Takeoff and landing performance isn't just determined by your airplane or the weather conditions. The runway surface, contamination, and slope make significant impacts too.

Performance Charts Assume A Best-Case Scenario

Varying runway conditions can dramatically change aircraft performance during takeoff and landing. What the runway's made of, surface contamination, and runway slope are the most critical factors that you should pay attention to.

Aircraft performance charts typically assume a level, dry, paved runway. Since no two runways are alike, pay close attention to the notes in your performance charts to adjust takeoff and landing distances based on the field conditions.

Runway Surface Material

Concrete and asphalt are the two most typical materials used for runway material at large airports. While concrete is generally more durable and lasts longer, it's also more expensive than asphalt. At some of the smallest airports in the country, you may find gravel, grass, or a mixture between concrete and asphalt used to construct a runway. The runway surface for a specific airport is noted in the FAA's Chart Supplement.

"Any surface that is not hard and smooth increases the ground roll during takeoff. This is due to the inability of the tires to roll smoothly along the runway. Tires can sink into soft, grassy, or muddy runways. Potholes or other ruts in the pavement can be the cause of poor tire movement along the runway" (FAA PHAK Chapter 11).

Grooved runways offer the best friction and drainage. Do you remember seeing large areas of black tires marks covering the runway around the touchdown zone at major airports?

Over time, rubber shreds off the tires of large aircraft and accumulates on top of the runway's surface. This can lead to the grooves or surface being filled or covered by rubber. With wet conditions, braking effectiveness and friction will degrade significantly on runways. While airports are required to power wash this residual rubber off, it's not something that happens enough to prevent negative effects.

For example, at Chicago O'Hare airport, Runway 28C often has the worst braking conditions in snowy conditions, compared to other parallel runways. This is in part because Runway 28C handles almost all widebody arrivals, and it has more rubber on the runway surface.

Runway Surface Contamination

Mud, snow, and standing water will reduce your airplane's acceleration down the runway. Although muddy and wet surface conditions can reduce friction between the runway and the tires, they can also act as obstructions and reduce the landing distance (FAA PHAK Chapter 11).

When you're flying a smaller aircraft, performance charts may not give you any guidance on how to re-calculate your landing distance based on surface contamination. Airports often issue braking action reports to assist pilots with current conditions.

The Flight Safety Foundation's "Approach and Landing Accident Reduction Tool Kit" (ALAR) provides some guidance:

• Wet Runways: Multiply the landing distance by a factor of 1.3 to 1.4
• Standing Water or Slush: Multiply by 2.0 to 2.3
• Snow-Covered Runways: Multiply by 1.6 to 1.7
• Icy Runways: The landing distance could be 3.5 to 4.5 times longer than normal

Once your calculations are complete, the FAA also recommends that you add a minimum of 15 percent as an additional safety margin.

Runway Slope

The gradient or slope of a runway is the amount of change in runway height over the full length of the runway. This figure is expressed as a percentage. If the gradient is 3%, for every 100 feet of runway length, the runway height changes by 3 feet. Positive gradients indicate increasing runway heights (upslope), and negative indicates the opposite (downslope).

Upsloping runways result in longer ground rolls during takeoff. Landing on upsloping runways can actually help deceleration, reducing the landing roll. The opposite is true for downsloping runways. Runway gradients can be found in the FAA's Chart Supplement.

What are some of the most challenging runway conditions you've faced? Tell us in the comments below.

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