Figure 6-9

STUDENT GUIDE

VISUAL NAVIGATION

A Note Regarding MEF Values:

Maximum Elevation Figures are computed by NIMA (National Imagery and

Mapping Agency) and take into account both terrain and obstacles.

If the highest feature within a Latitude/Longitude grid is terrain, NIMA adds 200 feet

to the terrain elevation, plus the vertical accuracy of the identified point. This value

is then rounded to the next hundred-foot value.

If the highest vertical obstruction (man-made) is higher than the highest terrain

elevation plus 200', then the MEF is computed using the elevation of the obstruction

plus its vertical accuracy, then rounded to the next higher hundred foot value.

What is critical to keep in mind is that the MEF may give over 200 feet or less than

50 feet of clearance, and does not necessarily insure absolute clearance of terrain or obstacles.

Information collected from DMAAC (MC) SOP 8440.2, 1 DEC 1989.

6.5.7. Measuring the Distance

6.5.7.1. The difference in measuring T-1A/T-39 VNAV distances is the turn radius. To measure

this distance, a pair of dividers may be spanned to represent 1 NM, and then "walked" around the

turn. Another method is to use the combat plotter as shown in Figure 6-9. Using the "dime"

sized radius, note the template is marked in 1 NM increments. Measure the distance flown for

the turn as shown in Figure

6-9, and then add the

remaining distance

measured from the roll-out

to the next point. For the

examples shown in Figures

6-9 and 6-10, this is 3nm +

14.5nm, or 17.5 NM.

Round all distances to the

nearest .5 NM. If using a

pair of dividers to "step"

out the distance of the turn,

use the same technique---

adding the distance for the

turn to the remaining leg

distance.

Figure 6-9

6-12