# Modern Threats to Precision Approach and Landing - The A380 and Windgenerators and their Adequate Numerical Analysis

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Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 Modern Threats to Precision Approach and Landing - The A380 and Windgenerators and their Adequate Numerical Analysis Gerhard Greving NAVCOM Consult Ziegelstr. 43 D-71672 Marbach/Germany navcom.consult@t-online.de http://www.navcom.de these objects by the systems themselves. ABSTRACT These objects can be terminals, hangars, Classical and modern navigation, landing large buildings, windgenerators and power and radar systems rely on the radio trans- lines as well as the aircraft itself. mission and reception. Relevant objects in A reliable prediction of the potential “threat”, the radiation field can harm the intended i.e. the unacceptable effects on the systems characteristics of these systems. Modern in question is required in advance before the state-of-the-art simulation can predict in an objects are built or before the objects appear. increasing number of complicated cases the This task can be solved today by system electrical performance in the presence of simulations using state of the art numerical these objects. Countermeasures can be de- methods. Quite a number of publications signed from this knowledge. have been released by the author in the past This paper deals with the "threat" (potentially /2-12/ on the subject of numerical system un-acceptable distortions) on these systems simulations. This paper highlights two types by the forthcoming new large aircraft A380 of objects somewhat more fully, namely the and by the windgenerators which are con- A380 and the windgenerators (Fig. 2). This structed in an increasing number sometimes paper is not intended to present rules and close to the systems. The mathematical and definitions for dimensions of safeguarding numerical analyses are outlined and some areas or safety distances. results are presented. It is in particular em- phasized to apply three-dimensional and sophisticated state-of-the-art methods which MODELING AND SYSTEM SIMULATION are adapted to the three-dimensional char- The modeling and simulation process (Fig. 3 acteristics of the objects in contrast to inade- and 4) must accomplish the following basic quately simple methods. tasks 3D-modeling examples for the A380 and · Sufficiently realistic modeling of the object windgenerators and some principle results having in mind that the subsequent are presented. simulation is treating the model and not the reality. The form, the shape and the materials of the object as well as the ex- INTRODUCTION citing field above ground have to be Almost all classic and modern navigation modeled sufficiently. The basic way of landing and radar systems rely on radio modeling depends also on the numerical transmission and reception. In a clean en- method used in the next steps. vironment these systems may work pretty · Detailed modeling of the system in ques- well, but the real life is different. More and tion which is generating the undistorted more complex distortion and interference signal. problems for navaids, landing and radar · Simulations of the reflection and scatter- systems are encountered today (Fig. 1). ing process by the application of ade- These so-called “problems” are caused by quately state-of-the-art numerical me- major objects around and in the vicinity of thods. The most accurate method should these systems, creating additional reflections be generally used; approximations may and scattering signals (“multipath signals”) be used only if the results are sufficiently by the principally unavoidable illumination of accurate. 1/12

