For TLOF, PANS-AIM requires some basic properties as part of the minimum AIP data set. These are
designator, centre point, length, width, surface type
The diagram below shows the AIXM classes, including the relevant data types, needed to encode that information:
TLOF designator
The TouchDownLiftOff.designator attribute represents the textual designator of the TLOF, used to distinguish physical TLOFs at an Aerodrome/Heliport that has more than one. The attribute value should reflect the local convention for physical TLOF naming at the Aerodrome/Heliport.
Sample TLOF designator values could be: HELIPAD-A, HELIPAD-B; TLOF1, TLOF2; etc.
If there is just one TLOF, the designator can be just "TLOF".
TLOF Centre Point (aimingPoint)
AIXM 5.1(.1)
In AIXM, only the aiming point of a TLOF can be coded. Is the aiming point the same as the centre point of a TLOF?
According to ICAO Annex 14, Volume II,
The geographical coordinates of the geometric centre of the TLOF and/or of each threshold of the FATO (where appropriate) shall be measured and reported to the aeronautical information services authority
...
An aiming point marking should be provided at a heliport where it is necessary for a pilot to make an approach to a particular point before proceeding to the TLOF.
The aiming point marking shall be located within the FATO.
This definitions give the impression that the aiming point is not the centre point of the TLOF. Currently in AIXM, it is not possible to define the two different points for a TLOF. Anyhow, it seems that the relationship hasAimingPoint and the property TLOF.aimingPoint is not correct. It should be rather hasCentrePoint and TLOF.centrePoint. Also, an aiming point may be independent from a TLOF and may also be marked and lighted. It seems that currently aiming point is not covered by AIXM 5. The workaround is to code that information in a Note.
A workaround is to code the centre point of the TLOF using the ElevatedPoint class linked by the hasAimingPoint relationship.
In case an aiming point and a centre point shall be coded for the TLOF, the actual aiming point has to be coded as Note.
TLOF Dimension (length & width)
The TLOF dimension attributes are used to describe the physical dimension of a TLOF.
The TouchDownLiftOff.length is the declared longitudinal extent of the TLOF.
The TouchDownLiftOff.width is the declared transversal extent of the TLOF.
AIXM 5.1(.1) issue
As a workaround, the accuracy value for the length and width may be encoded as note for the corresponding property.
Open Question circle TLOF
Surface
For the TLOF, PANS-AIM requires to provide the surface type.
In AIXM 5, the SurfaceCharacteristics.composition attribute is used to code the surface type, e.g. asphalt, concrete, grass, etc.
The SurfaceCharacteristics class groups together more attributes that model the characteristics of an airport surface, such as strength, material, etc.
For detailed information about the surface characteristics attributes & corresponding rules please refer to the topic Surface Characteristic [SCH].
Coding Rules for Basic Data for TLOF
| Identifier | Data Encoding Rule | Justification | Data Verification Rule (UID) | Remarks |
|---|---|---|---|---|
| TLA-101 | The TouchDownLiftOff.designator attribute is mandatory. | Minimum AIP data set | TBD | |
| TLA-102 | The TouchDownLiftOff.aimingPoint attribute is mandatory. | Minimum AIP data set | TBD | The aimingPoint property is used to actually code the centre point, see also AIXM 5.1(.1) issue above. |
| TLA-103 | The TouchDownLiftOff.length attribute is mandatory. | Minimum AIP data set | TBD | |
| TLA-104 | The TouchDownLiftOff.width attribute is mandatory. | Minimum AIP data set | TBD | |
| TLA-105 | If a value for the TouchDownLiftOff.length attribute is provided a Note for the TouchDownLiftOff with propertyName equal-to 'length' shall be coded to provide the corresponding accuracy. | Minimum AIP data set | TBD | |
| TLA-106 | If a value for the TouchDownLiftOff.width attribute is provided a Note for the TouchDownLiftOff with propertyName equal-to 'width' shall be coded to provide the corresponding accuracy. | Minimum AIP data set | TBD | |
| TLA-107 | For TouchDownLiftOff the SurfaceCharacteristic.composition attribute is mandatory. | Minimum AIP data set | TBD | |
| TLA-108 | The position given by ElevatedPoint must be plausibly close (less than 20 KM) to that of the ARP of the related AirportHeliport. | EAD | TBD | |
| TLA-109 | ElevatedPoint.geoidUndulation may be specified only if ElevatedPoint.elevation has been specified. | EAD | TBD | |
| TLA-110 | The related Runway should be related to the same AirportHeliport as the TouchDownLiftOff. | EAD | TBD |
Coding Examples
TBD in the scope of the DONLON AIXM AIP data set.