Displaced threshold

A landing threshold, (english threshold, THR) usually marks the beginning of the runway at an airfield. It is marked with white paint as boxes. At night, the landing threshold is particularly illuminated (fired ).

Displaced threshold

As a rule, the landing threshold at the beginning of the concrete surface of the airstrip. However, there are runways with a displaced threshold (english displaced threshold). A landing aircraft produced a particularly high pressure on the runway, which must be also designed for landing. From obstacle surfaces ( approach surface is penetrated by obstacles to aviation ) is shifted the threshold inward. That's the only reason for a displaced threshold. Displaced thresholds are seen particularly well on the outside fire chain (green lighting).

For the start of the aircraft can then also use the portion of the web ahead of the runway threshold. A landing threshold is only relevant for the landing, but not for the launch. However, only the portion of the web may be used behind the runway threshold for landing.