descent

Exemplary display of the artificial horizon when descending with a left turn

The descent is a flight maneuver of an aircraft to reduce the flight altitude (e.g. during a landing approach ).

The rate of descent, i.e. the vertical speed in descent, is given in feet per minute (fpm) or in meters per second (m / s) and measured with the variometer . 1 m / s corresponds to about 196.85 fpm.

Formulas

Landing approach

Rules of thumb for calculating the altitude or the distance for a standard 3 ° descent path (E = 1:19) for the landing approach:

• Flight altitude (in ft ) = distance (in NM ) * 1000/3 (1 ft = 30.48 cm; 1 NM = 1852 m)
• Distance (in NM) = altitude (in ft) * 3/1000

Rate of descent while gliding

The rate of descent or rate of descent in m / s of non-powered aircraft is calculated using the following formula:

${\displaystyle \textstyle v_{s}=c_{w}\cdot {\sqrt {\frac {2\cdot g\cdot G}{\rho \cdot A\cdot c_{a}^{3}}}}}$

${\displaystyle v_{s}}$ = Rate of descent in m / s

${\displaystyle G}$ = Aircraft mass in kg

${\displaystyle c_{w}}$= Drag coefficient of the aircraft

${\displaystyle g}$= Acceleration due to gravity in m / s ² (~ 9.8)

${\displaystyle \rho }$= Air density in kg / m³

${\displaystyle c_{a}}$= Lift coefficient for minimal sinking

${\displaystyle A}$= Wing area in m²

Special forms of descent

Boeing 777 on approach for landing, flaps fully extended

A special case of descent is the dive of fighter aircraft , in which the aircraft is steered steeply downwards.

For a few seconds the parabolic flight is also a steep descent.

In the case of balloons, parachutes and the like, one does not speak of a descent, but simply of "sinking".

The so-called emergency descent is a special form of descent in air traffic. It is carried out when it is impossible to remain at a great height (e.g. loss of pressure in the cabin ). Various measures such as setting the engines to idle and extending the spoilers , landing flaps , air brakes and the landing gear - depending on various factors such as the type of aircraft and the current altitude - achieve sink rates of around 5,000 feet (approx. 1,500 m) per minute and more.

See also

• glide
• Controlled flight into terrain

literature

• Niels Klußmann, Arnim Malik: Aviation Lexicon. Springer Verlag, Berlin Heidelberg. ISBN 978-3-540-49095-1 .
• US Department of Transportation - Federal Aviation Administration - Flight Standards Service, FAA-H-8083-15A "Instrument Flying Handbook 2008".

Web links

Wiktionary: Descent  - explanations of meanings, word origins, synonyms, translations