Semicircle flight rule

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Schematic representation of the semicircular flight altitude rule

The semicircular flight control (engl. Semicircular rule ) is a method selected from the aviation . The semicircle flight rule states that an aircraft must fly at a certain altitude depending on the magnetic course flown (over the ground) . The semicircle flight rule regulates the vertical separation between the aircraft. This is an added moment of safety for pilots at today's high airspeeds.

principle

According to the semicircle flight rule, an aircraft must maintain certain flight altitudes , which result from its magnetic course (over ground) (MC). A distinction must be made between IFR ( instrument flight ) and VFR ( visual flight ).

  • In the case of a magnetic course (MC: Magnetic Course) from 0 ° to 179 °, the flight altitudes for IFR pilots that correspond to "odd thousands" apply: FL 50/70/90 and so on, corresponding to 5,000 / 7,000 / 9,000 ft based on normal pressure. VFR pilots fly another 500 ft higher, ie FL 55/75/95 etc. Reminder: O st = o dd (English for "odd").
  • In the case of a magnetic course (MC: Magnetic Course) of 180 ° to 359 °, the altitudes for IFR pilots that correspond to "even thousands" apply: FL 60/80/100 and so on, corresponding to 6,000 / 8,000 / 10,000 ft based on normal pressure. VFR pilots also fly here 500 ft higher, i.e. FL 65/85/105 etc.

In Germany, this rule is linked to the transition height, i.e. H. Here the flight height can be freely selected below the transition height. In other countries transition height and height for the semicircle flight rule are independent, e.g. B. North America has a transition altitude of 18,000 feet, while the semi-circular flight rule applies at 3000 feet AGL.

advantages

Drawing of the semicircle flight rule
  • Example 1: On course 010, oncoming traffic can only be expected from the front and left (front left to rear left). The semicircle flight rules therefore reduce oncoming traffic, as the majority of the aircraft are flying in the same or a similar direction (maximum 180 ° course deviation from one another). In this way, the pilots can concentrate their airspace observation on 180 ° of the airspace without completely losing sight of the rest of the airspace.
  • Example 2: On course 090, other aircraft can only be expected from the rear right and left quadrants. The pilot only has to watch out for aircraft coming directly from the right or left. He can't see planes coming from behind anyway. They have to avoid him. Of course, on the example course 090, the aircraft can approach slower flying aircraft from behind, so the airspace in front must also be observed. However, one approaches these aircraft at a significantly lower relative speed than with direct oncoming traffic.

Even without ATC control, direct observation of the airspace, as shown in the examples above, appears anachronistic for jets with their high flight speeds. This is why commercial aircraft of a certain size also have a collision warning device ( TCAS ) that supplements direct observation.

Exceptions

This procedure can only be a rationale, other collision avoidance rules and procedures that may be used take precedence.

  • IFR traffic within controlled airspace does not have to adhere to the semicircular altitude as it is assigned its altitude by air traffic control (ATC). Air traffic control has the entire area around the aircraft on its radar. However, the aircraft are usually handed over to the neighboring sector conforming to semicircular flight altitudes.
  • The semicircular flight rules cannot be adhered to when climbing or descending . When flying straight ahead, the pilot must therefore expect planes descending or climbing from all possible directions.
  • From flight level 290, aircraft must be equipped with RVSM equipment in order to continue to be staggered at 1000 ft intervals. Otherwise, a minimum distance of 2000 ft is staggered. From flight level 410, due to the decreasing radar accuracy, only the 2000 ft graduation applies; flight levels in particular are then no longer applicable. That leaves FL 430 (westward direction), FL 450 (eastward direction), FL 470 (westward direction) etc.

special cases

Quadrant flight rules applied in Great Britain until April 2015 .

literature

  • Jeppesen Sanderson: Private Pilot Study Guide , 2000, ISBN 0-88487-265-3 .
  • Jeppesen Sanderson: Private Pilot Manual . 2001, ISBN 0-88487-238-6 .
  • Walter Air: CVFR textbook . Mariensiel 1994.
  • Wolfgang Kühr: The private pilot. Volume 5: Aviation Law, Air Traffic and Air Traffic Control Regulations (PPLA-C) . 1983, ISBN 3-921270-13-8 .

Individual evidence

  1. SERA - all you need to know