LOC-THR discussion - 4

11.11.2009

Submission:

The reason why no shorter LOC-THR distance is available is because the criteria is based on actual data. The data collection programme back in the seventies simply did not involve procedures on runways shorter than 2000m. Yes the width of the signal at Threshold has a huge effect on the areas. A larger sector width means that a plane flying at half scale deflection will be laterally closer to obstacles than the same case with a smaller sector width. The OAS must be simply constructed with a 2000m LOC-THR as Ian explained. This will be sufficiently conservative. Placing a fictitious point where the sector width is 210m is plain wrong. The guidance shall lead to the LTP and the approach is flown with half-scale deflection maximum. If the course width is smaller than 210 at threshold, use 210m at threshold for the construction of the LOC area.


Beat Zimmermann -Air Navigation Institute - Switzerland