Dr.-Ing. Gerhard Greving
NAVCOM Consult
Bahnhofstr. 4
D-71672 Marbach
navcom.consult@t-online.de

Abstract

The Navaids and Landing Systems have to be installed on the airports or en-route more and more in an potentially electrically adverse environment. A variety of potentially distorting objects or disadvantageous difficult ground conditions are facing the operators of these systems. These may be

• more and bigger aircraft
• terminals, hangars
• huge cranes during construction which are under the transitional surfaces
• high voltage lines, wind-generators for airport and en-route VOR/DVOR .

Also the systematic measurements of the effects of the objects may be a profitable job for the flightcheck companies, but they are very tedious and costly. The flight operation is distorted and will create additional costs also.

The author has described on the 8^th IFIS conference in Seattle a versatile 3D-GTD/UTD-method which has been applied successfully for ILS-LOC, ILS-GP and VOR/DVOR and other systems. Due to the fact that GTD/UTD is an asymptotic method as well as the standard PO-method, it cannot be applied to a class of objects which consists of wire type elements, e.g cranes, or for objects which are not very large compared to the wavelength, i.e. aircraft. Principal problems exist also for humped runways for all standard methods.

Newer methods exist which can handle theses classes of problems, i.e. the socalled integral equation method solved by the method of moments and the socalled parabolic equation method. The former is well suited for wire type structures and aircraft, the latter can be applied in principal for humped runways. These methods have been adapted and integrated to the system simulation of navaids and landing systems.

The principles of the methods as well as examples for both methods will be presented, in particular practical examples for the

• DDM effects of cranes and aircraft on the CATIII ILS on airports
• fieldstrength behaviour for humped runways
• other structures on VOR/DVOR .