| Home | Privacy | Contact |

Instrument Flying Handbook
Navigation Systems
Traditional Navigation Systems

| First | Previous | Next | Last |

Instrument Flying


Table of Contents

Chapter 1. Human Factors
Chapter 2. Aerodynamic Factors
Chapter 3. Flight Instruments
Chapter 4. Section I
Airplane Attitude Instrument
Using Analog Instrumentation
Chapter 4. Section II
Airplane Attitude Instrument
Using an Electronic Flight

Chapter 5. Section I
Airplane Basic
Flight Maneuvers
Using Analog Instrumentation
Chapter 5. Section II
Airplane Basic
Flight Maneuvers
Using an Electronic Flight

Chapter 6. Helicopter
Attitude Instrument Flying

Chapter 7. Navigation Systems
Chapter 8. The National
Airspace System

Chapter 9. The Air Traffic
Control System

Chapter 10. IFR Flight
Chapter 11. Emergency

Radio magnetic indicator(RMI).
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.

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, cheek 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 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 hearing
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.
[Figure 7-7] This will be your intercept angle to capture the
RB. Hold this heading until the needle is deflected 20° in
the opposite direction. That is, the deflection of the needle
equals the interception angle (in this case 20°). The track has
been intercepted, and the aircraft will remain on track as long
as the RB remains the same number of degrees as the wind
correction angle (WCA), the angle between the desired track
and the heading of the aircraft necessary to keep the aircraft
tracking over the desirable track. Lead the interception to avoid
overshooting the track. Turn 10° toward the inbound course.
You are now inbound with a 10° left correction angle.

NOTE: In Figure 7-7, for the aircraft closest to the station, the
WCA is 10° left and the RB is 10° right. If those values do
not change, the aircraft will track directly to the station. If you
observe off-course deflection in the original direction, turn
again to the original interception heading. When the desired
course has been re-intercepted, tarn 5° toward the inbound
course, proceeding inbound with a 15° drift correction. If the
initial 10° drift correction is excessive, as shown by needle
deflection away from the wind, turn to parallel the desired
course and let the wind drift you back on course. When the
needle is again zeroed, turn into the wind with a reduced
drift correction angle.