Diamond DA 40 Flight Manual page 192

Performance
For a safe landing the landing distance available (LDA) should
be at least equal to the landing distance over a 50 ft (15 m)
obstacle.
The figures in the following NOTE are typical values. On wet
ground or wet soft grass covered runways the landing
distance may become significantly longer than stated below.
In any case the pilot must allow for the condition of the runway
to ensure a safe landing.
For landings on dry, short-cut grass covered runways, the
following corrections must be taken into account, compared
to paved runways (typical values, see CAUTION above):
- Grass up to 5 cm (2 in) long: 5 % increase in landing roll.
- Grass 5 to 10 cm (2 to 4 in) long: 15 % increase in landing
roll.
- Grass longer than 10 cm (4 in): at least 25 % increase in
landing roll.
On wet grass, a further 10 % increase in landing roll must be
expected.
A downhill slope of 2 % (2 m per 100 m or 2 ft per 100 ft)
results in an increase in the landing distance of approximately
10 %. The effect on the landing roll can be greater.
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CAUTION
CAUTION
Rev. 8 01-Dec-2010
NOTE
NOTE
NOTE
DA 40 AFM
Doc. # 6.01.01-E