曝光台 注意防骗
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is 005°, and the MB from the station is 185°.
Function of ADF
The ADF can be used to plot your position, track inbound
and outbound, and intercept a bearing. These procedures
are used to execute holding patterns and nonprecision
instrument approaches.
Orientation
The ADF needle points TO the station, regardless of aircraft
heading or position. The RB indicated is thus the angular
relationship between the aircraft heading and the station,
measured clockwise from the nose of the aircraft. Think of
the nose/tail and left/right needle indications, visualizing the
ADF dial in terms of the longitudinal axis of the aircraft.
When the needle points to 0°, the nose of the aircraft points
directly to the station; with the pointer on 210°, the station
is 30° to the left of the tail; with the pointer on 090°, the
station is off the right wingtip. The RB alone does not indicate
aircraft position. The RB must be related to aircraft heading
in order to determine direction to or from the station.
Station Passage
When you are near the station, slight deviations from
the desired track result in large deflections of the needle.
Therefore, it is important to establish the correct drift
correction angle as soon as possible. Make small heading
corrections (not over 5°) as soon as the needle shows a
deviation from course, until it begins to rotate steadily toward
a wingtip position or shows erratic left/right oscillations. You
7-5
Figure 7-5. Radio magnetic indicator (RMI). Because the aircraft’s
magnetic heading is automatically changed, the relative bearing
(RB), in this case 095°, will indicate the magnetic bearing (095°)
to the station (no wind conditions) and the magnetic heading that
will take you there.
are abeam a station when the needle points 90° off your track.
Hold your last corrected heading constant and time station
passage when the needle shows either wingtip position or
settles at or near the 180° position. The time interval from
the first indications of station proximity to positive station
passage varies with altitude—a few seconds at low levels to
3 minutes at high altitude.
Homing
The ADF may be used to “home” in on a station. Homing
is flying the aircraft on any heading required to keep the
needle pointing directly to the 0° RB position. To home in
on a station, tune the station, identify the Morse code signal,
and then turn the aircraft to bring the ADF azimuth needle to
the 0° RB position. Turns should be made using the heading
indicator. When the turn is complete, check the ADF needle
and make small corrections as necessary.
Figure 7-6 illustrates homing starting from an initial MH of
050° and an RB of 310°, indicating a 50° left turn is needed
to produce an RB of zero. Turn left, rolling out at 50° minus
50° equals 360°. Small heading corrections are then made
to zero the ADF needle.
If there is no wind, the aircraft will home to the station on a
direct track over the ground. With a crosswind, the aircraft
will follow a circuitous path to the station on the downwind
side of the direct track to the station.
Tracking
Tracking uses a heading that will maintain the desired track
to or from the station regardless of crosswind conditions.
Interpretation of the heading indicator and needle is done to
maintain a constant MB to or from the station.
To track inbound, turn to the heading that will produce a zero
RB. Maintain this heading until off-course drift is indicated
by displacement of the needle, which will occur if there is a
crosswind (needle moving left = wind from the left; needle
moving right = wind from the right). A rapid rate of bearing
change with a constant heading indicates either a strong
crosswind or close proximity to the station or both. When
there is a definite (2° to 5°) change in needle reading, turn
in the direction of needle deflection to intercept the initial
MB. The angle of interception must be greater than the
number of degrees of drift, otherwise the aircraft will slowly
drift due to the wind pushing the aircraft. If repeated often
enough, the track to the station will appear circular and the
distance greatly increased as compared to a straight track.
The intercept angle depends on the rate of drift, the aircraft
speed, and station proximity. Initially, it is standard to double
the RB when turning toward your course.
For example, if your heading equals your course and the
needle points 10° left, turn 20° left, twice the initial RB.
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Instrument Flying Handbook仪表飞行手册下(10)
