Final approach

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An A330 on final approach to Zurich Airport
A P-3C Orion on final approach at Nordholz Air Base

With final approach (ger .: Final Approach ) is in the aviation of the last part landing approach called.

It begins when the aircraft is in the final approach area at the interface between the final approach altitude and the final approach level of the decision altitude.

At uncontrolled airports is absolutely a traffic pattern upstream.

The end of the final approach is usually the beginning of the landing , alternatively a missed approach .

Occasionally the flight route, e.g. B. under adverse weather conditions (black ice, fog, thunderstorms) above the destination airport, can be changed to an alternate airport .

Procedure of the final approach

Final approach for flights according to visual flight rules (VFR)

A traffic pattern is flown during visual flight . Approach and descent speeds are usually coordinated with one another in such a way that the descent in commercial aircraft is carried out at a three-degree angle to the horizontal. In visual flight, the final approach is the part of the traffic pattern that is flown directly to the runway in the landing direction. The cross approach precedes it.

Final approach for the precision instrument approach (ILS approach)

The instrument landing system of the destination airport is used for this. At ILS, the start of the final segment is the FAP (Final Approach Point). Depending on the ILS category (CAT) of the airport, the segment ends at a decision height greater than / equal to 200 feet (CAT I), 100 to less than 200 feet (CAT II) and less than 100 feet (CAT III) above the threshold height of the runway . According to ICAO, the glide angle for ILS approaches must be kept between 2.5 ° and 3.5 ° for CAT I and absolutely 3 ° for CAT II / III.

The resulting rate of descent depends on the aircraft's own speed and can be roughly calculated using the following rule of thumb:

V GS ground speed in knots * 5 = rate of descent in feet per minute

The final approach segment ends with the start of the landing or the abortion of the landing approach ( missed approach ) if the crew cannot clearly identify the runway when reaching the decision height or if there is another problem.

Final approach of aircraft at military airfields

An aircraft is taken over from the precision approach radar by an air traffic controller and verbally guided to the decision height (200ft GND - above Touch Down Zone Elevation). At this point, the pilot must have the runway in sight to visually end the approach. If this is not the case, a missed approach procedure , previously determined by the controller, must be initiated.

Risks on the final approach

Suddenly occurring turbulence in the approach sector is capable of bringing an aircraft on approach into an unstable approach and pressing it roughly onto the runway, which in extreme cases can damage the aircraft and injure people. There is also the risk of being caught by wind shear , which also represents a landing hazard.

Termination of the approach

  • Compelling reasons for an abort: insufficient visibility at the decision height, persistent wind shear detected, unstable approach, blocked runway;
  • Possible consequences of a canceled approach (delay, evasion to the alternate airport, uncertainty among passengers, higher demands on the pilots / controllers, etc., higher kerosene consumption).

Final approach in gliding

ASK 21 on final approach

In gliding , especially in long-distance gliding , the term final approach has an even more meaning. The final approach is the last straight gliding flight without further updraft before reaching the traffic area of the destination airfield. With him it is true that altitude before achieved performance optimized to consume. The basis for this is the speed polar or the glide ratio of the respective glider. When gliding, the last curve should be finished at a height of at least 100 meters above the current altitude. The final approach is started with a safety reserve (altitude and speed). A high-performance final approach is often started below the required altitude, since by choosing a skilful flight path it is possible to fly more through ascending than descending air masses and thus the required altitude is flown in the final approach in straight flight. Only if the exit from the final approach updraft coincides with the end of the convection, a safety reserve will also be cranked up for the final approach with optimal performance.

For competition pilots it is of great importance to calculate exactly or to have a final approach calculator calculate from what height it can reach the destination. Once a sufficient height has been reached, time-consuming circling in the updraft can be dispensed with. This increases the average speed and the chances of victory.

See also

Web links