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 · Evaluation of the decisive system pa- certain cases cross checks can be made for rameter which the aircraft uses for navi- approval by comparing the results of the gation or landing. preferred approximative IPO-method (im- The two objects of this paper (Fig. 2; A380, proved physical optics) with the results from windgenerator) are highly three-dimensional the rigorous MoM- or ML-FMM-methods and therefore a two-dimensional approach (method of moments, multi-level fast mul- and model is neither sufficient nor "state-of- tipole method). The latter family cannot be the-art". It is obvious that a three-dimen- applied efficiently for large aircraft and sional approach is not only necessary to windgenerators due to the "exploding" stor- apply, but also requires a lot more modeling age requirements and/or the excessive com- and computation work. No trade-off is ac- puter time for systematic simulations. ceptable between the accuracy and the effort Moreover, the ML-FMM has the general to be invested due to the safety issue in- problem of a questionable convergence of volved. A simple 2D-treatment which re- the iterative solution of the integral equation. duces a 3D-A380-aircraft to one rectangular Cases have been experienced where the plate in the most extreme simplification, or defined convergence criterion, e.g. 10-3, has several composed rectangular flat plates, not been achieved after 500 iterations for an can be up to many orders of magnitude aircraft. faster, but can also yield wrong and unpre- The GTD/UTD method is not the preferred dictable results /12/. Such kind of simple numerical method for the discussed applica- approaches cannot be cured by "some tions and three-dimensional curved objects measurements" at a few points under some due to the general caustic problem and the conditions. generally unavoidable discontinuities of the The simulation of the system must take into solution, which results in problematic discon- account all relevant details which affects the tinuities in the DDM-results for ILS. so-called "system-parameter" of that particu- lar system, i.e. the DDM (Difference of Depth For both cases (A380, windgenerator) the of Modulation) for the ILS (Instrument Land- structure is subdivided into a large number of ing System) or the "bearing error" for the metallic triangles (Fig. 7 and 10) where the VOR/DVOR (Very high frequency Omnidi- real exciting field is applied. rectional Range; Doppler-VOR). These de- Worst case principles may be applied as an tails comprise as an example (see for more example for the dielectric blades by assuming details Fig. 3) the metal material. · the correct geometrical and electrical set- ting and numerical installation of the ac- Great care and knowhow has to be applied tual system in the pre-processing section when carrying out these sophisticated meth- · the signal processing, the filtering, the ods and interpreting the results in each case, sampling, and the receiving antennas in because each of the methods can fail in the post-processing section. certain situations /12/. Conclusions on the Other field quantities (e.g. "field distortions") basis of incorrect results can yield a waste of cannot describe in general sufficiently the money or can be the reason for hardly ac- system effects. "Field distortions" are neces- ceptable, in fact unnecessary consequences, sary effects for system distortions, but are such as the closure of a taxiway for A380 not a sufficient parameter to quantify the taxiing /12/. system distortions. The verification of the correctness and the reliability of the system results is a particular PRACTICAL PROBLEMS challenging task as discussed in /12/. A sin- The A380 on Airports and ILS gle or “some measurements” are not suffi- The future A380 is currently the largest civil- cient. Each result has to be verified in princi- ian aircraft (Fig. 5,7) which will appear in ple. some years on the airports. Compared to the other large aircraft, this aircraft has a maxi- Fig. 4 shows the overall flow-chart of the mum height of the tail-fin of 24.1m. Due to applied IHSS (Integrated Hybrid System the horizontal polarization of the ILS-fields the Simulation). The best suited numerical higher parts of the aircraft may have stronger method is taken for the particular problem, effects compared to the lower parts. i.e. the A380 and the windgenerators. In However that does not mean that the tail-fin 2/12

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 can describe the total aircraft sufficiently. · type and characteristics of antennas Generally speaking, the larger and higher (medium, wide aperture, capture ratio, the aircraft, the larger the distortions for the pattern shape, sidelobe suppression etc.) ILS-subsystems. Therefore, the largest cur- · existing distortions by stationary objects rently existing (military) aircraft (AN225; Fig. (hangars etc.) 5) will not have necessarily the largest DDM- · structural details of the layout of the air- distortions. port (e.g. length of the runway) The A380 will be by nature on an airport in · topological details of the runway or air- several operational phases and by that in port, such as humped runways quite a number of relevant positions and · operational category CATI-III orientations (Fig. 6), such as : · type of the aircraft · landing, rolling out, taxiing, parking, · single or groups of aircraft (e.g. when starting queuing for takeoff) · on parallel or sometimes inclined taxi- · type of receiving antenna in the aircraft or ways in relation to the Localizer and/or to used for ground measurements. the glidepath The setting and installation of the ILS-anten- · rolling off after landing nas as well as the receiving antennas do · rolling on for starting have a great impact on the results. Simple · crossing the runway on taxiways in dif- unrealistic dipoles, adapted antennas (e.g. ferent angles R&S HE108) or 3 element Yagis will show · taxiing behind the Localizer and/or be- very much different DDM-results /1,6,9/ and hind the glidepath would result in quite different safeguarding · starting and flying over the Localizer areas or holding lines. It is problematic to while not precisely above the runway compare measurements results for verifica- centerline tion purposes and also to compare different The international specification ICAO Annex results of simulations when the boundary 10 defines the DDM-tolerance limits for each conditions and the underlying numerical operational category. The signal in space methods are not sufficiently known. must meet these specifications when a lan- ding aircraft is using ILS. The provider has The minimum separation between successive to guarantee the compliance with these landing aircraft is also a function of the specifications and has to take measures for preceding rolling-off aircraft or of the starting that. aircraft. It is a well-known effect that large As a matter of practical handling this basic DDM-oscillations occur when an aircraft is task is met by the following safeguarding lifting off and flying over the ILS-Localizer zones and lines which serves the signal for the next aircraft in · critical areas (forbidden to enter for all the landing sequence. Unlocks or discon- vehicles and aircraft; technically speak- nects of the autopilot may occur. ing small objects may enter in certain ar- It is obvious that only a large number of tedi- eas except the nearfield monitor area. A ous simulations for the particular case and at verification is recommended by adequate a given airport for a certain ILS can yield the methods.) required results. The providers and in par- · sensitive areas (controlled access pos- ticular the airports are highly interested to sible; e.g. for not too large vehicles and have the minimum size of the safeguarding small aircraft; verification recommended) areas without increasing the risk for unspeci- · holding lines . fied ILS-signals and reducing the safety. These zones and lines have to be redefined for the A380 aircraft. The sizes of these The Figures 8 and 9 show two examples of zones or the distances of the holding lines to simulations from a methodological point of centerline or on the taxiways depend on a view number of factors which have to be taken · A380 on a parallel taxiway for a medium into account, such as aperture Localizer antenna. The nose of · type of system (single/dual frequency; the A380 is assumed to be in the xy-co- installation of out-of-phase clearance ordinates, the axis is parallel to centerline. (/1/) Filtered DDM-data are presented. DDM- isolines are marked. From such results the lateral extension of the safeguarding 3/12

