Approach procedure

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Approach procedures refer to the possible variants of a landing approach to an airfield .

When visual flight serving as a landing approach traffic pattern .

When instrument flight following a distinction instrument approach procedures (IAP):

Non-precision approach (NPA) procedure
Non-precision approach procedures, instrument approach procedures in which lateral but no vertical guidance is available (e.g. VOR / DME approach, NDB / DME approach)
Approach procedure with vertical guidance (APV)
Instrument approach procedures with lateral and vertical guidance
Precision approach (PA) procedure
Precision approach procedures , instrument approach procedures with lateral and vertical precision guidance ( e.g. ILS , MLS )

The Ground Controlled Approach is a ground- based blind landing procedure .

Legal subdivision of the standard approach procedures

The legal subdivision is necessary for liability reasons and for the flight accident investigation in the event of an aircraft accident :

At the beginning of the initial approach , the pilot controls a radio beacon , usually indicated on his map, at the minimum initial approach altitude , which he uses to orientate the planned approach. The initial approach is by reaching the intermediate approach point (Engl. Intermediate approach fix ergo DH) in the intermediate approach (Engl. Intermediate approach ) over. In the so-called intermediate approach , either a holding pattern is flown or the traffic pattern to prepare for the final approach is started. The landing approach is finished when the taxiing is finished. The aircraft is then on the apron , from where it rolls either to the parking position or to a workshop. The following procedures are used for the entire approach:

Radio beacon

There are different types of radio beacons , directional and omnidirectional, overview:

NDB approach

Non-directional radio beacons are used as route and approach beacons on airfields. By the non-directional beacon (engl. N on- D irectional B eacon - NDB) radiated radio waves are received in the aircraft and in the ADF device shown (radio compass). The NDB transmitters are designed as double systems with one monitor. NDBs are also used for landing approaches and often at the position of the outer marker in the instrument landing system .


VOR transmitter (. From English V HF O mnidirectional R adio Range) give only the bearing line; With DME stations (from D istance M easuring E quipment) the associated distance is determined and displayed in the cockpit on a display device.


TACAN (Tactical Air Navigation) is a military rotary radio beacon and works similarly to a VOR, but is more precise by a factor of 1.2 to 2. In addition, the DME functionality is always integrated in the TACAN signal. TACAN transmits in the UHF range (962 to 1213 MHz). If the VOR and TACAN ground station are in the same place, the combination is referred to as VORTAC. To a civil aircraft, a TACAN ground station appears like a DME ground station and a VORTAC ground station appears like a VOR / DME ground station.


A VORTAC navigation system is used in the same way as a VOR / DME . In relation to a VORTAC station, pilots can measure or preselect a course line ( “radial” ) which indicates the angle between the magnetic north pole at the location of the navigation system and the current position of the aircraft. This means that the pilot knows his position line. The DME receiver also measures the distance to the navigation system. By combining the radial and the distance to the transmitter, you can then determine the exact position of the aircraft during the flight.

Different approach procedures

Standard approach

Approaching a lighted runway

With the standard approach procedure, the final landing configuration is adopted relatively early. The configuration here means the position of the landing gear and landing flaps.

Even before the descent is initiated, the landing flaps are started to extend to increase lift . At the latest 18.5 km (10  NM ) and 914 m (3,000 ft above the threshold) before landing, the descent is initiated, during which the speed is further reduced and the landing gear is extended. The final configuration for the final phase of the approach is reached at an altitude of 400 m (1300 ft). This procedure is the easiest approach procedure for the pilots, but it is also the most noise and pollutant- intensive procedure.

Low drag / low power approach

With this approach procedure, which places higher demands on the pilots, the landing flaps are only extended about 22.2 km (12 NM) before landing. As with the standard approach, the descent begins at 17.6 km (9.5 NM). However, the landing gear is only extended at less than 9.26 km (5 NM), and only then does the braking decelerate.

Since the engine power is reset in order to carry out the descent at constant speed, noise and kerosene consumption are reduced at the same time. However, anyone who speaks of an approach in “clean configuration” refers to the condition of the aircraft with the slats / flaps not extended and the landing gear retracted and not to the lower fuel consumption.

Continuous Descent Approach - CDA

Schematic representation of a CDA (green) compared to a normal approach (red).

