Frangible obstacles

Coding guidelines

Some specific obstacles, such as an ILS glide path antenna, may be located in the close vicinity of a runway due to operational needs, on condition that they have the lowest possible physical strength.

A dedicated attribute (VerticalStructurePart.frangible) allows coding the information that the obstacle is 'frangible', which is an operationally significant data element. This attribute is at the level of the obstacle part. For multi-part obstacles, it is quite common that only some parts are considered frangible, For example, an antenna on top of a building could be considered a frangible element, while the building is not. This information can be useful only if the elevation of both frangible and non-frangible parts is provided, so that the data user can decide which one is used in calculations, depending on their rules and practices.

According to ICAO Annex 14, information about frangibility of the obstacle needs to be provided only for obstacles situated in the vicinity of the runways, in particular for obstacles in the Clearway (CWY) and the Runway End Safety Area (RESA).

Coding example

Navaid as Obstacle (frangible)

Example 3: Glidepath

<!-- NAVAID OBSTACLE. Area 2a RWY 09L/27R and Area 3 (Glidepath) -->
	<message:hasMember>
		<aixm:VerticalStructure gml:id="uuid.c9bc6ea4-2b5e-4a71-af8a-eec2e4ff3dc3">
			<gml:identifier codeSpace="urn:uuid:">c9bc6ea4-2b5e-4a71-af8a-eec2e4ff3dc3</gml:identifier>
			...
					<aixm:name>OBS-EADD-1005 (GP 27R)</aixm:name>
					<aixm:type>NAVAID</aixm:type>
					...
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="vsp00013-1">
							<aixm:verticalExtent uom="M">5.0</aixm:verticalExtent>
							<aixm:verticalExtentAccuracy uom="M">0.5</aixm:verticalExtentAccuracy>
							<aixm:type>NAVAID</aixm:type>
							<aixm:frangible>YES</aixm:frangible>
							<aixm:horizontalProjection_location>
								<aixm:ElevatedPoint srsName="urn:ogc:def:crs:EPSG::4326" gml:id="ep00013-1">
									<gml:pos>52.378444 -31.926778</gml:pos>
									<aixm:horizontalAccuracy uom="M">0.5</aixm:horizontalAccuracy>
									<aixm:elevation uom="M">35.0</aixm:elevation>
									<aixm:verticalDatum>EGM_96</aixm:verticalDatum>
									<aixm:verticalAccuracy uom="M">0.5</aixm:verticalAccuracy>
								</aixm:ElevatedPoint>
							</aixm:horizontalProjection_location>
							<aixm:lighting>
								<aixm:LightElement gml:id="le00013-1">
									<aixm:colour>RED</aixm:colour>
								</aixm:LightElement>
							</aixm:lighting>
						</aixm:VerticalStructurePart>
					</aixm:part>
					<aixm:hostedNavaidEquipment xlink:href="urn:uuid:4c46c5be-b033-4673-ac70-48a5d72793d2" xlink:title="Glidepath 27R"/>
				</aixm:VerticalStructureTimeSlice>
			</aixm:timeSlice>
		</aixm:VerticalStructure>