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 areas can be defined taking into account the locus of the maximum DDM and the The WG are highly 3D-structures and need related maximum tolerance limits at this an equivalent modeling (Figure 13). Typically point. the shaft is a shaped metal tube or strongly Holding points result from similar simula- reinforced concrete. The cover of the gen- tions where the aircraft is inclined ac- erator house and the rotor blades are usually cording to the angle of the rollon taxi- made of glass-fibre material. The blades ways. have an integrated metallic lightning protec- It is noted that the safeguarding areas tion system. However, the total structure has ("critical, sensitive areas") cannot be de- been modeled for the "worst case" to be fully fined on the basis of the maximum DDM- metallic, i.e. by a large number of metallic limits. Some margin for existing distor- triangles. This takes into account envi- tions, stationary objects and superposing ronmental conditions. In principle the mod- aircraft has to be provided. Also, the eling strategy is identical for the A380 and the DDM-distortions increase drastically windgenerators. when the aircraft is positioned in an in- For the VOR/DVOR systems the scattered clined orientation to the centerline. This field components are superposed and proc- is operationally the case when the air- essed appropriately, yielding the decisive craft is turning towards the runway on the system parameter, i.e. the bearing error. The rollon taxiway. field distortions of the VOR/DVOR-field in · A380 rolling off on a high speed taxiway. itself are not a measure for the bearing errors Time dependant DDM-data are pre- and system distortions. Fig. 11 shows such sented. From these results the longitudi- kind of field distortions on a horizontal plane nal extension of the critical area can be in 3D-representation. The largest field defined. distortions are behind or beyond the In both cases large DDM-distortions are en- windgenerator, but the bearing errors are countered under the given circumstances. minimum in this region. Potential "shadowing effects" are negligible for realistic distances of the windgenerators to the VOR/DVOR- The windgenerator and navaids systems station. The acceptable bearing errors are Windgenerators (WG, "windmills", "windtur- defined in ICAO Annex 10 and in the flight bines") are constructed more and more in inspection manual DOC 8071. The bearing major quantities as a single installation or in errors have to be simulated at the lowest large arrays ("windparks"). Often these ob- height of the coverage volume defined for jects are close to navigation stations or in the each VOR/DVOR. Figure 12 shows an coverage volume of radars of various types. example where the VOR/DVOR bearing The advanced analysis of the effects of errors have been calculated on a horizontal these WG on the navigation and radar sys- plane (100km*100km) at a height of 3300ft tems is of increasing interest. The different MSL for a large windgenerator. nature and function of the navigation sys- In this 2D-result for a defined height, all radi- tems and radar suggest that the simulation als in that height are contained up to about also must be quite different. However, the 50km. It can be clearly seen that the maxi- introduced IHSS (Figure 4) and its imple- mum bearing errors of the DVOR are much mented features allow the adapted analysis. smaller compared to the VOR. Extensions in the pre-processing part and in the final post-processing part had to be inte- Doppler spectrum grated. This is especially true for the analysis The scattered Doppler-frequencies depend of the Doppler-shift characteristics of a turn- on the radial velocity of the scattering objects ing windgenerator (Fig. 10 and 13). The (Fig. 10 right). This fact has been used to Doppler shifted scattered fields may have define a method for the calculation of the adverse effects on the VOR/DVOR-system Doppler-spectrum of the reflected/scattered because these systems evaluate 30Hz am- field. plitude and 30Hz frequency modulations. In a side study it has been evaluated that the This frequency can easily be produced by bearing error of a 30Hz Doppler-shifted the fast turning blades (Fig. 10 right) even at component is larger by factors compared to a the VHF ILS/VOR-carrier frequency of about non-shifted component. By that, the su- 110MHz. perposed amplitude of the 30Hz shifted 4/12

