Safety Altitude
The maximum elevation figure (Engl. Minimum sector altitude , MSA) indicates the pilot, in what altitude it can fly straight yet sure without (houses, towers, mountains ...) colliding with ground objects. In some publications the wrong translation "minimum safe altitude" can be found.
A safety distance of 1,000 ft is already taken into account, and 2,000 ft for higher terrain. For example, if the safety altitude on the flight map is specified as 1,500 ft, the elevations in this area are no more than 500 ft high.
The safety altitude is given in relation to the ICAO standard atmosphere (barometric altitude measurement according to QNH ). The pilot must therefore take into account the local weather conditions and, if necessary, enter a correction value.
Flight card safety altitude
Safety altitudes may be indicated differently on the various flight cards . This is explained in the legend of the respective card. The safety altitude is given on the one hand for the entire map and on the other hand for the airways .
Example: The highest elevation on the entire map is 5,310 ft (e.g. mountain at 1750 m above sea level). With a safety margin of 1,000 ft, the safety altitude for the entire area shown would be 6,310 ft. It is rounded to the nearest safe hundred. So the front of the card says: MSA 6,400. The highest elevation is highlighted in the map itself with a thick frame. On other flight maps, the highest elevation is highlighted by a particularly thick arrow that points to the number for the highest elevation on the map.
The flight map is divided into individual grid squares. For each of these rectangles, a safe altitude is indicated with a pale blue number in the upper left corner or some other similar form. Here, for example, means what is known as an MGA ( minimum grid altitude ) of 4,500 ft.
Caution:
In the ICAO map 1: 500,000 the numbers = 4,500 feet do not stand for the MGA, but for the MEF ( maximum elevation figure ). The MEF is calculated from the height of the highest elevation in feet (ft) AMSL measured in the area of a rectangle drawn on the aeronautical map with an edge length of 30 minutes each ( lengths - as latitude minutes ), plus 328 ft (100 m) surcharge for elevations Any obstacles (trees, buildings) and an additional 30 ft safety reserve, thus a total surcharge of 358 ft; this is added to the height, then rounded up to a full hundred feet. In the case of artificial obstacles (which have an exact height), there is no extra surcharge, but a 60 ft safety reserve is added to the height. Here, too, it is rounded up to a full hundred feet. The maximum elevation figure can be less than the smallest permissible minimum safety height according to § 6 LuftVO of 500 ft.
Airway safety altitude
MTCA ( minimum terrain clearance altitude ) is specified for each airway .
Airfield MSA
For landings at airfields , the MSA is indicated on the approach charts. A radio beacon in the immediate vicinity of the field or the airport reference point is taken as the center of a circle with a radius of 25 NM . In this circle, different sectors are determined with the help of the radio guidance beams ( radial ), for which the different safety flight altitudes are specified.
Example: MSA at Los Angeles International Airport Safety altitude within 25 NM of the VOR (radio beacon) with the identifier "LAX", which is located directly at the airport. There are three different sectors of different safety altitudes. The sectors are divided by radio beams emitted by the VOR ( radial ). Aircraft in the northern sector (regardless of whether they are approaching, departing or passing) must maintain a safe altitude of 7,700 ft, because that is the mountain range on which the famous Hollywood sign is located. Aircraft in the southeast sector must maintain a minimum altitude of 2,700 ft because of some very small mountains. Aircraft in the southwest sector must maintain 4,400 ft, as the sector in the north reaches as far as the Santa Monica Mountains .