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

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

                                                   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.
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
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
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
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
                                                  /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-
                                                  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
                                                                               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-
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

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, ...

                                           PE                                        C
                                          pe   d runw

                                                      ILS GP
                                                      MLS El

     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

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"
          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

                                                                                                         Integrated Hybrid System Simulation

Fig. 3: General process flow and aspects for the modeling and the numerical treatment of the
A380 and the windgenerator

                              The real life problem, System + Environment - in advance
                       airport, enroute; ILS-LOC/GP, VOR/DVOR, MLS, DME/TACAN, ASR,SSR, weather radar, comm ...
                                                                                                                                              Landing Systems,
                                                                                                                                              Navaids, Radar
                                             Theoretical analysis - Selection process
                                         system related pre-processing, modeling, approximations
           data bases                                                                                                Hybrid
                                                                                                                                              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 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)

Paper ISPA2004 (Intern. Symposium on Precision Approach and Landing), Munich 10/2004

                                                                          Comparison of Sizes
                                                                          AN225 / A380 / B747
                                                  Height=18.2m              Numerical 3D-models






                                           A380-800     Span=79.8m

  a380c747an225.dsf 10/04

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


             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)

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

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

                LLZ 1                                                                                                                                                 THR


                                           10 1                                               10         7


                                                  54                   15                                                           4                   3



                                                              3             7            9                   8
                                   2                                                6

                                                                   1   2

 -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)

                0                  500                 1000                1500               2000               2500    3000           3500          4000
                                                                                                 X [m]

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

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

                                                 LOC-antenna: 21/7
                                                 distance LOC-THR: 4260m
                                                 norm factor Clr/Crs: 0.03 / 0.022
                10                               method: IPO

                                                                      4 Samples / sec
     DDM / mA

                 -5                                                8000
                                                                                        (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
                                                                   6000                                                                                                                          covered way of A380 / m                                                            t=4
                                                                                                                                                v=3                         /h
                                                                                                                                               (con 00 km                km t)                                                                                                            0s
                                                                                                                                                   stan /h             60 tan

                                                                                                                                                                                                                                angle of A380 / deg
                                                                                                                                                        t)           v= ons


                                                                                                                                                                                                                                                                                                       t= 3

                                                                                                                                                                                                                                                                            150                               0s

                                                                   4000                                                                               0                                                                    15
                                                                                                = p cale 80


                                                                                             0 ° ht s of A3

                                                                                                    ara )


                                                                                                                                       dw )                                                400                                                                              100
                                                                                                                                     re ale                                                                                                                                                                                       t=2
                                                                                              (rig gle

                                                                                                                                  ve sc                                                                                                                                                                                                   0s
                                                                                                                                co ght                                                                                     10

                                                                                                                                 (ri                                                                                                                                                                                                        ec
                                                                                                                                                                                                                                                                              50                                                                       t=1 0 sec          t=0 sec
                                                                                                                                                                                           200                             5
                -20                                                                                                                                                                                                                                                           0

                                                                                                                                                                             4 .1 0.0 4
                                                                                                                                                                                                                           0                                                       200           300              400             500            600           700        800         900   abroll3b
                                                                      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

                                                                                                                                                                                                                                                                       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
                                                                                                                                                                 -30          100

                                                                                                                                                                 -42           60

                                                                                                                                             -30                 -46
                                                                                                                                                                 -50           40


                                                                                                                                                                                    -20    0    20
                                                                                                                                                                 -66                      Y/m

                                                                                                                                                   Z / dB

                                                                                                                                                      DVOR reflector position
                                                                                                                                                      (X/Y/Z): 0 / 0 / 4.4
           OR                                                                                                                                         wind generator at (X/Y):
         DV                                                                                                                                            2000m / 0m
                           r at
                                                                                                                                                      azimuth rotation angle: 0°
                     e   ne                                                                                                                  -70      rotor: 0°
                                                                                                                                                      flat terrain
              win                  20                                                                                           -10                   frequency: 110 MHz
                                                                                                                                                      DVOR reflector diameter: 30m
                                                                                                                                X=                 29.04.04
                                                       km          40                                      10       k   m         0
                                                                                                                    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)

                                   wind generator                                    wind generator
                                        blades only                                    blades only
         -100                       speed: 18 x min

                                                                         2020                                                                                                                               0°
                            120                0° 30°                                                                                                                                                       30°
         -110                                          60°                                                                                                                                                  60°
                            100                                          2000
                     Z /m

                                                                                                                                      from windgenerator
                                                                        X /m

         -120               80                              90°
                                                                         1980                                                         without blades
dBV /m

         -130               60

         -140                 40   20      0     -20
                                                        -40       -60           20         0
                                                                                                     -20   -40                                                   band width: 1Hz




         -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

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° )
                              R                                                                                                                         250

            40                                                                                                                       4                  240



                                                                                                                                     1                  220

            30                                                                                                                       0.4                210

                                                                                                                                                                       1360              1340

                                                                                                                                     0.2                                 Y/m

            20                                                                                                                       0.1                      Enercon E7 0

                                                                                                                                     0         140

                                             1. 7                                                                                              120
            10                                                                                                                                 100


  X / km



             0                                                                                                                                     20

                                                                 WKA                                                                                0
                                                                                                                                                                 200               250                30 0
                                                                                        6. 9
            -10                                                                                °
                              ut h        10°
                         azim        rror                                                                             VOR Antenne:
                       WG earing e
            -20                                                                                                       Loop 1 bei z=3.60m U=1Ve -j15°
                                                                          1 59

                           b                                                                                          Loop 2 bei z=5.11m U=0.71Ve

                                                                                                                      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)

            -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

            40                                                                                                                   0.4               240

                                                                                                                                           X /m


                                                                                                                                 0.1               220

            30                                                                                                                   0.04              210
                                                                                                                                                                     1 360             13 40

                                                                                                                                 0.02                                  Y/m

            20                                                                                  gle 3                            0.01                     Enercon E70

                                                                                       imu th an r 0.72°                         0
                                                                                      z          ro
                                                                                  WG a earing er

                                             1 .7
            10                                                                    max                                                      100

   X / km



              0                                                                                                                             20

                                                                 WKA                                                                           0
                                                                                                                                                               200               250            300
            -10                                                                               °

                                                                          1 59

                                                                                                                      DVOR Antenne:

                                                                                                                      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)


            -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

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