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 component at some field point yields the horizontal plane in some minimum coverage potential bearing error. height. The Doppler spectrum of the It can be easily understood that for the turn- windgenerator has been discussed with re- ing blades, the Doppler spectrum must be spect to the VOR/DVOR. A numerical result symmetrical in principle around the un- has been presented showing the time variant shifted zero line caused by the stationary spectrum of small amplitudes for several subparts of the windgenerator, i.e. the shaft blade positions. and the machine house. Fig. 13 shows such an example of the Dop- pler amplitude spectrum of a windgenerator REFERENCES in some geometrical configuration. The Not all references are explicitly cited in this paper. The spectrum is calculated and plotted for sev- references are sequenced according to the time of eral angular positions of the blades. It can appearance. be seen and understood that the spectral /1/ GREVING G. ILS CATIII site problems - A new verified system solution, 7th Intern. flight inspection amplitudes for a certain frequency are time symposium, London 1992, p.224-236 periodic and time dependant. The ampli- /2/ GREVING G. Computer aided site analysis and site tudes are small compared to the static zero- adapted installation - Efficient commissioning of landing line. The results so far indicate that this systems, 8th IFIS International flight inspection Doppler-spectrum does not seem to be a symposium, Denver USA, June 1994 problem for the VOR/DVOR . /3/ GREVING G. Numerical system-simulations in- cluding antennas and propagation exemplified for a radio navigation system, AEÜ, Inter, J. of Electronics and Communications, Vol. 54 (2000) No.3, pp. 183-189 CONCLUSION /4/ GREVING G. Hybrid-Methods in Antennas and Large objects close to navigation, landing 3D-Scattering for Navaids and Radar System Simu- and radar systems can distort the electrical lations; Antenna and Propagation Conference AP2000, April 2000, Davos Switzerland characteristics of these systems. The new /5/ GREVING G. Recent Advances and New Results large aircraft A380 will appear relatively soon of Numerical Simulations for Navaids and Landing on the airports. An increasing number of th Systems, 11 IFIS International Flight Inspection windgenerators are constructed often close Conference, Santiago Chile, June 2000 to these systems. /6/ G. GREVING, N. SPOHNHEIMER Problems and The numerical 3D-treatment using "state-of- Solutions for ILS Category III Airborne and Ground the-art-principles" of these objects has been Measurements - European and US Views and Per- th spectives, 11 IFIS International Flight Inspection outlined and contrasted to simplified 2D- Symposium, Chile 2000, Proc. pp. 51-62 approaches. /7/ GREVING G. Application of Modern Numerical A380 aircraft will be present in many differ- Methods for Navaids and Landing Systems - Theory ent positions, in many orientations and op- and Results, ISPA 2000, International Symposium on erational phases on the airports. Safe- Precision Approach and Landing, DGON, Munich, Proc. guarding areas ("critical and sensitive ar- pp.49-61 eas", holding lines) have to be defined and /8/ GREVING G. Latest Advances and Results of Complex Numerical Simulations for Navaids and installed to protect the ILS. The case of the Landing Systems, 12 th IFIS International Flight In- "parallel taxiway" is a relatively simple case spection Symposium, Rome/Italy 2002, Proc. pp. 152- in terms of the amplitudes of the DDM-dis- 162 tortions. Some principle results for the A380 /9/ G. GREVING, N. SPOHNHEIMER Problems and have been presented, one for a parallel taxi- Solutions for Navaids Airborne and Ground Measure- th way and one for the dynamic rolloff case. As ments – Focus on receiver Sampling and TCH; 12 IFIS International Flight Inspection Symposium, expected, these results and further results Rome/Italy 2002, Proc. pp. 90-99 show that the ILS-distortions by the A380 are /10/ G. GREVING, H. WIPF Flight Inspection Aircraft remarkably larger than for the B747. By th in Multipath Environment; 12 IFIS International Flight systematic simulations for the individual Inspection Symposium, Rome/Italy 2002 Proc. pp. 198- situation on a given airport the adapted and 207 minimized safeguarding areas can be de- /11/ GREVING G. Status and experiences of advan- termined. ced threedimensional system simulations for navaids and radar, Aviation World Conference, Kiew/Ukraine, The numerical treatment of the windgenera- September 2003, pp. 5.1-5.5 tor with respect to a VOR/DVOR navigation /12/ GREVING G. Advanced Numerical System system has been outlined. Some principle Simulations for Navaids and Surveillance Radar - The results have been presented, showing the th Verification Problem, 13 IFIS, June 2004, Mont- bearing errors for a large windgenerator on a real/Canada, pp.173-186 5/12

