1) The document defines different runway surface conditions including dry, damp, wet, contaminated runways and provides criteria for classifying each condition based on factors like depth of water, slush, snow, etc. 2) It explains that for takeoff performance calculations on wet or contaminated runways, the screen height is 15 feet rather than 35 feet and reverse thrust can be considered. 3) Charts for different levels of water, slush or snow contamination are used to determine the takeoff weight penalty and speeds compared to a dry runway under the same conditions. An example calculation is provided.

1. 10. CONTAMINATED RUNWAYS
Performance JAR 25

2. CONTAMINATED RUNWAYS
 Definitions
 Screen height
 Distances
 Takeoff charts
 Example

3. DEFINITIONS
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.
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.
According to JAA regulations, a damp runway is considered dry as far
as performance calculations are concerned. This may change in the
future.

4. DEFINITIONS
Damp runway

5. DEFINITIONS
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.
A wet runway has a shiny appearance, but without risk of
hydroplaning.

6. DEFINITIONS
Wet runway

7. DEFINITIONS
CONTAMINATED RUNWAY
A runway is considered to be contaminated when more than 25% of
the runway surface area within the required length and width being
used is covered by the following:
Standing water: Caused by heavy rainfall and/or insufficient runway
drainage with a depth of more than 3 mm (0.125 in).
Slush: Water saturated with snow, which spatters when stepping
firmly on it.
Wet snow: If compacted by hand, snow will stick together and tend to
form a snowball.
Dry snow: Snow can be blown if loose, or if compacted by hand, will
fall apart again upon release.
Compacted snow: Snow has been compressed
Ice: The friction coefficient is 0.05 or below.

8. DEFINITIONS
Contaminated runway

9. DEFINITIONS
Equivalent of wet runway is runway covered with less than:
• 2 mm (0.08 inch) slush
• 3 mm (0.12 inch) standing water
• 4 mm (0.16 inch) wet snow
• 15 mm (0.59 inch) dry snow

10. SCREEN HEIGHT
On wet and contaminated runways, the screen height is measured at
15 feet rather than 35 feet on dry runways. Moreover, the use of
reverse thrust is allowed for ASD determination on wet and
contaminated runways, whereas it is forbidden to take it into account
for the ASD determination on dry runways.
Therefore, it is possible to obtain shorter TODs and ASDs on wet and
contaminated runways than on dry runways for the same takeoff
conditions. Thus, it is possible to obtain higher takeoff weights on
surfaces covered with water, slush, or snow than on dry runways. This
is why the regulation indicates that:
On a wet or contaminated runway, the takeoff mass must not exceed
that permitted for a takeoff on a dry runway under the same
conditions.

11. DISTANCES
ASD, TOD and TOR for wet runways are measured in the same way as
for dry runways, except that the screen height is 15 ft and reverse
thrust is considered.
TOD
15 ft

12. TAKEOFF CHARTS
Depending on the depth of water, we will use a different chart for takeoff
performance calculations:
• Under 3 mm of water, use the WET RUNWAY correction.
• Between 3 mm and 6.3 mm, use the 6.3 mm (1/4 inch) WATER chart.
• Between 6.3 mm and 12.7 mm, use the 12.7 mm (1/2 inch) WATER chart.

13. TAKEOFF CHARTS
Depending on the depth of slush, we will use a different chart for takeoff
performance calculations:
• Under 2 mm of slush, use the WET RUNWAY correction.
• Between 2 mm and 6.3 mm, use the 6.3 mm (1/4 inch) SLUSH chart.
• Between 6.3 mm and 12.7 mm, use the 12.7 mm (1/2 inch) SLUSH chart.
For compacted snow, a special chart is provided (COMPACTED SNOW).

14. TAKEOFF CHARTS
Equivalent of wet runway is runway covered with less than:
• 2 mm (0.08 inch) slush
• 3 mm (0.12 inch) standing water
• 4 mm (0.16 inch) wet snow
• 15 mm (0.59 inch) dry snow

15. TAKEOFF CHARTS
We have to main targets:
1. Determine PTOW.
2. Determine V1, VR and V2.
 Remember that flexible takeoff is not allowed when taking off from a
contaminated runway.
In most aircraft, thrust reverse, anti-skid system and ground spoilers
must be operative in order to takeoff from a contaminated runway. For
a wet runway, reverse thrust is not required.
 Since runway contamination will affect braking much more than
acceleration, the ASD will increase much more than the TOD as well.
As a result, takeoff speeds will be lower than those for a dry runway.

16. TAKEOFF CHARTS
How to calculate PTOW:
1. Calculate the PTOW for dry runway (for each configuration), and
correct it by QNH and bleed.
2. Determine the weight penalty on the appropriate chart for each
configuration.
3. Apply corrections to the PTOWs calculated on (1) and choose the
configuration that gives the highest PTOW.

17. TAKEOFF CHARTS
How to calculate takeoff speeds:
1. With the configuration and ATOW, use the appropriate chart to find
takeoff speeds.

18. EXAMPLE
Let’s calculate PTOW and takeoff speeds with this conditions:
• LFPO Runway 08
• TORA: 3320 m
• Runway covered with 7 mm slush
• PTOW (dry): 72000 Kg (CONF 1+F)
71100 Kg (CONF 2)
71200 Kg (CONF 3)
We will use the 12.7
mm slush chart

19. EXAMPLE

20. EXAMPLE

22. EXAMPLE
V1 = 124 ; VR = 133 ; V2 = 133