airplane hydroplanes when the tires ride up onto water causing them to lose contact with the ground. In this case, since the water separates the tires from the ground, the airplanes brakes are completely ineffective. Many airports have grooved runways and runways with high centers to drain water from the runway. However, general aviation runways are commonly built with less funding and water may stand or puddle. Hydroplaning will occur only above a certain airspeed, which can be found by taking the square root of the tire pressure and multiplying it by nine. For a typical small, light airplane, the hydroplaning speed is about 54 knots. If an airplane begins to hydroplane, it can keep hydroplaning well slower than the its hydroplaning speed.
Pilot Technique
The data published by the manufacturer is based on the pilot flying an established procedure. For example, the minimum takeoff distance chart more than likely will contain notes describing how the pilot is to takeoff to achieve the minimum takeoff distance, such as rotating at a certain speed. If a pilot does not rotate at that correct speed, the takeoff distance will be longer. The manufacturer's takeoff data is supposed to be based on the average pilot's ability.
One item that cannot be stressed enough, is performing the landing on the close end of the runway. This may seem like common sense, but it is disturbing how commonly it does not happen. Pilots of all experience levels have made the mistake of trying to land in the middle or even near the far end of the runway. Make sure the airplane touches down in the first third of the runway. If you are unable to land in the first third of the runway, go around and try it again. Trying to land from a bad approach is an example of incredibly poor judgment. It is careless and reckless. Do not be the pilot that lands anywhere other than the close end of the runway.
Weight
A more loaded airplane accelerates slower, and must accelerate to a faster airspeed to fly. Additionally, the higher weight presses the tires against the runway surface, increasing the ground friction and further slowing acceleration during takeoff. These factors increase the takeoff distance.
Since the heavier airplane has a higher stalling speed, the landing speed will be higher. With more momentum compared to a lighter load, the airplane will be more difficult to stop after touchdown. These factors result in a longer landing roll.
Airframe and Engine
Most general aviation airplanes are not exactly perfect. The airplane may contain many superficial flaws that increase drag. The engine may not produce power as well as it once did. As a result, the airplane may not accelerate as quickly as the manufacturer publishes.
Density Altitude
Density altitude has a significant effect on takeoff and landing performance. At a high density altitude (thinner air), the engine produces less power and propeller is less efficient at converting that lesser power into thrust. The other airfoils, such as the wings, are less able to produce lift. This results in the airplane accelerating more slowly to a higher takeoff speed, increasing the takeoff roll. The airplane will also land faster, which increases the landing distance.
It may be possible for the density altitude to be high enough to prohibit a safe takeoff. For example, a pilot may find that on a hot, humid summer day the density altitude is very high. This causes the takeoff distance to be too high for a safe takeoff with the available runway length. The pilot has to wait for the density altitude to come down, at which point the takeoff distance is lower, safe distance. Perhaps, the pilot waits until the following dawn, the coldest part of the day. By examining performance before the flight to such an airport, the pilot is able to avoid such a situation by finding a larger, more suitable airport.