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 buildings, hangars, cranes, MoM layout, system position, safe- aircraft, tanks, towers, fences, guarding areas, holding points, high voltage lines, ... grading, earth movement, ... A380 PO/IPO PE C L ay pe d runw hum DVOR/DME ILS LOC MLS Az,PDME GO/GTD/UTD ILS GP MLS El hybrid_11.dsf not scaled ASR/SSR windgenerator Fig. 1: Sketch of an airport, humped runway, the subsystems of an ILS and MLS, some dis- torting objects and a landing aircraft Fig. 2: The large A380 aircraft and windgenerators pose a potential threat to all introduced classic and modern navigation, landing and radar systems 6/12

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 ispa04sota.dsf 10/04 "State-of-the-art" system analysis reality model numerical method MoM, ,... 3D ML-FMM, GTD/UTD, PE, PO/IPO geometrical, electrical aspects "tool", math engine 3D, curved surfaces "reflections, scattering" materials field excitation best adapted for the model/reality (amplitude, phases) least approximations finite distances most advanced as realistic as possible best approved/verified as realistic as needed highest accuracy promising no compromise for speed latest scientific results m te s Sy IHSS Integrated Hybrid System Simulation Fig. 3: General process flow and aspects for the modeling and the numerical treatment of the A380 and the windgenerator System inthybsim4c.dsf The real life problem, System + Environment - in advance airport, enroute; ILS-LOC/GP, VOR/DVOR, MLS, DME/TACAN, ASR,SSR, weather radar, comm ... pre-processing Landing Systems, Navaids, Radar Theoretical analysis - Selection process Modeling system related pre-processing, modeling, approximations data bases Hybrid A/C,cranes,materials,... combinations Numerical Methods GO/GTD/UTD MoM, wire/patch ML-FMM PE PO, IPO, EPO Antennas, medium objects, aircraft, large objects, ground, ... cranes, aircraft ... convergence? humped runways, ... windmills, ... scattering objects Multilayer, Green ground effects, snow,rain,glas, ... wave propagation Details Superpositions System Post-processing Filtering, sampling, RX-antenna, ... System post-processing System results, System parameter Annex 10; DDM, bearing error, mod%, PFE,CMN , System proposals, actions design,installation range error, monopulse error, false target, ... parameter Fig. 4: Process flow of the IHSS (Integrated Hybrid System Simulation) 7/12

