310
15 Goniometric Radio Navigation Systems
evening time. Ionosphere instability is especially observable before two hours of
sunset (sunrise) and during two hours after sunset (sunrise).
Herewith, not only parameters of polarization ellipse are considerably changed,
but incidence angle of radio wave arrival to a frame. As a result, sizes of additional
directional pattern will be changed, and HA indicator needle will swing.
At adverse conditions, the pointer swinging can be a dozen of degrees. The
phenomenon was named as “night effect.”
To decrease a bearing error, stipulated by “night effect,” it is necessary to keep up
with the following:
• average out the measured values of HA;
• If there is a possibility to select LB, it is better to use for bearing radio stations
located at close range from an aircraft, since at small distances (dozens of
kilometers) the measurements are performed at surface wave;
• If there is a possibility to select LB, it is necessary to use for bearing radio stations
operating at longer wave (low-frequency waves).
Radio bearing deviation error is stipulated by effect of reradiators, i.e., by
aircraft construction components, which are excited under action of incoming signal
and radiate its own electromagnetic field. Radio bearing deviation depends on
installation place of a frame and on HA. At ARC installation on an aircraft, the
deviation dependence from direction of radio waves arrival (radio deviation chart).
Then using a deviation compensator, installed in HA data transmission system to
indicator, a deviation is eliminated (deducted) until the certain minimum. Residual
deviation (error) value is usually not exceeding 1…2°.
“High-terrain (mountain) effect” is observed in mountain terrain during flights
at relatively low altitudes. In these conditions, the radio waves are coming to ARC
frame directly from LB and reflected from mountains. During an aircraft, moving a
direction of resulting signal is constantly changed, and indicator needle position is
correspondingly changed.
15 Goniometric Radio Navigation Systems
evening time. Ionosphere instability is especially observable before two hours of
sunset (sunrise) and during two hours after sunset (sunrise).
Herewith, not only parameters of polarization ellipse are considerably changed,
but incidence angle of radio wave arrival to a frame. As a result, sizes of additional
directional pattern will be changed, and HA indicator needle will swing.
At adverse conditions, the pointer swinging can be a dozen of degrees. The
phenomenon was named as “night effect.”
To decrease a bearing error, stipulated by “night effect,” it is necessary to keep up
with the following:
• average out the measured values of HA;
• If there is a possibility to select LB, it is better to use for bearing radio stations
located at close range from an aircraft, since at small distances (dozens of
kilometers) the measurements are performed at surface wave;
• If there is a possibility to select LB, it is necessary to use for bearing radio stations
operating at longer wave (low-frequency waves).
Radio bearing deviation error is stipulated by effect of reradiators, i.e., by
aircraft construction components, which are excited under action of incoming signal
and radiate its own electromagnetic field. Radio bearing deviation depends on
installation place of a frame and on HA. At ARC installation on an aircraft, the
deviation dependence from direction of radio waves arrival (radio deviation chart).
Then using a deviation compensator, installed in HA data transmission system to
indicator, a deviation is eliminated (deducted) until the certain minimum. Residual
deviation (error) value is usually not exceeding 1…2°.
“High-terrain (mountain) effect” is observed in mountain terrain during flights
at relatively low altitudes. In these conditions, the radio waves are coming to ARC
frame directly from LB and reflected from mountains. During an aircraft, moving a
direction of resulting signal is constantly changed, and indicator needle position is
correspondingly changed.