getting to grips with aircraft performance 如何掌握飞机性能 1(33)

Consequently, when the Outside Air Temperature increases, the takeoff distances are longer and takeoff climb gradients are reduced.

5.3.3. Summary
When the Outside Temperature . .. Takeoff distances . . Takeoff climb gradients .
.. MTOW .
5.4. Runway Slope
A slope is generally expressed in percentages, preceded by a plus sign when it is upward, or a minus sign when it is downward.
Airbus aircraft are all basically certified for takeoff on runways whose slopes are between -2% and +2%. Nevertheless, these values can be extended to higher limits for operations on particular runways, but it remains marginal as it requires additional certification tests.
From a performance point of view, an upward slope degrades the aircraft’s acceleration capability and, consequently, increases takeoff distance. On the other hand, the stopping distance is shortened in case of a rejected takeoff. This is why, depending on the takeoff limitation, an upward slope can sometimes improve MTOW and sometimes lower it.
Upward slope .. Takeoff distances . . Accelerate stop distance .
Downward slope .. Takeoff distances . . Accelerate stop distance .
5.5. Runway Conditions (Dry, Damp, Wet, Contaminated)

The previously-discussed performance aspects only concerned dry and wet runways. But contaminants also affect takeoff performance, and have to be considered for takeoff weight calculation. The following section aims at defining the different runway states that can be encountered at takeoff.

5.5.1. Definitions
“JAR-OPS 1.480
 (4)
Dry runway: A dry runway is one which is neither wet nor contaminated, and includes those paved runways which have been specially prepared with grooves or porous pavement and maintained to retain ‘effectively dry’ braking action even when moisture is present”

“JAR-OPS 1.480

(3)
Damp runway: A runway is considered damp when the surface is not dry, but when the moisture on it does not give it a shiny appearance.”

The FAA does not make any reference to damp runways, which are considered as wet, whereas JAR-OPS 1.475 states that a damp runway is equivalent to a dry one in terms of takeoff performance. Recently, JAR 25 and JAR-OPS Study Groups came to the conclusion that a damp runway should be considered closer to a wet one than to a dry one in terms of friction coefficient (μ)1. As of today, a JAA Notice for Proposed Amendment (NPA) is under discussion, so that in the future, a damp runway may have to be considered as wet.
“JAR-OPS 1.480
(10) Wet runway: A runway is considered wet when the runway surface is covered with water or equivalent, [with a depth less than or equal to 3 mm], or when there is a sufficient moisture on the runway surface to cause it to appear reflective, but without significant areas of standing water.”
In other words, a runway is considered to be wet, as soon as it has a shiny appearance, but without risk of hydroplaning due to standing water on one part of its surface. The water depth is assumed to be less than 3 mm.
　
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