Observations/Measurements:
Large and unacceptable discrepancies
between the theoretically determined and the practically measured TCH are
encountered (sometimes some meters).
In these cases, the reflection plane
is tridimensional and/or truncated.
In these cases, the position of
the glidepath antenna must be changed adequately.
In parts, very rough approximations
for the TCH are in use in the analysis as well as in the flightcheck procedures,
claiming to be acc. Annex 10 Fig. C5 (Fig. 1).
Extended approximations use simplified
parameters (longitudinal/forward and lateral slopes Fig. 2).
Approximations are applicable only
in simple cases (e.g. flat large plain plane).
These slopes cannot be defined uniquely
in the general tridimensional case (Fig. 3).
Some "virtually correcting" and
costly dislocations of glidepath positions on the base of flightchecks
may be unncessary and wrong depending on the methods.
The formally stated and commissioned
TCH will be physically wrong in certain cases and may pose a safety critical
issue if too crude approximations are used.
Numerical Analysis/Solution anbd
Flight check procedure
Improved and accurate numerical
methods are available for the tridimensional case where the reflection
plane may be skewed or truncated
(see the publication of NAVCOM Consult
on the 10th IFIS International Flight Inspection Symposium,
Seattle ; See also the full paper on this homepage in the Navaids publication
section.
The solution is fully compliant
with the unique definition of Annex 10.
The flight check measurement procedure
must be independant of any antenna parameter.
A recalculation of the TCH via the
measured glidepath angle and the needed external reference point (O(x,y))
is not a valid measurement of the TCH.
The often "requested" reference
point (O(x,y)) does not exist physically in general in the tridimensional
case.
The flight check measurement procedure
must be also independant of any parameter of the reflection plane.
A verification of the installation
design parameters by a flight check procedure based on the same approximations
is invalid.
|
News
About us
