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4.16.1.1. Plot the wind on the computer in the normal manner. Use the square grid side of the computer
slide for the distance.
150 AFPAM11-216 1 MARCH 2001
Figure 4.46. Convert Wind to Rectangular Coordinates.
4.16.1.2. Rotate the compass rose until north, the nearest cardinal heading, is under the true index.
4.16.1.3. Read down the vertical scale to the line upon which the head of the wind vector is now located.
The component value (23) is from the north under the true index.
4.16.1.4. Read across the horizontal scale from the center line to the head of the wind vector. The
component value (9) is from the west. The wind is stated rectangularly as N-23, W-9.
4.16.2. Given: Coordinates, S-30, E-36, to convert to a wind.
4.16.2.1. Use the square grid side of the computer.
4.16.2.2. Place south cardinal heading under the true index and the grommet on zero of the square grid.
4.16.2.3. Read down from the grommet along the centerline for the value (30) of the cardinal direction
under the true index.
4.16.2.4. Place east cardinal heading, read horizontally along the value located in Step 3 from the
centerline of the value of the second cardinal direction and mark the point.
4.16.2.5. Rotate the compass rose until the marked point is over the centerline of the computer.
4.16.2.6. Read the WD (130) under the true index and velocity (47 knots) from the grommet to the point
marked.
AFPAM11-216 1 MARCH 2001 151
Chapter 5
RADIO AID FIXING
Section 5A— Bearings and Lines of Position
5.1. Basics. Good dead reckoning (DR) techniques can result in fairly accurate positions. But, even
when employing the very best techniques, the DR position will become less accurate as time increases
beyond the last known position. Small errors tend to accumulate into one total error which is
unacceptable. To minimize this error, the navigator must be able to establish an accurate position from
which to restart DR. This accurate position is free of any DR errors and is called a fix. A fix is simply a
point from which the navigator can restart DR, just as if it were the takeoff point. We will begin our
discussion of fixing with an explanation of lines of position (LOP).
5.2. LOP Explained. It is possible to solve part of the fix problem without knowing your exact location.
For example, assume you are in a strange town and you call a friend to meet you downtown. If you tell
this person that you are somewhere on Park Street, your friend can limit any search for you to that
particular street. In this case, Park Street is an LOP. An LOP is a series of possible positions or fixes. It
can be a straight line (such as a city street) or a curved line (such as a river), but it gives a definite clue
to your position.
5.2.1. If you tell your friend that you are at Park Street where it crosses the Karuzas River, it would then
establish your exact location. You have used two LOPs to determine your exact position. Thus, two
intersecting LOPs identify a point which establishes a fix.
5.2.2. You can use the same procedure as a navigator. You may be flying along a railroad that you
identify as the Jedicke Railroad on your chart. As you continue on this course, you notice the railroad
crosses a river that is labeled the King River on your chart. When you fly over the point where these two
visual LOPs cross, you know your exact location over the ground and on your chart. You now have a fix
from which you can continue to DR.
5.3. Types of LOPs. A fix gives definite information as to both track and groundspeed (GS) of an
aircraft since the last fix, but a single LOP can only define either the track or the GS--not both. And it
may not clearly define either. The evidence obtained from an LOP depends upon the angle at which it
intersects the track. LOPs are sometimes classified according to this angle.
5.3.1. Course Line. An LOP which is parallel or nearly parallel to the course is called a course line
(Figure 5.1). It gives information as to possible locations of the aircraft laterally in relation to the course;
that is, whether it is to the right or left of course. Because it does not indicate how far the aircraft is
along the track, no speed information is provided.
5.3.2. Speed Line. An LOP which is perpendicular, or nearly so, to the track is called a speed line
(Figure 5.2) because it indicates how far the aircraft has traveled along the track and, thus, is a measure
of GS. It does not indicate whether the aircraft is to the right or left of the course.
152 AFPAM11-216 1 MARCH 2001
Figure 5.1. Line of Position Parallel to Track Is Course Line.
Figure 5.2. Line of Position Perpendicular to Track Is Speed Line.
5.3.3. LOPs by Bearings. One method of determining an LOP is to establish the direction of the line of
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