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 Comparison of Sizes AN225 / A380 / B747 Height=18.2m Numerical 3D-models Length=84m Height=24.1m Span=88.4m AN225 Length=78.9m Height= 19.4m A380-800 Span=79.8m Length=70.7m a380c747an225.dsf 10/04 Span=64.4m B747-400 Fig. 5: Numerical 3D-models of 3 large aircraft AN225, A380-800, B747-400; size comparison A380 aircraft in various positions and orientations on the airport a380casa1.dsf 10/04 D1 d starting crossing GP LOC GP holding D2 points d D3 landing, roll-out, exiting rolling on taxiing on parallel TWY Fig. 6: The A380 aircraft on airports (runways, taxiways, landing, starting) with regard to ILS (Localizer LOC, glidepath GP) 8/12

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 Analysis by the IPO-method Basic Dimensions: improved and extended PO : length = 78.9m span = 79.8m height = 24.1m (modified) basic PO-currents 37054 triangular patches (110MHz) + rim currents + Fock currents + shadowing effects tail fin 3D-geometry composed of canonical structural elements subdivided into triangles Fig. 7: Numerical 3D-model of the aircraft A380-800 consisting of 37054 triangular metallic patches at 110MHz (ILS Localizer). A reduced number of triangles is displayed. loca380w137f.dsf 09/04 Max. DDM (CAT III) on RWY (LOCALIZER) |DDM| [mA] 100 THR (x/y): 4350 / 0 LOCALIZER (x/y): 0 / 0 Antenna: THALES 13/7 Y [m] 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Sensor: R&S HR-108 0 LLZ 1 THR 1 -100 4 8 10 1 10 7 4312 106 6 8 54 15 4 3 11 3 3 -200 2 3 7 9 8 2 6 1 1 2 1 5 -300 4 position of A380 (nose) INDEPENDENT with highest DDM values SCALE ! filtered data A380 rotation: 0 deg on RWY-CL at x=350...4350m (height above RWY: 4m) -400 0 500 1000 1500 2000 2500 3000 3500 4000 X [m] 16.09.04 loca380w0f13 Fig. 8: DDM-distortions on the runway for CATIII applications of an A380 on parallel taxiway; medium aperture dual frequency Localizer; Filtered data; R&S HE108 RX antenna 9/12

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 DDM distortions on glidepath with moving A380 from centerline to fast roll-off taxiway abroll2_a.xls 15 LOC-antenna: 21/7 distance LOC-THR: 4260m norm factor Clr/Crs: 0.03 / 0.022 10 method: IPO 5 4 Samples / sec 0 DDM / mA -5 8000 po 1000 30 (lef sition point "A" time vs position of A380 t sc of fly ale ing ) distance of flying aircraft to THR / m a ircra ft 25 800 6000 covered way of A380 / m t=4 -10 v=3 /h (con 00 km km t) 0s stan /h 60 tan angle of A380 / deg t) v= ons 20 ec (c 200 e) 600 rlin t= 3 nte 150 0s ce 4000 0 15 ec = p cale 80 8 A3 to -15 0 ° ht s of A3 of ara ) llel ay Y/m dw ) 400 100 re ale t=2 (rig gle ve sc 0s co ght 10 an (ri ec 50 t=1 0 sec t=0 sec 2000 200 5 -20 0 4 .1 0.0 4 0 200 300 400 500 600 700 800 900 abroll3b 8.10.04 0 abroll2 0 0 5 10 15 20 25 30 35 40 45 distance from LOC / m Time / sec -25 abroll2 0 5 10 15 20 25 30 35 40 45 time / sec Fig. 9: Time dependant dynamic DDM-distortions by an A380 when rolling on a fast-roll-off taxiway; The landing aircraft is on the glidepath and moving also. Windgenerator 6119 Patches / 110MHz ILS/VOR Windgenerator ca. 130-150m ca. 100-133m Vestas V80 2MW 499291 Patches / 1030MHz SSR 12482 Patches / 110MHz ILS/VOR Enercon E66 1088080 Patches / 1030MHz SSR 3D-model ca. 4Mio Patches / 3GHz PSR 1.8/2MW 3D-model time variant scattering

