Chapter 17
Radio-Navigational Speed and Drift
Angle Meters
Doppler speed and drift angle meters (DSDM) are intended for determination of AV
velocity vector components relatively to underlying surface and information output
for aircrew and to data navigational complex, necessary for tasks performing of
aircraft navigation.
DSDM are classified into airborne and helicopter-borne by the purpose. Airborne
DSDM are designed for measuring of actual (ground) speed and drift angle. Nowadays, DSDM gauges are not installed on civil aircraft. An exception is only for
aircraft of old types. Helicopter-borne DSDM are intended for determination of
vector components of full longitudinal, transverse (lateral) and sometimes vertical
velocity. The main distinction of helicopter-borne DSDM from airborne DSDM
concludes that they should measure a Doppler frequency shift almost from a zero
and consider its sign, and airborne, since an aircraft flies only forward with certain
speed, measure only absolute magnitude (modulus) of Doppler frequency shift and
with minimum values at that, differing from a zero. Helicopter-borne DSDM are
more complicated in terms of design structure.
In practice, we found DSDM application with three- and four-beam antenna
system. The most frequently DSDM beams are directed as ribs of regular pyramid
with a base located in horizontal plane. DSDM antenna systems as a rule are rigidly
body-mounted on AV, however can be installed on rotating platforms.
Let’s examine DSDM operation principle in terms of three-beam system. Let’s
consider that DSDM antenna coordinate system is coincided with aircraft in reference
system XYZ (Fig. 17.1). Determine a relation between measured values of Doppler
frequencies and AV flight-path velocity projection in horizontal earth-referenced
coordinate system.
For simplicity, we consider that air-velocity vector is directed along OX-axis.
Flight-path velocity projections of AV on XYZ coordinate system denote as W x , W y ,
W z correspondingly, and through
k,
l,
m,
n—unit vectors along conjugated beams.
Doppler frequency shift value for k beam is defined as follows:
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
D. A. Akmaykin et al., Theoretical Foundations of Radar Location
and Radio Navigation, Springer Aerospace Technology,
https://doi.org/10.1007/978-981-33-6514-8_17
319
Radio-Navigational Speed and Drift
Angle Meters
Doppler speed and drift angle meters (DSDM) are intended for determination of AV
velocity vector components relatively to underlying surface and information output
for aircrew and to data navigational complex, necessary for tasks performing of
aircraft navigation.
DSDM are classified into airborne and helicopter-borne by the purpose. Airborne
DSDM are designed for measuring of actual (ground) speed and drift angle. Nowadays, DSDM gauges are not installed on civil aircraft. An exception is only for
aircraft of old types. Helicopter-borne DSDM are intended for determination of
vector components of full longitudinal, transverse (lateral) and sometimes vertical
velocity. The main distinction of helicopter-borne DSDM from airborne DSDM
concludes that they should measure a Doppler frequency shift almost from a zero
and consider its sign, and airborne, since an aircraft flies only forward with certain
speed, measure only absolute magnitude (modulus) of Doppler frequency shift and
with minimum values at that, differing from a zero. Helicopter-borne DSDM are
more complicated in terms of design structure.
In practice, we found DSDM application with three- and four-beam antenna
system. The most frequently DSDM beams are directed as ribs of regular pyramid
with a base located in horizontal plane. DSDM antenna systems as a rule are rigidly
body-mounted on AV, however can be installed on rotating platforms.
Let’s examine DSDM operation principle in terms of three-beam system. Let’s
consider that DSDM antenna coordinate system is coincided with aircraft in reference
system XYZ (Fig. 17.1). Determine a relation between measured values of Doppler
frequencies and AV flight-path velocity projection in horizontal earth-referenced
coordinate system.
For simplicity, we consider that air-velocity vector is directed along OX-axis.
Flight-path velocity projections of AV on XYZ coordinate system denote as W x , W y ,
W z correspondingly, and through
k,
l,
m,
n—unit vectors along conjugated beams.
Doppler frequency shift value for k beam is defined as follows:
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
D. A. Akmaykin et al., Theoretical Foundations of Radar Location
and Radio Navigation, Springer Aerospace Technology,
https://doi.org/10.1007/978-981-33-6514-8_17
319