T-45A UJPT & E2-C2 INAV08
Fuel, Weather, and Alternate Airfield Planning
You will be primarily working with the FLIP Enroute High Altitude Charts which depict radials (courses) in
degrees magnetic. These are the radials you set in the course selector of the HSI. You will fly a magnetic
heading on your HSI to make good the course, or track-over-the-ground, you have selected. In flight
planning, therefore, if you are faced with TRUE WINDS and MAGNETIC COURSES, it is obvious
something has to be done to make them compatible.
The circular computer solves this by providing a magnetic-true conversion scale on either side of the True
Course (TC) index. From the FLIP Enroute Charts, you obtain your desired Magnetic Course and also the
Magnetic Variation in the area. By setting the Magnetic Course on the "Degree Scale" over the Variation
(East or West), the wind dot is automatically aligned to use the True Winds Aloft which you received from
the forecaster. You use this method for each leg to compute groundspeeds for each leg of flight.
NOTE: Lines of Magnetic Variation are depicted at 4-degree intervals. You should interpolate between
lines to obtain the approximate variation in your area of flight. An alternate method would be to look at a
field diagram in the area of flight.
Computing ground speed with crab angle less than 10 degrees - You obtain the following
information to complete one leg of flight on the Jet Flight Log:
OPPOSITE 340 KTAS
Figure 4 (Part 1): COMPUTING GROUND SPEED WITH CRAB ANGLE LESS THAN 10 DEGREES