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 DVOR fieldstrength on a plane DVORfield1.dsf 07/04 horizontal plane in 2000ft above ground; 40km*50km dB wind generator -26 -30 100 -34 80 -38 -42 60 Z/m -30 -46 -50 40 -54 -58 20 -40 -62 -20 0 20 -66 Y/m Z / dB -50 -60 DVOR reflector position (X/Y/Z): 0 / 0 / 4.4 OR wind generator at (X/Y): DV 2000m / 0m 0 or r at azimuth rotation angle: 0° e ne -70 rotor: 0° dg -20 flat terrain win 20 -10 frequency: 110 MHz DVOR reflector diameter: 30m 0 X= 29.04.04 zapel2 Y/ km 40 10 k m 0 X/ 20 line of maximum field distortions, but minimum DVOR bearing errors Fig. 11: Distorted field of a DVOR on a horizontal plane caused by a nearby windgenerator DVOR with rotating wind generator windspekt.dsf 10/04 Spektrum at (x/y/z): -25km / 25km / 2000ft - blades only (at point of maximum Doppler shift) -90 wind generator wind generator blades only blades only -100 speed: 18 x min -1 2020 0° 120 0° 30° 30° -110 60° 60° 100 2000 90° Z /m from windgenerator X /m -120 80 90° 1980 without blades dBV /m -130 60 1960 40 -140 40 20 0 -20 Y/m -40 -60 20 0 Y/m -20 -40 band width: 1Hz -150 -160 -170 -180-50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 Doppler Shift / Hz Fig. 13: Simulated Dopplerspectrum for VOR/DVOR-frequency of the rotating blades in diffe- rent angular positions 11/12

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004 VOR station - bearing errors by E70 ispa04vordvor.dsf 10/04 horizontal plane 100km*100km, 3300ftMSL 50 Fehler / Grad Enercon E70 Dra ufsicht (Drehwinkel: 3 09° ) 9 R 250 VO 40 4 240 2 X/m 230 1 220 30 0.4 210 1360 1340 0.2° 0.2 Y/m 20 0.1 Enercon E7 0 30 0 140 1. 7 120 ° 10 100 80 Z X / km 60 40 0 20 WKA 0 200 250 30 0 Y 11 6. 9 -10 ° 309° angle ut h 10° azim rror VOR Antenne: WG earing e j0° -20 Loop 1 bei z=3.60m U=1Ve -j15° 1 59 b Loop 2 bei z=5.11m U=0.71Ve max .1° Freq.: 111.2MHz VOR bei (X/Y): 0 / 0 WKA bei (X/Y): 228m / 1351m -30 WKA (E70) Nabenhöhe: 115m Azimutaler Drehwinkel der WKA: 309° (Bild rechts oben) -40 11.8.04 -50 allersb_vor7d 40 30 20 10 0 -10 -20 -30 -40 -50 Y / km DVOR station - bearing errors by E70 horizontal plane 100km*100km, 3300ftMSL 50 Fehler / Grad Enercon E70 Draufsicht (Drehwinkel: 309 °) O R 0.7 250 DV 40 0.4 240 0.2 X /m 230 0.1 220 30 0.04 210 1 360 13 40 0.2° 0.02 Y/m 09° 20 gle 3 0.01 Enercon E70 imu th an r 0.72° 0 z ro 30 WG a earing er 140 1 .7 b 120 ° 10 max 100 80 Z X / km 60 40 0 20 WKA 0 200 250 300 Y 11 6.9 -10 ° -20 1 59 DVOR Antenne: .1° Reflektordurchmesser: 30m Reflektorhöhe: 4.4m über Boden Antenne: 1.2m über Reflektor -30 Freq.: 111.2MHz DVOR bei (X/Y): 0 / 0 WKA bei (X/Y): 228m / 1351m WKA (E70) Nabenhöhe: 115m -40 Azimutaler Drehwinkel der WKA: 309° (Bild rechts oben) 11.8.04 -50 allersb_vor7e 40 30 20 10 0 -10 -20 -30 -40 -50 Y / km Fig. 12: VOR/DVOR bearing errors caused by a windgenerator type Enercon E70; identical geometrical configuration. Some used radials are marked. Note the different color coding of the bearing errors 12/12

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