Garmin Aera 660 Pilot's Manual page 216

Appendix G
Total Air Temp— required entry for density altitude/true airspeed calculation. Total
Air Temperature (TAT) is the temperature of the air including the heating effect caused
by speed. The temperature reading on a standard outside air temperature gauge found
on most piston aircraft is TAT.
Heading— required entry for winds aloft calculation. Use heading from the aircraft's
heading indicator or directional gyro.
True Airspeed— (calculated or user-entered figure) determined from entry of
calibrated airspeed, barometric pressure, and total air temperature. This can also be
entered directly for winds aloft calculations.
Tail Wind— (calculated figure) determined from entry of heading and true airspeed.
Wind From—(calculated figure) determined from entry of heading and true airspeed.
Wind Speed—(calculated figure) determined from entry of heading and true air-
speed.
Density Altitude— (calculated figure) determined from entry of indicated altitude,
barometric pressure and total air temperature.
Calculating true airspeed and density altitude:
1) From the Main Menu, touch Tools > E6B, enter the altitude shown on
the altimeter into the 'Indicated Altitude' field.
2) Repeat for 'Calibrated Airspeed', 'Baro Pressure', and 'Total Air
Temperature' fields. (For Calibrated Airspeed, use the speed shown on
the airspeed indicator. Use the current altimeter setting for Baro Pressure.
Total Air Temperature is the temperature of the outside air including the
heating effect caused by speed. For most aircraft, this is the temperature
reading on a standard outside air temperature gauge.) The calculated
figures for True Airspeed and Density Altitude are shown in the designated
fields.
Calculating winds aloft:
1) From the Main Menu, touch Tools > E6B, calculate or enter the true
airspeed into the 'True Airspeed' field.
2) Enter the aircraft heading shown on the directional gyro or compass into
the 'Heading' field. Tail Wind, Wind From, and Wind Speed are calculated.
200
Garmin aera 660 Pilot's Guide
190-02017-20 Rev. E