Top of Descent

The Top of Descent (TOD or T / D; literally: highest point of the descent, or: Starting point of the descent ) is in aviation, the point is passed to the of the flight phase of cruise flight to descend.

At this point, the planned descent to approach altitude ( engl. approach altitude ) must start.

The Top of Descent is mostly from the Flight Management System (on-board computer ) calculated on the navigation screen (English navigation display) is displayed. The type of display on the navigation screen is not standardized, the TOD is displayed, for example as a green arc. The Top of Descent is calculated so that it allows the most economical descent to approach altitude. Sometimes the Top of Descent, however, is not optimized on cost, but on other criteria towards, for example, the fastest descent or longest range.

The Top of Descent can also be calculated manually by the pilot, but this requires considerable effort.

Since a jet aircraft at high altitude significantly less fuel consumed than at low altitude, it is to stay on the cruising altitude of the efforts of the pilots as long as possible. The aircraft must not remain on its cruising altitude over the top of descent addition, however, since it would then have to perform a very steep descent. Due to a steep descent, the aircraft would, however, be too fast, so it would possibly exceed the load limits of its structure. The increasing speed of descent can indeed be reduced by the deployment of spoilers; However, there is energy wasted, so that the aircraft is not flying energy efficient. Also the fly from additional loops or detours would allow a further height reduction, but would be very uneconomical. The most economical descent is performed with minimal fuel consumption, with the engines at flight idle ( engl. flight idle) are reduced. The top of descent is calculated and displayed by the Flight Management System. Is this not on the plane yet, it is an important responsibility of the pilot to calculate this point, or at least estimate.

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