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17.4. Chart Selection. One of several charts may be appropriate for low altitude navigation. One chart
designed for low-level use is the Operational Navigation Chart (ONC). The 1:1,000,000 scale permits
identification of all visual and radar significant features and the chart has good cultural and relief
portrayal. For increased detail or slower speed aircraft, the Tactical Pilotage Chart (TPC) (1:500,000) or
a Joint Operations Graphic (JOG) (1:250,000) may be used.
17.4.1. It is possible to mix navigation charts. The en route portion of the low-level mission can be
plotted on an ONC, while the TPC or JOG may be used for the target area or for specific identification
of checkpoints. If available, aerial photos are very useful for route study.
17.4.2. Annotate items of importance to navigation (turn points, descent points, high terrain, emergency
airfields, etc.) on the chart. Label preplanned fixes with planned radar range and bearing information. In
all cases, the annotations should be neat and compact for quick reference. Time is critical at high speed
and low altitude, so minimize the time you spend interpreting your chart in flight.
17.5. Planned Pacing. Choose suitable topographic or cultural returns for in-flight fixing and determine
a pacing schedule to accommodate these fixes. Plan the entire mission before takeoff. What you
accomplish in the air is merely a follow-through of what you have previously flight planned. Because
navigation demands flexibility, planning a pacing schedule involves two separate steps. First, complete a
premission plan based on expected in-flight conditions. Then, construct an alternate plan in case the
unexpected happens. For example, a 120-NM navigation leg, flown at 360, knots might accommodate
three radar fixes. This plan becomes the primary pacing schedule for the leg. A secondary pacing plan
might consider an unforeseen increase in GS and it would incorporate only two fixes. These principles
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apply to visual navigation as well as radar, but the fixes are generally closer together in visual
navigation.
17.6. Route Study. For a successful low-level mission, you must conduct a thorough route study. Route
study involves the entire crew, not just the navigator. In some missions, a pilot, loadmaster, flight
engineer, or boom operator can act as your map-reader, so they must know the same basic information
you know. Plan your en route updates during route study.
17.7. Radar Prediction. Radarscope interpretation can be preplanned for low-level flights. Note
significant returns, such as land-water contrast, unique terrain features, and towns. The time of year is
also important since radar returns during the winter may not appear the same as in other seasons of the
year.
17.7.1. At low altitudes, the appearance of a radar return changes rapidly as the aircraft approaches or
passes over the return. Often, the best identifying features of a checkpoint cannot be distinguished by
radar at low altitude. Because of this reduced radar range, the navigator should use DR procedures to
verify and identify radar returns.
17.7.2. No-return areas like lakes and rivers are better for radar prediction and navigation because they
furnish more accurate fixes than do towns or similar type returns. Constantly fine-tune your tilt and gain
settings; they are critical at low altitude. Use radar navigation in conjunction with an INS or GPS at lowlevel
for best effect.
17.8. Visual Prediction. In addition to the problems mentioned in radar prediction, other problems are
encountered with forecasting map-reading fixes. Weather effects, such as precipitation, smoke, haze, or
blowing dust, may obscure features intended for fixing. Visual navigation is especially difficult when
looking into the sun, particularly in hazy conditions. Avoid using cultural features for checkpoints
because they contain people and perhaps enemy forces, and during conflict should be avoided.
Section 17C— Course Control
17.9. Maintaining Track. To meet controlled times of arrival and to avoid terrain hazards, attempt to
fly the low-level flight exactly as planned. Every low-level navigation leg is planned within a flight
corridor for safety-of-flight reasons. There are several ways to maintain course, each of which has
advantages and limitations. Some of the methods are described here.
17.9.1. Correction to a Point on Centerline. When radar is an available aid, use the manual cursor to
correct back to centerline. Locate a suitable target on centerline and determine the intercept return to
centerline. The intercept correction (degrees of heading change) is an arbitrary determination based
primarily on the distance of the target from the aircraft. The closer the target is, the larger the correction
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