Separation (aeronautics)

Graduation, even separation (English: separation, traffic resolution), is a method of air traffic control. It means the line or pilotage of aircraft with the aim of creating a safe distance between each aircraft. The graduation is performed by located at the base air traffic control units or the pilots themselves.

ICAO minimum separation distances

The minimum separation distances are related to the different weight or wake turbulence categories of aircraft. This is necessary because at higher angles of attack aircraft generate vortices that can threaten a following aircraft ( turbulence ), especially when the preceding aircraft flying is relatively much larger. Subsequently, the following aircraft weight categories are used:

• L → light → to 7 tonnes MTOW
• M → medium → about 7 tons to less than 136 tonnes MTOW
• H → heavy → 136 tonnes MTOW and heavier
• J → → super currently only Airbus A380

The following term aircraft refers to all aircraft - thus also on airships, helicopters, paragliders, etc.

Radar separation

In general, radar air traffic controllers are responsible for the actions of the pilots with instructions by radio. The pilots are assigned to courses and altitudes. We also speak of radar separation, because the assessment will be based on radar data.

Not every plane is staggered by air traffic controllers. This depends on whether the aircraft is in a controlled or uncontrolled airspace and whether the flight by instrument flight rules ( IFR) or visual flight rules ( VFR) is performed ( cf. airspace structure ).

The radar separation must be at least 2.5 NM ( nautical mile or sea mile ) amount on final approach - otherwise 3 NM. Prerequisite for this is that a heavier category flies in front of a lighter. So Allows the approach sequence: LL, MM, LM, LH, MH. In heavy behind heavy (HH), a distance of 4 NM must be adhered to.

General, the following values ​​for radar separation between two aircraft are in Germany and Austria:

• The distance in the same amount is 3 NM near the airport and 5 NM on the route ( Lateralstaffelung ) large.
• The level spacing is generally 1000 ft. It is from flight level 290 to 2000 ft. increased ( vertical differentiation ). From the 2000 ft. grading at higher altitudes distance is increasing thanks to improved technology and for better utilization of the congested air space again taken (Reduced Vertical Separation Minimum).

Vortices graduation

Since vortices are mainly dependent on the mass of the airplane, this means for the pilots that they must adhere to an increased distance when a heavy aircraft herfliegt in front of a light. So between a jumbo and a Cessna 172 Keep a minimum distance of at least 6 NM, during approximately the same aircraft should comply only 3 NM distance.

Two aircraft of the heavy weight category (HH) must maintain a minimum distance of 4 NM because of wake turbulence.

• Light behind medium → 5 NM (M -L)
• Medium behind heavy → 5 NM (H -M)
• Light behind heavy → 6 NM (H -L)

Personal responsibility for Graduation

• Pilots operating under VFR rules, depending on the airspace in have an obligation to ensure their own graduation. In a controlled VFR staggering optionally restored by the air traffic control unit. This tends to happen when VFR flyer located in areas where aircraft under IFR rules can be on the road, such as arrival and departure areas of airports.

• The air traffic controller can transmit the staggering commitment to the aircraft commander (pilot ) during a flight under IFR rules when it agrees. Before the responsibility for Graduation ( delegation of separation ) it is passed, is determined in advance by the air traffic control unit if the pilot can see the other aircraft. The pilot may then during the day time ( locally defined by meteorological services ) fall below the minimum distance at your own risk ( between sunrise and sunset) and on a clear day, bringing the number of the airspace at the same time (control zone of the airport, airway, etc.) located aircraft can be increased. It can be observed in the control zones of large commercial airports this during peak times.

• A fictional, but quite possible scenario as a responsible handover of the scale in the air traffic control unit ( FVKSt. ) to the pilots could be played by radio about so that abbreviations are pronounced as follows:

• AUA540 is an Austrian Airlines flight pronounced: Austrian Five Four Zero

The ... FVKSt is a traffic information and asks for visual contact ...

• FVKSt: AUA540, traffic, Airbus 380, one o'clock, one zero miles, crossing right to left, one thousand feet above, fast moving, report traffic in sight.

... The pilot confirms the receipt of the call ...

• Pilot: AUA540, looking out.

If ... the pilot sighted the Airbus, he calls ...

• Pilot: AUA540, traffic in sight.
• If the pilot does not sifts through the traffic, updates the FVKSt. after a certain time the message on the circulation:
• FVKSt: AUA540, Mentioned traffic, twelve o'clock, five miles.

The ... FVKSt. asks whether a delegation is possible ...

• FVKSt: AUA540, are you able to maintain own separation to Mentioned traffic?

The pilot ... confirmed ...

• Pilot: AUA540, affirm.

The ... FVKSt. over responsibility to the pilot ...

• FVKSt: AUA540, maintain own separation.

Individual talk groups may optionally be combined to reduce the frequency of exposure.

