Community Research and Development Information Service - CORDIS


SOURDINE I I Report Summary

Project ID: 11011
Funded under: FP5-GROWTH
Country: Spain

Improved modelling of continuous descent approaches in fast time simulators

Arrival Procedures in TAAM are defined geometrically as a succession of waypoints or special points called NoName Stars, from the STAR fix to the runway threshold. In those points the user can set altitude restrictions, IAS restrictions or DME restrictions.
Once the procedure is geometrically defined in TAAM, the tool randomises automatically aircraft performances to adapt the trajectory for each aircraft to the ideal profile represented by the geometric procedure.

When the procedures are defined in terms of thrust or configuration setting, additional pre-processing work is required to model them in TAAM since the tool does not consider these parameters. In this case, it is needed that the procedures are translated into parameters understandable by TAAM (rate of climb and descent, climb speed etc, specified in Level Bands).

When the procedures are defined in terms of geometry and speed, they can be modelled in TAAM with a degree of realism that depends on the specific procedure and on the intrinsic limitations of the tool.

The first limitation is related to the relative distance between successive Star points: two consecutive STAR points must be at least 0,5 NM far between them. If one of the new procedures contains significant speed changes or altitude changes in less than 0,5 NM (as it occurs), we should make assumptions to simulate that stage of the procedure. There is also another limitation regarding the minimum distance between two consecutive and ordinary waypoints; they must be at least at 3 NM.

Other limitation is that the last point of the STAR before the runway threshold is understood by TAAM as the initial point of a final descent of 3 degrees glide slope to the runway. We should do this last point as little as TAAM lets us maintaining the definition of the procedure.

Once the user has set the altitude and speed restrictions in each waypoint of the star, aircraft will comply them if the aircraft characteristic file (performance data) contains within its limits the necessary rate of descent, descent IAS, etc to reach those values. In order to make aircraft comply with these restrictions, the user must modify and adapt, for each procedure, the parameters related with the descent of the aircraft: descent IAS, rate of descent, speed on final, and so on. This means that for each real aircraft model, there will be in the simulation as many models as different procedures are going to be analysed.

Descent IAS and rate of descent are specified in Level Bands, where the value is the upper limit of the Band, specified as a Flight Level. The maximum number of Level Bands for each stage of flight is 20. If the user want to include in the scenario a very detailed procedure, he must increase the number of level bands in order to describe all the altitude, speed, and rate of descent changes performed by the aircraft flying the procedure.

Although the aircraft complies with the altitudes and speed restrictions included in the definition of the procedures, this does not mean that the aircraft performs a correct profile. Once the aircraft passes through a waypoint at the required altitude and speed, TAAM establishes a pseudo-cruise phase that can last even more than a minute. So the descent is stepped and not continuous. Making a fine-tuning of the performances we can reduce this cruise phases and obtain a realistic profile.

The main risk we assume is that modifying the aircraft performance data and establishing so many altitude and speed restrictions can make the model not flexible enough to sequence properly the arrival flow to the airport. One of the most important objectives of the pre-calibration tests is to determine whether or not the TAAM output is realistic.


Alfredo GÓMEZ DE SEGURA, (Aeronautical Engineer)
Tel.: +34-91-3213468
Fax: +34-91-3212031
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