This gliding approach procedure includes a continuous descent with horizontal segments of max. 4.6 km (2.5 NM), which enables a reduced engine power. The descent begins here already 37 km (20 NM) before landing at about 1.5 km (5000 ft) altitude. The flaps are extended 20.3 km (11 NM) before landing at about 1 km (3300 ft), higher than in the previous procedures. At an altitude of 914 m (3000 ft) the engine power (and with it the fuel consumption , the CO 2 emissions and the aircraft noise ) is reduced and the descent is continued at a constant speed. About 9.26 km (5 NM) before the touchdown point, the landing gear is extended and the speed is reduced. The final configuration setting is then completed at 5.5 km (3 NM) prior to landing at an altitude of approximately 305 m (1000 ft). According to the German Air Traffic Control , this procedure is usually only used at night when there is less traffic or on secondary routes where there is no time window ( slot ) at the destination airport. And only in connection with the instrument landing system (ILS) all-weather flight operating level CAT I.

The CDA has been tested at Brussels-Zaventem Airport since July 2009 and is already being implemented at night at most German airports such as Cologne / Bonn.

Ideally, the destination airfield is approached directly after the cruise in an uninterrupted gliding flight (engines almost idling). Thanks to almost optimal flight paths, there are no holding patterns.

According to the voluntary organization “Our Airspace”, the FAA has renamed the procedure “Optimized Profile Descent” because CDA was burdened with negative experiences with noise and safety.

Two segment approach

Characteristic for this approach procedure is the late start of the descent, about 11.1 km (6 NM) before landing. Then a “steep” descent begins at 6 ° to an altitude of 305 m (1000 ft), after which the glide angle is changed back to 3 ° and the final configuration is set and stabilized. At the beginning of the descent, the landing gear is also extended, while the landing flaps were extended considerably earlier. The engine is left idling. The high sink rates pose a risk, as there are fewer safety reserves. The pilots are challenged accordingly. In addition, a lower rate of descent represents greater comfort for the passengers. The advantage of this method is the lower level of noise pollution , since the aircraft flies longer at a higher altitude.

Delayed flap approach

Steep approach of a C-160 Transall of the Air Force, BIAF Airshow 2011, Plovdiv , Bulgaria.

The procedure is initially carried out in a manner similar to the Continuous Descent Approach with a continuous descent, which also begins at 1500 m (5000 ft) altitude. However, from an altitude of 914 m (3000 ft), the engine power is put into idle, 14.8 km (8 NM) before touchdown the flaps are extended. The final configuration is only established at a height of only 152 m (500 ft). The lower noise emissions are offset by a significantly greater safety risk due to the late reaching of the final configuration and stable flight status.

Combat approach

This combat approach procedure , also called Sarajevo Approach , describes a steep landing approach from a great height. This method, in which the aircraft with the engines idling (in some special cases, such as the C-17 also with downward thrust deflection.) And fully extended landing and airbrakes, quickly sinks from a great height, takes its name from the Bosnian War , in which the besieged Sarajevo was supplied by international troops by airlift . This approach procedure has been established to stay out of the range of handguns for as long as possible. In addition, this ensures the maneuverability that is required in order to avoid approaching missiles.

The Sarajevo Approach reaches rates of descent of more than 30.5 m / s (6000 ft / min). During the approach, the flaps are extended to 40 ° or 60 °. So they not only generate buoyancy, but also a lot of drag.

Approach speeds

It is divided into 5 different approach categories:

  • Category A: less than 168.5 km / h (91  knots )
  • Category B: 168.5–223 km / h (91–120 knots)
  • Category C: 223–260 km / h (121–140 knots)
  • Category D: 260–306 km / h (141–165 knots)
  • Category E: 306 km / h (166 knots) and more (unofficial, only in the FAA area)

The approach speed is defined according to PANS-OPS (Doc 8168, Volume I) as follows: Speed ​​at threshold based on 1.3 times stall speed in the landing configuration at maximum certified landing mass.


  • Procedures for Air Navigation Services - Aircraft Operations . Doc 8168 OPS / 611 ("PANS OPS"). In: ICAO (Ed.): International Standards and Recommended Practices . 5th edition. Volume I: Flight Procedures, 2006 ( Online [PDF; 1.6 MB ]).

Individual evidence

  1. ^ ICAO: Procedures for Air Navigation Services , pp. I-1-1-1-3
  2. The 'Continuous Descent Approach' procedure in test phase at Brussels Airport ( Memento of the original from July 1, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot /
  3. Tagesanzeiger: How airplanes land in a climate-friendly way
  5. ↑ Flight demonstration by the Air Force at the ILA 2008: Rescuing quickly from danger
  6. GlobalSecurity: C-17 Globemaster III. Retrieved January 4, 2010 .
  7. ^ Combat approach on Sarajevo . In: Der Spiegel . No. 38 , 1992 ( online article on operating conditions for aid flights in Bosnia).