Safety / problem

The vertical separation may be difficult to assess a pilot at oncoming aircraft, also there is very little time available. Line machines or jets flying at around 900 km / h, ie approximately 250 m / s toward each other (5 km are thus carried served by two in 10 seconds). The time of the sighting to a potential collision is thus in excellent visibility (50 km or more) only a few seconds and is reduced to zero in poor visibility. This is particularly extremely dangerous if

• The air space " is full " and graduations are reduced to a minimum,
• Other traffic is not known ( under IFR extremely unlikely)
• Other traffic can not, or only poorly recognized ( faulty or improperly adjusted Instruments - Transponder, faulty radar equipment, etc. ),
• Transport is believed to a different position than real ( false or incorrect information from pilots, incomplete or false positions of other pilots, etc.),
• Of being due to faulty board instruments or sensors at a different location than you really believe (for example: frozen inlets of the altimeter, GPS malfunction )
• Contradictory information is available, but this one, while acknowledging in a short time can not see what is right and wrong ( common cause ),

And it thus weighs under circumstances in false security. Pilots operating under IFR rules, rely mainly on their instruments and the air traffic control centers. You therefore do not last permanently in the airspace out for other aircraft. This is often not possible and also not effective in poor visibility conditions ( at night, in clouds ), since the monitoring of the instruments under IFR priority. To avoid collision, therefore, also have all the lines and transport aircraft ( at least if approved in Europe or the U.S.) a TCAS, a collision warning and Vermeidungsssystem on board. The TCAS operates completely independently of ground stations and evaluates the transponder signals from other aircraft of possible dangers from. It suggests appropriate, alert, calculated a possible evasive action and suggests that the pilot before.

VFR pilots must keep a rule always on the lookout for other aircraft. Since VFR pilots are usually traveling with airplanes that reach a relatively low cruising speed unlike jets, also gives more time for detection and collision avoidance in accordance with the prescribed way rules.

The following circumstances make it difficult to apprehension (views ) and increase the risk of collision as a visual merge with the background done:

• Weather phenomena,
• Flights beside, above and below clouds,
• Flights from the sun,
• Transition effects or reflections of clouds, layers of air and ground events (lakes, water, wilderness ),
• Heavily textured terrain (cities, dense residential areas, etc.)
• Flights in mountainous terrain at the same or lower level of the surrounding peaks levels,
• Aircraft with camouflage paint (military ) and
• Unusual (not turned on ) position lights and strobes.

In an aircraft that comes flying towards the pilot, can also be difficult to assess whether it ft at the same altitude, and thus on a collision course, or completely safe 1000 ( about 300 m ) counter is lower or higher. As a general rule, that an airplane that appears in height of the horizon line, flying at the same altitude as the own aircraft.

Under difficult flight conditions and assuming potential external traffic in the sky you can make attention to itself using the following methods:

• Compliance with general / all rules under VFR and IFR
• Compliance with local air traffic restrictions and rules
• Use of a transponder with altitude encoding
• Rather bright colors / paint on the plane top and dark on the bottom ( contrast to the surroundings )
• Use and monitoring of TCAS

• Observation of airspace (95 % of the time, 5% and navigation instruments - under VFR)
• Increased attention in zones of high activity ( gliders and paragliders areas, airfields, etc. )
• Turn on the landing lights ( and any other lights )
• Attempt to contact, best on the frequency of the air traffic control unit or the nearest airfield and position report
• Serpentine flight ( an object that flies wide wavy lines, is easier to recognize than a rigid straight flying ) or an orientation curve (360 ° ) or short tilting and rotating, so that even blind spots ( below or above the plane ) can be viewed.
• Avoidance of flights at low altitude ( lifting from the landscape / structure)

Consequences of inadequate grading

If the graduation is not observed, it was due to pilot or pilot errors, the consequences of near - collisions can range up to the clash, even if other security systems such as TCAS should prevent this.

Are usually collisions in the air for everyone involved usually be deadly ( except usually only possible for aircraft with parachute / ejection seat )

• The worst air crash over Germany is the collision under IFR rules of a Russian passenger aircraft of type Tupolev Tu -154 cargo plane and a DHL Boeing 757 totaling 11 000 m above Lake Constance near Überlingen on 1 July 2002; see Bashkirian Airlines Flight 2937, although both machines TCAS had on board.
• Collision under VFR-Bedingungen/Regeln a helicopter (Super Puma) and a small aircraft ( katana ) in Zell am See in Austria.
• Head-on collision under IFR rules of two passenger planes in Zagreb, Croatia ... ( Chronicle of aviation disasters 1976)
• The collision of a Brazilian Boeing 737 and an Embraer Legacy 600 about the rain forests of Brazil. All occupants of the Embraer have survived the disaster.

Swell